Merge branch 'master' into 6518-crunch2-dispatch-slurm
[arvados.git] / sdk / python / arvados / collection.py
index 41df5558e205f107c0d14ee9e535dfb81066eabb..8450bd1ca086687928c43e09b2d497ae598c5128 100644 (file)
@@ -3,15 +3,18 @@ import logging
 import os
 import re
 import errno
+import hashlib
 import time
+import threading
 
 from collections import deque
 from stat import *
 
-from .arvfile import split, FileLikeObjectBase, 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 .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 config
 import errors
@@ -35,7 +38,8 @@ 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.
@@ -54,197 +58,7 @@ class CollectionBase(object):
         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 populate_first_wrapper(self, *args, **kwargs):
-            if self._streams is None:
-                self._populate()
-            return orig_func(self, *args, **kwargs)
-        return populate_first_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(FileLikeObjectBase):
+class _WriterFile(_FileLikeObjectBase):
     def __init__(self, coll_writer, name):
         super(_WriterFile, self).__init__(name, 'wb')
         self.dest = coll_writer
@@ -253,16 +67,16 @@ class _WriterFile(FileLikeObjectBase):
         super(_WriterFile, self).close()
         self.dest.finish_current_file()
 
-    @FileLikeObjectBase._before_close
+    @_FileLikeObjectBase._before_close
     def write(self, data):
         self.dest.write(data)
 
-    @FileLikeObjectBase._before_close
+    @_FileLikeObjectBase._before_close
     def writelines(self, seq):
         for data in seq:
             self.write(data)
 
-    @FileLikeObjectBase._before_close
+    @_FileLikeObjectBase._before_close
     def flush(self):
         self.dest.flush_data()
 
@@ -656,13 +470,15 @@ 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 SynchronizedCollectionBase(CollectionBase):
+class RichCollectionBase(CollectionBase):
     """Base class for Collections and Subcollections.
 
     Implements the majority of functionality relating to accessing items in the
@@ -672,7 +488,8 @@ class SynchronizedCollectionBase(CollectionBase):
 
     def __init__(self, parent=None):
         self.parent = parent
-        self._modified = True
+        self._committed = False
+        self._callback = None
         self._items = {}
 
     def _my_api(self):
@@ -684,10 +501,7 @@ class SynchronizedCollectionBase(CollectionBase):
     def _my_block_manager(self):
         raise NotImplementedError()
 
-    def _populate(self):
-        raise NotImplementedError()
-
-    def sync_mode(self):
+    def writable(self):
         raise NotImplementedError()
 
     def root_collection(self):
@@ -696,6 +510,9 @@ class SynchronizedCollectionBase(CollectionBase):
     def notify(self, event, collection, name, item):
         raise NotImplementedError()
 
+    def stream_name(self):
+        raise NotImplementedError()
+
     @must_be_writable
     @synchronized
     def find_or_create(self, path, create_type):
@@ -707,47 +524,39 @@ class SynchronizedCollectionBase(CollectionBase):
         the path.
 
         :create_type:
-          One of `arvado.collection.FILE` or
-          `arvado.collection.COLLECTION`.  If the path is not found, and value
+          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 self.sync_mode() == SYNC_READONLY:
-            raise IOError((errno.EROFS, "Collection is read only"))
-
-        pathcomponents = path.split("/")
-        if pathcomponents[0] == '.':
-            del pathcomponents[0]
-
-        if pathcomponents and pathcomponents[0]:
+        pathcomponents = path.split("/", 1)
+        if pathcomponents[0]:
             item = self._items.get(pathcomponents[0])
             if len(pathcomponents) == 1:
-                # item must be a file
                 if item is None:
                     # create new file
                     if create_type == COLLECTION:
-                        item = Subcollection(self)
+                        item = Subcollection(self, pathcomponents[0])
                     else:
-                        item = ArvadosFile(self)
+                        item = ArvadosFile(self, pathcomponents[0])
                     self._items[pathcomponents[0]] = item
-                    self._modified = True
+                    self._committed = False
                     self.notify(ADD, self, pathcomponents[0], item)
                 return item
             else:
                 if item is None:
                     # create new collection
-                    item = Subcollection(self)
+                    item = Subcollection(self, pathcomponents[0])
                     self._items[pathcomponents[0]] = item
-                    self._modified = True
+                    self._committed = False
                     self.notify(ADD, self, pathcomponents[0], item)
-                del pathcomponents[0]
-                if isinstance(item, SynchronizedCollectionBase):
-                    return item.find_or_create("/".join(pathcomponents), create_type)
+                if isinstance(item, RichCollectionBase):
+                    return item.find_or_create(pathcomponents[1], create_type)
                 else:
-                    raise errors.ArgumentError("Interior path components must be subcollection")
+                    raise IOError(errno.ENOTDIR, "Not a directory: '%s'" % pathcomponents[0])
         else:
             return self
 
