refs #13667 "Merge branch '13667-add-version-file'".
[arvados.git] / sdk / python / arvados / collection.py
index ddf2eae674d12fd32a25236f94db2c4577c9dc80..e38a6bd475c7b8a4aee7787a537a40656fd93b36 100644 (file)
@@ -1,26 +1,43 @@
+# Copyright (C) The Arvados Authors. All rights reserved.
+#
+# SPDX-License-Identifier: Apache-2.0
+
+from __future__ import absolute_import
+from future.utils import listitems, listvalues, viewkeys
+from builtins import str
+from past.builtins import basestring
+from builtins import object
 import functools
 import logging
 import os
 import re
 import errno
+import hashlib
+import datetime
+import ciso8601
 import time
+import threading
 
 from collections import deque
 from stat import *
 
-from .arvfile import ArvadosFileBase, split, ArvadosFile, ArvadosFileWriter, ArvadosFileReader, BlockManager, _synchronized, _must_be_writable, SYNC_READONLY, SYNC_EXPLICIT, SYNC_LIVE, NoopLock
-from keep import *
-from .stream import StreamReader, normalize_stream, locator_block_size
-from .ranges import Range, LocatorAndRange
-from .safeapi import SafeApi
-import config
-import errors
-import util
-import events
+from .arvfile import split, _FileLikeObjectBase, ArvadosFile, ArvadosFileWriter, ArvadosFileReader, _BlockManager, synchronized, must_be_writable, NoopLock
+from .keep import KeepLocator, KeepClient
+from .stream import StreamReader
+from ._normalize_stream import normalize_stream
+from ._ranges import Range, LocatorAndRange
+from .safeapi import ThreadSafeApiCache
+import arvados.config as config
+import arvados.errors as errors
+import arvados.util
+import arvados.events as events
+from arvados.retry import retry_method
 
 _logger = logging.getLogger('arvados.collection')
 
 class CollectionBase(object):
+    """Abstract base class for Collection classes."""
+
     def __enter__(self):
         return self
 
@@ -34,7 +51,8 @@ class CollectionBase(object):
         return self._keep_client
 
     def stripped_manifest(self):
-        """
+        """Get the manifest with locator hints stripped.
+
         Return the manifest for the current collection with all
         non-portable hints (i.e., permission signatures and other
         hints other than size hints) removed from the locators.
@@ -46,204 +64,14 @@ class CollectionBase(object):
             if fields:
                 clean_fields = fields[:1] + [
                     (re.sub(r'\+[^\d][^\+]*', '', x)
-                     if re.match(util.keep_locator_pattern, x)
+                     if re.match(arvados.util.keep_locator_pattern, x)
                      else x)
                     for x in fields[1:]]
                 clean += [' '.join(clean_fields), "\n"]
         return ''.join(clean)
 
 
-class CollectionReader(CollectionBase):
-    def __init__(self, manifest_locator_or_text, api_client=None,
-                 keep_client=None, num_retries=0):
-        """Instantiate a CollectionReader.
-
-        This class parses Collection manifests to provide a simple interface
-        to read its underlying files.
-
-        Arguments:
-        * manifest_locator_or_text: One of a Collection UUID, portable data
-          hash, or full manifest text.
-        * api_client: The API client to use to look up Collections.  If not
-          provided, CollectionReader will build one from available Arvados
-          configuration.
-        * keep_client: The KeepClient to use to download Collection data.
-          If not provided, CollectionReader will build one from available
-          Arvados configuration.
-        * num_retries: The default number of times to retry failed
-          service requests.  Default 0.  You may change this value
-          after instantiation, but note those changes may not
-          propagate to related objects like the Keep client.
-        """
-        self._api_client = api_client
-        self._keep_client = keep_client
-        self.num_retries = num_retries
-        if re.match(util.keep_locator_pattern, manifest_locator_or_text):
-            self._manifest_locator = manifest_locator_or_text
-            self._manifest_text = None
-        elif re.match(util.collection_uuid_pattern, manifest_locator_or_text):
-            self._manifest_locator = manifest_locator_or_text
-            self._manifest_text = None
-        elif re.match(util.manifest_pattern, manifest_locator_or_text):
-            self._manifest_text = manifest_locator_or_text
-            self._manifest_locator = None
-        else:
-            raise errors.ArgumentError(
-                "Argument to CollectionReader must be a manifest or a collection UUID")
-        self._api_response = None
-        self._streams = None
-
-    def _populate_from_api_server(self):
-        # As in KeepClient itself, we must wait until the last
-        # possible moment to instantiate an API client, in order to
-        # avoid tripping up clients that don't have access to an API
-        # server.  If we do build one, make sure our Keep client uses
-        # it.  If instantiation fails, we'll fall back to the except
-        # clause, just like any other Collection lookup
-        # failure. Return an exception, or None if successful.
-        try:
-            if self._api_client is None:
-                self._api_client = arvados.api('v1')
-                self._keep_client = None  # Make a new one with the new api.
-            self._api_response = self._api_client.collections().get(
-                uuid=self._manifest_locator).execute(
-                num_retries=self.num_retries)
-            self._manifest_text = self._api_response['manifest_text']
-            return None
-        except Exception as e:
-            return e
-
-    def _populate_from_keep(self):
-        # Retrieve a manifest directly from Keep. This has a chance of
-        # working if [a] the locator includes a permission signature
-        # or [b] the Keep services are operating in world-readable
-        # mode. Return an exception, or None if successful.
-        try:
-            self._manifest_text = self._my_keep().get(
-                self._manifest_locator, num_retries=self.num_retries)
-        except Exception as e:
-            return e
-
-    def _populate(self):
-        error_via_api = None
-        error_via_keep = None
-        should_try_keep = ((self._manifest_text is None) and
-                           util.keep_locator_pattern.match(
-                self._manifest_locator))
-        if ((self._manifest_text is None) and
-            util.signed_locator_pattern.match(self._manifest_locator)):
-            error_via_keep = self._populate_from_keep()
-        if self._manifest_text is None:
-            error_via_api = self._populate_from_api_server()
-            if error_via_api is not None and not should_try_keep:
-                raise error_via_api
-        if ((self._manifest_text is None) and
-            not error_via_keep and
-            should_try_keep):
-            # Looks like a keep locator, and we didn't already try keep above
-            error_via_keep = self._populate_from_keep()
-        if self._manifest_text is None:
-            # Nothing worked!
-            raise arvados.errors.NotFoundError(
-                ("Failed to retrieve collection '{}' " +
-                 "from either API server ({}) or Keep ({})."
-                 ).format(
-                    self._manifest_locator,
-                    error_via_api,
-                    error_via_keep))
-        self._streams = [sline.split()
-                         for sline in self._manifest_text.split("\n")
-                         if sline]
-
-    def _populate_first(orig_func):
-        # Decorator for methods that read actual Collection data.
-        @functools.wraps(orig_func)
-        def wrapper(self, *args, **kwargs):
-            if self._streams is None:
-                self._populate()
-            return orig_func(self, *args, **kwargs)
-        return wrapper
-
-    @_populate_first
-    def api_response(self):
-        """api_response() -> dict or None
-
-        Returns information about this Collection fetched from the API server.
-        If the Collection exists in Keep but not the API server, currently
-        returns None.  Future versions may provide a synthetic response.
-        """
-        return self._api_response
-
-    @_populate_first
-    def normalize(self):
-        # Rearrange streams
-        streams = {}
-        for s in self.all_streams():
-            for f in s.all_files():
-                streamname, filename = split(s.name() + "/" + f.name())
-                if streamname not in streams:
-                    streams[streamname] = {}
-                if filename not in streams[streamname]:
-                    streams[streamname][filename] = []
-                for r in f.segments:
-                    streams[streamname][filename].extend(s.locators_and_ranges(r.locator, r.range_size))
-
-        self._streams = [normalize_stream(s, streams[s])
-                         for s in sorted(streams)]
-
-        # Regenerate the manifest text based on the normalized streams
-        self._manifest_text = ''.join(
-            [StreamReader(stream, keep=self._my_keep()).manifest_text()
-             for stream in self._streams])
-
-    @_populate_first
-    def open(self, streampath, filename=None):
-        """open(streampath[, filename]) -> file-like object
-
-        Pass in the path of a file to read from the Collection, either as a
-        single string or as two separate stream name and file name arguments.
-        This method returns a file-like object to read that file.
-        """
-        if filename is None:
-            streampath, filename = split(streampath)
-        keep_client = self._my_keep()
-        for stream_s in self._streams:
-            stream = StreamReader(stream_s, keep_client,
-                                  num_retries=self.num_retries)
-            if stream.name() == streampath:
-                break
-        else:
-            raise ValueError("stream '{}' not found in Collection".
-                             format(streampath))
-        try:
-            return stream.files()[filename]
-        except KeyError:
-            raise ValueError("file '{}' not found in Collection stream '{}'".
-                             format(filename, streampath))
-
-    @_populate_first
-    def all_streams(self):
-        return [StreamReader(s, self._my_keep(), num_retries=self.num_retries)
-                for s in self._streams]
-
-    def all_files(self):
-        for s in self.all_streams():
-            for f in s.all_files():
-                yield f
-
-    @_populate_first
-    def manifest_text(self, strip=False, normalize=False):
-        if normalize:
-            cr = CollectionReader(self.manifest_text())
-            cr.normalize()
-            return cr.manifest_text(strip=strip, normalize=False)
-        elif strip:
-            return self.stripped_manifest()
-        else:
-            return self._manifest_text
-
-
-class _WriterFile(ArvadosFileBase):
+class _WriterFile(_FileLikeObjectBase):
     def __init__(self, coll_writer, name):
         super(_WriterFile, self).__init__(name, 'wb')
         self.dest = coll_writer
@@ -252,22 +80,24 @@ class _WriterFile(ArvadosFileBase):
         super(_WriterFile, self).close()
         self.dest.finish_current_file()
 
-    @ArvadosFileBase._before_close
+    @_FileLikeObjectBase._before_close
     def write(self, data):
         self.dest.write(data)
 
-    @ArvadosFileBase._before_close
+    @_FileLikeObjectBase._before_close
     def writelines(self, seq):
         for data in seq:
             self.write(data)
 
-    @ArvadosFileBase._before_close
+    @_FileLikeObjectBase._before_close
     def flush(self):
         self.dest.flush_data()
 
 
 class CollectionWriter(CollectionBase):
-    def __init__(self, api_client=None, num_retries=0):
+    """Deprecated, use Collection instead."""
+
+    def __init__(self, api_client=None, num_retries=0, replication=None):
         """Instantiate a CollectionWriter.
 
