wireprotov2: define and use stream encoders

wireprotov2: define and use stream encoders

Now that we have basic support for defining stream encoding, it is
time to start doing something with it.

We define various classes implementing stream encoders/decoders for
the defined encoding profiles. This is relatively straightforward.

We teach the inputstream and outputstream classes how to encode,
decode, and flush data.

We then teach the clientreactor how to filter received data through
the inputstream decoder.

One of the features of the framing format is that streams can span
requests. This is a differentiating feature from say HTTP/2, which
associates streams with requests. By allowing streams to span requests,
we can reuse compression context data across requests/responses. But
in order to do this, we need a mechanism to "flush" the encoder at
logical boundaries so that receivers receive all data where it is
expected. And a "flush" event is distinct from a "finish" event from
the perspective of certain compressors because a "flush" will retain
compression context state whereas a "finish" operation will not. This
is why encoders have both a flush() and a finish() and each uses
specific flushing semantics on the underlying compressor.

The added tests verify various behavior of decoders via clientreactor.
These tests do test some compression behavior via use of outputstream.
But for all intents and purposes, server reactor support for encoding
is not yet implemented.

Differential Revision: https://phab.mercurial-scm.org/D4921

--- a/mercurial/wireprotoframing.py	Thu Oct 04 17:39:16 2018 -0700
+++ b/mercurial/wireprotoframing.py	Mon Oct 08 17:10:59 2018 -0700
@@ -648,6 +648,140 @@
             flags=FLAG_COMMAND_RESPONSE_CONTINUATION,
             payload=payload)
 
+# TODO consider defining encoders/decoders using the util.compressionengine
+# mechanism.
+
+class identityencoder(object):
+    """Encoder for the "identity" stream encoding profile."""
+    def __init__(self, ui):
+        pass
+
+    def encode(self, data):
+        return data
+
+    def flush(self):
+        return b''
+
+    def finish(self):
+        return b''
+
+class identitydecoder(object):
+    """Decoder for the "identity" stream encoding profile."""
+
+    def __init__(self, ui, extraobjs):
+        if extraobjs:
+            raise error.Abort(_('identity decoder received unexpected '
+                                'additional values'))
+
+    def decode(self, data):
+        return data
+
+class zlibencoder(object):
+    def __init__(self, ui):
+        import zlib
+        self._zlib = zlib
+        self._compressor = zlib.compressobj()
+
+    def encode(self, data):
+        return self._compressor.compress(data)
+
+    def flush(self):
+        # Z_SYNC_FLUSH doesn't reset compression context, which is
+        # what we want.
+        return self._compressor.flush(self._zlib.Z_SYNC_FLUSH)
+
+    def finish(self):
+        res = self._compressor.flush(self._zlib.Z_FINISH)
+        self._compressor = None
+        return res
+
+class zlibdecoder(object):
+    def __init__(self, ui, extraobjs):
+        import zlib
+
+        if extraobjs:
+            raise error.Abort(_('zlib decoder received unexpected '
+                                'additional values'))
+
+        self._decompressor = zlib.decompressobj()
+
+    def decode(self, data):
+        # Python 2's zlib module doesn't use the buffer protocol and can't
+        # handle all bytes-like types.
+        if not pycompat.ispy3 and isinstance(data, bytearray):
+            data = bytes(data)
+
+        return self._decompressor.decompress(data)
+
+class zstdbaseencoder(object):
+    def __init__(self, level):
+        from . import zstd
+
+        self._zstd = zstd
+        cctx = zstd.ZstdCompressor(level=level)
+        self._compressor = cctx.compressobj()
+
+    def encode(self, data):
+        return self._compressor.compress(data)
+
+    def flush(self):
+        # COMPRESSOBJ_FLUSH_BLOCK flushes all data previously fed into the
+        # compressor and allows a decompressor to access all encoded data
+        # up to this point.
+        return self._compressor.flush(self._zstd.COMPRESSOBJ_FLUSH_BLOCK)
+
+    def finish(self):
+        res = self._compressor.flush(self._zstd.COMPRESSOBJ_FLUSH_FINISH)
+        self._compressor = None
+        return res
+
+class zstd8mbencoder(zstdbaseencoder):
+    def __init__(self, ui):
+        super(zstd8mbencoder, self).__init__(3)
+
+class zstdbasedecoder(object):
+    def __init__(self, maxwindowsize):
+        from . import zstd
+        dctx = zstd.ZstdDecompressor(max_window_size=maxwindowsize)
+        self._decompressor = dctx.decompressobj()
+
+    def decode(self, data):
+        return self._decompressor.decompress(data)
+
+class zstd8mbdecoder(zstdbasedecoder):
+    def __init__(self, ui, extraobjs):
+        if extraobjs:
+            raise error.Abort(_('zstd8mb decoder received unexpected '
+                                'additional values'))
+
+        super(zstd8mbdecoder, self).__init__(maxwindowsize=8 * 1048576)
+
+# We lazily populate this to avoid excessive module imports when importing
+# this module.
+STREAM_ENCODERS = {}
+STREAM_ENCODERS_ORDER = []
+
+def populatestreamencoders():
+    if STREAM_ENCODERS:
+        return
+
+    try:
+        from . import zstd
+        zstd.__version__
+    except ImportError:
+        zstd = None
+
+    # zstandard is fastest and is preferred.
+    if zstd:
+        STREAM_ENCODERS[b'zstd-8mb'] = (zstd8mbencoder, zstd8mbdecoder)
+        STREAM_ENCODERS_ORDER.append(b'zstd-8mb')
+
+    STREAM_ENCODERS[b'zlib'] = (zlibencoder, zlibdecoder)
+    STREAM_ENCODERS_ORDER.append(b'zlib')
+
+    STREAM_ENCODERS[b'identity'] = (identityencoder, identitydecoder)
+    STREAM_ENCODERS_ORDER.append(b'identity')
+
 class stream(object):
     """Represents a logical unidirectional series of frames."""
 
