Client side implementation of new /content-gs isolate protocol.

isolateserver.py

Index: isolateserver.py
diff --git a/isolateserver.py b/isolateserver.py
index 2205a182ea81eedf2dd366438ddc8ae5a12d4e25..c11fa7f0117a3ed01bf69b399338a7913b66c957 100755
--- a/isolateserver.py
+++ b/isolateserver.py
@@ -7,12 +7,10 @@
 
 __version__ = '0.2'
 
-import binascii
 import hashlib
 import json
 import logging
 import os
-import random
 import re
 import sys
 import threading
@@ -29,14 +27,15 @@ from utils import threading_utils
 from utils import tools
 
 
-# The minimum size of files to upload directly to the blobstore.
-MIN_SIZE_FOR_DIRECT_BLOBSTORE = 20 * 1024
+# Version of isolate protocol passed to the server in /handshake request.
+ISOLATE_PROTOCOL_VERSION = '1.0'
 
-# The number of files to check the isolate server per /contains query.
+
+# The number of files to check the isolate server per /pre-upload query.
 # All files are sorted by likelihood of a change in the file content
 # (currently file size is used to estimate this: larger the file -> larger the
 # possibility it has changed). Then first ITEMS_PER_CONTAINS_QUERIES[0] files
-# are taken and send to '/contains', then next ITEMS_PER_CONTAINS_QUERIES[1],
+# are taken and send to '/pre-upload', then next ITEMS_PER_CONTAINS_QUERIES[1],
 # and so on. Numbers here is a trade-off; the more per request, the lower the
 # effect of HTTP round trip latency and TCP-level chattiness. On the other hand,
 # larger values cause longer lookups, increasing the initial latency to start
@@ -62,10 +61,12 @@ UNKNOWN_FILE_SIZE = None
 # The size of each chunk to read when downloading and unzipping files.
 ZIPPED_FILE_CHUNK = 16 * 1024
 
-
 # Chunk size to use when doing disk I/O.
 DISK_FILE_CHUNK = 1024 * 1024
 
+# Chunk size to use when reading from network stream.
+NET_IO_FILE_CHUNK = 16 * 1024
+
 
 # Read timeout in seconds for downloads from isolate storage. If there's no
 # response from the server within this timeout whole download will be aborted.
@@ -106,63 +107,6 @@ class MappingError(OSError):
   pass
 
 
-def randomness():
-  """Generates low-entropy randomness for MIME encoding.
-
-  Exists so it can be mocked out in unit tests.
-  """
-  return str(time.time())
-
-
-def encode_multipart_formdata(fields, files,
-                              mime_mapper=lambda _: 'application/octet-stream'):
-  """Encodes a Multipart form data object.
-
-  Args:
-    fields: a sequence (name, value) elements for
-      regular form fields.
-    files: a sequence of (name, filename, value) elements for data to be
-      uploaded as files.
-    mime_mapper: function to return the mime type from the filename.
-  Returns:
-    content_type: for httplib.HTTP instance
-    body: for httplib.HTTP instance
-  """
-  boundary = hashlib.md5(randomness()).hexdigest()
-  body_list = []
-  for (key, value) in fields:
-    if isinstance(key, unicode):
-      value = key.encode('utf-8')
-    if isinstance(value, unicode):
-      value = value.encode('utf-8')
-    body_list.append('--' + boundary)
-    body_list.append('Content-Disposition: form-data; name="%s"' % key)
-    body_list.append('')
-    body_list.append(value)
-    body_list.append('--' + boundary)
-    body_list.append('')
-  for (key, filename, value) in files:
-    if isinstance(key, unicode):
-      value = key.encode('utf-8')
-    if isinstance(filename, unicode):
-      value = filename.encode('utf-8')
-    if isinstance(value, unicode):
-      value = value.encode('utf-8')
-    body_list.append('--' + boundary)
-    body_list.append('Content-Disposition: form-data; name="%s"; '
-                     'filename="%s"' % (key, filename))
-    body_list.append('Content-Type: %s' % mime_mapper(filename))
-    body_list.append('')
-    body_list.append(value)
-    body_list.append('--' + boundary)
-    body_list.append('')
-  if body_list:
-    body_list[-2] += '--'
-  body = '\r\n'.join(body_list)
-  content_type = 'multipart/form-data; boundary=%s' % boundary
-  return content_type, body
-
-
 def is_valid_hash(value, algo):
   """Returns if the value is a valid hash for the corresponding algorithm."""
   size = 2 * algo().digest_size
@@ -184,6 +128,15 @@ def hash_file(filepath, algo):
   return digest.hexdigest()
 