         CollectionWriter lets you build a new Arvados Collection from scratch.
@@ -283,9 +113,13 @@ class CollectionWriter(CollectionBase):
           service requests.  Default 0.  You may change this value
           after instantiation, but note those changes may not
           propagate to related objects like the Keep client.
+        * replication: The number of copies of each block to store.
+          If this argument is None or not supplied, replication is
+          the server-provided default if available, otherwise 2.
         """
         self._api_client = api_client
         self.num_retries = num_retries
+        self.replication = (2 if replication is None else replication)
         self._keep_client = None
         self._data_buffer = []
         self._data_buffer_len = 0
@@ -361,7 +195,7 @@ class CollectionWriter(CollectionBase):
 
     def _work_trees(self):
         path, stream_name, max_manifest_depth = self._queued_trees[0]
-        d = util.listdir_recursive(
+        d = arvados.util.listdir_recursive(
             path, max_depth = (None if max_manifest_depth == 0 else 0))
         if d:
             self._queue_dirents(stream_name, d)
@@ -397,7 +231,11 @@ class CollectionWriter(CollectionBase):
         self.do_queued_work()
 
     def write(self, newdata):
-        if hasattr(newdata, '__iter__'):
+        if isinstance(newdata, bytes):
+            pass
+        elif isinstance(newdata, str):
+            newdata = newdata.encode()
+        elif hasattr(newdata, '__iter__'):
             for s in newdata:
                 self.write(s)
             return
@@ -437,10 +275,12 @@ class CollectionWriter(CollectionBase):
         return self._last_open
 
     def flush_data(self):
-        data_buffer = ''.join(self._data_buffer)
+        data_buffer = b''.join(self._data_buffer)
         if data_buffer:
             self._current_stream_locators.append(
-                self._my_keep().put(data_buffer[0:config.KEEP_BLOCK_SIZE]))
+                self._my_keep().put(
+                    data_buffer[0:config.KEEP_BLOCK_SIZE],
+                    copies=self.replication))
             self._data_buffer = [data_buffer[config.KEEP_BLOCK_SIZE:]]
             self._data_buffer_len = len(self._data_buffer[0])
 
@@ -486,7 +326,8 @@ class CollectionWriter(CollectionBase):
     def set_current_stream_name(self, newstreamname):
         if re.search(r'[\t\n]', newstreamname):
             raise errors.AssertionError(
-                "Manifest stream names cannot contain whitespace")
+                "Manifest stream names cannot contain whitespace: '%s'" %
+                (newstreamname))
         self._current_stream_name = '.' if newstreamname=='' else newstreamname
 
     def current_stream_name(self):
@@ -515,12 +356,21 @@ class CollectionWriter(CollectionBase):
         self._current_file_name = None
 
     def finish(self):
-        # Store the manifest in Keep and return its locator.
-        return self._my_keep().put(self.manifest_text())
+        """Store the manifest in Keep and return its locator.
+
+        This is useful for storing manifest fragments (task outputs)
+        temporarily in Keep during a Crunch job.
+
+        In other cases you should make a collection instead, by
+        sending manifest_text() to the API server's "create
+        collection" endpoint.
+        """
+        return self._my_keep().put(self.manifest_text().encode(),
+                                   copies=self.replication)
 
     def portable_data_hash(self):
-        stripped = self.stripped_manifest()
-        return hashlib.md5(stripped).hexdigest() + '+' + str(len(stripped))
+        stripped = self.stripped_manifest().encode()
+        return '{}+{}'.format(hashlib.md5(stripped).hexdigest(), len(stripped))
 
     def manifest_text(self):
         self.finish_current_stream()
@@ -542,18 +392,27 @@ class CollectionWriter(CollectionBase):
             ret += locators
         return ret
 
+    def save_new(self, name=None):
+        return self._api_client.collections().create(
+            ensure_unique_name=True,
+            body={
+                'name': name,
+                'manifest_text': self.manifest_text(),
+            }).execute(num_retries=self.num_retries)
+
 
 class ResumableCollectionWriter(CollectionWriter):
+    """Deprecated, use Collection instead."""
+
     STATE_PROPS = ['_current_stream_files', '_current_stream_length',
                    '_current_stream_locators', '_current_stream_name',
                    '_current_file_name', '_current_file_pos', '_close_file',
                    '_data_buffer', '_dependencies', '_finished_streams',
                    '_queued_dirents', '_queued_trees']
 
-    def __init__(self, api_client=None, num_retries=0):
+    def __init__(self, api_client=None, **kwargs):
         self._dependencies = {}
-        super(ResumableCollectionWriter, self).__init__(
-            api_client, num_retries=num_retries)
+        super(ResumableCollectionWriter, self).__init__(api_client, **kwargs)
 
     @classmethod
     def from_state(cls, state, *init_args, **init_kwargs):
@@ -589,7 +448,7 @@ class ResumableCollectionWriter(CollectionWriter):
         return writer
 
     def check_dependencies(self):
-        for path, orig_stat in self._dependencies.items():
+        for path, orig_stat in listitems(self._dependencies):
             if not S_ISREG(orig_stat[ST_MODE]):
                 raise errors.StaleWriterStateError("{} not file".format(path))
             try:
@@ -642,12 +501,26 @@ class ResumableCollectionWriter(CollectionWriter):
                 "resumable writer can't accept unsourced data")
         return super(ResumableCollectionWriter, self).write(data)
 
+
 ADD = "add"
 DEL = "del"
+MOD = "mod"
+TOK = "tok"
+FILE = "file"
+COLLECTION = "collection"
+
+class RichCollectionBase(CollectionBase):
+    """Base class for Collections and Subcollections.
+
+    Implements the majority of functionality relating to accessing items in the
+    Collection.
+
+    """
 
-class SynchronizedCollectionBase(CollectionBase):
     def __init__(self, parent=None):
         self.parent = parent
+        self._committed = False
+        self._callback = None
         self._items = {}
 
     def _my_api(self):
@@ -659,74 +532,122 @@ class SynchronizedCollectionBase(CollectionBase):
     def _my_block_manager(self):
         raise NotImplementedError()
 
-    def _root_lock(self):
+    def writable(self):
         raise NotImplementedError()
 
-    def _populate(self):
+    def root_collection(self):
         raise NotImplementedError()
 
-    def sync_mode(self):
+    def notify(self, event, collection, name, item):
         raise NotImplementedError()
 
-    def notify(self, collection, event, name, item):
+    def stream_name(self):
         raise NotImplementedError()
 
-    @_synchronized
-    def find(self, path, create=False, create_collection=False):
-        """Recursively search the specified file path.  May return either a Collection
-        or ArvadosFile.
+    @must_be_writable
+    @synchronized
+    def find_or_create(self, path, create_type):
+        """Recursively search the specified file path.
 
-        :create:
-          If true, create path components (i.e. Collections) that are
-          missing.  If "create" is False, return None if a path component is
-          not found.
+        May return either a `Collection` or `ArvadosFile`.  If not found, will
+        create a new item at the specified path based on `create_type`.  Will
+        create intermediate subcollections needed to contain the final item in
+        the path.
 
-        :create_collection:
-          If the path is not found, "create" is True, and
-          "create_collection" is False, then create and return a new
-          ArvadosFile for the last path component.  If "create_collection" is
-          True, then create and return a new Collection for the last path
-          component.
+        :create_type:
+          One of `arvados.collection.FILE` or
+          `arvados.collection.COLLECTION`.  If the path is not found, and value
+          of create_type is FILE then create and return a new ArvadosFile for
+          the last path component.  If COLLECTION, then create and return a new
+          Collection for the last path component.
 
