9897: Changes as per discussion in #9897.
[arvados.git] / sdk / python / arvados / arvfile.py
index 2d38866aeb2d4837d214e94b011104b41c173f95..517d617d8c4f8403953b5d0b105808e0bd18ac0d 100644 (file)
@@ -9,6 +9,9 @@ import Queue
 import copy
 import errno
 import re
+import logging
+import collections
+import uuid
 
 from .errors import KeepWriteError, AssertionError, ArgumentError
 from .keep import KeepLocator
@@ -16,6 +19,11 @@ from ._normalize_stream import normalize_stream
 from ._ranges import locators_and_ranges, replace_range, Range
 from .retry import retry_method
 
+MOD = "mod"
+WRITE = "write"
+
+_logger = logging.getLogger('arvados.arvfile')
+
 def split(path):
     """split(path) -> streamname, filename
 
@@ -102,6 +110,7 @@ class ArvadosFileReaderBase(_FileLikeObjectBase):
         cache_pos, cache_data = self._readline_cache
         if self.tell() == cache_pos:
             data = [cache_data]
+            self._filepos += len(cache_data)
         else:
             data = ['']
         data_size = len(data[-1])
@@ -117,13 +126,14 @@ class ArvadosFileReaderBase(_FileLikeObjectBase):
         except ValueError:
             nextline_index = len(data)
         nextline_index = min(nextline_index, size)
+        self._filepos -= len(data) - nextline_index
         self._readline_cache = (self.tell(), data[nextline_index:])
         return data[:nextline_index]
 
     @_FileLikeObjectBase._before_close
     @retry_method
     def decompress(self, decompress, size, num_retries=None):
-        for segment in self.readall(size, num_retries):
+        for segment in self.readall(size, num_retries=num_retries):
             data = decompress(segment)
             if data:
                 yield data
@@ -230,6 +240,13 @@ def synchronized(orig_func):
             return orig_func(self, *args, **kwargs)
     return synchronized_wrapper
 
+
+class StateChangeError(Exception):
+    def __init__(self, message, state, nextstate):
+        super(StateChangeError, self).__init__(message)
+        self.state = state
+        self.nextstate = nextstate
+
 class _BufferBlock(object):
     """A stand-in for a Keep block that is in the process of being written.
 
@@ -253,6 +270,7 @@ class _BufferBlock(object):
     WRITABLE = 0
     PENDING = 1
     COMMITTED = 2
+    ERROR = 3
 
     def __init__(self, blockid, starting_capacity, owner):
         """
@@ -274,6 +292,8 @@ class _BufferBlock(object):
         self._locator = None
         self.owner = owner
         self.lock = threading.Lock()
+        self.wait_for_commit = threading.Event()
+        self.error = None
 
     @synchronized
     def append(self, data):
@@ -295,17 +315,30 @@ class _BufferBlock(object):
         else:
             raise AssertionError("Buffer block is not writable")
 
+    STATE_TRANSITIONS = frozenset([
+            (WRITABLE, PENDING),
+            (PENDING, COMMITTED),
+            (PENDING, ERROR),
+            (ERROR, PENDING)])
+
     @synchronized
-    def set_state(self, nextstate, loc=None):
-        if ((self._state == _BufferBlock.WRITABLE and nextstate == _BufferBlock.PENDING) or
-            (self._state == _BufferBlock.PENDING and nextstate == _BufferBlock.COMMITTED)):
-            self._state = nextstate
-            if self._state == _BufferBlock.COMMITTED:
-                self._locator = loc
-                self.buffer_view = None
-                self.buffer_block = None
-        else:
-            raise AssertionError("Invalid state change from %s to %s" % (self.state, nextstate))
+    def set_state(self, nextstate, val=None):
+        if (self._state, nextstate) not in self.STATE_TRANSITIONS:
+            raise StateChangeError("Invalid state change from %s to %s" % (self._state, nextstate), self._state, nextstate)
+        self._state = nextstate
+
+        if self._state == _BufferBlock.PENDING:
+            self.wait_for_commit.clear()
+
+        if self._state == _BufferBlock.COMMITTED:
+            self._locator = val
+            self.buffer_view = None
+            self.buffer_block = None
+            self.wait_for_commit.set()
+
+        if self._state == _BufferBlock.ERROR:
+            self.error = val
+            self.wait_for_commit.set()
 