@@ -759,34 +568,37 @@ class SynchronizedCollectionBase(CollectionBase):
         found.
 
         """
-        pathcomponents = path.split("/")
-        if pathcomponents[0] == '.':
-            del pathcomponents[0]
+        if not path:
+            raise errors.ArgumentError("Parameter 'path' is empty.")
 
-        if pathcomponents and pathcomponents[0]:
-            item = self._items.get(pathcomponents[0])
-            if len(pathcomponents) == 1:
-                # item must be a file
-                return item
-            else:
-                del pathcomponents[0]
-                if isinstance(item, SynchronizedCollectionBase):
-                    return item.find("/".join(pathcomponents))
-                else:
-                    raise errors.ArgumentError("Interior path components must be subcollection")
+        pathcomponents = path.split("/", 1)
+        item = self._items.get(pathcomponents[0])
+        if len(pathcomponents) == 1:
+            return item
         else:
-            return self
+            if isinstance(item, RichCollectionBase):
+                if pathcomponents[1]:
+                    return item.find(pathcomponents[1])
+                else:
+                    return item
+            else:
+                raise IOError(errno.ENOTDIR, "Is not a directory: %s" % pathcomponents[0])
 
-    def mkdirs(path):
+    @synchronized
+    def mkdirs(self, path):
         """Recursive subcollection create.
 
-        Like `os.mkdirs()`.  Will create intermediate subcollections needed to
-        contain the leaf subcollection path.
+        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: '%s'" % path)
+
         return self.find_or_create(path, COLLECTION)
 
-    def open(self, path, mode):
+    def open(self, path, mode="r"):
         """Open a file-like object for access.
 
         :path:
@@ -806,11 +618,11 @@ class SynchronizedCollectionBase(CollectionBase):
         """
         mode = mode.replace("b", "")
         if len(mode) == 0 or mode[0] not in ("r", "w", "a"):
-            raise ArgumentError("Bad mode '%s'" % mode)
+            raise errors.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 create and not self.writable():
+            raise IOError(errno.EROFS, "Collection is read only")
 
         if create:
             arvfile = self.find_or_create(path, FILE)
@@ -818,57 +630,59 @@ class SynchronizedCollectionBase(CollectionBase):
             arvfile = self.find(path)
 
         if arvfile is None:
-            raise IOError((errno.ENOENT, "File not found"))
+            raise IOError(errno.ENOENT, "File not found")
         if not isinstance(arvfile, ArvadosFile):
-            raise IOError((errno.EISDIR, "Path must refer to a file."))
+            raise IOError(errno.EISDIR, "Is a directory: %s" % path)
 
         if mode[0] == "w":
             arvfile.truncate(0)
 
+        name = os.path.basename(path)
+
         if mode == "r":
-            return ArvadosFileReader(arvfile, path, mode, num_retries=self.num_retries)
+            return ArvadosFileReader(arvfile, num_retries=self.num_retries)
         else:
-            return ArvadosFileWriter(arvfile, path, mode, num_retries=self.num_retries)
+            return ArvadosFileWriter(arvfile, mode, num_retries=self.num_retries)
 
-    @synchronized
     def modified(self):
-        """Test if the collection (or any subcollection or file) has been modified
-        since it was created."""
-        if self._modified:
-            return True
-        for k,v in self._items.items():
-            if v.modified():
-                return True
-        return False
+        """Determine if the collection has been modified since last commited."""
+        return not self.committed()
 
