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view tests/test-bundle2-pushback.t @ 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 | 1ee1a42bfdae |
children | 4c358bdaada8 |
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#testcases sshv1 sshv2 #if sshv2 $ cat >> $HGRCPATH << EOF > [experimental] > sshpeer.advertise-v2 = true > sshserver.support-v2 = true > EOF #endif $ cat > bundle2.py << EOF > """A small extension to test bundle2 pushback parts. > Current bundle2 implementation doesn't provide a way to generate those > parts, so they must be created by extensions. > """ > from __future__ import absolute_import > from mercurial import bundle2, exchange, pushkey, util > def _newhandlechangegroup(op, inpart): > """This function wraps the changegroup part handler for getbundle. > It issues an additional pushkey part to send a new > bookmark back to the client""" > result = bundle2.handlechangegroup(op, inpart) > if 'pushback' in op.reply.capabilities: > params = {'namespace': 'bookmarks', > 'key': 'new-server-mark', > 'old': '', > 'new': 'tip'} > encodedparams = [(k, pushkey.encode(v)) for (k,v) in params.items()] > op.reply.newpart('pushkey', mandatoryparams=encodedparams) > else: > op.reply.newpart('output', data='pushback not enabled') > return result > _newhandlechangegroup.params = bundle2.handlechangegroup.params > bundle2.parthandlermapping['changegroup'] = _newhandlechangegroup > EOF $ cat >> $HGRCPATH <<EOF > [ui] > ssh = $PYTHON "$TESTDIR/dummyssh" > username = nobody <no.reply@example.com> > > [alias] > tglog = log -G -T "{desc} [{phase}:{node|short}]" > EOF Set up server repository $ hg init server $ cd server $ echo c0 > f0 $ hg commit -Am 0 adding f0 Set up client repository $ cd .. $ hg clone ssh://user@dummy/server client -q $ cd client Enable extension $ cat >> $HGRCPATH <<EOF > [extensions] > bundle2=$TESTTMP/bundle2.py > EOF Without config $ cd ../client $ echo c1 > f1 $ hg commit -Am 1 adding f1 $ hg push pushing to ssh://user@dummy/server searching for changes remote: adding changesets remote: adding manifests remote: adding file changes remote: added 1 changesets with 1 changes to 1 files remote: pushback not enabled $ hg bookmark no bookmarks set $ cd ../server $ hg tglog o 1 [public:2b9c7234e035] | @ 0 [public:6cee5c8f3e5b] With config $ cd ../client $ echo '[experimental]' >> .hg/hgrc $ echo 'bundle2.pushback = True' >> .hg/hgrc $ echo c2 > f2 $ hg commit -Am 2 adding f2 $ hg push pushing to ssh://user@dummy/server searching for changes remote: adding changesets remote: adding manifests remote: adding file changes remote: added 1 changesets with 1 changes to 1 files $ hg bookmark new-server-mark 2:0a76dfb2e179 $ cd ../server $ hg tglog o 2 [public:0a76dfb2e179] | o 1 [public:2b9c7234e035] | @ 0 [public:6cee5c8f3e5b]