         """
-        if create and self.sync_mode() == SYNC_READONLY:
-            raise IOError((errno.EROFS, "Collection is read only"))
-
-        p = path.split("/")
-        if p[0] == '.':
-            del p[0]
-
-        if p and p[0]:
-            item = self._items.get(p[0])
-            if len(p) == 1:
-                # item must be a file
-                if item is None and create:
+
+        pathcomponents = path.split("/", 1)
+        if pathcomponents[0]:
+            item = self._items.get(pathcomponents[0])
+            if len(pathcomponents) == 1:
+                if item is None:
                     # create new file
-                    if create_collection:
-                        item = Subcollection(self)
+                    if create_type == COLLECTION:
+                        item = Subcollection(self, pathcomponents[0])
                     else:
-                        item = ArvadosFile(self)
-                    self._items[p[0]] = item
-                    self.notify(self, ADD, p[0], item)
+                        item = ArvadosFile(self, pathcomponents[0])
+                    self._items[pathcomponents[0]] = item
+                    self.set_committed(False)
+                    self.notify(ADD, self, pathcomponents[0], item)
                 return item
             else:
-                if item is None and create:
+                if item is None:
                     # create new collection
-                    item = Subcollection(self)
-                    self._items[p[0]] = item
-                    self.notify(self, ADD, p[0], item)
-                del p[0]
-                return item.find("/".join(p), create=create)
+                    item = Subcollection(self, pathcomponents[0])
+                    self._items[pathcomponents[0]] = item
+                    self.set_committed(False)
+                    self.notify(ADD, self, pathcomponents[0], item)
+                if isinstance(item, RichCollectionBase):
+                    return item.find_or_create(pathcomponents[1], create_type)
+                else:
+                    raise IOError(errno.ENOTDIR, "Not a directory", pathcomponents[0])
         else:
             return self
 
-    def open(self, path, mode):
+    @synchronized
+    def find(self, path):
+        """Recursively search the specified file path.
+
+        May return either a Collection or ArvadosFile. Return None if not
+        found.
+        If path is invalid (ex: starts with '/'), an IOError exception will be
+        raised.
+
+        """
+        if not path:
+            raise errors.ArgumentError("Parameter 'path' is empty.")
+
+        pathcomponents = path.split("/", 1)
+        if pathcomponents[0] == '':
+            raise IOError(errno.ENOTDIR, "Not a directory", pathcomponents[0])
+
+        item = self._items.get(pathcomponents[0])
+        if item is None:
+            return None
+        elif len(pathcomponents) == 1:
+            return item
+        else:
+            if isinstance(item, RichCollectionBase):
+                if pathcomponents[1]:
+                    return item.find(pathcomponents[1])
+                else:
+                    return item
+            else:
+                raise IOError(errno.ENOTDIR, "Not a directory", pathcomponents[0])
+
+    @synchronized
+    def mkdirs(self, path):
+        """Recursive subcollection create.
+
+        Like `os.makedirs()`.  Will create intermediate subcollections needed
+        to contain the leaf subcollection path.
+
+        """
+
+        if self.find(path) != None:
+            raise IOError(errno.EEXIST, "Directory or file exists", path)
+
+        return self.find_or_create(path, COLLECTION)
+
+    def open(self, path, mode="r"):
         """Open a file-like object for access.
 
         :path:
           path to a file in the collection
         :mode:
-          one of "r", "r+", "w", "w+", "a", "a+"
+          a string consisting of "r", "w", or "a", optionally followed
+          by "b" or "t", optionally followed by "+".
+          :"b":
+            binary mode: write() accepts bytes, read() returns bytes.
+          :"t":
+            text mode (default): write() accepts strings, read() returns strings.
           :"r":
             opens for reading
           :"r+":
@@ -738,333 +659,693 @@ class SynchronizedCollectionBase(CollectionBase):
             the end of the file.  Writing does not affect the file pointer for
             reading.
         """
-        mode = mode.replace("b", "")
-        if len(mode) == 0 or mode[0] not in ("r", "w", "a"):
-            raise ArgumentError("Bad mode '%s'" % mode)
-        create = (mode != "r")
 
-        if create and self.sync_mode() == SYNC_READONLY:
-            raise IOError((errno.EROFS, "Collection is read only"))
+        if not re.search(r'^[rwa][bt]?\+?$', mode):
+            raise errors.ArgumentError("Invalid mode {!r}".format(mode))
+
+        if mode[0] == 'r' and '+' not in mode:
+            fclass = ArvadosFileReader
+            arvfile = self.find(path)
+        elif not self.writable():
+            raise IOError(errno.EROFS, "Collection is read only")
+        else:
+            fclass = ArvadosFileWriter
+            arvfile = self.find_or_create(path, FILE)
+
+        if arvfile is None:
+            raise IOError(errno.ENOENT, "File not found", path)
+        if not isinstance(arvfile, ArvadosFile):
+            raise IOError(errno.EISDIR, "Is a directory", path)
+
+        if mode[0] == 'w':
+            arvfile.truncate(0)
+
+        return fclass(arvfile, mode=mode, num_retries=self.num_retries)
+
+    def modified(self):
+        """Determine if the collection has been modified since last commited."""
+        return not self.committed()
 
-        f = self.find(path, create=create)
+    @synchronized
+    def committed(self):
+        """Determine if the collection has been committed to the API server."""
+        return self._committed
 
-        if f is None:
-            raise IOError((errno.ENOENT, "File not found"))
-        if not isinstance(f, ArvadosFile):
-            raise IOError((errno.EISDIR, "Path must refer to a file."))
+    @synchronized
+    def set_committed(self, value=True):
+        """Recursively set committed flag.
 
-        if mode[0] == "w":
-            f.truncate(0)
+        If value is True, set committed to be True for this and all children.
 
-        if mode == "r":
-            return ArvadosFileReader(f, path, mode, num_retries=self.num_retries)
+        If value is False, set committed to be False for this and all parents.
+        """
+        if value == self._committed:
+            return
+        if value:
+            for k,v in listitems(self._items):
+                v.set_committed(True)
+            self._committed = True
         else:
-            return ArvadosFileWriter(f, path, mode, num_retries=self.num_retries)
+            self._committed = False
+            if self.parent is not None:
+                self.parent.set_committed(False)
 
-    @_synchronized
-    def modified(self):
-        """Test if the collection (or any subcollection or file) has been modified
-        since it was created."""
-        for k,v in self._items.items():
-            if v.modified():
-                return True
-        return False
-
-    @_synchronized
-    def set_unmodified(self):
-        """Recursively clear modified flag"""
-        for k,v in self._items.items():
-            v.set_unmodified()
-
-    @_synchronized
+    @synchronized
     def __iter__(self):
         """Iterate over names of files and collections contained in this collection."""
-        return self._items.keys()
+        return iter(viewkeys(self._items))
 
-    @_synchronized
-    def iterkeys(self):
-        """Iterate over names of files and collections directly contained in this collection."""
-        return self._items.keys()
-
-    @_synchronized
+    @synchronized
     def __getitem__(self, k):
-        """Get a file or collection that is directly contained by this collection.  If
-        you want to search a path, use `find()` instead.
+        """Get a file or collection that is directly contained by this collection.
+
+        If you want to search a path, use `find()` instead.
+
         """
         return self._items[k]
 
-    @_synchronized
+    @synchronized
     def __contains__(self, k):
-        """If there is a file or collection a directly contained by this collection
-        with name "k"."""
+        """Test if there is a file or collection a directly contained by this collection."""
         return k in self._items
 
-    @_synchronized
+    @synchronized
     def __len__(self):
-        """Get the number of items directly contained in this collection"""
+        """Get the number of items directly contained in this collection."""
         return len(self._items)
 
-    @_must_be_writable
-    @_synchronized
+    @must_be_writable
+    @synchronized
     def __delitem__(self, p):
         """Delete an item by name which is directly contained by this collection."""
         del self._items[p]
-        self.notify(self, DEL, p, None)
+        self.set_committed(False)
+        self.notify(DEL, self, p, None)
 
-    @_synchronized
+    @synchronized
     def keys(self):
         """Get a list of names of files and collections directly contained in this collection."""
         return self._items.keys()
 
-    @_synchronized
+    @synchronized
     def values(self):
         """Get a list of files and collection objects directly contained in this collection."""
-        return self._items.values()
+        return listvalues(self._items)
 
-    @_synchronized
+    @synchronized
     def items(self):
         """Get a list of (name, object) tuples directly contained in this collection."""
-        return self._items.items()
+        return listitems(self._items)
 
     def exists(self, path):
-        """Test if there is a file or collection at "path" """
-        return self.find(path) != None
+        """Test if there is a file or collection at `path`."""
+        return self.find(path) is not None
 
-    @_must_be_writable
-    @_synchronized
-    def remove(self, path, rm_r=False):
+    @must_be_writable
+    @synchronized
+    def remove(self, path, recursive=False):
         """Remove the file or subcollection (directory) at `path`.
-        :rm_r:
+
+        :recursive:
           Specify whether to remove non-empty subcollections (True), or raise an error (False).
         """
-        p = path.split("/")
-        if p[0] == '.':
-            # Remove '.' from the front of the path
-            del p[0]
-
-        if len(p) > 0:
-            item = self._items.get(p[0])
-            if item is None:
-                raise IOError((errno.ENOENT, "File not found"))
-            if len(p) == 1:
-                if isinstance(self._items[p[0]], SynchronizedCollectionBase) and len(self._items[p[0]]) > 0 and not rm_r:
-                    raise IOError((errno.ENOTEMPTY, "Subcollection not empty"))
-                del self._items[p[0]]
-                self.notify(self, DEL, p[0], None)
-            else:
-                del p[0]
-                item.remove("/".join(p))
+
+        if not path:
+            raise errors.ArgumentError("Parameter 'path' is empty.")
+
+        pathcomponents = path.split("/", 1)
+        item = self._items.get(pathcomponents[0])
+        if item is None:
+            raise IOError(errno.ENOENT, "File not found", path)
+        if len(pathcomponents) == 1:
+            if isinstance(self._items[pathcomponents[0]], RichCollectionBase) and len(self._items[pathcomponents[0]]) > 0 and not recursive:
+                raise IOError(errno.ENOTEMPTY, "Directory not empty", path)
+            deleteditem = self._items[pathcomponents[0]]
+            del self._items[pathcomponents[0]]
+            self.set_committed(False)
+            self.notify(DEL, self, pathcomponents[0], deleteditem)
         else:
-            raise IOError((errno.ENOENT, "File not found"))
+            item.remove(pathcomponents[1])
 