     @synchronized
-    def set_unmodified(self):
-        """Recursively clear modified flag."""
-        self._modified = False
+    def committed(self):
+        """Determine if the collection has been committed to the API server."""
+
+        if self._committed is False:
+            return False
+        for v in self._items.values():
+            if v.committed() is False:
+                return False
+        return True
+
+    @synchronized
+    def set_committed(self):
+        """Recursively set committed flag to True."""
+        self._committed = True
         for k,v in self._items.items():
-            v.set_unmodified()
+            v.set_committed()
 
     @synchronized
     def __iter__(self):
         """Iterate over names of files and collections contained in this collection."""
         return iter(self._items.keys())
 
-    @synchronized
-    def iterkeys(self):
-        """Iterate over names of files and collections directly contained in this collection."""
-        return self._items.keys()
-
     @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
     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
@@ -881,7 +695,7 @@ class SynchronizedCollectionBase(CollectionBase):
     def __delitem__(self, p):
         """Delete an item by name which is directly contained by this collection."""
         del self._items[p]
-        self._modified = True
+        self._committed = False
         self.notify(DEL, self, p, None)
 
     @synchronized
@@ -901,7 +715,7 @@ class SynchronizedCollectionBase(CollectionBase):
 
     def exists(self, path):
         """Test if there is a file or collection at `path`."""
-        return self.find(path) != None
+        return self.find(path) is not None
 
     @must_be_writable
     @synchronized
@@ -911,63 +725,84 @@ class SynchronizedCollectionBase(CollectionBase):
         :recursive:
           Specify whether to remove non-empty subcollections (True), or raise an error (False).
         """
-        pathcomponents = path.split("/")
-        if pathcomponents[0] == '.':
-            # Remove '.' from the front of the path
-            del pathcomponents[0]
 
-        if len(pathcomponents) > 0:
-            item = self._items.get(pathcomponents[0])
-            if item is None:
-                raise IOError((errno.ENOENT, "File not found"))
-            if len(pathcomponents) == 1:
-                if isinstance(self._items[pathcomponents[0]], SynchronizedCollectionBase) and len(self._items[pathcomponents[0]]) > 0 and not recursive:
-                    raise IOError((errno.ENOTEMPTY, "Subcollection not empty"))
-                deleteditem = self._items[pathcomponents[0]]
-                del self._items[pathcomponents[0]]
-                self._modified = True
-                self.notify(DEL, self, pathcomponents[0], deleteditem)
-            else:
-                del pathcomponents[0]
-                item.remove("/".join(pathcomponents))
+        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")
+        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, "Subcollection not empty")
+            deleteditem = self._items[pathcomponents[0]]
+            del self._items[pathcomponents[0]]
+            self._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.items():
-            target._items[k] = v.clone(target)
+    def _clonefrom(self, source):
+        for k,v in source.items():
+            self._items[k] = v.clone(self, k)
 
     def clone(self):
         raise NotImplementedError()
 
     @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.
+    def add(self, source_obj, target_name, overwrite=False, reparent=False):
+        """Copy or move a file or subcollection to this collection.
 
-        :source:
-          An ArvadosFile, Subcollection, or 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_obj:
+          An ArvadosFile, or Subcollection object
 
-        :source_collection:
-          Collection to copy `source_path` from (default `self`)
+        :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")
+
+        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._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
+        # 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"))
+                raise IOError(errno.ENOENT, "File not found")
             sourcecomponents = source.split("/")
         else:
             source_obj = source
@@ -977,52 +812,156 @@ class SynchronizedCollectionBase(CollectionBase):
         targetcomponents = target_path.split("/")
 
         # Determine the name to use.
-        target_name = targetcomponents[-1] if targetcomponents[-1] else (sourcecomponents[-1] if sourcecomponents else None)
+        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.")
 
-        target_dir = self.find_or_create("/".join(targetcomponents[0:-1]), COLLECTION)
+        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.")
 
-        with target_dir.lock:
-            if target_name in target_dir:
-                if isinstance(target_dir[target_name], SynchronizedCollectionBase) and sourcecomponents:
-                    target_dir = target_dir[target_name]
-                    target_name = sourcecomponents[-1]
-                elif not overwrite:
-                    raise IOError((errno.EEXIST, "File already exists"))
+        if target_name in target_dir and isinstance(self[target_name], RichCollectionBase) and sourcecomponents:
+            target_dir = target_dir[target_name]
+            target_name = sourcecomponents[-1]
 
-            modified_from = None
-            if target_name in target_dir:
-                modified_from = target_dir[target_name]
+        return (source_obj, target_dir, target_name)
 
-            # Actually make the copy.
-            dup = source_obj.clone(target_dir)
-            target_dir._items[target_name] = dup
-            target_dir._modified = True
+    @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.
 