     @synchronized
     def state(self):
@@ -325,11 +358,17 @@ class _BufferBlock(object):
     @synchronized
     def clone(self, new_blockid, owner):
         if self._state == _BufferBlock.COMMITTED:
-            raise AssertionError("Can only duplicate a writable or pending buffer block")
+            raise AssertionError("Cannot duplicate committed buffer block")
         bufferblock = _BufferBlock(new_blockid, self.size(), owner)
         bufferblock.append(self.buffer_view[0:self.size()])
         return bufferblock
 
+    @synchronized
+    def clear(self):
+        self.owner = None
+        self.buffer_block = None
+        self.buffer_view = None
+
 
 class NoopLock(object):
     def __enter__(self):
@@ -349,7 +388,7 @@ def must_be_writable(orig_func):
     @functools.wraps(orig_func)
     def must_be_writable_wrapper(self, *args, **kwargs):
         if not self.writable():
-            raise IOError((errno.EROFS, "Collection must be writable."))
+            raise IOError(errno.EROFS, "Collection is read-only.")
         return orig_func(self, *args, **kwargs)
     return must_be_writable_wrapper
 
@@ -361,19 +400,25 @@ class _BlockManager(object):
     Collection of ArvadosFiles.
 
     """
-    def __init__(self, keep):
+
+    DEFAULT_PUT_THREADS = 2
+    DEFAULT_GET_THREADS = 2
+
+    def __init__(self, keep, copies=None):
         """keep: KeepClient object to use"""
         self._keep = keep
-        self._bufferblocks = {}
+        self._bufferblocks = collections.OrderedDict()
         self._put_queue = None
-        self._put_errors = None
         self._put_threads = None
         self._prefetch_queue = None
         self._prefetch_threads = None
         self.lock = threading.Lock()
         self.prefetch_enabled = True
-        self.num_put_threads = 2
-        self.num_get_threads = 2
+        self.num_put_threads = _BlockManager.DEFAULT_PUT_THREADS
+        self.num_get_threads = _BlockManager.DEFAULT_GET_THREADS
+        self.copies = copies
+        self._pending_write_size = 0
+        self.threads_lock = threading.Lock()
 
     @synchronized
     def alloc_bufferblock(self, blockid=None, starting_capacity=2**14, owner=None):
@@ -389,8 +434,11 @@ class _BlockManager(object):
           ArvadosFile that owns this block
 
         """
+        return self._alloc_bufferblock(blockid, starting_capacity, owner)
+
+    def _alloc_bufferblock(self, blockid=None, starting_capacity=2**14, owner=None):
         if blockid is None:
-            blockid = "bufferblock%i" % len(self._bufferblocks)
+            blockid = "%s" % uuid.uuid4()
         bufferblock = _BufferBlock(blockid, starting_capacity=starting_capacity, owner=owner)
         self._bufferblocks[bufferblock.blockid] = bufferblock
         return bufferblock
@@ -415,6 +463,73 @@ class _BlockManager(object):
     def is_bufferblock(self, locator):
         return locator in self._bufferblocks
 
+    def _commit_bufferblock_worker(self):
+        """Background uploader thread."""
+
+        while True:
+            try:
+                bufferblock = self._put_queue.get()
+                if bufferblock is None:
+                    return
+
+                if self.copies is None:
+                    loc = self._keep.put(bufferblock.buffer_view[0:bufferblock.write_pointer].tobytes())
+                else:
+                    loc = self._keep.put(bufferblock.buffer_view[0:bufferblock.write_pointer].tobytes(), copies=self.copies)
+                bufferblock.set_state(_BufferBlock.COMMITTED, loc)
+
+            except Exception as e:
+                bufferblock.set_state(_BufferBlock.ERROR, e)
+            finally:
+                if self._put_queue is not None:
+                    self._put_queue.task_done()
+
+    def start_put_threads(self):
+        with self.threads_lock:
+            if self._put_threads is None:
+                # Start uploader threads.
+
+                # If we don't limit the Queue size, the upload queue can quickly
+                # grow to take up gigabytes of RAM if the writing process is
+                # generating data more quickly than it can be send to the Keep
+                # servers.
+                #
+                # With two upload threads and a queue size of 2, this means up to 4
+                # blocks pending.  If they are full 64 MiB blocks, that means up to
+                # 256 MiB of internal buffering, which is the same size as the
+                # default download block cache in KeepClient.
+                self._put_queue = Queue.Queue(maxsize=2)
+
+                self._put_threads = []
+                for i in xrange(0, self.num_put_threads):
+                    thread = threading.Thread(target=self._commit_bufferblock_worker)
+                    self._put_threads.append(thread)
+                    thread.daemon = True
+                    thread.start()
+
+    def _block_prefetch_worker(self):
+        """The background downloader thread."""
+        while True:
+            try:
+                b = self._prefetch_queue.get()
+                if b is None:
+                    return
+                self._keep.get(b)
+            except Exception:
+                _logger.exception("Exception doing block prefetch")
+
+    @synchronized
+    def start_get_threads(self):
+        if self._prefetch_threads is None:
+            self._prefetch_queue = Queue.Queue()
+            self._prefetch_threads = []
+            for i in xrange(0, self.num_get_threads):
+                thread = threading.Thread(target=self._block_prefetch_worker)
+                self._prefetch_threads.append(thread)
+                thread.daemon = True
+                thread.start()
+
+
     @synchronized
     def stop_threads(self):
         """Shut down and wait for background upload and download threads to finish."""
@@ -426,7 +541,6 @@ class _BlockManager(object):
                 t.join()
         self._put_threads = None
         self._put_queue = None
-        self._put_errors = None
 