@@ -671,16 +805,70 @@
 class inputstream(stream):
     """Represents a stream used for receiving data."""
 
-    def setdecoder(self, name, extraobjs):
+    def __init__(self, streamid, active=False):
+        super(inputstream, self).__init__(streamid, active=active)
+        self._decoder = None
+
+    def setdecoder(self, ui, name, extraobjs):
         """Set the decoder for this stream.
 
         Receives the stream profile name and any additional CBOR objects
         decoded from the stream encoding settings frame payloads.
         """
+        if name not in STREAM_ENCODERS:
+            raise error.Abort(_('unknown stream decoder: %s') % name)
+
+        self._decoder = STREAM_ENCODERS[name][1](ui, extraobjs)
+
+    def decode(self, data):
+        # Default is identity decoder. We don't bother instantiating one
+        # because it is trivial.
+        if not self._decoder:
+            return data
+
+        return self._decoder.decode(data)
+
+    def flush(self):
+        if not self._decoder:
+            return b''
+
+        return self._decoder.flush()
 
 class outputstream(stream):
     """Represents a stream used for sending data."""
 
+    def __init__(self, streamid, active=False):
+        super(outputstream, self).__init__(streamid, active=active)
+        self._encoder = None
+
+    def setencoder(self, ui, name):
+        """Set the encoder for this stream.
+
+        Receives the stream profile name.
+        """
+        if name not in STREAM_ENCODERS:
+            raise error.Abort(_('unknown stream encoder: %s') % name)
+
+        self._encoder = STREAM_ENCODERS[name][0](ui)
+
+    def encode(self, data):
+        if not self._encoder:
+            return data
+
+        return self._encoder.encode(data)
+
+    def flush(self):
+        if not self._encoder:
+            return b''
+
+        return self._encoder.flush()
+
+    def finish(self):
+        if not self._encoder:
+            return b''
+
+        self._encoder.finish()
+
 def ensureserverstream(stream):
     if stream.streamid % 2:
         raise error.ProgrammingError('server should only write to even '
@@ -786,6 +974,8 @@
         # Sender protocol settings are optional. Set implied default values.
         self._sendersettings = dict(DEFAULT_PROTOCOL_SETTINGS)
 
+        populatestreamencoders()
+
     def onframerecv(self, frame):
         """Process a frame that has been received off the wire.
 
@@ -1384,6 +1574,8 @@
         self._incomingstreams = {}
         self._streamsettingsdecoders = {}
 
+        populatestreamencoders()
+
     def callcommand(self, name, args, datafh=None, redirect=None):
         """Request that a command be executed.
 