-    def _cloneinto(self, target):
-        for k,v in self._items:
-            target._items[k] = v.clone(new_parent=target)
+    def _clonefrom(self, source):
+        for k,v in listitems(source):
+            self._items[k] = v.clone(self, k)
 
     def clone(self):
         raise NotImplementedError()
 
-    @_must_be_writable
-    @_synchronized
-    def copy(self, source_path, target_path, source_collection=None, overwrite=False):
-        """
-        copyto('/foo', '/bar') will overwrite 'foo' if it exists.
-        copyto('/foo/', '/bar') will place 'bar' in subcollection 'foo'
+    @must_be_writable
+    @synchronized
+    def add(self, source_obj, target_name, overwrite=False, reparent=False):
+        """Copy or move a file or subcollection to this collection.
+
+        :source_obj:
+          An ArvadosFile, or Subcollection object
+
+        :target_name:
+          Destination item name.  If the target name already exists and is a
+          file, this will raise an error unless you specify `overwrite=True`.
+
+        :overwrite:
+          Whether to overwrite target file if it already exists.
+
+        :reparent:
+          If True, source_obj will be moved from its parent collection to this collection.
+          If False, source_obj will be copied and the parent collection will be
+          unmodified.
+
         """
+
+        if target_name in self and not overwrite:
+            raise IOError(errno.EEXIST, "File already exists", target_name)
+
+        modified_from = None
+        if target_name in self:
+            modified_from = self[target_name]
+
+        # Actually make the move or copy.
+        if reparent:
+            source_obj._reparent(self, target_name)
+            item = source_obj
+        else:
+            item = source_obj.clone(self, target_name)
+
+        self._items[target_name] = item
+        self.set_committed(False)
+
+        if modified_from:
+            self.notify(MOD, self, target_name, (modified_from, item))
+        else:
+            self.notify(ADD, self, target_name, item)
+
+    def _get_src_target(self, source, target_path, source_collection, create_dest):
         if source_collection is None:
             source_collection = self
 
-        # Find the object to copy
-        sp = source_path.split("/")
-        source_obj = source_collection.find(source_path)
-        if source_obj is None:
-            raise IOError((errno.ENOENT, "File not found"))
+        # Find the object
+        if isinstance(source, basestring):
+            source_obj = source_collection.find(source)
+            if source_obj is None:
+                raise IOError(errno.ENOENT, "File not found", source)
+            sourcecomponents = source.split("/")
+        else:
+            source_obj = source
+            sourcecomponents = None
 
         # Find parent collection the target path
-        tp = target_path.split("/")
-        target_dir = self.find("/".join(tp[0:-1]), create=True, create_collection=True)
+        targetcomponents = target_path.split("/")
 
         # Determine the name to use.
-        target_name = tp[-1] if tp[-1] else sp[-1]
+        target_name = targetcomponents[-1] if targetcomponents[-1] else sourcecomponents[-1]
+
+        if not target_name:
+            raise errors.ArgumentError("Target path is empty and source is an object.  Cannot determine destination filename to use.")
+
+        if create_dest:
+            target_dir = self.find_or_create("/".join(targetcomponents[0:-1]), COLLECTION)
+        else:
+            if len(targetcomponents) > 1:
+                target_dir = self.find("/".join(targetcomponents[0:-1]))
+            else:
+                target_dir = self
+
+        if target_dir is None:
+            raise IOError(errno.ENOENT, "Target directory not found", target_name)
+
+        if target_name in target_dir and isinstance(target_dir[target_name], RichCollectionBase) and sourcecomponents:
+            target_dir = target_dir[target_name]
+            target_name = sourcecomponents[-1]
+
+        return (source_obj, target_dir, target_name)
+
+    @must_be_writable
+    @synchronized
+    def copy(self, source, target_path, source_collection=None, overwrite=False):
+        """Copy a file or subcollection to a new path in this collection.
+
+        :source:
+          A string with a path to source file or subcollection, or an actual ArvadosFile or Subcollection object.
+
+        :target_path:
+          Destination file or path.  If the target path already exists and is a
+          subcollection, the item will be placed inside the subcollection.  If
+          the target path already exists and is a file, this will raise an error
+          unless you specify `overwrite=True`.
+
+        :source_collection:
+          Collection to copy `source_path` from (default `self`)
+
+        :overwrite:
+          Whether to overwrite target file if it already exists.
+        """
+
+        source_obj, target_dir, target_name = self._get_src_target(source, target_path, source_collection, True)
+        target_dir.add(source_obj, target_name, overwrite, False)
+
+    @must_be_writable
+    @synchronized
+    def rename(self, source, target_path, source_collection=None, overwrite=False):
+        """Move a file or subcollection from `source_collection` to a new path in this collection.
+
+        :source:
+          A string with a path to source file or subcollection.
+
+        :target_path:
+          Destination file or path.  If the target path already exists and is a
+          subcollection, the item will be placed inside the subcollection.  If
+          the target path already exists and is a file, this will raise an error
+          unless you specify `overwrite=True`.
+
+        :source_collection:
+          Collection to copy `source_path` from (default `self`)
+
+        :overwrite:
+          Whether to overwrite target file if it already exists.
+        """
+
+        source_obj, target_dir, target_name = self._get_src_target(source, target_path, source_collection, False)
+        if not source_obj.writable():
+            raise IOError(errno.EROFS, "Source collection is read only", source)
+        target_dir.add(source_obj, target_name, overwrite, True)
+
+    def portable_manifest_text(self, stream_name="."):
+        """Get the manifest text for this collection, sub collections and files.
+
+        This method does not flush outstanding blocks to Keep.  It will return
+        a normalized manifest with access tokens stripped.
+
+        :stream_name:
+          Name to use for this stream (directory)
+
+        """
+        return self._get_manifest_text(stream_name, True, True)
+
+    @synchronized
+    def manifest_text(self, stream_name=".", strip=False, normalize=False,
+                      only_committed=False):
+        """Get the manifest text for this collection, sub collections and files.
+
+        This method will flush outstanding blocks to Keep.  By default, it will
+        not normalize an unmodified manifest or strip access tokens.
+
+        :stream_name:
+          Name to use for this stream (directory)
+
+        :strip:
+          If True, remove signing tokens from block locators if present.
+          If False (default), block locators are left unchanged.
 
-        if target_name in target_dir:
-            if isinstance(target_dir[target_name], SynchronizedCollectionBase):
-                target_dir = target_dir[target_name]
-                target_name = sp[-1]
-            elif not overwrite:
-                raise IOError((errno.EEXIST, "File already exists"))
+        :normalize:
+          If True, always export the manifest text in normalized form
+          even if the Collection is not modified.  If False (default) and the collection
+          is not modified, return the original manifest text even if it is not
+          in normalized form.
 
-        # Actually make the copy.
-        dup = source_obj.clone(target_dir)
-        with target_dir.lock:
-            target_dir._items[target_name] = dup
+        :only_committed:
+          If True, don't commit pending blocks.
 
-        self.notify(target_dir, ADD, target_name, dup)
+        """
 
+        if not only_committed:
+            self._my_block_manager().commit_all()
+        return self._get_manifest_text(stream_name, strip, normalize,
+                                       only_committed=only_committed)
 
-    @_synchronized
-    def manifest_text(self, strip=False, normalize=False):
+    @synchronized
+    def _get_manifest_text(self, stream_name, strip, normalize, only_committed=False):
         """Get the manifest text for this collection, sub collections and files.
 
+        :stream_name:
+          Name to use for this stream (directory)
+
         :strip:
           If True, remove signing tokens from block locators if present.
-          If False, block locators are left unchanged.
+          If False (default), block locators are left unchanged.
 
         :normalize:
           If True, always export the manifest text in normalized form
-          even if the Collection is not modified.  If False and the collection
+          even if the Collection is not modified.  If False (default) and the collection
           is not modified, return the original manifest text even if it is not
           in normalized form.
 
+        :only_committed:
+          If True, only include blocks that were already committed to Keep.
+
         """
-        if self.modified() or self._manifest_text is None or normalize:
-            return export_manifest(self, stream_name=".", portable_locators=strip)
+
+        if not self.committed() or self._manifest_text is None or normalize:
+            stream = {}
+            buf = []
+            sorted_keys = sorted(self.keys())
+            for filename in [s for s in sorted_keys if isinstance(self[s], ArvadosFile)]:
+                # Create a stream per file `k`
+                arvfile = self[filename]
+                filestream = []
+                for segment in arvfile.segments():
+                    loc = segment.locator
+                    if arvfile.parent._my_block_manager().is_bufferblock(loc):
+                        if only_committed:
+                            continue
+                        loc = arvfile.parent._my_block_manager().get_bufferblock(loc).locator()
+                    if strip:
+                        loc = KeepLocator(loc).stripped()
+                    filestream.append(LocatorAndRange(loc, KeepLocator(loc).size,
+                                         segment.segment_offset, segment.range_size))
+                stream[filename] = filestream
+            if stream:
+                buf.append(" ".join(normalize_stream(stream_name, stream)) + "\n")
+            for dirname in [s for s in sorted_keys if isinstance(self[s], RichCollectionBase)]:
+                buf.append(self[dirname].manifest_text(stream_name=os.path.join(stream_name, dirname), strip=strip, normalize=True, only_committed=only_committed))
+            return "".join(buf)
         else:
             if strip:
                 return self.stripped_manifest()
             else:
                 return self._manifest_text
 