         if self._prefetch_threads is not None:
             for t in self._prefetch_threads:
@@ -436,63 +550,105 @@ class _BlockManager(object):
         self._prefetch_threads = None
         self._prefetch_queue = None
 
-    def commit_bufferblock(self, block):
-        """Initiate a background upload of a bufferblock.
+    def __enter__(self):
+        return self
 
-        This will block if the upload queue is at capacity, otherwise it will
-        return immediately.
+    def __exit__(self, exc_type, exc_value, traceback):
+        self.stop_threads()
 
-        """
+    @synchronized
+    def repack_small_blocks(self, force=False, sync=False, closed_file_size=0):
+        """Packs small blocks together before uploading"""
+        self._pending_write_size += closed_file_size
 
-        def commit_bufferblock_worker(self):
-            """Background uploader thread."""
+        # Check if there are enough small blocks for filling up one in full
+        if force or (self._pending_write_size >= config.KEEP_BLOCK_SIZE):
 
-            while True:
-                try:
-                    bufferblock = self._put_queue.get()
-                    if bufferblock is None:
-                        return
-                    loc = self._keep.put(bufferblock.buffer_view[0:bufferblock.write_pointer].tobytes())
-                    bufferblock.set_state(_BufferBlock.COMMITTED, loc)
+            # Search blocks ready for getting packed together before being committed to Keep.
+            # A WRITABLE block always has an owner.
+            # A WRITABLE block with its owner.closed() implies that it's
+            # size is <= KEEP_BLOCK_SIZE/2.
+            small_blocks = [b for b in self._bufferblocks.values() if b.state() == _BufferBlock.WRITABLE and b.owner.closed()]
 
-                except Exception as e:
-                    self._put_errors.put((bufferblock.locator(), e))
-                finally:
-                    if self._put_queue is not None:
-                        self._put_queue.task_done()
+            if len(small_blocks) <= 1:
+                # Not enough small blocks for repacking
+                return
 
-        with self.lock:
-            if self._put_threads is None:
-                # Start uploader threads.
+            # Update the pending write size count with its true value, just in case
+            # some small file was opened, written and closed several times.
+            self._pending_write_size = sum([b.size() for b in small_blocks])
+            if self._pending_write_size < config.KEEP_BLOCK_SIZE and not force:
+                return
 
-                # If we don't limit the Queue size, the upload queue can quickly
-                # grow to take up gigabytes of RAM if the writing process is
-                # generating data more quickly than it can be send to the Keep
-                # servers.
-                #
-                # With two upload threads and a queue size of 2, this means up to 4
-                # blocks pending.  If they are full 64 MiB blocks, that means up to
-                # 256 MiB of internal buffering, which is the same size as the
-                # default download block cache in KeepClient.
-                self._put_queue = Queue.Queue(maxsize=2)
-                self._put_errors = Queue.Queue()
+            new_bb = self._alloc_bufferblock()
+            while len(small_blocks) > 0 and (new_bb.write_pointer + small_blocks[0].size()) <= config.KEEP_BLOCK_SIZE:
+                bb = small_blocks.pop(0)
+                arvfile = bb.owner
+                self._pending_write_size -= bb.size()
+                new_bb.append(bb.buffer_view[0:bb.write_pointer].tobytes())
+                arvfile.set_segments([Range(new_bb.blockid,
+                                            0,
+                                            bb.size(),
+                                            new_bb.write_pointer - bb.size())])
+                self._delete_bufferblock(bb.blockid)
+            self.commit_bufferblock(new_bb, sync=sync)
+
+    def commit_bufferblock(self, block, sync):
+        """Initiate a background upload of a bufferblock.
 