@@ -1494,9 +1686,13 @@
             self._incomingstreams[frame.streamid] = inputstream(
                 frame.streamid)
 
+        stream = self._incomingstreams[frame.streamid]
+
+        # If the payload is encoded, ask the stream to decode it. We
+        # merely substitute the decoded result into the frame payload as
+        # if it had been transferred all along.
         if frame.streamflags & STREAM_FLAG_ENCODING_APPLIED:
-            raise error.ProgrammingError('support for decoding stream '
-                                         'payloads not yet implemneted')
+            frame.payload = stream.decode(frame.payload)
 
         if frame.streamflags & STREAM_FLAG_END_STREAM:
             del self._incomingstreams[frame.streamid]
@@ -1573,7 +1769,8 @@
             }
 
         try:
-            self._incomingstreams[frame.streamid].setdecoder(decoded[0],
+            self._incomingstreams[frame.streamid].setdecoder(self._ui,
+                                                             decoded[0],
                                                              decoded[1:])
         except Exception as e:
             return 'error', {

--- a/tests/test-wireproto-clientreactor.py	Thu Oct 04 17:39:16 2018 -0700
+++ b/tests/test-wireproto-clientreactor.py	Mon Oct 08 17:10:59 2018 -0700
@@ -1,6 +1,7 @@
 from __future__ import absolute_import
 
 import unittest
+import zlib
 
 from mercurial import (
     error,
@@ -11,6 +12,12 @@
     cborutil,
 )
 
+try:
+    from mercurial import zstd
+    zstd.__version__
+except ImportError:
+    zstd = None
+
 ffs = framing.makeframefromhumanstring
 
 globalui = uimod.ui()
@@ -261,8 +268,11 @@
         action, meta = sendframe(reactor,
             ffs(b'1 2 stream-begin stream-settings eos %s' % data))
 
-        self.assertEqual(action, b'noop')
-        self.assertEqual(meta, {})
+        self.assertEqual(action, b'error')
+        self.assertEqual(meta, {
+            b'message': b'error setting stream decoder: identity decoder '
+                        b'received unexpected additional values',
+        })
 
     def testmultipleframes(self):
         reactor = framing.clientreactor(globalui, buffersends=False)
@@ -286,6 +296,309 @@
         self.assertEqual(action, b'noop')
         self.assertEqual(meta, {})
 
