Mercurial > hg
view tests/test-update-reverse.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> |
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date | Fri, 13 Apr 2018 11:02:34 -0700 |
parents | bd625cd4e5e7 |
children | 5c2a4f37eace |
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$ hg init $ touch a $ hg add a $ hg commit -m "Added a" $ touch main $ hg add main $ hg commit -m "Added main" $ hg checkout 0 0 files updated, 0 files merged, 1 files removed, 0 files unresolved 'main' should be gone: $ ls a $ touch side1 $ hg add side1 $ hg commit -m "Added side1" created new head $ touch side2 $ hg add side2 $ hg commit -m "Added side2" $ hg log changeset: 3:91ebc10ed028 tag: tip user: test date: Thu Jan 01 00:00:00 1970 +0000 summary: Added side2 changeset: 2:b932d7dbb1e1 parent: 0:c2eda428b523 user: test date: Thu Jan 01 00:00:00 1970 +0000 summary: Added side1 changeset: 1:71a760306caf user: test date: Thu Jan 01 00:00:00 1970 +0000 summary: Added main changeset: 0:c2eda428b523 user: test date: Thu Jan 01 00:00:00 1970 +0000 summary: Added a $ hg heads changeset: 3:91ebc10ed028 tag: tip user: test date: Thu Jan 01 00:00:00 1970 +0000 summary: Added side2 changeset: 1:71a760306caf user: test date: Thu Jan 01 00:00:00 1970 +0000 summary: Added main $ ls a side1 side2 $ hg update --debug -C 1 resolving manifests branchmerge: False, force: True, partial: False ancestor: 91ebc10ed028+, local: 91ebc10ed028+, remote: 71a760306caf side1: other deleted -> r removing side1 side2: other deleted -> r removing side2 main: remote created -> g getting main 1 files updated, 0 files merged, 2 files removed, 0 files unresolved $ ls a main