-                self._put_threads = []
-                for i in xrange(0, self.num_put_threads):
-                    thread = threading.Thread(target=commit_bufferblock_worker, args=(self,))
-                    self._put_threads.append(thread)
-                    thread.daemon = True
-                    thread.start()
+        :block:
+          The block object to upload
+
+        :sync:
+          If `sync` is True, upload the block synchronously.
+          If `sync` is False, upload the block asynchronously.  This will
+          return immediately unless the upload queue is at capacity, in
+          which case it will wait on an upload queue slot.
 
-        if block.state() == _BufferBlock.WRITABLE:
+        """
+        try:
             # Mark the block as PENDING so to disallow any more appends.
             block.set_state(_BufferBlock.PENDING)
+        except StateChangeError as e:
+            if e.state == _BufferBlock.PENDING:
+                if sync:
+                    block.wait_for_commit.wait()
+                else:
+                    return
+            if block.state() == _BufferBlock.COMMITTED:
+                return
+            elif block.state() == _BufferBlock.ERROR:
+                raise block.error
+            else:
+                raise
+
+        if sync:
+            try:
+                if self.copies is None:
+                    loc = self._keep.put(block.buffer_view[0:block.write_pointer].tobytes())
+                else:
+                    loc = self._keep.put(block.buffer_view[0:block.write_pointer].tobytes(), copies=self.copies)
+                block.set_state(_BufferBlock.COMMITTED, loc)
+            except Exception as e:
+                block.set_state(_BufferBlock.ERROR, e)
+                raise
+        else:
+            self.start_put_threads()
             self._put_queue.put(block)
 
     @synchronized
     def get_bufferblock(self, locator):
         return self._bufferblocks.get(locator)
 
+    @synchronized
+    def delete_bufferblock(self, locator):
+        self._delete_bufferblock(locator)
+
+    def _delete_bufferblock(self, locator):
+        bb = self._bufferblocks[locator]
+        bb.clear()
+        del self._bufferblocks[locator]
+
     def get_block_contents(self, locator, num_retries, cache_only=False):
         """Fetch a block.
 
@@ -515,30 +671,36 @@ class _BlockManager(object):
     def commit_all(self):
         """Commit all outstanding buffer blocks.
 
-        Unlike commit_bufferblock(), this is a synchronous call, and will not
-        return until all buffer blocks are uploaded.  Raises
-        KeepWriteError() if any blocks failed to upload.
+        This is a synchronous call, and will not return until all buffer blocks
+        are uploaded.  Raises KeepWriteError() if any blocks failed to upload.
 
         """
+        self.repack_small_blocks(force=True, sync=True)
+
         with self.lock:
             items = self._bufferblocks.items()
 
         for k,v in items:
-            v.owner.flush()
+            if v.state() != _BufferBlock.COMMITTED and v.owner:
+                v.owner.flush(sync=False)
 
         with self.lock:
             if self._put_queue is not None:
                 self._put_queue.join()
 
-                if not self._put_errors.empty():
-                    err = []
-                    try:
-                        while True:
-                            err.append(self._put_errors.get(False))
-                    except Queue.Empty:
-                        pass
+                err = []
+                for k,v in items:
+                    if v.state() == _BufferBlock.ERROR:
+                        err.append((v.locator(), v.error))
+                if err:
                     raise KeepWriteError("Error writing some blocks", err, label="block")
 
+        for k,v in items:
+            # flush again with sync=True to remove committed bufferblocks from
+            # the segments.
+            if v.owner:
+                v.owner.flush(sync=True)
+
     def block_prefetch(self, locator):
         """Initiate a background download of a block.
 
