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view tests/test-mq-symlinks.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 | c2380b448265 |
children | 55c6ebd11cb9 |
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#require symlink $ echo "[extensions]" >> $HGRCPATH $ echo "mq=" >> $HGRCPATH $ hg init $ hg qinit $ hg qnew base.patch $ echo aaa > a $ echo bbb > b $ echo ccc > c $ hg add a b c $ hg qrefresh $ readlink.py a a -> a not a symlink test replacing a file with a symlink $ hg qnew symlink.patch $ rm a $ ln -s b a $ hg qrefresh --git $ readlink.py a a -> b $ hg qpop popping symlink.patch now at: base.patch $ hg qpush applying symlink.patch now at: symlink.patch $ readlink.py a a -> b test updating a symlink $ rm a $ ln -s c a $ hg qnew --git -f updatelink $ readlink.py a a -> c $ hg qpop popping updatelink now at: symlink.patch $ hg qpush --debug applying updatelink patching file a committing files: a committing manifest committing changelog updating the branch cache now at: updatelink $ readlink.py a a -> c $ hg st test replacing a symlink with a file $ ln -s c s $ hg add s $ hg qnew --git -f addlink $ rm s $ echo sss > s $ hg qnew --git -f replacelinkwithfile $ hg qpop popping replacelinkwithfile now at: addlink $ hg qpush applying replacelinkwithfile now at: replacelinkwithfile $ cat s sss $ hg st test symlink removal $ hg qnew removesl.patch $ hg rm a $ hg qrefresh --git $ hg qpop popping removesl.patch now at: replacelinkwithfile $ hg qpush applying removesl.patch now at: removesl.patch $ hg st -c C b C c C s replace broken symlink with another broken symlink $ ln -s linka linka $ hg add linka $ hg qnew link $ hg mv linka linkb $ rm linkb $ ln -s linkb linkb $ hg qnew movelink $ hg qpop popping movelink now at: link $ hg qpush applying movelink now at: movelink $ readlink.py linkb linkb -> linkb