wireprotov2peer: stream decoded responses
Previously, wire protocol version 2 would buffer all response data.
Only once all data was received did we CBOR decode it and resolve
the future associated with the command. This was obviously not
desirable. In future commits that introduce large response payloads,
this caused significant memory bloat and slowed down client
operations due to waiting on the server.
This commit refactors the response handling code so that response
data can be streamed.
Command response objects now contain a buffered CBOR decoder. As
new data arrives, it is fed into the decoder. Decoded objects are
made available to the generator as they are decoded.
Because there is a separate thread processing incoming frames and
feeding data into the response object, there is the potential for
race conditions when mutating response objects. So a lock has been
added to guard access to critical state variables.
Because the generator emitting decoded objects needs to wait on
those objects to become available, we've added an Event for the
generator to wait on so it doesn't busy loop. This does mean
there is the potential for deadlocks. And I'm pretty sure they can
occur in some scenarios. We already have a handful of TODOs around
this. But I've added some more. Fixing this will likely require
moving the background thread receiving frames into clienthandler.
We likely would have done this anyway when implementing the client
bits for the SSH transport.
Test output changes because the initial CBOR map holding the overall
response state is now always handled internally by the response
object.
Differential Revision: https://phab.mercurial-scm.org/D4474
#require no-chg
$ . $TESTDIR/wireprotohelpers.sh
$ hg init server
zstd isn't present in plain builds. Make tests easier by removing
zstd from the equation.
$ cat >> server/.hg/hgrc << EOF
> [server]
> compressionengines = zlib
> EOF
$ hg -R server serve -p $HGPORT -d --pid-file hg.pid -E error.log
$ cat hg.pid > $DAEMON_PIDS
A normal capabilities request is serviced for version 1
$ sendhttpraw << EOF
> httprequest GET ?cmd=capabilities
> user-agent: test
> EOF
using raw connection to peer
s> GET /?cmd=capabilities HTTP/1.1\r\n
s> Accept-Encoding: identity\r\n
s> user-agent: test\r\n
s> host: $LOCALIP:$HGPORT\r\n (glob)
s> \r\n
s> makefile('rb', None)
s> HTTP/1.1 200 Script output follows\r\n
s> Server: testing stub value\r\n
s> Date: $HTTP_DATE$\r\n
s> Content-Type: application/mercurial-0.1\r\n
s> Content-Length: *\r\n (glob)
s> \r\n
s> batch branchmap $USUAL_BUNDLE2_CAPS_SERVER$ changegroupsubset compression=$BUNDLE2_COMPRESSIONS$ getbundle httpheader=1024 httpmediatype=0.1rx,0.1tx,0.2tx known lookup pushkey streamreqs=generaldelta,revlogv1 unbundle=HG10GZ,HG10BZ,HG10UN unbundlehash
A proper request without the API server enabled returns the legacy response
$ sendhttpraw << EOF
> httprequest GET ?cmd=capabilities
> user-agent: test
> x-hgupgrade-1: foo
> x-hgproto-1: cbor
> EOF
using raw connection to peer
s> GET /?cmd=capabilities HTTP/1.1\r\n
s> Accept-Encoding: identity\r\n
s> user-agent: test\r\n
s> x-hgproto-1: cbor\r\n
s> x-hgupgrade-1: foo\r\n
s> host: $LOCALIP:$HGPORT\r\n (glob)
s> \r\n
s> makefile('rb', None)
s> HTTP/1.1 200 Script output follows\r\n
s> Server: testing stub value\r\n
s> Date: $HTTP_DATE$\r\n
s> Content-Type: application/mercurial-0.1\r\n
s> Content-Length: *\r\n (glob)
s> \r\n
s> batch branchmap $USUAL_BUNDLE2_CAPS_SERVER$ changegroupsubset compression=$BUNDLE2_COMPRESSIONS$ getbundle httpheader=1024 httpmediatype=0.1rx,0.1tx,0.2tx known lookup pushkey streamreqs=generaldelta,revlogv1 unbundle=HG10GZ,HG10BZ,HG10UN unbundlehash
Restart with just API server enabled. This enables serving the new format.