-        if modified_from:
-            self.notify(MOD, target_dir, target_name, (modified_from, dup))
-        else:
-            self.notify(ADD, target_dir, target_name, dup)
+        :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.")
+        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, strip=False, normalize=False):
+    def manifest_text(self, stream_name=".", strip=False, normalize=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, 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.
 
         """
-        if self.modified() or self._manifest_text is None or normalize:
-            return export_manifest(self, stream_name=".", portable_locators=strip)
+
+        self._my_block_manager().commit_all()
+        return self._get_manifest_text(stream_name, strip, normalize)
+
+    @synchronized
+    def _get_manifest_text(self, stream_name, strip, normalize):
+        """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 (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 (default) and the collection
+          is not modified, return the original manifest text even if it is not
+          in normalized form.
+
+        """
+
+        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):
+                        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))
+            return "".join(buf)
         else:
             if strip:
                 return self.stripped_manifest()
@@ -1031,24 +970,27 @@ class SynchronizedCollectionBase(CollectionBase):
 
     @synchronized
     def diff(self, end_collection, prefix=".", holding_collection=None):
-        """
-        Generate list of add/modify/delete actions which, when given to `apply`, will
-        change `self` to match `end_collection`
+        """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(), sync=SYNC_EXPLICIT)
+            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)))
+               changes.append((DEL, os.path.join(prefix, k), self[k].clone(holding_collection, "")))
         for k in end_collection:
             if k in self:
                 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)))
+                    changes.append((MOD, os.path.join(prefix, k), self[k].clone(holding_collection, ""), end_collection[k].clone(holding_collection, "")))
+                else:
+                    changes.append((TOK, os.path.join(prefix, k), self[k].clone(holding_collection, ""), end_collection[k].clone(holding_collection, "")))
             else:
-                changes.append((ADD, os.path.join(prefix, k), end_collection[k].clone(holding_collection)))
+                changes.append((ADD, os.path.join(prefix, k), end_collection[k].clone(holding_collection, "")))
         return changes
 
     @must_be_writable
@@ -1060,12 +1002,14 @@ class SynchronizedCollectionBase(CollectionBase):
         alternate path indicating the conflict.
 
         """
+        if changes:
+            self._committed = False
         for change in changes:
             event_type = change[0]
             path = change[1]
             initial = change[2]
             local = self.find(path)
-            conflictpath = "%s~conflict-%s~" % (path, time.strftime("%Y-%m-%d-%H:%M:%S",
+            conflictpath = "%s~%s~conflict~" % (path, time.strftime("%Y%m%d-%H%M%S",
                                                                     time.gmtime()))
             if event_type == ADD:
                 if local is None:
@@ -1075,7 +1019,7 @@ class SynchronizedCollectionBase(CollectionBase):
                     # There is already local file and it is different:
                     # save change to conflict file.
                     self.copy(initial, conflictpath)
-            elif event_type == MOD:
+            elif event_type == MOD or event_type == TOK:
                 final = change[3]
                 if local == initial:
                     # Local matches the "initial" item so it has not
@@ -1100,14 +1044,32 @@ class SynchronizedCollectionBase(CollectionBase):
 
     def portable_data_hash(self):
         """Get the portable data hash for this collection's manifest."""
-        stripped = self.manifest_text(strip=True)
+        stripped = self.portable_manifest_text()
         return hashlib.md5(stripped).hexdigest() + '+' + str(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, SynchronizedCollectionBase):
+        if not isinstance(other, RichCollectionBase):
             return False
         if len(self._items) != len(other):
             return False
@@ -1121,11 +1083,22 @@ class SynchronizedCollectionBase(CollectionBase):
     def __ne__(self, other):
         return not self.__eq__(other)
 
-class Collection(SynchronizedCollectionBase):
-    """Represents the root of an Arvados Collection, which may be associated with
-    an API server Collection record.
+    @synchronized
+    def flush(self):
+        """Flush bufferblocks to Keep."""
+        for e in self.values():
+            e.flush()
+
+
+class Collection(RichCollectionBase):
+    """Represents the root of an Arvados Collection.
 