-    @_must_be_writable
-    @_synchronized
-    def merge(self, other):
-        for k in other.keys():
+    @synchronized
+    def diff(self, end_collection, prefix=".", holding_collection=None):
+        """Generate list of add/modify/delete actions.
+
+        When given to `apply`, will change `self` to match `end_collection`
+
+        """
+        changes = []
+        if holding_collection is None:
+            holding_collection = Collection(api_client=self._my_api(), keep_client=self._my_keep())
+        for k in self:
+            if k not in end_collection:
+               changes.append((DEL, os.path.join(prefix, k), self[k].clone(holding_collection, "")))
+        for k in end_collection:
             if k in self:
-                if isinstance(self[k], Subcollection) and isinstance(other[k], Subcollection):
-                    self[k].merge(other[k])
+                if isinstance(end_collection[k], Subcollection) and isinstance(self[k], Subcollection):
+                    changes.extend(self[k].diff(end_collection[k], os.path.join(prefix, k), holding_collection))
+                elif end_collection[k] != self[k]:
+                    changes.append((MOD, os.path.join(prefix, k), self[k].clone(holding_collection, ""), end_collection[k].clone(holding_collection, "")))
                 else:
-                    if self[k] != other[k]:
-                        name = "%s~conflict-%s~" % (k, time.strftime("%Y-%m-%d_%H:%M%:%S",
-                                                                     time.gmtime()))
-                        self[name] = other[k].clone(self)
-                        self.notify(self, name, ADD, self[name])
+                    changes.append((TOK, os.path.join(prefix, k), self[k].clone(holding_collection, ""), end_collection[k].clone(holding_collection, "")))
             else:
-                self[k] = other[k].clone(self)
-                self.notify(self, k, ADD, self[k])
+                changes.append((ADD, os.path.join(prefix, k), end_collection[k].clone(holding_collection, "")))
+        return changes
+
+    @must_be_writable
+    @synchronized
+    def apply(self, changes):
+        """Apply changes from `diff`.
+
+        If a change conflicts with a local change, it will be saved to an
+        alternate path indicating the conflict.
+
+        """
+        if changes:
+            self.set_committed(False)
+        for change in changes:
+            event_type = change[0]
+            path = change[1]
+            initial = change[2]
+            local = self.find(path)
+            conflictpath = "%s~%s~conflict~" % (path, time.strftime("%Y%m%d-%H%M%S",
+                                                                    time.gmtime()))
+            if event_type == ADD:
+                if local is None:
+                    # No local file at path, safe to copy over new file
+                    self.copy(initial, path)
+                elif local is not None and local != initial:
+                    # There is already local file and it is different:
+                    # save change to conflict file.
+                    self.copy(initial, conflictpath)
+            elif event_type == MOD or event_type == TOK:
+                final = change[3]
+                if local == initial:
+                    # Local matches the "initial" item so it has not
+                    # changed locally and is safe to update.
+                    if isinstance(local, ArvadosFile) and isinstance(final, ArvadosFile):
+                        # Replace contents of local file with new contents
+                        local.replace_contents(final)
+                    else:
+                        # Overwrite path with new item; this can happen if
+                        # path was a file and is now a collection or vice versa
+                        self.copy(final, path, overwrite=True)
+                else:
+                    # Local is missing (presumably deleted) or local doesn't
+                    # match the "start" value, so save change to conflict file
+                    self.copy(final, conflictpath)
+            elif event_type == DEL:
+                if local == initial:
+                    # Local item matches "initial" value, so it is safe to remove.
+                    self.remove(path, recursive=True)
+                # else, the file is modified or already removed, in either
+                # case we don't want to try to remove it.
 
     def portable_data_hash(self):
         """Get the portable data hash for this collection's manifest."""
-        stripped = self.manifest_text(strip=True)
-        return hashlib.md5(stripped).hexdigest() + '+' + str(len(stripped))
+        if self._manifest_locator and self.committed():
+            # If the collection is already saved on the API server, and it's committed
+            # then return API server's PDH response.
+            return self._portable_data_hash
+        else:
+            stripped = self.portable_manifest_text().encode()
+            return '{}+{}'.format(hashlib.md5(stripped).hexdigest(), len(stripped))
+
+    @synchronized
+    def subscribe(self, callback):
+        if self._callback is None:
+            self._callback = callback
+        else:
+            raise errors.ArgumentError("A callback is already set on this collection.")
+
+    @synchronized
+    def unsubscribe(self):
+        if self._callback is not None:
+            self._callback = None
+
+    @synchronized
+    def notify(self, event, collection, name, item):
+        if self._callback:
+            self._callback(event, collection, name, item)
+        self.root_collection().notify(event, collection, name, item)
+
+    @synchronized
+    def __eq__(self, other):
+        if other is self:
+            return True
+        if not isinstance(other, RichCollectionBase):
+            return False
+        if len(self._items) != len(other):
+            return False
+        for k in self._items:
+            if k not in other:
+                return False
+            if self._items[k] != other[k]:
+                return False
+        return True
+
+    def __ne__(self, other):
+        return not self.__eq__(other)
+
+    @synchronized
+    def flush(self):
+        """Flush bufferblocks to Keep."""
+        for e in listvalues(self):
+            e.flush()
+
+
+class Collection(RichCollectionBase):
+    """Represents the root of an Arvados Collection.
+
+    This class is threadsafe.  The root collection object, all subcollections
+    and files are protected by a single lock (i.e. each access locks the entire
+    collection).
+
+    Brief summary of
+    useful methods:
+
+    :To read an existing file:
+      `c.open("myfile", "r")`
+
+    :To write a new file:
+      `c.open("myfile", "w")`
+
+    :To determine if a file exists:
+      `c.find("myfile") is not None`
+
+    :To copy a file:
+      `c.copy("source", "dest")`
+
+    :To delete a file:
+      `c.remove("myfile")`
 
+    :To save to an existing collection record:
+      `c.save()`
+
+    :To save a new collection record:
+    `c.save_new()`
+
+    :To merge remote changes into this object:
+      `c.update()`
+
+    Must be associated with an API server Collection record (during
+    initialization, or using `save_new`) to use `save` or `update`
 
-class Collection(SynchronizedCollectionBase):
-    """Store an Arvados collection, consisting of a set of files and
-    sub-collections.
     """
 
     def __init__(self, manifest_locator_or_text=None,
-                 parent=None,
-                 config=None,
                  api_client=None,
                  keep_client=None,
                  num_retries=None,
+                 parent=None,
+                 apiconfig=None,
                  block_manager=None,
-                 sync=SYNC_READONLY):
-        """:manifest_locator_or_text:
-          One of Arvados collection UUID, block locator of
-          a manifest, raw manifest text, or None (to create an empty collection).
+                 replication_desired=None,
+                 put_threads=None):
+        """Collection constructor.
+
+        :manifest_locator_or_text:
+          An Arvados collection UUID, portable data hash, raw manifest
+          text, or (if creating an empty collection) None.
+
         :parent:
           the parent Collection, may be None.
-        :config:
-          the arvados configuration to get the hostname and api token.
+
+        :apiconfig:
+          A dict containing keys for ARVADOS_API_HOST and ARVADOS_API_TOKEN.
           Prefer this over supplying your own api_client and keep_client (except in testing).
           Will use default config settings if not specified.
+
         :api_client:
-          The API client object to use for requests.  If not specified, create one using `config`.
+          The API client object to use for requests.  If not specified, create one using `apiconfig`.
+
         :keep_client:
-          the Keep client to use for requests.  If not specified, create one using `config`.
+          the Keep client to use for requests.  If not specified, create one using `apiconfig`.
+
         :num_retries:
           the number of retries for API and Keep requests.
+
         :block_manager:
           the block manager to use.  If not specified, create one.
-        :sync:
-          Set synchronization policy with API server collection record.
-          :SYNC_READONLY:
-            Collection is read only.  No synchronization.  This mode will
-            also forego locking, which gives better performance.
-          :SYNC_EXPLICIT:
-            Synchronize on explicit request via `update()` or `save()`
-          :SYNC_LIVE:
-            Synchronize with server in response to background websocket events,
-            on block write, or on file close.
+
+        :replication_desired:
+          How many copies should Arvados maintain. If None, API server default
+          configuration applies. If not None, this value will also be used
+          for determining the number of block copies being written.
 
         """
         super(Collection, self).__init__(parent)
         self._api_client = api_client
         self._keep_client = keep_client
         self._block_manager = block_manager
-        self._config = config
-        self.num_retries = num_retries
+        self.replication_desired = replication_desired
+        self.put_threads = put_threads
+
+        if apiconfig:
+            self._config = apiconfig
+        else:
+            self._config = config.settings()
+
+        self.num_retries = num_retries if num_retries is not None else 0
         self._manifest_locator = None
         self._manifest_text = None
+        self._portable_data_hash = None
         self._api_response = None
-        self._sync = sync
+        self._past_versions = set()
+
         self.lock = threading.RLock()
-        self.callbacks = []
         self.events = None
 
         if manifest_locator_or_text:
-            if re.match(util.keep_locator_pattern, manifest_locator_or_text):
+            if re.match(arvados.util.keep_locator_pattern, manifest_locator_or_text):
                 self._manifest_locator = manifest_locator_or_text
-            elif re.match(util.collection_uuid_pattern, manifest_locator_or_text):
+            elif re.match(arvados.util.collection_uuid_pattern, manifest_locator_or_text):
                 self._manifest_locator = manifest_locator_or_text
-            elif re.match(util.manifest_pattern, manifest_locator_or_text):
+            elif re.match(arvados.util.manifest_pattern, manifest_locator_or_text):
                 self._manifest_text = manifest_locator_or_text
             else:
                 raise errors.ArgumentError(
-                    "Argument to CollectionReader must be a manifest or a collection UUID")
-
-            self._populate()
-
-            if self._sync == SYNC_LIVE:
-                if not self._manifest_locator or not re.match(util.collection_uuid_pattern, self._manifest_locator):
-                    raise errors.ArgumentError("Cannot SYNC_LIVE unless a collection uuid is specified")
-                self.events = events.subscribe(arvados.api(), [["object_uuid", "=", self._manifest_locator]], self.on_message)
+                    "Argument to CollectionReader is not a manifest or a collection UUID")
 