$ killdaemons.py
$ cat error.log
$ cat >> server/.hg/hgrc << EOF
> [experimental]
> web.apiserver = true
> EOF
$ hg -R server serve -p $HGPORT -d --pid-file hg.pid -E error.log
$ cat hg.pid > $DAEMON_PIDS
X-HgUpgrade-<N> without CBOR advertisement uses legacy response
$ sendhttpraw << EOF
> httprequest GET ?cmd=capabilities
> user-agent: test
> x-hgupgrade-1: foo bar
> EOF
using raw connection to peer
s> GET /?cmd=capabilities HTTP/1.1\r\n
s> Accept-Encoding: identity\r\n
s> user-agent: test\r\n
s> x-hgupgrade-1: foo bar\r\n
s> host: $LOCALIP:$HGPORT\r\n (glob)
s> \r\n
s> makefile('rb', None)
s> HTTP/1.1 200 Script output follows\r\n
s> Server: testing stub value\r\n
s> Date: $HTTP_DATE$\r\n
s> Content-Type: application/mercurial-0.1\r\n
s> Content-Length: *\r\n (glob)
s> \r\n
s> batch branchmap $USUAL_BUNDLE2_CAPS_SERVER$ changegroupsubset compression=$BUNDLE2_COMPRESSIONS$ getbundle httpheader=1024 httpmediatype=0.1rx,0.1tx,0.2tx known lookup pushkey streamreqs=generaldelta,revlogv1 unbundle=HG10GZ,HG10BZ,HG10UN unbundlehash
X-HgUpgrade-<N> without known serialization in X-HgProto-<N> uses legacy response
$ sendhttpraw << EOF
> httprequest GET ?cmd=capabilities
> user-agent: test
> x-hgupgrade-1: foo bar
> x-hgproto-1: some value
> EOF
using raw connection to peer
s> GET /?cmd=capabilities HTTP/1.1\r\n
s> Accept-Encoding: identity\r\n
s> user-agent: test\r\n
s> x-hgproto-1: some value\r\n
s> x-hgupgrade-1: foo bar\r\n
s> host: $LOCALIP:$HGPORT\r\n (glob)
s> \r\n
s> makefile('rb', None)
s> HTTP/1.1 200 Script output follows\r\n
s> Server: testing stub value\r\n
s> Date: $HTTP_DATE$\r\n
s> Content-Type: application/mercurial-0.1\r\n
s> Content-Length: *\r\n (glob)
s> \r\n
s> batch branchmap $USUAL_BUNDLE2_CAPS_SERVER$ changegroupsubset compression=$BUNDLE2_COMPRESSIONS$ getbundle httpheader=1024 httpmediatype=0.1rx,0.1tx,0.2tx known lookup pushkey streamreqs=generaldelta,revlogv1 unbundle=HG10GZ,HG10BZ,HG10UN unbundlehash
X-HgUpgrade-<N> + X-HgProto-<N> headers trigger new response format
$ sendhttpraw << EOF
> httprequest GET ?cmd=capabilities
> user-agent: test
> x-hgupgrade-1: foo bar
> x-hgproto-1: cbor
> EOF
using raw connection to peer
s> GET /?cmd=capabilities HTTP/1.1\r\n
s> Accept-Encoding: identity\r\n
s> user-agent: test\r\n
s> x-hgproto-1: cbor\r\n
s> x-hgupgrade-1: foo bar\r\n
s> host: $LOCALIP:$HGPORT\r\n (glob)
s> \r\n
s> makefile('rb', None)
s> HTTP/1.1 200 OK\r\n
s> Server: testing stub value\r\n
s> Date: $HTTP_DATE$\r\n
s> Content-Type: application/mercurial-cbor\r\n
s> Content-Length: *\r\n (glob)
s> \r\n
s> \xa3GapibaseDapi/Dapis\xa0Nv1capabilitiesY\x01\xc5batch branchmap $USUAL_BUNDLE2_CAPS_SERVER$ changegroupsubset compression=$BUNDLE2_COMPRESSIONS$ getbundle httpheader=1024 httpmediatype=0.1rx,0.1tx,0.2tx known lookup pushkey streamreqs=generaldelta,revlogv1 unbundle=HG10GZ,HG10BZ,HG10UN unbundlehash