-    Brief summary of useful methods:
+    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")`
@@ -1151,20 +1124,18 @@ class Collection(SynchronizedCollectionBase):
     :To merge remote changes into this object:
       `c.update()`
 
-    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).
+    Must be associated with an API server Collection record (during
+    initialization, or using `save_new`) to use `save` or `update`
 
     """
 
     def __init__(self, manifest_locator_or_text=None,
-                 parent=None,
-                 apiconfig=None,
                  api_client=None,
                  keep_client=None,
                  num_retries=None,
-                 block_manager=None,
-                 sync=None):
+                 parent=None,
+                 apiconfig=None,
+                 block_manager=None):
         """Collection constructor.
 
         :manifest_locator_or_text:
@@ -1184,16 +1155,6 @@ class Collection(SynchronizedCollectionBase):
           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:
-            Collection is writable.  Synchronize on explicit request via `update()` or `save()`
-          :SYNC_LIVE:
-            Collection is writable.  Synchronize with server in response to
-            background websocket events, on block write, or on file close.
 
         """
         super(Collection, self).__init__(parent)
@@ -1206,17 +1167,13 @@ class Collection(SynchronizedCollectionBase):
         else:
             self._config = config.settings()
 
-        self.num_retries = num_retries if num_retries is not None else 2
+        self.num_retries = num_retries if num_retries is not None else 0
         self._manifest_locator = None
         self._manifest_text = None
         self._api_response = None
+        self._past_versions = set()
 
-        if sync is None:
-            raise errors.ArgumentError("Must specify sync mode")
-
-        self._sync = sync
         self.lock = threading.RLock()
-        self.callbacks = []
         self.events = None
 
         if manifest_locator_or_text:
@@ -1228,44 +1185,48 @@ class Collection(SynchronizedCollectionBase):
                 self._manifest_text = manifest_locator_or_text
             else:
                 raise errors.ArgumentError(
-                    "Argument to CollectionReader must be a manifest or a collection UUID")
-
-            self._populate()
-            self._subscribe_events()
+                    "Argument to CollectionReader is not a manifest or a collection UUID")
 
+            try:
+                self._populate()
+            except (IOError, errors.SyntaxError) as e:
+                raise errors.ArgumentError("Error processing manifest text: %s", e)
 
     def root_collection(self):
         return self
 
-    def sync_mode(self):
-        return self._sync
+    def stream_name(self):
+        return "."
 
-    def _subscribe_events(self):
-        if self._sync == SYNC_LIVE and self.events is None:
-            if not self._has_collection_uuid():
-                raise errors.ArgumentError("Cannot SYNC_LIVE associated with a collection uuid")
-            self.events = events.subscribe(arvados.api(apiconfig=self._config),
-                                           [["object_uuid", "=", self._manifest_locator]],
-                                           self.on_message)
+    def writable(self):
+        return True
 
-    def on_message(self, event):
-        if event.get("object_uuid") == self._manifest_locator:
-            self.update()
+    @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):
-        """Fetch the latest collection record on the API server and merge it with the
-        current collection contents.
+        """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)
-            other = import_manifest(response["manifest_text"])
-        baseline = import_manifest(self._manifest_text)
+            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
     def _my_api(self):
@@ -1280,15 +1241,19 @@ class Collection(SynchronizedCollectionBase):
             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
     def _my_block_manager(self):
         if self._block_manager is None:
-            self._block_manager = BlockManager(self._my_keep())
+            self._block_manager = _BlockManager(self._my_keep())
         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
@@ -1298,9 +1263,9 @@ class Collection(SynchronizedCollectionBase):
         # clause, just like any other Collection lookup
         # failure. Return an exception, or None if successful.
         try:
-            self._api_response = self._my_api().collections().get(
+            self._remember_api_response(self._my_api().collections().get(
                 uuid=self._manifest_locator).execute(
-                    num_retries=self.num_retries)
+                    num_retries=self.num_retries))
             self._manifest_text = self._api_response['manifest_text']
             return None
         except Exception as e:
@@ -1339,7 +1304,7 @@ class Collection(SynchronizedCollectionBase):
             error_via_keep = self._populate_from_keep()
         if self._manifest_text is None:
             # Nothing worked!
-            raise arvados.errors.NotFoundError(
+            raise errors.NotFoundError(
                 ("Failed to retrieve collection '{}' " +
                  "from either API server ({}) or Keep ({})."
                  ).format(
@@ -1348,12 +1313,8 @@ class Collection(SynchronizedCollectionBase):
                     error_via_keep))
         # populate
         self._baseline_manifest = self._manifest_text
-        import_manifest(self._manifest_text, self)
+        self._import_manifest(self._manifest_text)
 
