wireproto: define and implement HTTP handshake to upgrade protocol
When clients connect to repositories over HTTP, they issue a request
to the well-known URL "?cmd=capabilities" to fetch the repository
capabilities. This is the handshake portion of the HTTP protocol.
This commit defines a mechanism to use that HTTP request to return
information about modern server features.
If a client sends an X-HgUpgrade-* header containing a list of
client-supported API names, the server responds with a response
containing information about available services. This includes
the normal capabilities string. So if the server doesn't support
any newer services, the client can easily fall back.
By advertising supported services from clients, server operators
can see and log what client support exists in the wild. This will
also help with debugging.
The response contains the base path to API services. We know there
are potential issues with the <repo>/api/ URL space conflicting with
hgwebdir and subrepos. By making the API URL dynamic from the
perspective of the client, the URL for APIs is not subject to backwards
compatibility concerns - at least as long as a ?cmd=capabilities request
is made.
We've also defined the ``cbor`` client capability for the X-HgProto-*
header. This MUST be sent in order to get the modern response from
"?cmd=capabilities". During implementation, I initially always sent
an application/mercurial-cbor response. However, the handshake
mechanism will be more future compatible if the client is in charge
of which formats to request. We already perform content negotiation
from X-HgProto-*, so keying off this for the capabilities response
feels appropriate.
In addition, I initially used application/cbor. However, it is
conceivable that a non-Mercurial server could serve application/cbor.
To rule out this possibility, I've invented a new media type that
is Mercurial specific and can't be confused for generic CBOR.
Differential Revision: https://phab.mercurial-scm.org/D3242
$ . $TESTDIR/wireprotohelpers.sh
$ hg init server
$ 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: 458\r\n
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: 458\r\n
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: 458\r\n
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: 458\r\n
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: 496\r\n
s> \r\n
s> \xa3Dapis\xa0GapibaseDapi/Nv1capabilitiesY\x01\xcabatch 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
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: 496\r\n
s> \r\n
s> \xa3Dapis\xa0GapibaseDapi/Nv1capabilitiesY\x01\xcabatch 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: 879\r\n
s> \r\n
s> \xa3Dapis\xa1Pexp-http-v2-0001\xa2Hcommands\xa7Eheads\xa2Dargs\xa1Jpubliconly\xf4Kpermissions\x81DpullEknown\xa2Dargs\xa1Enodes\x81HdeadbeefKpermissions\x81DpullFlookup\xa2Dargs\xa1CkeyCfooKpermissions\x81DpullGpushkey\xa2Dargs\xa4CkeyCkeyCnewCnewColdColdInamespaceBnsKpermissions\x81DpushHlistkeys\xa2Dargs\xa1InamespaceBnsKpermissions\x81DpullIbranchmap\xa2Dargs\xa0Kpermissions\x81DpullLcapabilities\xa2Dargs\xa0Kpermissions\x81DpullKcompression\x82\xa1DnameDzstd\xa1DnameDzlibGapibaseDapi/Nv1capabilitiesY\x01\xcabatch 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'zstd'}, {b'name': b'zlib'}]}}, 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
$ sendhttpv2peer << EOF
> command capabilities
> EOF
creating http peer for wire protocol version 2
sending capabilities command
s> POST /api/exp-http-v2-0001/ro/capabilities HTTP/1.1\r\n
s> Accept-Encoding: identity\r\n
s> accept: application/mercurial-exp-framing-0003\r\n
s> content-type: application/mercurial-exp-framing-0003\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-0003\r\n
s> Transfer-Encoding: chunked\r\n
s> \r\n
s> *\r\n (glob)
s> *\x00\x01\x00\x02\x01F (glob)
s> \xa2Hcommands\xa7Eheads\xa2Dargs\xa1Jpubliconly\xf4Kpermissions\x81DpullEknown\xa2Dargs\xa1Enodes\x81HdeadbeefKpermissions\x81DpullFlookup\xa2Dargs\xa1CkeyCfooKpermissions\x81DpullGpushkey\xa2Dargs\xa4CkeyCkeyCnewCnewColdColdInamespaceBnsKpermissions\x81DpushHlistkeys\xa2Dargs\xa1InamespaceBnsKpermissions\x81DpullIbranchmap\xa2Dargs\xa0Kpermissions\x81DpullLcapabilities\xa2Dargs\xa0Kpermissions\x81DpullKcompression\x82\xa1DnameDzstd\xa1DnameDzlib
s> \r\n
received frame(size=*; request=1; stream=2; streamflags=stream-begin; type=bytes-response; flags=eos|cbor) (glob)
s> 0\r\n
s> \r\n
response: [{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'zstd'}, {b'name': b'zlib'}]}]
$ cat error.log