 
+def stream_read(stream, chunk_size):
+  """Reads chunks from |stream| and yields them."""
+  while True:
+    data = stream.read(chunk_size)
+    if not data:
+      break
+    yield data
+
+
 def file_read(filepath, chunk_size=DISK_FILE_CHUNK):
   """Yields file content in chunks of given |chunk_size|."""
   with open(filepath, 'rb') as f:
@@ -226,6 +179,37 @@ def zip_compress(content_generator, level=7):
     yield tail
 
 
+def zip_decompress(content_generator, chunk_size=DISK_FILE_CHUNK):
+  """Reads zipped data from |content_generator| and yields decompressed data.
+
+  Decompresses data in small chunks (no larger than |chunk_size|) so that
+  zip bomb file doesn't cause zlib to preallocate huge amount of memory.
+
+  Raises IOError if data is corrupted or incomplete.
+  """
+  decompressor = zlib.decompressobj()
+  compressed_size = 0
+  try:
+    for chunk in content_generator:
+      compressed_size += len(chunk)
+      data = decompressor.decompress(chunk, chunk_size)
+      if data:
+        yield data
+      while decompressor.unconsumed_tail:
+        data = decompressor.decompress(decompressor.unconsumed_tail, chunk_size)
+        if data:
+          yield data
+    tail = decompressor.flush()
+    if tail:
+      yield tail
+  except zlib.error as e:
+    raise IOError(
+        'Corrupted zip stream (read %d bytes) - %s' % (compressed_size, e))
+  # Ensure all data was read and decompressed.
+  if decompressor.unused_data or decompressor.unconsumed_tail:
+    raise IOError('Not all data was decompressed')
+
+
 def get_zip_compression_level(filename):
   """Given a filename calculates the ideal zip compression level to use."""
   file_ext = os.path.splitext(filename)[1].lower()
@@ -301,15 +285,6 @@ def try_remove(filepath):
     pass
 
 
-def url_read(url, **kwargs):
-  result = net.url_read(url, **kwargs)
-  if result is None:
-    # If we get no response from the server, assume it is down and raise an
-    # exception.
-    raise MappingError('Unable to connect to server %s' % url)
-  return result
-
-
 class Storage(object):
   """Efficiently downloads or uploads large set of files via StorageApi."""
 
@@ -540,84 +515,132 @@ class StorageApi(object):
 
 
 class IsolateServer(StorageApi):
-  """StorageApi implementation that downloads and uploads to Isolate Server."""
+  """StorageApi implementation that downloads and uploads to Isolate Server.
+
+  It uploads and downloads directly from Google Storage whenever appropriate.
+  """
+
   def __init__(self, base_url, namespace):
     super(IsolateServer, self).__init__()
     assert base_url.startswith('http'), base_url
-    self.content_url = base_url.rstrip('/') + '/content/'
+    self.base_url = base_url.rstrip('/')
     self.namespace = namespace
     self.algo = get_hash_algo(namespace)
-    self._token = None
+    self._use_zip = is_namespace_with_compression(namespace)
     self._lock = threading.Lock()
+    self._server_caps = None
+
+  @staticmethod
+  def generate_handshake_request():
+    """Returns a dict to be sent as handshake request body."""
+    # TODO(vadimsh): Set 'pusher' and 'fetcher' according to intended usage.
+    return {
+        'protocol_version': ISOLATE_PROTOCOL_VERSION,
+        'client_app_version': __version__,
+        'fetcher': True,
+        'pusher': True,
+    }
+
+  @staticmethod
+  def validate_handshake_response(caps):
+    """Validates and normalizes handshake response."""
+    logging.info('Protocol version: %s', caps['protocol_version'])
+    logging.info('Server version: %s', caps['server_app_version'])
+    if caps.get('error'):
+      raise MappingError(caps['error'])
+    if not caps['access_token']:
+      raise ValueError('access_token is missing')
+    return caps
 
   @property
-  def token(self):
+  def server_capabilities(self):
+    """Performs handshake with the server if not yet done.
+
+    Returns:
+      Server capabilities dictionary as returned by /handshake endpoint.
+
+    Raises:
+      MappingError if server rejects the handshake.
+    """
     # TODO(maruel): Make this request much earlier asynchronously while the
     # files are being enumerated.
     with self._lock:
-      if not self._token:
-        self._token = urllib.quote(url_read(self.content_url + 'get_token'))
-      return self._token
+      if self._server_caps is None:
+        request_body = json.dumps(
+            self.generate_handshake_request(), separators=(',', ':'))
+        response = net.url_read(
+            url=self.base_url + '/content-gs/handshake',
+            data=request_body,
+            content_type='application/json',
+            method='POST')
+        if response is None:
+          raise MappingError('Failed to perform handshake.')
+        try:
+          caps = json.loads(response)
+          if not isinstance(caps, dict):
+            raise ValueError('Expecting JSON dict')
+          self._server_caps = self.validate_handshake_response(caps)
+        except (ValueError, KeyError, TypeError) as exc:
+          # KeyError exception has very confusing str conversion: it's just a
+          # missing key value and nothing else. So print exception class name
+          # as well.
+          raise MappingError('Invalid handshake response (%s): %s' % (
+              exc.__class__.__name__, exc))
+      return self._server_caps
 