-        if self._sync == SYNC_READONLY:
-            # Now that we're populated, knowing that this will be readonly,
-            # forego any further locking.
-            self.lock = NoopLock()
 
     def _has_collection_uuid(self):
         return self._manifest_locator is not None and re.match(util.collection_uuid_pattern, self._manifest_locator)
@@ -1363,20 +1324,39 @@ class Collection(SynchronizedCollectionBase):
 
     def __exit__(self, exc_type, exc_value, traceback):
         """Support scoped auto-commit in a with: block."""
-        if self._sync != SYNC_READONLY and self._has_collection_uuid():
-            self.save()
+        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):
+    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
-        newcollection = Collection(parent=new_parent, apiconfig=new_config, sync=SYNC_EXPLICIT)
-        if new_sync == SYNC_READONLY:
-            newcollection.lock = NoopLock()
-        self._cloneinto(newcollection)
-        newcollection._sync = new_sync
+        if readonly:
+            newcollection = CollectionReader(parent=new_parent, apiconfig=new_config)
+        else:
+            newcollection = Collection(parent=new_parent, apiconfig=new_config)
+
+        newcollection._clonefrom(self)
         return newcollection
 
     @synchronized
@@ -1389,55 +1369,91 @@ class Collection(SynchronizedCollectionBase):
         """
         return self._api_response
 
+    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, merge=True, num_retries=None):
-        """Commit pending buffer blocks to Keep, merge with remote record (if
-        update=True), write the manifest to Keep, and update the collection
-        record.
+        """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()`.
 
-        :update:
+        :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)
+
         """
-        if self.modified():
+        if not self.committed():
             if not self._has_collection_uuid():
-                raise AssertionError("Collection manifest_locator must be a collection uuid.  Use save_new() for new collections.")
+                raise AssertionError("Collection manifest_locator is not a collection uuid.  Use save_new() for new collections.")
+
             self._my_block_manager().commit_all()
+
             if merge:
                 self.update()
-            self._my_keep().put(self.manifest_text(strip=True), num_retries=num_retries)
 
             text = self.manifest_text(strip=False)
-            self._api_response = self._my_api().collections().update(
+            self._remember_api_response(self._my_api().collections().update(
                 uuid=self._manifest_locator,
                 body={'manifest_text': text}
                 ).execute(
-                    num_retries=num_retries)
+                    num_retries=num_retries))
             self._manifest_text = self._api_response["manifest_text"]
-            self.set_unmodified()
+            self.set_committed()
+
+        return self._manifest_text
+
 
     @must_be_writable
     @synchronized
     @retry_method
-    def save_new(self, name=None, create_collection_record=True, owner_uuid=None, ensure_unique_name=False, num_retries=None):
-        """Commit pending buffer blocks to Keep, write the manifest to Keep, and create
-        a new collection record (if create_collection_record True).
-
-        After creating a new collection record, this Collection object will be
-        associated with the new record for `save()` and SYNC_LIVE updates.
+    def save_new(self, name=None,
+                 create_collection_record=True,
+                 owner_uuid=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.
 
-        :keep_only:
-          Only save the manifest to keep, do not create a collection record.
+        :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.
@@ -1448,135 +1464,122 @@ class Collection(SynchronizedCollectionBase):
           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)
+
         """
         self._my_block_manager().commit_all()
-        self._my_keep().put(self.manifest_text(strip=True), num_retries=num_retries)
         text = self.manifest_text(strip=False)
 
         if create_collection_record:
             if name is None:
-                name = "Collection created %s" % (time.strftime("%Y-%m-%d %H:%M:%S %Z", time.localtime()))
+                name = "New collection"
+                ensure_unique_name = True
 
             body = {"manifest_text": text,
                     "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=num_retries)
+            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"]
 
