Mercurial > public > mercurial-scm > hg
diff mercurial/wireprotov2server.py @ 39559:07b58266bce3
wireprotov2: implement commands as a generator of objects
Previously, wire protocol version 2 inherited version 1's model of
having separate types to represent the results of different wire
protocol commands.
As I implemented more powerful commands in future commits, I found
I was using a common pattern of returning a special type to hold a
generator. This meant the command function required a closure to
do most of the work. That made logic flow more difficult to follow.
I also noticed that many commands were effectively a sequence of
objects to be CBOR encoded.
I think it makes sense to define version 2 commands as generators.
This way, commands can simply emit the data structures they wish to
send to the client. This eliminates the need for a closure in
command functions and removes encoding from the bodies of commands.
As part of this commit, the handling of response objects has been
moved into the serverreactor class. This puts the reactor in the
driver's seat with regards to CBOR encoding and error handling.
Having error handling in the function that emits frames is
particularly important because exceptions in that function can lead
to things getting in a bad state: I'm fairly certain that uncaught
exceptions in the frame generator were causing deadlocks.
I also introduced a dedicated error type for explicit error reporting
in command handlers. This will be used in subsequent commits.
There's still a bit of work to be done here, especially around
formalizing the error handling "protocol." I've added yet another
TODO to track this so we don't forget.
Test output changed because we're using generators and no longer know
we are at the end of the data until we hit the end of the generator.
This means we can't emit the end-of-stream flag until we've exhausted
the generator. Hence the introduction of 0-sized end-of-stream frames.
Differential Revision: https://phab.mercurial-scm.org/D4472
| author | Gregory Szorc <gregory.szorc@gmail.com> |
|---|---|
| date | Wed, 05 Sep 2018 09:06:40 -0700 |
| parents | 660879e49b46 |
| children | 9c2c77c73f23 |
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--- a/mercurial/wireprotov2server.py Mon Aug 27 13:30:44 2018 -0700 +++ b/mercurial/wireprotov2server.py Wed Sep 05 09:06:40 2018 -0700 @@ -19,7 +19,6 @@ wireprototypes, ) from .utils import ( - cborutil, interfaceutil, ) @@ -295,31 +294,19 @@ res.setbodybytes(_('command in frame must match command in URL')) return True - rsp = dispatch(repo, proto, command['command']) - res.status = b'200 OK' res.headers[b'Content-Type'] = FRAMINGTYPE - # TODO consider adding a type to represent an iterable of values to - # be CBOR encoded. - if isinstance(rsp, wireprototypes.cborresponse): - # TODO consider calling oncommandresponsereadygen(). - encoded = b''.join(cborutil.streamencode(rsp.value)) - action, meta = reactor.oncommandresponseready(outstream, - command['requestid'], - encoded) - elif isinstance(rsp, wireprototypes.v2streamingresponse): - action, meta = reactor.oncommandresponsereadygen(outstream, - command['requestid'], - rsp.gen) - elif isinstance(rsp, wireprototypes.v2errorresponse): - action, meta = reactor.oncommanderror(outstream, - command['requestid'], - rsp.message, - rsp.args) - else: + try: + objs = dispatch(repo, proto, command['command']) + + action, meta = reactor.oncommandresponsereadyobjects( + outstream, command['requestid'], objs) + + except Exception as e: action, meta = reactor.onservererror( - _('unhandled response type from wire proto command')) + outstream, command['requestid'], + _('exception when invoking command: %s') % e) if action == 'sendframes': res.setbodygen(meta['framegen']) @@ -430,6 +417,12 @@ respectively. Default is to assume command requires ``push`` permissions because otherwise commands not declaring their permissions could modify a repository that is supposed to be read-only. + + Wire protocol commands are generators of objects to be serialized and + sent to the client. + + If a command raises an uncaught exception, this will be translated into + a command error. """ transports = {k for k, v in wireprototypes.TRANSPORTS.items() if v['version'] == 2} @@ -460,16 +453,12 @@ @wireprotocommand('branchmap', permission='pull') def branchmapv2(repo, proto): - branchmap = {encoding.fromlocal(k): v - for k, v in repo.branchmap().iteritems()} - - return wireprototypes.cborresponse(branchmap) + yield {encoding.fromlocal(k): v + for k, v in repo.branchmap().iteritems()} @wireprotocommand('capabilities', permission='pull') def capabilitiesv2(repo, proto): - caps = _capabilitiesv2(repo, proto) - - return wireprototypes.cborresponse(caps) + yield _capabilitiesv2(repo, proto) @wireprotocommand('heads', args={ @@ -480,7 +469,7 @@ if publiconly: repo = repo.filtered('immutable') - return wireprototypes.cborresponse(repo.heads()) + yield repo.heads() @wireprotocommand('known', args={ @@ -490,7 +479,7 @@ def knownv2(repo, proto, nodes=None): nodes = nodes or [] result = b''.join(b'1' if n else b'0' for n in repo.known(nodes)) - return wireprototypes.cborresponse(result) + yield result @wireprotocommand('listkeys', args={ @@ -502,7 +491,7 @@ keys = {encoding.fromlocal(k): encoding.fromlocal(v) for k, v in keys.iteritems()} - return wireprototypes.cborresponse(keys) + yield keys @wireprotocommand('lookup', args={ @@ -515,7 +504,7 @@ # TODO handle exception. node = repo.lookup(key) - return wireprototypes.cborresponse(node) + yield node @wireprotocommand('pushkey', args={ @@ -527,9 +516,7 @@ permission='push') def pushkeyv2(repo, proto, namespace, key, old, new): # TODO handle ui output redirection - r = repo.pushkey(encoding.tolocal(namespace), - encoding.tolocal(key), - encoding.tolocal(old), - encoding.tolocal(new)) - - return wireprototypes.cborresponse(r) + yield repo.pushkey(encoding.tolocal(namespace), + encoding.tolocal(key), + encoding.tolocal(old), + encoding.tolocal(new))