@@ -552,28 +714,14 @@ class _BlockManager(object):
         if not self.prefetch_enabled:
             return
 
-        def block_prefetch_worker(self):
-            """The background downloader thread."""
-            while True:
-                try:
-                    b = self._prefetch_queue.get()
-                    if b is None:
-                        return
-                    self._keep.get(b)
-                except Exception:
-                    pass
+        if self._keep.get_from_cache(locator) is not None:
+            return
 
         with self.lock:
             if locator in self._bufferblocks:
                 return
-            if self._prefetch_threads is None:
-                self._prefetch_queue = Queue.Queue()
-                self._prefetch_threads = []
-                for i in xrange(0, self.num_get_threads):
-                    thread = threading.Thread(target=block_prefetch_worker, args=(self,))
-                    self._prefetch_threads.append(thread)
-                    thread.daemon = True
-                    thread.start()
+
+        self.start_get_threads()
         self._prefetch_queue.put(locator)
 
 
@@ -588,7 +736,7 @@ class ArvadosFile(object):
 
     """
 
-    def __init__(self, parent, stream=[], segments=[]):
+    def __init__(self, parent, name, stream=[], segments=[]):
         """
         ArvadosFile constructor.
 
@@ -599,7 +747,9 @@ class ArvadosFile(object):
           a list of Range objects representing segments
         """
         self.parent = parent
-        self._modified = True
+        self.name = name
+        self._writers = set()
+        self._committed = False
         self._segments = []
         self.lock = parent.root_collection().lock
         for s in segments:
@@ -614,9 +764,9 @@ class ArvadosFile(object):
         return copy.copy(self._segments)
 
     @synchronized
-    def clone(self, new_parent):
+    def clone(self, new_parent, new_name):
         """Make a copy of this file."""
-        cp = ArvadosFile(new_parent)
+        cp = ArvadosFile(new_parent, new_name)
         cp.replace_contents(self)
         return cp
 
@@ -640,7 +790,7 @@ class ArvadosFile(object):
 
             self._segments.append(Range(new_loc, other_segment.range_start, other_segment.range_size, other_segment.segment_offset))
 
-        self._modified = True
+        self._committed = False
 
     def __eq__(self, other):
         if other is self:
@@ -676,14 +826,46 @@ class ArvadosFile(object):
         return not self.__eq__(other)
 
     @synchronized
-    def set_unmodified(self):
-        """Clear the modified flag"""
-        self._modified = False
+    def set_segments(self, segs):
+        self._segments = segs
+
+    @synchronized
+    def set_committed(self):
+        """Set committed flag to True"""
+        self._committed = True
+
+    @synchronized
+    def committed(self):
+        """Get whether this is committed or not."""
+        return self._committed
+
+    @synchronized
+    def add_writer(self, writer):
+        """Add an ArvadosFileWriter reference to the list of writers"""
+        if isinstance(writer, ArvadosFileWriter):
+            self._writers.add(writer)
 
     @synchronized
-    def modified(self):
-        """Test the modified flag"""
-        return self._modified
+    def remove_writer(self, writer, flush):
+        """
+        Called from ArvadosFileWriter.close(). Remove a writer reference from the list
+        and do some block maintenance tasks.
+        """
+        self._writers.remove(writer)
+
+        if flush or self.size() > config.KEEP_BLOCK_SIZE / 2:
+            # File writer closed, not small enough for repacking
+            self.flush()
+        elif self.closed():
+            # All writers closed and size is adequate for repacking
+            self.parent._my_block_manager().repack_small_blocks(closed_file_size=self.size())
+
+    def closed(self):
+        """
+        Get whether this is closed or not. When the writers list is empty, the file
+        is supposed to be closed.
+        """
+        return len(self._writers) == 0
 
     @must_be_writable
     @synchronized
@@ -711,10 +893,9 @@ class ArvadosFile(object):
                     new_segs.append(r)
 
             self._segments = new_segs
-            self._modified = True
+            self._committed = False
         elif size > self.size():
-            raise IOError("truncate() does not support extending the file size")
-
+            raise IOError(errno.EINVAL, "truncate() does not support extending the file size")
 
     def readfrom(self, offset, size, num_retries, exact=False):
         """Read up to `size` bytes from the file starting at `offset`.
@@ -728,19 +909,25 @@ class ArvadosFile(object):
         with self.lock:
             if size == 0 or offset >= self.size():
                 return ''
-            prefetch = locators_and_ranges(self._segments, offset, size + config.KEEP_BLOCK_SIZE)
             readsegs = locators_and_ranges(self._segments, offset, size)
+            prefetch = locators_and_ranges(self._segments, offset + size, config.KEEP_BLOCK_SIZE, limit=32)
 