cbor> {
b'apibase': b'api/',
b'apis': {},
b'v1capabilities': b'batch branchmap $USUAL_BUNDLE2_CAPS_SERVER$ changegroupsubset compression=$BUNDLE2_COMPRESSIONS$ getbundle httpheader=1024 httpmediatype=0.1rx,0.1tx,0.2tx known lookup pushkey streamreqs=generaldelta,revlogv1 unbundle=HG10GZ,HG10BZ,HG10UN unbundlehash'
}
Restart server to enable HTTPv2
$ killdaemons.py
$ enablehttpv2 server
$ hg -R server serve -p $HGPORT -d --pid-file hg.pid -E error.log
$ cat hg.pid > $DAEMON_PIDS
Only requested API services are returned
$ sendhttpraw << EOF
> httprequest GET ?cmd=capabilities
> user-agent: test
> x-hgupgrade-1: foo bar
> x-hgproto-1: cbor
> EOF
using raw connection to peer
s> GET /?cmd=capabilities HTTP/1.1\r\n
s> Accept-Encoding: identity\r\n
s> user-agent: test\r\n
s> x-hgproto-1: cbor\r\n
s> x-hgupgrade-1: foo bar\r\n
s> host: $LOCALIP:$HGPORT\r\n (glob)
s> \r\n
s> makefile('rb', None)
s> HTTP/1.1 200 OK\r\n
s> Server: testing stub value\r\n
s> Date: $HTTP_DATE$\r\n
s> Content-Type: application/mercurial-cbor\r\n
s> Content-Length: *\r\n (glob)
s> \r\n
s> \xa3GapibaseDapi/Dapis\xa0Nv1capabilitiesY\x01\xc5batch branchmap $USUAL_BUNDLE2_CAPS_SERVER$ changegroupsubset compression=$BUNDLE2_COMPRESSIONS$ getbundle httpheader=1024 httpmediatype=0.1rx,0.1tx,0.2tx known lookup pushkey streamreqs=generaldelta,revlogv1 unbundle=HG10GZ,HG10BZ,HG10UN unbundlehash
cbor> {
b'apibase': b'api/',
b'apis': {},
b'v1capabilities': b'batch branchmap $USUAL_BUNDLE2_CAPS_SERVER$ changegroupsubset compression=$BUNDLE2_COMPRESSIONS$ getbundle httpheader=1024 httpmediatype=0.1rx,0.1tx,0.2tx known lookup pushkey streamreqs=generaldelta,revlogv1 unbundle=HG10GZ,HG10BZ,HG10UN unbundlehash'
}
Request for HTTPv2 service returns information about it
$ sendhttpraw << EOF
> httprequest GET ?cmd=capabilities
> user-agent: test
> x-hgupgrade-1: exp-http-v2-0001 foo bar
> x-hgproto-1: cbor
> EOF
using raw connection to peer
s> GET /?cmd=capabilities HTTP/1.1\r\n
s> Accept-Encoding: identity\r\n
s> user-agent: test\r\n
s> x-hgproto-1: cbor\r\n
s> x-hgupgrade-1: exp-http-v2-0001 foo bar\r\n
s> host: $LOCALIP:$HGPORT\r\n (glob)
s> \r\n
s> makefile('rb', None)
s> HTTP/1.1 200 OK\r\n
s> Server: testing stub value\r\n
s> Date: $HTTP_DATE$\r\n
s> Content-Type: application/mercurial-cbor\r\n
s> Content-Length: *\r\n (glob)
s> \r\n