-            if self.events:
-                self.events.unsubscribe(filters=[["object_uuid", "=", self._manifest_locator]])
-
             self._manifest_locator = self._api_response["uuid"]
 
-            if self.events:
-                self.events.subscribe(filters=[["object_uuid", "=", self._manifest_locator]])
-
-        self._manifest_text = text
-        self.set_unmodified()
-
-    @synchronized
-    def subscribe(self, callback):
-        self.callbacks.append(callback)
+            self._manifest_text = text
+            self.set_committed()
 
-    @synchronized
-    def unsubscribe(self, callback):
-        self.callbacks.remove(callback)
+        return text
 
     @synchronized
-    def notify(self, event, collection, name, item):
-        for c in self.callbacks:
-            c(event, collection, name, item)
-
-def ReadOnlyCollection(*args, **kwargs):
-    """Create a read-only collection object from an api collection record locator,
-    a portable data hash of a manifest, or raw manifest text.
-
-    See `Collection` constructor for detailed options.
-
-    """
-    kwargs["sync"] = SYNC_READONLY
-    return Collection(*args, **kwargs)
-
-def WritableCollection(*args, **kwargs):
-    """Create a writable collection object from an api collection record locator,
-    a portable data hash of a manifest, or raw manifest text.
-
-    See `Collection` constructor for detailed options.
-
-    """
-
-    kwargs["sync"] = SYNC_EXPLICIT
-    return Collection(*args, **kwargs)
-
-def LiveCollection(*args, **kwargs):
-    """Create a writable, live updating collection object representing an existing
-    collection record on the API server.
-
-    See `Collection` constructor for detailed options.
-
-    """
-    kwargs["sync"] = SYNC_LIVE
-    return Collection(*args, **kwargs)
-
-def createWritableCollection(name, owner_uuid=None, apiconfig=None):
-    """Create an empty, writable collection object and create an associated api
-    collection record.
-
-    :name:
-      The collection name
-
-    :owner_uuid:
-      The parent project.
+    def _import_manifest(self, manifest_text):
+        """Import a manifest into a `Collection`.
 
-    :apiconfig:
-      Optional alternate api configuration to use (to specify alternate API
-      host or token than the default.)
+        :manifest_text:
+          The manifest text to import from.
 
-    """
-    newcollection = Collection(sync=SYNC_EXPLICIT, apiconfig=apiconfig)
-    newcollection.save_new(name, owner_uuid=owner_uuid, ensure_unique_name=True)
-    return newcollection
+        """
+        if len(self) > 0:
+            raise ArgumentError("Can only import manifest into an empty collection")
 
-def createLiveCollection(name, owner_uuid=None, apiconfig=None):
-    """Create an empty, writable, live updating Collection object and create an
-    associated collection record on the API server.
+        STREAM_NAME = 0
+        BLOCKS = 1
+        SEGMENTS = 2
+
+        stream_name = None
+        state = STREAM_NAME
+
+        for token_and_separator in re.finditer(r'(\S+)(\s+|$)', 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 = 0L
+                state = BLOCKS
+                self.find_or_create(stream_name, COLLECTION)
+                continue
+
+            if state == BLOCKS:
+                block_locator = re.match(r'[0-9a-f]{32}\+(\d+)(\+\S+)*', tok)
+                if block_locator:
+                    blocksize = long(block_locator.group(1))
+                    blocks.append(Range(tok, streamoffset, blocksize, 0))
+                    streamoffset += blocksize
+                else:
+                    state = SEGMENTS
+
+            if state == SEGMENTS:
+                file_segment = re.search(r'^(\d+):(\d+):(\S+)', tok)
+                if file_segment:
+                    pos = long(file_segment.group(1))
+                    size = long(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)
 
-    :name:
-      The collection name
+            if sep == "\n":
+                stream_name = None
+                state = STREAM_NAME
 
-    :owner_uuid:
-      The parent project.
+        self.set_committed()
 
-    :apiconfig:
-      Optional alternate api configuration to use (to specify alternate API
-      host or token than the default.)
+    @synchronized
+    def notify(self, event, collection, name, item):
+        if self._callback:
+            self._callback(event, collection, name, item)
 
-    """
-    newcollection = Collection(sync=SYNC_EXPLICIT, apiconfig=apiconfig)
-    newcollection.save_new(name, owner_uuid=owner_uuid, ensure_unique_name=True)
-    newcollection._sync = SYNC_LIVE
-    newcollection._subscribe_events()
-    return newcollection
 
-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.
+    Subcollection locking falls under the umbrella lock of its root collection.
 