-    @staticmethod
-    def create(name, owner_uuid=None, sync=SYNC_EXPLICIT):
-        c = Collection(sync=sync)
-        c.save_as(name, owner_uuid=owner_uuid, ensure_unique_name=True)
-        return c
+            try:
+                self._populate()
+            except (IOError, errors.SyntaxError) as e:
+                raise errors.ArgumentError("Error processing manifest text: %s", e)
 
-    def _root_lock(self):
-        return self.lock
+    def root_collection(self):
+        return self
 
-    def sync_mode(self):
-        return self._sync
+    def get_properties(self):
+        if self._api_response and self._api_response["properties"]:
+            return self._api_response["properties"]
+        else:
+            return {}
 
-    def on_message(self):
-        self.update()
+    def get_trash_at(self):
+        if self._api_response and self._api_response["trash_at"]:
+            return ciso8601.parse_datetime(self._api_response["trash_at"])
+        else:
+            return None
 
-    @_synchronized
-    def update(self):
-        n = self._my_api().collections().get(uuid=self._manifest_locator, select=["manifest_text"]).execute()
-        other = import_collection(n["manifest_text"])
-        self.merge(other)
+    def stream_name(self):
+        return "."
+
+    def writable(self):
+        return True
+
+    @synchronized
+    def known_past_version(self, modified_at_and_portable_data_hash):
+        return modified_at_and_portable_data_hash in self._past_versions
+
+    @synchronized
+    @retry_method
+    def update(self, other=None, num_retries=None):
+        """Merge the latest collection on the API server with the current collection."""
+
+        if other is None:
+            if self._manifest_locator is None:
+                raise errors.ArgumentError("`other` is None but collection does not have a manifest_locator uuid")
+            response = self._my_api().collections().get(uuid=self._manifest_locator).execute(num_retries=num_retries)
+            if (self.known_past_version((response.get("modified_at"), response.get("portable_data_hash"))) and
+                response.get("portable_data_hash") != self.portable_data_hash()):
+                # The record on the server is different from our current one, but we've seen it before,
+                # so ignore it because it's already been merged.
+                # However, if it's the same as our current record, proceed with the update, because we want to update
+                # our tokens.
+                return
+            else:
+                self._past_versions.add((response.get("modified_at"), response.get("portable_data_hash")))
+            other = CollectionReader(response["manifest_text"])
+        baseline = CollectionReader(self._manifest_text)
+        self.apply(baseline.diff(other))
+        self._manifest_text = self.manifest_text()
 
-    @_synchronized
+    @synchronized
     def _my_api(self):
         if self._api_client is None:
-            self._api_client = arvados.SafeApi(self._config)
-            self._keep_client = self._api_client.keep
+            self._api_client = ThreadSafeApiCache(self._config)
+            if self._keep_client is None:
+                self._keep_client = self._api_client.keep
         return self._api_client
 
-    @_synchronized
+    @synchronized
     def _my_keep(self):
         if self._keep_client is None:
             if self._api_client is None:
                 self._my_api()
             else:
-                self._keep_client = KeepClient(api=self._api_client)
+                self._keep_client = KeepClient(api_client=self._api_client)
         return self._keep_client
 
-    @_synchronized
+    @synchronized
     def _my_block_manager(self):
         if self._block_manager is None:
-            self._block_manager = BlockManager(self._my_keep())
+            copies = (self.replication_desired or
+                      self._my_api()._rootDesc.get('defaultCollectionReplication',
+                                                   2))
+            self._block_manager = _BlockManager(self._my_keep(), copies=copies, put_threads=self.put_threads)
         return self._block_manager
 
+    def _remember_api_response(self, response):
+        self._api_response = response
+        self._past_versions.add((response.get("modified_at"), response.get("portable_data_hash")))
+
     def _populate_from_api_server(self):
         # As in KeepClient itself, we must wait until the last
         # possible moment to instantiate an API client, in order to
@@ -1073,335 +1354,464 @@ class Collection(SynchronizedCollectionBase):
         # it.  If instantiation fails, we'll fall back to the except
         # clause, just like any other Collection lookup
         # failure. Return an exception, or None if successful.
-        try:
-            self._api_response = self._my_api().collections().get(
-                uuid=self._manifest_locator).execute(
-                    num_retries=self.num_retries)
-            self._manifest_text = self._api_response['manifest_text']
-            return None
-        except Exception as e:
-            return e
-
-    def _populate_from_keep(self):
-        # Retrieve a manifest directly from Keep. This has a chance of
-        # working if [a] the locator includes a permission signature
-        # or [b] the Keep services are operating in world-readable
-        # mode. Return an exception, or None if successful.
-        try:
-            self._manifest_text = self._my_keep().get(
-                self._manifest_locator, num_retries=self.num_retries)
-        except Exception as e:
-            return e
+        self._remember_api_response(self._my_api().collections().get(
+            uuid=self._manifest_locator).execute(
+                num_retries=self.num_retries))
+        self._manifest_text = self._api_response['manifest_text']
+        self._portable_data_hash = self._api_response['portable_data_hash']
+        # If not overriden via kwargs, we should try to load the
+        # replication_desired from the API server
+        if self.replication_desired is None:
+            self.replication_desired = self._api_response.get('replication_desired', None)
 
     def _populate(self):
-        if self._manifest_locator is None and self._manifest_text is None:
-            return
-        error_via_api = None
-        error_via_keep = None
-        should_try_keep = ((self._manifest_text is None) and
-                           util.keep_locator_pattern.match(
-                               self._manifest_locator))
-        if ((self._manifest_text is None) and
-            util.signed_locator_pattern.match(self._manifest_locator)):
-            error_via_keep = self._populate_from_keep()
-        if self._manifest_text is None:
-            error_via_api = self._populate_from_api_server()
-            if error_via_api is not None and not should_try_keep:
-                raise error_via_api
-        if ((self._manifest_text is None) and
-            not error_via_keep and
-            should_try_keep):
-            # Looks like a keep locator, and we didn't already try keep above
-            error_via_keep = self._populate_from_keep()
         if self._manifest_text is None:
-            # Nothing worked!
-            raise arvados.errors.NotFoundError(
-                ("Failed to retrieve collection '{}' " +
-                 "from either API server ({}) or Keep ({})."
-                 ).format(
-                    self._manifest_locator,
-                    error_via_api,
-                    error_via_keep))
-        # populate
-        import_manifest(self._manifest_text, self)
-
-        if self._sync == SYNC_READONLY:
-            # Now that we're populated, knowing that this will be readonly,
-            # forego any further locking.
-            self.lock = NoopLock()
+            if self._manifest_locator is None:
+                return
+            else:
+                self._populate_from_api_server()
+        self._baseline_manifest = self._manifest_text
+        self._import_manifest(self._manifest_text)
+
+    def _has_collection_uuid(self):
+        return self._manifest_locator is not None and re.match(arvados.util.collection_uuid_pattern, self._manifest_locator)
 
     def __enter__(self):
         return self
 
     def __exit__(self, exc_type, exc_value, traceback):
-        """Support scoped auto-commit in a with: block"""
-        if self._sync != SYNC_READONLY:
-            self.save(allow_no_locator=True)
+        """Support scoped auto-commit in a with: block."""
+        if exc_type is None:
+            if self.writable() and self._has_collection_uuid():
+                self.save()
+        self.stop_threads()
+
+    def stop_threads(self):
         if self._block_manager is not None:
             self._block_manager.stop_threads()
 
-    @_synchronized
-    def clone(self, new_parent=None, new_sync=SYNC_READONLY, new_config=None):
+    @synchronized
+    def manifest_locator(self):
+        """Get the manifest locator, if any.
+
+        The manifest locator will be set when the collection is loaded from an
+        API server record or the portable data hash of a manifest.
+
+        The manifest locator will be None if the collection is newly created or
+        was created directly from manifest text.  The method `save_new()` will
+        assign a manifest locator.
+
+        """
+        return self._manifest_locator
+
+    @synchronized
+    def clone(self, new_parent=None, new_name=None, readonly=False, new_config=None):
         if new_config is None:
-            new_config = self.config
-        c = Collection(parent=new_parent, config=new_config, sync=new_sync)
-        if new_sync == SYNC_READONLY:
-            c.lock = NoopLock()
-        c._items = {}
-        self._cloneinto(c)
-        return c
+            new_config = self._config
+        if readonly:
+            newcollection = CollectionReader(parent=new_parent, apiconfig=new_config)
+        else:
+            newcollection = Collection(parent=new_parent, apiconfig=new_config)
 
-    @_synchronized
+        newcollection._clonefrom(self)
+        return newcollection
+
+    @synchronized
     def api_response(self):
-        """
-        api_response() -> dict or None
+        """Returns information about this Collection fetched from the API server.
 