s> \xa3GapibaseDapi/Dapis\xa1Pexp-http-v2-0001\xa4Hcommands\xa7Ibranchmap\xa2Dargs\xa0Kpermissions\x81DpullLcapabilities\xa2Dargs\xa0Kpermissions\x81DpullEheads\xa2Dargs\xa1Jpubliconly\xf4Kpermissions\x81DpullEknown\xa2Dargs\xa1Enodes\x81HdeadbeefKpermissions\x81DpullHlistkeys\xa2Dargs\xa1InamespaceBnsKpermissions\x81DpullFlookup\xa2Dargs\xa1CkeyCfooKpermissions\x81DpullGpushkey\xa2Dargs\xa4CkeyCkeyInamespaceBnsCnewCnewColdColdKpermissions\x81DpushKcompression\x81\xa1DnameDzlibQframingmediatypes\x81X&application/mercurial-exp-framing-0005Nrawrepoformats\x82LgeneraldeltaHrevlogv1Nv1capabilitiesY\x01\xc5batch branchmap $USUAL_BUNDLE2_CAPS_SERVER$ changegroupsubset compression=$BUNDLE2_COMPRESSIONS$ getbundle httpheader=1024 httpmediatype=0.1rx,0.1tx,0.2tx known lookup pushkey streamreqs=generaldelta,revlogv1 unbundle=HG10GZ,HG10BZ,HG10UN unbundlehash
cbor> {
b'apibase': b'api/',
b'apis': {
b'exp-http-v2-0001': {
b'commands': {
b'branchmap': {
b'args': {},
b'permissions': [
b'pull'
]
},
b'capabilities': {
b'args': {},
b'permissions': [
b'pull'
]
},
b'heads': {
b'args': {
b'publiconly': False
},
b'permissions': [
b'pull'
]
},
b'known': {
b'args': {
b'nodes': [
b'deadbeef'
]
},
b'permissions': [
b'pull'
]
},
b'listkeys': {
b'args': {
b'namespace': b'ns'
},
b'permissions': [
b'pull'
]
},
b'lookup': {
b'args': {
b'key': b'foo'
},
b'permissions': [
b'pull'
]
},
b'pushkey': {
b'args': {
b'key': b'key',
b'namespace': b'ns',
b'new': b'new',
b'old': b'old'
},
b'permissions': [
b'push'
]
}
},
b'compression': [
{
b'name': b'zlib'
}
],
b'framingmediatypes': [
b'application/mercurial-exp-framing-0005'
],
b'rawrepoformats': [
b'generaldelta',
b'revlogv1'
]
}
},
b'v1capabilities': b'batch branchmap $USUAL_BUNDLE2_CAPS_SERVER$ changegroupsubset compression=$BUNDLE2_COMPRESSIONS$ getbundle httpheader=1024 httpmediatype=0.1rx,0.1tx,0.2tx known lookup pushkey streamreqs=generaldelta,revlogv1 unbundle=HG10GZ,HG10BZ,HG10UN unbundlehash'
}
capabilities command returns expected info
$ sendhttpv2peerhandshake << EOF
> command capabilities
> EOF
creating http peer for wire protocol version 2
s> GET /?cmd=capabilities HTTP/1.1\r\n
s> Accept-Encoding: identity\r\n
s> vary: X-HgProto-1,X-HgUpgrade-1\r\n
s> x-hgproto-1: cbor\r\n
s> x-hgupgrade-1: exp-http-v2-0001\r\n
s> accept: application/mercurial-0.1\r\n
s> host: $LOCALIP:$HGPORT\r\n (glob)
s> user-agent: Mercurial debugwireproto\r\n
s> \r\n
s> makefile('rb', None)
s> HTTP/1.1 200 OK\r\n
s> Server: testing stub value\r\n
s> Date: $HTTP_DATE$\r\n
s> Content-Type: application/mercurial-cbor\r\n
s> Content-Length: *\r\n (glob)
s> \r\n
s> \xa3GapibaseDapi/Dapis\xa1Pexp-http-v2-0001\xa4Hcommands\xa7Ibranchmap\xa2Dargs\xa0Kpermissions\x81DpullLcapabilities\xa2Dargs\xa0Kpermissions\x81DpullEheads\xa2Dargs\xa1Jpubliconly\xf4Kpermissions\x81DpullEknown\xa2Dargs\xa1Enodes\x81HdeadbeefKpermissions\x81DpullHlistkeys\xa2Dargs\xa1InamespaceBnsKpermissions\x81DpullFlookup\xa2Dargs\xa1CkeyCfooKpermissions\x81DpullGpushkey\xa2Dargs\xa4CkeyCkeyInamespaceBnsCnewCnewColdColdKpermissions\x81DpushKcompression\x81\xa1DnameDzlibQframingmediatypes\x81X&application/mercurial-exp-framing-0005Nrawrepoformats\x82LgeneraldeltaHrevlogv1Nv1capabilitiesY\x01\xc5batch branchmap $USUAL_BUNDLE2_CAPS_SERVER$ changegroupsubset compression=$BUNDLE2_COMPRESSIONS$ getbundle httpheader=1024 httpmediatype=0.1rx,0.1tx,0.2tx known lookup pushkey streamreqs=generaldelta,revlogv1 unbundle=HG10GZ,HG10BZ,HG10UN unbundlehash