-        for lr in prefetch:
-            self.parent._my_block_manager().block_prefetch(lr.locator)
-
+        locs = set()
         data = []
         for lr in readsegs:
             block = self.parent._my_block_manager().get_block_contents(lr.locator, num_retries=num_retries, cache_only=(bool(data) and not exact))
             if block:
-                data.append(block[lr.segment_offset:lr.segment_offset+lr.segment_size])
+                blockview = memoryview(block)
+                data.append(blockview[lr.segment_offset:lr.segment_offset+lr.segment_size].tobytes())
+                locs.add(lr.locator)
             else:
                 break
+
+        for lr in prefetch:
+            if lr.locator not in locs:
+                self.parent._my_block_manager().block_prefetch(lr.locator)
+                locs.add(lr.locator)
+
         return ''.join(data)
 
     def _repack_writes(self, num_retries):
@@ -787,14 +974,13 @@ class ArvadosFile(object):
         if len(data) > config.KEEP_BLOCK_SIZE:
             # Chunk it up into smaller writes
             n = 0
-            while (n + config.KEEP_BLOCK_SIZE) < len(data):
-                self.writeto(self, offset+n, data[n:n + config.KEEP_BLOCK_SIZE], num_retries)
+            dataview = memoryview(data)
+            while n < len(data):
+                self.writeto(offset+n, dataview[n:n + config.KEEP_BLOCK_SIZE].tobytes(), num_retries)
                 n += config.KEEP_BLOCK_SIZE
-            if n < len(data):
-                self.writeto(self, offset+n, data[n:], num_retries)
             return
 
-        self._modified = True
+        self._committed = False
 
         if self._current_bblock is None or self._current_bblock.state() != _BufferBlock.WRITABLE:
             self._current_bblock = self.parent._my_block_manager().alloc_bufferblock(owner=self)
@@ -802,18 +988,47 @@ class ArvadosFile(object):
         if (self._current_bblock.size() + len(data)) > config.KEEP_BLOCK_SIZE:
             self._repack_writes(num_retries)
             if (self._current_bblock.size() + len(data)) > config.KEEP_BLOCK_SIZE:
-                self.parent._my_block_manager().commit_bufferblock(self._current_bblock)
+                self.parent._my_block_manager().commit_bufferblock(self._current_bblock, sync=False)
                 self._current_bblock = self.parent._my_block_manager().alloc_bufferblock(owner=self)
 
         self._current_bblock.append(data)
 
         replace_range(self._segments, offset, len(data), self._current_bblock.blockid, self._current_bblock.write_pointer - len(data))
 
+        self.parent.notify(WRITE, self.parent, self.name, (self, self))
+
+        return len(data)
+
     @synchronized
-    def flush(self, num_retries=0):
-        if self._current_bblock:
-            self._repack_writes(num_retries)
-            self.parent._my_block_manager().commit_bufferblock(self._current_bblock)
+    def flush(self, sync=True, num_retries=0):
+        """Flush the current bufferblock to Keep.
+
+        :sync:
+          If True, commit block synchronously, wait until buffer block has been written.
+          If False, commit block asynchronously, return immediately after putting block into
+          the keep put queue.
+        """
+        if self.committed():
+            return
+
+        if self._current_bblock and self._current_bblock.state() != _BufferBlock.COMMITTED:
+            if self._current_bblock.state() == _BufferBlock.WRITABLE:
+                self._repack_writes(num_retries)
+            self.parent._my_block_manager().commit_bufferblock(self._current_bblock, sync=sync)
+
+        if sync:
+            to_delete = set()
+            for s in self._segments:
+                bb = self.parent._my_block_manager().get_bufferblock(s.locator)
+                if bb:
+                    if bb.state() != _BufferBlock.COMMITTED:
+                        self.parent._my_block_manager().commit_bufferblock(bb, sync=True)
+                    to_delete.add(s.locator)
+                    s.locator = bb.locator()
+            for s in to_delete:
+               self.parent._my_block_manager().delete_bufferblock(s)
+
+        self.parent.notify(MOD, self.parent, self.name, (self, self))
 