   def fetch(self, item, expected_size):
     assert isinstance(item, basestring)
-    assert (
-        isinstance(expected_size, (int, long)) or
+    assert (isinstance(expected_size, (int, long)) or
         expected_size == UNKNOWN_FILE_SIZE)
-    zipped_url = '%sretrieve/%s/%s' % (self.content_url, self.namespace, item)
-    logging.debug('download_file(%s)', zipped_url)
+
+    source_url = '%s/content-gs/retrieve/%s/%s' % (
+        self.base_url, self.namespace, item)
+    logging.debug('download_file(%s)', source_url)
 
     # Because the app engine DB is only eventually consistent, retry 404 errors
     # because the file might just not be visible yet (even though it has been
     # uploaded).
     connection = net.url_open(
-        zipped_url, retry_404=True, read_timeout=DOWNLOAD_READ_TIMEOUT)
+        source_url, retry_404=True, read_timeout=DOWNLOAD_READ_TIMEOUT)
     if not connection:
-      raise IOError('Unable to open connection to %s' % zipped_url)
+      raise IOError('Unable to open connection to %s' % source_url)
 
-    # TODO(maruel): Must only decompress when needed.
-    decompressor = zlib.decompressobj()
     try:
-      compressed_size = 0
-      decompressed_size = 0
-      while True:
-        chunk = connection.read(ZIPPED_FILE_CHUNK)
-        if not chunk:
-          break
-        compressed_size += len(chunk)
-        decompressed = decompressor.decompress(chunk)
-        decompressed_size += len(decompressed)
-        yield decompressed
-
-      # Ensure that all the data was properly decompressed.
-      uncompressed_data = decompressor.flush()
-      if uncompressed_data:
-        raise IOError('Decompression failed')
-      if (expected_size != UNKNOWN_FILE_SIZE and
-          decompressed_size != expected_size):
-        raise IOError('File incorrect size after download of %s. Got %s and '
-                      'expected %s' % (item, decompressed_size, expected_size))
-    except zlib.error as e:
-      msg = 'Corrupted zlib for item %s. Processed %d of %s bytes.\n%s' % (
-          item, compressed_size, connection.content_length, e)
-      logging.warning(msg)
-
-      # Testing seems to show that if a few machines are trying to download
-      # the same blob, they can cause each other to fail. So if we hit a zip
-      # error, this is the most likely cause (it only downloads some of the
-      # data). Randomly sleep for between 5 and 25 seconds to try and spread
-      # out the downloads.
-      sleep_duration = (random.random() * 20) + 5
-      time.sleep(sleep_duration)
-      raise IOError(msg)
+      # Prepare reading pipeline.
+      generator = stream_read(connection, NET_IO_FILE_CHUNK)
+      if self._use_zip:
+        generator = zip_decompress(generator, DISK_FILE_CHUNK)
+
+      # Read and yield data, calculate total length of the decompressed stream.
+      total_size = 0
+      for chunk in generator:
+        total_size += len(chunk)
+        yield chunk
+
+      # Verify data length matches expectation.
+      if expected_size != UNKNOWN_FILE_SIZE and total_size != expected_size:
+        raise IOError('Incorrect file size: expected %d, got %d' % (
+            expected_size, total_size))
+
+    except IOError as err:
+      logging.warning('Failed to fetch %s: %s', item, err)
+      raise
 
   def push(self, item, expected_size, content_generator, push_urls=None):
     assert isinstance(item, basestring)
     assert isinstance(expected_size, int) or expected_size == UNKNOWN_FILE_SIZE
-    item = str(item)
+    assert push_urls and len(push_urls) == 2
+    upload_url, finalize_url = push_urls
 
     # TODO(maruel): Support large files. This would require streaming support.
 
+    # TODO(vadimsh): Do not read from |content_generator| when retrying push.
+    # If |content_generator| is indeed a generator, it can not be re-winded back
+    # to the beginning of the stream. A retry will find it exhausted. A possible
+    # solution is to wrap content_generator with some sort of caching
+    # restartable generator. It should be done alongside streaming support
+    # implementation.
+
     # A cheese way to avoid memcpy of (possibly huge) file, until streaming
     # upload support is implemented.
     if isinstance(content_generator, list) and len(content_generator) == 1:
@@ -625,64 +648,76 @@ class IsolateServer(StorageApi):
     else:
       content = ''.join(content_generator)
 