+    def testinvalidencoder(self):
+        reactor = framing.clientreactor(globalui, buffersends=False)
+
+        request, action, meta = reactor.callcommand(b'foo', {})
+        for f in meta[b'framegen']:
+            pass
+
+        action, meta = sendframe(reactor,
+            ffs(b'1 2 stream-begin stream-settings eos cbor:b"badvalue"'))
+
+        self.assertEqual(action, b'error')
+        self.assertEqual(meta, {
+            b'message': b'error setting stream decoder: unknown stream '
+                        b'decoder: badvalue',
+        })
+
+    def testzlibencoding(self):
+        reactor = framing.clientreactor(globalui, buffersends=False)
+
+        request, action, meta = reactor.callcommand(b'foo', {})
+        for f in meta[b'framegen']:
+            pass
+
+        action, meta = sendframe(reactor,
+            ffs(b'%d 2 stream-begin stream-settings eos cbor:b"zlib"' %
+                request.requestid))
+
+        self.assertEqual(action, b'noop')
+        self.assertEqual(meta, {})
+
+        result = {
+            b'status': b'ok',
+        }
+        encoded = b''.join(cborutil.streamencode(result))
+
+        compressed = zlib.compress(encoded)
+        self.assertEqual(zlib.decompress(compressed), encoded)
+
+        action, meta = sendframe(reactor,
+            ffs(b'%d 2 encoded command-response eos %s' %
+                (request.requestid, compressed)))
+
+        self.assertEqual(action, b'responsedata')
+        self.assertEqual(meta[b'data'], encoded)
+
+    def testzlibencodingsinglebyteframes(self):
+        reactor = framing.clientreactor(globalui, buffersends=False)
+
+        request, action, meta = reactor.callcommand(b'foo', {})
+        for f in meta[b'framegen']:
+            pass
+
+        action, meta = sendframe(reactor,
+            ffs(b'%d 2 stream-begin stream-settings eos cbor:b"zlib"' %
+                request.requestid))
+
+        self.assertEqual(action, b'noop')
+        self.assertEqual(meta, {})
+
+        result = {
+            b'status': b'ok',
+        }
+        encoded = b''.join(cborutil.streamencode(result))
+
+        compressed = zlib.compress(encoded)
+        self.assertEqual(zlib.decompress(compressed), encoded)
+
+        chunks = []
+
+        for i in range(len(compressed)):
+            char = compressed[i:i + 1]
+            if char == b'\\':
+                char = b'\\\\'
+            action, meta = sendframe(reactor,
+                ffs(b'%d 2 encoded command-response continuation %s' %
+                    (request.requestid, char)))
+
+            self.assertEqual(action, b'responsedata')
+            chunks.append(meta[b'data'])
+            self.assertTrue(meta[b'expectmore'])
+            self.assertFalse(meta[b'eos'])
+
+        # zlib will have the full data decoded at this point, even though
+        # we haven't flushed.
+        self.assertEqual(b''.join(chunks), encoded)
+
+        # End the stream for good measure.
+        action, meta = sendframe(reactor,
+            ffs(b'%d 2 stream-end command-response eos ' % request.requestid))
+
+        self.assertEqual(action, b'responsedata')
+        self.assertEqual(meta[b'data'], b'')
+        self.assertFalse(meta[b'expectmore'])
+        self.assertTrue(meta[b'eos'])
+
+    def testzlibmultipleresponses(self):
+        # We feed in zlib compressed data on the same stream but belonging to
+        # 2 different requests. This tests our flushing behavior.
+        reactor = framing.clientreactor(globalui, buffersends=False,
+                                        hasmultiplesend=True)
+
+        request1, action, meta = reactor.callcommand(b'foo', {})
+        for f in meta[b'framegen']:
+            pass
+
+        request2, action, meta = reactor.callcommand(b'foo', {})
+        for f in meta[b'framegen']:
+            pass
+
+        outstream = framing.outputstream(2)
+        outstream.setencoder(globalui, b'zlib')
+
+        response1 = b''.join(cborutil.streamencode({
+            b'status': b'ok',
+            b'extra': b'response1' * 10,
+        }))
+
+        response2 = b''.join(cborutil.streamencode({
+            b'status': b'error',
+            b'extra': b'response2' * 10,
+        }))
+
+        action, meta = sendframe(reactor,
+            ffs(b'%d 2 stream-begin stream-settings eos cbor:b"zlib"' %
+                request1.requestid))
+
+        self.assertEqual(action, b'noop')
+        self.assertEqual(meta, {})
+
+        # Feeding partial data in won't get anything useful out.
+        action, meta = sendframe(reactor,
+            ffs(b'%d 2 encoded command-response continuation %s' % (
+                request1.requestid, outstream.encode(response1))))
+        self.assertEqual(action, b'responsedata')
+        self.assertEqual(meta[b'data'], b'')
+
+        # But flushing data at both ends will get our original data.
+        action, meta = sendframe(reactor,
+            ffs(b'%d 2 encoded command-response eos %s' % (
+                request1.requestid, outstream.flush())))
+        self.assertEqual(action, b'responsedata')
+        self.assertEqual(meta[b'data'], response1)
+
+        # We should be able to reuse the compressor/decompressor for the
+        # 2nd response.
+        action, meta = sendframe(reactor,
+            ffs(b'%d 2 encoded command-response continuation %s' % (
+                request2.requestid, outstream.encode(response2))))
+        self.assertEqual(action, b'responsedata')
+        self.assertEqual(meta[b'data'], b'')
+
+        action, meta = sendframe(reactor,
+            ffs(b'%d 2 encoded command-response eos %s' % (
+                request2.requestid, outstream.flush())))
+        self.assertEqual(action, b'responsedata')