     """
 
-    def __init__(self, parent):
+    def __init__(self, parent, name):
         super(Subcollection, self).__init__(parent)
         self.lock = self.root_collection().lock
+        self._manifest_text = None
+        self.name = name
+        self.num_retries = parent.num_retries
 
     def root_collection(self):
         return self.parent.root_collection()
 
-    def sync_mode(self):
-        return self.root_collection().sync_mode()
+    def writable(self):
+        return self.root_collection().writable()
 
     def _my_api(self):
         return self.root_collection()._my_api()
@@ -1587,151 +1590,93 @@ class Subcollection(SynchronizedCollectionBase):
     def _my_block_manager(self):
         return self.root_collection()._my_block_manager()
 
-    def _populate(self):
-        self.root_collection()._populate()
-
-    def notify(self, event, collection, name, item):
-        return self.root_collection().notify(event, collection, 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)
-        self._cloneinto(c)
+    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._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 an api collection record locator, a portable data hash of a
+    manifest, 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")
-    else:
-        into_collection = Collection(api_client=api_client, keep_client=keep, num_retries=num_retries, sync=sync)
-
-    save_sync = into_collection.sync_mode()
-    into_collection._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 = into_collection.find_or_create("%s/%s" % (stream_name, name), FILE)
-                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
 
-    into_collection.set_unmodified()
-    into_collection._sync = save_sync
-    return into_collection
+    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):
-    """Export a manifest from the contents of a SynchronizedCollectionBase.
+    @_populate_streams
+    def normalize(self):
+        """Normalize the streams returned by `all_streams`.
+
+        This method is kept for backwards compatability and only affects the
+        behavior of `all_streams()` and `all_files()`
 
-    :item:
-      Create a manifest for `item` (must be a `SynchronizedCollectionBase` or `ArvadosFile`).  If
-      `item` is a is a `Collection`, this will also export subcollections.
+        """
 
-    :stream_name:
-      the name of the stream when exporting `item`.
+        # 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))
 
-    :portable_locators:
-      If True, strip any permission hints on block locators.
-      If False, use block locators as-is.
+        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]
 
-    """
-    buf = ""
-    if isinstance(item, SynchronizedCollectionBase):
-        stream = {}
-        sorted_keys = sorted(item.keys())
-        for filename in [s for s in sorted_keys if isinstance(item[s], ArvadosFile)]:
-            # Create a stream per file `k`
-            arvfile = item[filename]
-            filestream = []
-            for segment in arvfile.segments():
-                loc = segment.locator
-                if loc.startswith("bufferblock"):
-                    loc = arvfile.parent._my_block_manager()._bufferblocks[loc].locator()
-                if portable_locators:
-                    loc = KeepLocator(loc).stripped()
-                filestream.append(LocatorAndRange(loc, locator_block_size(loc),
-                                     segment.segment_offset, segment.range_size))
-            stream[filename] = filestream
-        if stream:
-            buf += ' '.join(normalize_stream(stream_name, stream))
-            buf += "\n"
-        for dirname in [s for s in sorted_keys if isinstance(item[s], SynchronizedCollectionBase)]:
-            buf += export_manifest(item[dirname], stream_name=os.path.join(stream_name, dirname), portable_locators=portable_locators)
-    elif isinstance(item, ArvadosFile):
-        filestream = []
-        for segment in item.segments:
-            loc = segment.locator
-            if loc.startswith("bufferblock"):
-                loc = item._bufferblocks[loc].calculate_locator()
-            if portable_locators:
-                loc = KeepLocator(loc).stripped()
-            filestream.append(LocatorAndRange(loc, locator_block_size(loc),
-                                 segment.segment_offset, segment.range_size))
-        stream[stream_name] = filestream
-        buf += ' '.join(normalize_stream(stream_name, stream))
-        buf += "\n"
-    return buf
+    @_populate_streams
+    def all_files(self):
+        for s in self.all_streams():
+            for f in s.all_files():
+                yield f