-    if len(content) > MIN_SIZE_FOR_DIRECT_BLOBSTORE:
-      return self._upload_hash_content_to_blobstore(item, content)
-
-    url = '%sstore/%s/%s?token=%s' % (
-        self.content_url, self.namespace, item, self.token)
-    return url_read(url, data=content, content_type='application/octet-stream')
+    # PUT file to |upload_url|.
+    response = net.url_read(
+        url=upload_url,
+        data=content,
+        content_type='application/octet-stream',
+        method='PUT')
+    if response is None:
+      raise IOError('Failed to upload a file %s to %s' % (item, upload_url))
+
+    # Optionally notify the server that it's done.
+    if finalize_url:
+      # TODO(vadimsh): Calculate MD5 sum while uploading a file and send it to
+      # isolated server. That way isolate server can verify that the data safely
+      # reached Google Storage (GS provides MD5 of stored files).
+      response = net.url_read(
+          url=finalize_url,
+          data='',
+          content_type='application/json',
+          method='POST')
+      # TODO(vadimsh): Do not reupload item again if only finalize_url request
+      # failed.
+      if response is None:
+        raise IOError('Failed to finalize an upload of %s' % item)
 
   def contains(self, files):
     logging.info('Checking existence of %d files...', len(files))
 
-    body = ''.join(
-        (binascii.unhexlify(metadata['h']) for (_, metadata) in files))
-    assert (len(body) % self.algo().digest_size) == 0, repr(body)
+    # Request body is a json encoded list of dicts.
+    body = [
+        {
+          'h': metadata['h'],
+          's': metadata['s'],
+          'i': 1 if metadata.get('priority') == '0' else 0,
+        } for _, metadata in files
+    ]
 
-    query_url = '%scontains/%s?token=%s' % (
-        self.content_url, self.namespace, self.token)
-    response = url_read(
-        query_url, data=body, content_type='application/octet-stream')
-    if len(files) != len(response):
+    query_url = '%s/content-gs/pre-upload/%s?token=%s' % (
+        self.base_url,
+        self.namespace,
+        urllib.quote(self.server_capabilities['access_token']))
+    response_body = net.url_read(
+        url=query_url,
+        data=json.dumps(body, separators=(',', ':')),
+        content_type='application/json',
+        method='POST')
+    if response_body is None:
+      raise MappingError('Failed to execute /pre-upload query')
+
+    # Response body is a list of push_urls (or null if file is already present).
+    try:
+      response = json.loads(response_body)
+      if not isinstance(response, list):
+        raise ValueError('Expecting response with json-encoded list')
+      if len(response) != len(files):
+        raise ValueError(
+            'Incorrect number of items in the list, expected %d, '
+            'but got %d' % (len(files), len(response)))
+    except ValueError as err:
       raise MappingError(
-          'Got an incorrect number of responses from the server. Expected %d, '
-          'but got %d' % (len(files), len(response)))
+          'Invalid response from server: %s, body is %s' % (err, response_body))
 
-    # This implementation of IsolateServer doesn't use push_urls field,
-    # set it to None.
+    # Convert response into a list of triplets with info about missing files.
     missing_files = [
-        files[i] + (None,) for i, flag in enumerate(response) if flag == '\x00'
+        files[i] + (push_urls,) for i, push_urls in enumerate(response)
+        if push_urls
     ]
     logging.info('Queried %d files, %d cache hit',
         len(files), len(files) - len(missing_files))
     return missing_files
 
-  def _upload_hash_content_to_blobstore(self, item, content):
-    """Uploads the content directly to the blobstore via a generated url."""
-    # TODO(maruel): Support large files. This would require streaming support.
-    gen_url = '%sgenerate_blobstore_url/%s/%s' % (
-        self.content_url, self.namespace, item)
-    # Token is guaranteed to be already quoted but it is unnecessary here, and
-    # only here.
-    data = [('token', urllib.unquote(self.token))]
-    content_type, body = encode_multipart_formdata(
-        data, [('content', item, content)])
-    last_url = gen_url
-    for _ in net.retry_loop(max_attempts=net.URL_OPEN_MAX_ATTEMPTS):
-      # Retry HTTP 50x here but not 404.
-      upload_url = net.url_read(gen_url, data=data)
-      if not upload_url:
-        raise MappingError('Unable to connect to server %s' % gen_url)
-      last_url = upload_url
-
-      # Do not retry this request on HTTP 50x. Regenerate an upload url each
-      # time since uploading "consumes" the upload url.
-      result = net.url_read(
-          upload_url, data=body, content_type=content_type, retry_50x=False)
-      if result is not None:
-        return result
-    raise MappingError('Unable to connect to server %s' % last_url)
-
 
 class FileSystem(StorageApi):
   """StorageApi implementation that fetches data from the file system.