Mercurial > hg
view tests/flagprocessorext.py @ 37631:2f626233859b
wireproto: implement batching on peer executor interface
This is a bit more complicated than non-batch requests because we
need to buffer sends until the last request arrives *and* we need
to support resolving futures as data arrives from the remote.
In a classical concurrent.futures executor model, the future
"starts" as soon as it is submitted. However, we have nothing to
start until the last command is submitted.
If we did nothing, calling result() would deadlock, since the future
hasn't "started." So in the case where we queue the command, we return
a special future type whose result() will trigger sendcommands().
This eliminates the deadlock potential. It also serves as a check
against callers who may be calling result() prematurely, as it will
prevent any subsequent callcommands() from working. This behavior
is slightly annoying and a bit restrictive. But it's the world
that half duplex connections forces on us.
In order to support streaming responses, we were previously using
a generator. But with a futures-based API, we're using futures
and not generators. So in order to get streaming, we need a
background thread to read data from the server.
The approach taken in this patch is to leverage the ThreadPoolExecutor
from concurrent.futures for managing a background thread. We create
an executor and future that resolves when all response data is
processed (or an error occurs). When exiting the context manager,
we wait on that background reading before returning.
I was hoping we could manually spin up a threading.Thread and this
would be simple. But I ran into a few deadlocks when implementing.
After looking at the source code to concurrent.futures, I figured
it would just be easier to use a ThreadPoolExecutor than implement
all the code needed to manually manage a thread.
To prove this works, a use of the batch API in discovery has been
updated.
Differential Revision: https://phab.mercurial-scm.org/D3269
author | Gregory Szorc <gregory.szorc@gmail.com> |
---|---|
date | Fri, 13 Apr 2018 11:02:34 -0700 |
parents | 9d4f09bfe3ec |
children | fad627d2047c |
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# coding=UTF-8 from __future__ import absolute_import import base64 import zlib from mercurial import ( changegroup, exchange, extensions, revlog, util, ) # Test only: These flags are defined here only in the context of testing the # behavior of the flag processor. The canonical way to add flags is to get in # touch with the community and make them known in revlog. REVIDX_NOOP = (1 << 3) REVIDX_BASE64 = (1 << 2) REVIDX_GZIP = (1 << 1) REVIDX_FAIL = 1 def validatehash(self, text): return True def bypass(self, text): return False def noopdonothing(self, text): return (text, True) def b64encode(self, text): return (base64.b64encode(text), False) def b64decode(self, text): return (base64.b64decode(text), True) def gzipcompress(self, text): return (zlib.compress(text), False) def gzipdecompress(self, text): return (zlib.decompress(text), True) def supportedoutgoingversions(orig, repo): versions = orig(repo) versions.discard(b'01') versions.discard(b'02') versions.add(b'03') return versions def allsupportedversions(orig, ui): versions = orig(ui) versions.add(b'03') return versions def makewrappedfile(obj): class wrappedfile(obj.__class__): def addrevision(self, text, transaction, link, p1, p2, cachedelta=None, node=None, flags=revlog.REVIDX_DEFAULT_FLAGS): if b'[NOOP]' in text: flags |= REVIDX_NOOP if b'[BASE64]' in text: flags |= REVIDX_BASE64 if b'[GZIP]' in text: flags |= REVIDX_GZIP # This addrevision wrapper is meant to add a flag we will not have # transforms registered for, ensuring we handle this error case. if b'[FAIL]' in text: flags |= REVIDX_FAIL return super(wrappedfile, self).addrevision(text, transaction, link, p1, p2, cachedelta=cachedelta, node=node, flags=flags) obj.__class__ = wrappedfile def reposetup(ui, repo): class wrappingflagprocessorrepo(repo.__class__): def file(self, f): orig = super(wrappingflagprocessorrepo, self).file(f) makewrappedfile(orig) return orig repo.__class__ = wrappingflagprocessorrepo def extsetup(ui): # Enable changegroup3 for flags to be sent over the wire wrapfunction = extensions.wrapfunction wrapfunction(changegroup, 'supportedoutgoingversions', supportedoutgoingversions) wrapfunction(changegroup, 'allsupportedversions', allsupportedversions) # Teach revlog about our test flags flags = [REVIDX_NOOP, REVIDX_BASE64, REVIDX_GZIP, REVIDX_FAIL] revlog.REVIDX_KNOWN_FLAGS |= util.bitsfrom(flags) revlog.REVIDX_FLAGS_ORDER.extend(flags) # Teach exchange to use changegroup 3 for k in exchange._bundlespeccontentopts.keys(): exchange._bundlespeccontentopts[k]["cg.version"] = "03" # Register flag processors for each extension revlog.addflagprocessor( REVIDX_NOOP, ( noopdonothing, noopdonothing, validatehash, ) ) revlog.addflagprocessor( REVIDX_BASE64, ( b64decode, b64encode, bypass, ), ) revlog.addflagprocessor( REVIDX_GZIP, ( gzipdecompress, gzipcompress, bypass ) )