view tests/test-bundle-vs-outgoing.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

this structure seems to tickle a bug in bundle's search for
changesets, so first we have to recreate it

o  8
|
| o  7
| |
| o  6
|/|
o |  5
| |
o |  4
| |
| o  3
| |
| o  2
|/
o  1
|
o  0

  $ mkrev()
  > {
  >     revno=$1
  >     echo "rev $revno"
  >     echo "rev $revno" > foo.txt
  >     hg -q ci -m"rev $revno"
  > }

setup test repo1

  $ hg init repo1
  $ cd repo1
  $ echo "rev 0" > foo.txt
  $ hg ci -Am"rev 0"
  adding foo.txt
  $ mkrev 1
  rev 1

first branch

  $ mkrev 2
  rev 2
  $ mkrev 3
  rev 3

back to rev 1 to create second branch

  $ hg up -r1
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ mkrev 4
  rev 4
  $ mkrev 5
  rev 5

merge first branch to second branch

  $ hg up -C -r5
  0 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ HGMERGE=internal:local hg merge
  0 files updated, 1 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  $ echo "merge rev 5, rev 3" > foo.txt
  $ hg ci -m"merge first branch to second branch"

one more commit following the merge

  $ mkrev 7
  rev 7

back to "second branch" to make another head

  $ hg up -r5
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ mkrev 8
  rev 8

the story so far

  $ hg log -G --template "{rev}\n"
  @  8
  |
  | o  7
  | |
  | o  6
  |/|
  o |  5
  | |
  o |  4
  | |
  | o  3
  | |
  | o  2
  |/
  o  1
  |
  o  0
  

check that "hg outgoing" really does the right thing

sanity check of outgoing: expect revs 4 5 6 7 8

  $ hg clone -r3 . ../repo2
  adding changesets
  adding manifests
  adding file changes
  added 4 changesets with 4 changes to 1 files
  new changesets 6ae4cca4e39a:478f191e53f8
  updating to branch default
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved

this should (and does) report 5 outgoing revisions: 4 5 6 7 8

  $ hg outgoing --template "{rev}\n" ../repo2
  comparing with ../repo2
  searching for changes
  4
  5
  6
  7
  8

test bundle (destination repo): expect 5 revisions

this should bundle the same 5 revisions that outgoing reported, but it

actually bundles 7

  $ hg bundle foo.bundle ../repo2
  searching for changes
  5 changesets found

test bundle (base revision): expect 5 revisions

this should (and does) give exactly the same result as bundle

with a destination repo... i.e. it's wrong too

  $ hg bundle --base 3 foo.bundle
  5 changesets found

  $ cd ..