sending capabilities command
s> POST /api/exp-http-v2-0001/ro/capabilities HTTP/1.1\r\n
s> Accept-Encoding: identity\r\n
s> *\r\n (glob)
s> content-type: application/mercurial-exp-framing-0005\r\n
s> content-length: 27\r\n
s> host: $LOCALIP:$HGPORT\r\n (glob)
s> user-agent: Mercurial debugwireproto\r\n
s> \r\n
s> \x13\x00\x00\x01\x00\x01\x01\x11\xa1DnameLcapabilities
s> makefile('rb', None)
s> HTTP/1.1 200 OK\r\n
s> Server: testing stub value\r\n
s> Date: $HTTP_DATE$\r\n
s> Content-Type: application/mercurial-exp-framing-0005\r\n
s> Transfer-Encoding: chunked\r\n
s> \r\n
s> 13\r\n
s> \x0b\x00\x00\x01\x00\x02\x011
s> \xa1FstatusBok
s> \r\n
received frame(size=11; request=1; stream=2; streamflags=stream-begin; type=command-response; flags=continuation)
s> 1cc\r\n
s> \xc4\x01\x00\x01\x00\x02\x001
s> \xa4Hcommands\xa7Ibranchmap\xa2Dargs\xa0Kpermissions\x81DpullLcapabilities\xa2Dargs\xa0Kpermissions\x81DpullEheads\xa2Dargs\xa1Jpubliconly\xf4Kpermissions\x81DpullEknown\xa2Dargs\xa1Enodes\x81HdeadbeefKpermissions\x81DpullHlistkeys\xa2Dargs\xa1InamespaceBnsKpermissions\x81DpullFlookup\xa2Dargs\xa1CkeyCfooKpermissions\x81DpullGpushkey\xa2Dargs\xa4CkeyCkeyInamespaceBnsCnewCnewColdColdKpermissions\x81DpushKcompression\x81\xa1DnameDzlibQframingmediatypes\x81X&application/mercurial-exp-framing-0005Nrawrepoformats\x82LgeneraldeltaHrevlogv1
s> \r\n
received frame(size=452; request=1; stream=2; streamflags=; type=command-response; flags=continuation)
s> 8\r\n
s> \x00\x00\x00\x01\x00\x02\x002
s> \r\n
s> 0\r\n
s> \r\n
received frame(size=0; request=1; stream=2; streamflags=; type=command-response; flags=eos)
response: gen[
{
b'commands': {
b'branchmap': {
b'args': {},
b'permissions': [
b'pull'
]
},
b'capabilities': {
b'args': {},
b'permissions': [
b'pull'
]
},
b'heads': {
b'args': {
b'publiconly': False
},
b'permissions': [
b'pull'
]
},
b'known': {
b'args': {
b'nodes': [
b'deadbeef'
]
},
b'permissions': [
b'pull'
]
},
b'listkeys': {
b'args': {
b'namespace': b'ns'
},
b'permissions': [
b'pull'
]
},
b'lookup': {
b'args': {
b'key': b'foo'
},
b'permissions': [
b'pull'
]
},
b'pushkey': {
b'args': {
b'key': b'key',
b'namespace': b'ns',
b'new': b'new',
b'old': b'old'
},
b'permissions': [
b'push'
]
}
},
b'compression': [
{
b'name': b'zlib'
}
],
b'framingmediatypes': [
b'application/mercurial-exp-framing-0005'
],
b'rawrepoformats': [
b'generaldelta',
b'revlogv1'
]
}
]
$ cat error.log