     @must_be_writable
     @synchronized
@@ -828,7 +1043,7 @@ class ArvadosFile(object):
 
     def _add_segment(self, blocks, pos, size):
         """Internal implementation of add_segment."""
-        self._modified = True
+        self._committed = False
         for lr in locators_and_ranges(blocks, pos, size):
             last = self._segments[-1] if self._segments else Range(0, 0, 0, 0)
             r = Range(lr.locator, last.range_start+last.range_size, lr.segment_size, lr.segment_offset)
@@ -859,6 +1074,16 @@ class ArvadosFile(object):
         buf += "\n"
         return buf
 
+    @must_be_writable
+    @synchronized
+    def _reparent(self, newparent, newname):
+        self._committed = False
+        self.flush(sync=True)
+        self.parent.remove(self.name)
+        self.parent = newparent
+        self.name = newname
+        self.lock = self.parent.root_collection().lock
+
 
 class ArvadosFileReader(ArvadosFileReaderBase):
     """Wraps ArvadosFile in a file-like object supporting reading only.
@@ -868,8 +1093,8 @@ class ArvadosFileReader(ArvadosFileReaderBase):
 
     """
 
-    def __init__(self, arvadosfile, name, mode="r", num_retries=None):
-        super(ArvadosFileReader, self).__init__(name, mode, num_retries=num_retries)
+    def __init__(self, arvadosfile, num_retries=None):
+        super(ArvadosFileReader, self).__init__(arvadosfile.name, "r", num_retries=num_retries)
         self.arvadosfile = arvadosfile
 
     def size(self):
@@ -880,16 +1105,32 @@ class ArvadosFileReader(ArvadosFileReaderBase):
 
     @_FileLikeObjectBase._before_close
     @retry_method
-    def read(self, size, num_retries=None):
-        """Read up to `size` bytes from the stream, starting at the current file position."""
-        data = self.arvadosfile.readfrom(self._filepos, size, num_retries, exact=True)
-        self._filepos += len(data)
-        return data
+    def read(self, size=None, num_retries=None):
+        """Read up to `size` bytes from the file and return the result.
+
+        Starts at the current file position.  If `size` is None, read the
+        entire remainder of the file.
+        """
+        if size is None:
+            data = []
+            rd = self.arvadosfile.readfrom(self._filepos, config.KEEP_BLOCK_SIZE, num_retries)
+            while rd:
+                data.append(rd)
+                self._filepos += len(rd)
+                rd = self.arvadosfile.readfrom(self._filepos, config.KEEP_BLOCK_SIZE, num_retries)
+            return ''.join(data)
+        else:
+            data = self.arvadosfile.readfrom(self._filepos, size, num_retries, exact=True)
+            self._filepos += len(data)
+            return data
 
     @_FileLikeObjectBase._before_close
     @retry_method
     def readfrom(self, offset, size, num_retries=None):
-        """Read up to `size` bytes from the stream, starting at the current file position."""
+        """Read up to `size` bytes from the stream, starting at the specified file offset.
+
+        This method does not change the file position.
+        """
         return self.arvadosfile.readfrom(offset, size, num_retries)
 
     def flush(self):
@@ -904,8 +1145,10 @@ class ArvadosFileWriter(ArvadosFileReader):
 
     """
 
-    def __init__(self, arvadosfile, name, mode, num_retries=None):
-        super(ArvadosFileWriter, self).__init__(arvadosfile, name, mode, num_retries=num_retries)
+    def __init__(self, arvadosfile, mode, num_retries=None):
+        super(ArvadosFileWriter, self).__init__(arvadosfile, num_retries=num_retries)
+        self.mode = mode
+        self.arvadosfile.add_writer(self)
 
     @_FileLikeObjectBase._before_close
     @retry_method
@@ -915,12 +1158,13 @@ class ArvadosFileWriter(ArvadosFileReader):
         else:
             self.arvadosfile.writeto(self._filepos, data, num_retries)
             self._filepos += len(data)
+        return len(data)
 
     @_FileLikeObjectBase._before_close
     @retry_method
     def writelines(self, seq, num_retries=None):
         for s in seq:
-            self.write(s, num_retries)
+            self.write(s, num_retries=num_retries)
 
     @_FileLikeObjectBase._before_close
     def truncate(self, size=None):
@@ -934,7 +1178,7 @@ class ArvadosFileWriter(ArvadosFileReader):
     def flush(self):
         self.arvadosfile.flush()
 
-    def close(self):
+    def close(self, flush=True):
         if not self.closed:
-            self.flush()
+            self.arvadosfile.remove_writer(self, flush)
             super(ArvadosFileWriter, self).close()