-        Returns information about this Collection fetched from the API server.
         If the Collection exists in Keep but not the API server, currently
         returns None.  Future versions may provide a synthetic response.
+
         """
         return self._api_response
 
-    @_must_be_writable
-    @_synchronized
-    def save(self, allow_no_locator=False):
-        """Commit pending buffer blocks to Keep, write the manifest to Keep, and
-        update the collection record to Keep.
+    def find_or_create(self, path, create_type):
+        """See `RichCollectionBase.find_or_create`"""
+        if path == ".":
+            return self
+        else:
+            return super(Collection, self).find_or_create(path[2:] if path.startswith("./") else path, create_type)
+
+    def find(self, path):
+        """See `RichCollectionBase.find`"""
+        if path == ".":
+            return self
+        else:
+            return super(Collection, self).find(path[2:] if path.startswith("./") else path)
+
+    def remove(self, path, recursive=False):
+        """See `RichCollectionBase.remove`"""
+        if path == ".":
+            raise errors.ArgumentError("Cannot remove '.'")
+        else:
+            return super(Collection, self).remove(path[2:] if path.startswith("./") else path, recursive)
+
+    @must_be_writable
+    @synchronized
+    @retry_method
+    def save(self,
+             properties=None,
+             storage_classes=None,
+             trash_at=None,
+             merge=True,
+             num_retries=None):
+        """Save collection to an existing collection record.
+
+        Commit pending buffer blocks to Keep, merge with remote record (if
+        merge=True, the default), and update the collection record. Returns
+        the current manifest text.
+
+        Will raise AssertionError if not associated with a collection record on
+        the API server.  If you want to save a manifest to Keep only, see
+        `save_new()`.
+
+        :properties:
+          Additional properties of collection. This value will replace any existing
+          properties of collection.
+
+        :storage_classes:
+          Specify desirable storage classes to be used when writing data to Keep.
+
+        :trash_at:
+          A collection is *expiring* when it has a *trash_at* time in the future.
+          An expiring collection can be accessed as normal,
+          but is scheduled to be trashed automatically at the *trash_at* time.
+
+        :merge:
+          Update and merge remote changes before saving.  Otherwise, any
+          remote changes will be ignored and overwritten.
+
+        :num_retries:
+          Retry count on API calls (if None,  use the collection default)
 
-        :allow_no_locator:
-          If there is no collection uuid associated with this
-          Collection and `allow_no_locator` is False, raise an error.  If True,
-          do not raise an error.
         """
-        if self.modified():
+        if properties and type(properties) is not dict:
+            raise errors.ArgumentError("properties must be dictionary type.")
+
+        if storage_classes and type(storage_classes) is not list:
+            raise errors.ArgumentError("storage_classes must be list type.")
+
+        if trash_at and type(trash_at) is not datetime.datetime:
+            raise errors.ArgumentError("trash_at must be datetime type.")
+
+        body={}
+        if properties:
+            body["properties"] = properties
+        if storage_classes:
+            body["storage_classes_desired"] = storage_classes
+        if trash_at:
+            t = trash_at.strftime("%Y-%m-%dT%H:%M:%S.%fZ")
+            body["trash_at"] = t
+
+        if not self.committed():
+            if not self._has_collection_uuid():
+                raise AssertionError("Collection manifest_locator is not a collection uuid.  Use save_new() for new collections.")
+
             self._my_block_manager().commit_all()
-            self._my_keep().put(self.manifest_text(strip=True))
-            if self._manifest_locator is not None and re.match(util.collection_uuid_pattern, self._manifest_locator):
-                self._api_response = self._my_api().collections().update(
-                    uuid=self._manifest_locator,
-                    body={'manifest_text': self.manifest_text(strip=False)}
-                    ).execute(
-                        num_retries=self.num_retries)
-            elif not allow_no_locator:
-                raise AssertionError("Collection manifest_locator must be a collection uuid.  Use save_as() for new collections.")
-            self.set_unmodified()
-
-    @_must_be_writable
-    @_synchronized
-    def save_as(self, name, owner_uuid=None, ensure_unique_name=False):
-        """Save a new collection record.
+
+            if merge:
+                self.update()
+
+            text = self.manifest_text(strip=False)
+            body['manifest_text'] = text
+
+            self._remember_api_response(self._my_api().collections().update(
+                uuid=self._manifest_locator,
+                body=body
+                ).execute(num_retries=num_retries))
+            self._manifest_text = self._api_response["manifest_text"]
+            self._portable_data_hash = self._api_response["portable_data_hash"]
+            self.set_committed(True)
+        elif body:
+            self._remember_api_response(self._my_api().collections().update(
+                uuid=self._manifest_locator,
+                body=body
+                ).execute(num_retries=num_retries))
+
+        return self._manifest_text
+
+
+    @must_be_writable
+    @synchronized
+    @retry_method
+    def save_new(self, name=None,
+                 create_collection_record=True,
+                 owner_uuid=None,
+                 properties=None,
+                 storage_classes=None,
+                 trash_at=None,
+                 ensure_unique_name=False,
+                 num_retries=None):
+        """Save collection to a new collection record.
+
+        Commit pending buffer blocks to Keep and, when create_collection_record
+        is True (default), create a new collection record.  After creating a
+        new collection record, this Collection object will be associated with
+        the new record used by `save()`. Returns the current manifest text.
 
         :name:
           The collection name.
 
+        :create_collection_record:
+           If True, create a collection record on the API server.
+           If False, only commit blocks to Keep and return the manifest text.
+
         :owner_uuid:
           the user, or project uuid that will own this collection.
           If None, defaults to the current user.
 
+        :properties:
+          Additional properties of collection. This value will replace any existing
+          properties of collection.
+
+        :storage_classes:
+          Specify desirable storage classes to be used when writing data to Keep.
+
+        :trash_at:
+          A collection is *expiring* when it has a *trash_at* time in the future.
+          An expiring collection can be accessed as normal,
+          but is scheduled to be trashed automatically at the *trash_at* time.
+
         :ensure_unique_name:
           If True, ask the API server to rename the collection
           if it conflicts with a collection with the same name and owner.  If
           False, a name conflict will result in an error.
 
+        :num_retries:
+          Retry count on API calls (if None,  use the collection default)
+
         """
+        if properties and type(properties) is not dict:
+            raise errors.ArgumentError("properties must be dictionary type.")
+
+        if storage_classes and type(storage_classes) is not list:
+            raise errors.ArgumentError("storage_classes must be list type.")
+
+        if trash_at and type(trash_at) is not datetime.datetime:
+            raise errors.ArgumentError("trash_at must be datetime type.")
+
         self._my_block_manager().commit_all()
-        self._my_keep().put(self.manifest_text(strip=True))
-        body = {"manifest_text": self.manifest_text(strip=False),
-                "name": name}
-        if owner_uuid:
-            body["owner_uuid"] = owner_uuid
-        self._api_response = self._my_api().collections().create(ensure_unique_name=ensure_unique_name, body=body).execute(num_retries=self.num_retries)
+        text = self.manifest_text(strip=False)
 
-        if self.events:
-            self.events.unsubscribe(filters=[["object_uuid", "=", self._manifest_locator]])
+        if create_collection_record:
+            if name is None:
+                name = "New collection"
+                ensure_unique_name = True
 
-        self._manifest_locator = self._api_response["uuid"]
+            body = {"manifest_text": text,
+                    "name": name,
+                    "replication_desired": self.replication_desired}
+            if owner_uuid:
+                body["owner_uuid"] = owner_uuid
+            if properties:
+                body["properties"] = properties
+            if storage_classes:
+                body["storage_classes_desired"] = storage_classes
+            if trash_at:
+                t = trash_at.strftime("%Y-%m-%dT%H:%M:%S.%fZ")
+                body["trash_at"] = t
 
-        if self.events:
-            self.events.subscribe(filters=[["object_uuid", "=", self._manifest_locator]])
+            self._remember_api_response(self._my_api().collections().create(ensure_unique_name=ensure_unique_name, body=body).execute(num_retries=num_retries))
+            text = self._api_response["manifest_text"]
 
-        self.set_unmodified()
+            self._manifest_locator = self._api_response["uuid"]
+            self._portable_data_hash = self._api_response["portable_data_hash"]
 
-    @_synchronized
-    def subscribe(self, callback):
-        self.callbacks.append(callback)
+            self._manifest_text = text
+            self.set_committed(True)
+
+        return text
+
+    _token_re = re.compile(r'(\S+)(\s+|$)')
+    _block_re = re.compile(r'[0-9a-f]{32}\+(\d+)(\+\S+)*')
+    _segment_re = re.compile(r'(\d+):(\d+):(\S+)')
+
+    @synchronized
+    def _import_manifest(self, manifest_text):
+        """Import a manifest into a `Collection`.
+
+        :manifest_text:
+          The manifest text to import from.
+
+        """
+        if len(self) > 0:
+            raise ArgumentError("Can only import manifest into an empty collection")
+
+        STREAM_NAME = 0
+        BLOCKS = 1
+        SEGMENTS = 2
+
+        stream_name = None
+        state = STREAM_NAME
+
+        for token_and_separator in self._token_re.finditer(manifest_text):
+            tok = token_and_separator.group(1)
+            sep = token_and_separator.group(2)
+
+            if state == STREAM_NAME:
+                # starting a new stream
+                stream_name = tok.replace('\\040', ' ')
+                blocks = []
+                segments = []
+                streamoffset = 0
+                state = BLOCKS
+                self.find_or_create(stream_name, COLLECTION)
+                continue
+
+            if state == BLOCKS:
+                block_locator = self._block_re.match(tok)
+                if block_locator:
+                    blocksize = int(block_locator.group(1))
+                    blocks.append(Range(tok, streamoffset, blocksize, 0))
+                    streamoffset += blocksize
+                else:
+                    state = SEGMENTS
+
+            if state == SEGMENTS:
+                file_segment = self._segment_re.match(tok)
+                if file_segment:
+                    pos = int(file_segment.group(1))
+                    size = int(file_segment.group(2))
+                    name = file_segment.group(3).replace('\\040', ' ')
+                    filepath = os.path.join(stream_name, name)
+                    afile = self.find_or_create(filepath, FILE)
+                    if isinstance(afile, ArvadosFile):
+                        afile.add_segment(blocks, pos, size)
+                    else:
+                        raise errors.SyntaxError("File %s conflicts with stream of the same name.", filepath)
+                else:
+                    # error!
+                    raise errors.SyntaxError("Invalid manifest format, expected file segment but did not match format: '%s'" % tok)
+
+            if sep == "\n":
+                stream_name = None
+                state = STREAM_NAME
+
+        self.set_committed(True)
 
-    @_synchronized
-    def unsubscribe(self, callback):
-        self.callbacks.remove(callback)
+    @synchronized
+    def notify(self, event, collection, name, item):
+        if self._callback:
+            self._callback(event, collection, name, item)
 
-    @_synchronized
-    def notify(self, collection, event, name, item):
-        for c in self.callbacks:
-            c(collection, event, name, item)
 
-class Subcollection(SynchronizedCollectionBase):
+class Subcollection(RichCollectionBase):
     """This is a subdirectory within a collection that doesn't have its own API
-    server record.  It falls under the umbrella of the root collection."""
+    server record.
 