+        self.assertEqual(meta[b'data'], response2)
+
+    @unittest.skipUnless(zstd, 'zstd not available')
+    def testzstd8mbencoding(self):
+        reactor = framing.clientreactor(globalui, buffersends=False)
+
+        request, action, meta = reactor.callcommand(b'foo', {})
+        for f in meta[b'framegen']:
+            pass
+
+        action, meta = sendframe(reactor,
+            ffs(b'%d 2 stream-begin stream-settings eos cbor:b"zstd-8mb"' %
+                request.requestid))
+
+        self.assertEqual(action, b'noop')
+        self.assertEqual(meta, {})
+
+        result = {
+            b'status': b'ok',
+        }
+        encoded = b''.join(cborutil.streamencode(result))
+
+        encoder = framing.zstd8mbencoder(globalui)
+        compressed = encoder.encode(encoded) + encoder.finish()
+        self.assertEqual(zstd.ZstdDecompressor().decompress(
+            compressed, max_output_size=len(encoded)), encoded)
+
+        action, meta = sendframe(reactor,
+            ffs(b'%d 2 encoded command-response eos %s' %
+                (request.requestid, compressed)))
+
+        self.assertEqual(action, b'responsedata')
+        self.assertEqual(meta[b'data'], encoded)
+
+    @unittest.skipUnless(zstd, 'zstd not available')
+    def testzstd8mbencodingsinglebyteframes(self):
+        reactor = framing.clientreactor(globalui, buffersends=False)
+
+        request, action, meta = reactor.callcommand(b'foo', {})
+        for f in meta[b'framegen']:
+            pass
+
+        action, meta = sendframe(reactor,
+            ffs(b'%d 2 stream-begin stream-settings eos cbor:b"zstd-8mb"' %
+                request.requestid))
+
+        self.assertEqual(action, b'noop')
+        self.assertEqual(meta, {})
+
+        result = {
+            b'status': b'ok',
+        }
+        encoded = b''.join(cborutil.streamencode(result))
+
+        compressed = zstd.ZstdCompressor().compress(encoded)
+        self.assertEqual(zstd.ZstdDecompressor().decompress(compressed),
+                         encoded)
+
+        chunks = []
+
+        for i in range(len(compressed)):
+            char = compressed[i:i + 1]
+            if char == b'\\':
+                char = b'\\\\'
+            action, meta = sendframe(reactor,
+                ffs(b'%d 2 encoded command-response continuation %s' %
+                    (request.requestid, char)))
+
+            self.assertEqual(action, b'responsedata')
+            chunks.append(meta[b'data'])
+            self.assertTrue(meta[b'expectmore'])
+            self.assertFalse(meta[b'eos'])
+
+        # zstd decompressor will flush at frame boundaries.
+        self.assertEqual(b''.join(chunks), encoded)
+
+        # End the stream for good measure.
+        action, meta = sendframe(reactor,
+            ffs(b'%d 2 stream-end command-response eos ' % request.requestid))
+
+        self.assertEqual(action, b'responsedata')
+        self.assertEqual(meta[b'data'], b'')
+        self.assertFalse(meta[b'expectmore'])
+        self.assertTrue(meta[b'eos'])
+
+    @unittest.skipUnless(zstd, 'zstd not available')
+    def testzstd8mbmultipleresponses(self):
+        # We feed in zstd compressed data on the same stream but belonging to
+        # 2 different requests. This tests our flushing behavior.
+        reactor = framing.clientreactor(globalui, buffersends=False,
+                                        hasmultiplesend=True)
+
+        request1, action, meta = reactor.callcommand(b'foo', {})
+        for f in meta[b'framegen']:
+            pass
+
+        request2, action, meta = reactor.callcommand(b'foo', {})
+        for f in meta[b'framegen']:
+            pass
+
+        outstream = framing.outputstream(2)
+        outstream.setencoder(globalui, b'zstd-8mb')
+
+        response1 = b''.join(cborutil.streamencode({
+            b'status': b'ok',
+            b'extra': b'response1' * 10,
+        }))
+
+        response2 = b''.join(cborutil.streamencode({
+            b'status': b'error',
+            b'extra': b'response2' * 10,
+        }))
+
+        action, meta = sendframe(reactor,
+            ffs(b'%d 2 stream-begin stream-settings eos cbor:b"zstd-8mb"' %
+                request1.requestid))
+
+        self.assertEqual(action, b'noop')
+        self.assertEqual(meta, {})
+
+        # Feeding partial data in won't get anything useful out.
+        action, meta = sendframe(reactor,
+            ffs(b'%d 2 encoded command-response continuation %s' % (
+                request1.requestid, outstream.encode(response1))))
+        self.assertEqual(action, b'responsedata')
+        self.assertEqual(meta[b'data'], b'')
+
+        # But flushing data at both ends will get our original data.
+        action, meta = sendframe(reactor,
+            ffs(b'%d 2 encoded command-response eos %s' % (
+                request1.requestid, outstream.flush())))
+        self.assertEqual(action, b'responsedata')
+        self.assertEqual(meta[b'data'], response1)
+
+        # We should be able to reuse the compressor/decompressor for the
+        # 2nd response.
+        action, meta = sendframe(reactor,
+            ffs(b'%d 2 encoded command-response continuation %s' % (
+                request2.requestid, outstream.encode(response2))))
+        self.assertEqual(action, b'responsedata')
+        self.assertEqual(meta[b'data'], b'')
+
+        action, meta = sendframe(reactor,
+            ffs(b'%d 2 encoded command-response eos %s' % (
+                request2.requestid, outstream.flush())))
+        self.assertEqual(action, b'responsedata')
+        self.assertEqual(meta[b'data'], response2)
+
 if __name__ == '__main__':
     import silenttestrunner
     silenttestrunner.main(__name__)