-    def __init__(self, parent):
+    Subcollection locking falls under the umbrella lock of its root collection.
+
+    """
+
+    def __init__(self, parent, name):
         super(Subcollection, self).__init__(parent)
-        self.lock = parent._root_lock()
+        self.lock = self.root_collection().lock
+        self._manifest_text = None
+        self.name = name
+        self.num_retries = parent.num_retries
 
-    def _root_lock(self):
-        return self.parent._root_lock()
+    def root_collection(self):
+        return self.parent.root_collection()
 
-    def sync_mode(self):
-        return self.parent.sync_mode()
+    def writable(self):
+        return self.root_collection().writable()
 
     def _my_api(self):
-        return self.parent._my_api()
+        return self.root_collection()._my_api()
 
     def _my_keep(self):
-        return self.parent._my_keep()
+        return self.root_collection()._my_keep()
 
     def _my_block_manager(self):
-        return self.parent._my_block_manager()
-
-    def _populate(self):
-        self.parent._populate()
+        return self.root_collection()._my_block_manager()
 
-    def notify(self, collection, event, name, item):
-        self.parent.notify(collection, event, name, item)
+    def stream_name(self):
+        return os.path.join(self.parent.stream_name(), self.name)
 
-    @_synchronized
-    def clone(self, new_parent):
-        c = Subcollection(new_parent)
-        c._items = {}
-        self._cloneinto(c)
+    @synchronized
+    def clone(self, new_parent, new_name):
+        c = Subcollection(new_parent, new_name)
+        c._clonefrom(self)
         return c
 
-def import_manifest(manifest_text,
-                    into_collection=None,
-                    api_client=None,
-                    keep=None,
-                    num_retries=None,
-                    sync=SYNC_READONLY):
-    """Import a manifest into a `Collection`.
+    @must_be_writable
+    @synchronized
+    def _reparent(self, newparent, newname):
+        self.set_committed(False)
+        self.flush()
+        self.parent.remove(self.name, recursive=True)
+        self.parent = newparent
+        self.name = newname
+        self.lock = self.parent.root_collection().lock
 
-    :manifest_text:
-      The manifest text to import from.
 
-    :into_collection:
-      The `Collection` that will be initialized (must be empty).
-      If None, create a new `Collection` object.
+class CollectionReader(Collection):
+    """A read-only collection object.
 
-    :api_client:
-      The API client object that will be used when creating a new `Collection` object.
+    Initialize from a collection UUID or portable data hash, or raw
+    manifest text.  See `Collection` constructor for detailed options.
 
-    :keep:
-      The keep client object that will be used when creating a new `Collection` object.
+    """
+    def __init__(self, manifest_locator_or_text, *args, **kwargs):
+        self._in_init = True
+        super(CollectionReader, self).__init__(manifest_locator_or_text, *args, **kwargs)
+        self._in_init = False
 
-    :num_retries:
-      the default number of api client and keep retries on error.
+        # Forego any locking since it should never change once initialized.
+        self.lock = NoopLock()
 
-    :sync:
-      Collection sync mode (only if into_collection is None)
-    """
-    if into_collection is not None:
-        if len(into_collection) > 0:
-            raise ArgumentError("Can only import manifest into an empty collection")
-        c = into_collection
-    else:
-        c = Collection(api_client=api_client, keep_client=keep, num_retries=num_retries, sync=sync)
-
-    save_sync = c.sync_mode()
-    c._sync = None
-
-    STREAM_NAME = 0
-    BLOCKS = 1
-    SEGMENTS = 2
-
-    stream_name = None
-    state = STREAM_NAME
-
-    for n in re.finditer(r'(\S+)(\s+|$)', manifest_text):
-        tok = n.group(1)
-        sep = n.group(2)
-
-        if state == STREAM_NAME:
-            # starting a new stream
-            stream_name = tok.replace('\\040', ' ')
-            blocks = []
-            segments = []
-            streamoffset = 0L
-            state = BLOCKS
-            continue
-
-        if state == BLOCKS:
-            s = re.match(r'[0-9a-f]{32}\+(\d+)(\+\S+)*', tok)
-            if s:
-                blocksize = long(s.group(1))
-                blocks.append(Range(tok, streamoffset, blocksize))
-                streamoffset += blocksize
-            else:
-                state = SEGMENTS
-
-        if state == SEGMENTS:
-            s = re.search(r'^(\d+):(\d+):(\S+)', tok)
-            if s:
-                pos = long(s.group(1))
-                size = long(s.group(2))
-                name = s.group(3).replace('\\040', ' ')
-                f = c.find("%s/%s" % (stream_name, name), create=True)
-                f.add_segment(blocks, pos, size)
-            else:
-                # error!
-                raise errors.SyntaxError("Invalid manifest format")
+        # Backwards compatability with old CollectionReader
+        # all_streams() and all_files()
+        self._streams = None
 
-        if sep == "\n":
-            stream_name = None
-            state = STREAM_NAME
+    def writable(self):
+        return self._in_init
 
-    c.set_unmodified()
-    c._sync = save_sync
-    return c
+    def _populate_streams(orig_func):
+        @functools.wraps(orig_func)
+        def populate_streams_wrapper(self, *args, **kwargs):
+            # Defer populating self._streams until needed since it creates a copy of the manifest.
+            if self._streams is None:
+                if self._manifest_text:
+                    self._streams = [sline.split()
+                                     for sline in self._manifest_text.split("\n")
+                                     if sline]
+                else:
+                    self._streams = []
+            return orig_func(self, *args, **kwargs)
+        return populate_streams_wrapper
 
-def export_manifest(item, stream_name=".", portable_locators=False):
-    """
-    :item:
-      Create a manifest for `item` (must be a `Collection` or `ArvadosFile`).  If
-      `item` is a is a `Collection`, this will also export subcollections.
+    @_populate_streams
+    def normalize(self):
+        """Normalize the streams returned by `all_streams`.
 
-    :stream_name:
-      the name of the stream when exporting `item`.
+        This method is kept for backwards compatability and only affects the
+        behavior of `all_streams()` and `all_files()`
 
-    :portable_locators:
-      If True, strip any permission hints on block locators.
-      If False, use block locators as-is.
-    """
-    buf = ""
-    if isinstance(item, SynchronizedCollectionBase):
-        stream = {}
-        sorted_keys = sorted(item.keys())
-        for k in [s for s in sorted_keys if isinstance(item[s], ArvadosFile)]:
-            v = item[k]
-            st = []
-            for s in v.segments():
-                loc = s.locator
-                if loc.startswith("bufferblock"):
-                    loc = v.parent._my_block_manager()._bufferblocks[loc].locator()
-                if portable_locators:
-                    loc = KeepLocator(loc).stripped()
-                st.append(LocatorAndRange(loc, locator_block_size(loc),
-                                     s.segment_offset, s.range_size))
-            stream[k] = st
-        if stream:
-            buf += ' '.join(normalize_stream(stream_name, stream))
-            buf += "\n"
-        for k in [s for s in sorted_keys if isinstance(item[s], SynchronizedCollectionBase)]:
-            buf += export_manifest(item[k], stream_name=os.path.join(stream_name, k), portable_locators=portable_locators)
-    elif isinstance(item, ArvadosFile):
-        st = []
-        for s in item.segments:
-            loc = s.locator
-            if loc.startswith("bufferblock"):
-                loc = item._bufferblocks[loc].calculate_locator()
-            if portable_locators:
-                loc = KeepLocator(loc).stripped()
-            st.append(LocatorAndRange(loc, locator_block_size(loc),
-                                 s.segment_offset, s.range_size))
-        stream[stream_name] = st
-        buf += ' '.join(normalize_stream(stream_name, stream))
-        buf += "\n"
-    return buf
+        """
+
+        # Rearrange streams
+        streams = {}
+        for s in self.all_streams():
+            for f in s.all_files():
+                streamname, filename = split(s.name() + "/" + f.name())
+                if streamname not in streams:
+                    streams[streamname] = {}
+                if filename not in streams[streamname]:
+                    streams[streamname][filename] = []
+                for r in f.segments:
+                    streams[streamname][filename].extend(s.locators_and_ranges(r.locator, r.range_size))
+
+        self._streams = [normalize_stream(s, streams[s])
+                         for s in sorted(streams)]
+    @_populate_streams
+    def all_streams(self):
+        return [StreamReader(s, self._my_keep(), num_retries=self.num_retries)
+                for s in self._streams]
+
+    @_populate_streams
+    def all_files(self):
+        for s in self.all_streams():
+            for f in s.all_files():
+                yield f