view tests/test-narrow-commit.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

#testcases flat tree

  $ . "$TESTDIR/narrow-library.sh"

#if tree
  $ cat << EOF >> $HGRCPATH
  > [experimental]
  > treemanifest = 1
  > EOF
#endif

create full repo

  $ hg init master
  $ cd master

  $ mkdir inside
  $ echo inside > inside/f1
  $ mkdir outside
  $ echo outside > outside/f1
  $ hg ci -Aqm 'initial'

  $ echo modified > inside/f1
  $ hg ci -qm 'modify inside'

  $ echo modified > outside/f1
  $ hg ci -qm 'modify outside'

  $ cd ..

(The lfs extension does nothing here, but this test ensures that its hook that
determines whether to add the lfs requirement, respects the narrow boundaries.)

  $ hg --config extensions.lfs= clone --narrow ssh://user@dummy/master narrow \
  >    --include inside
  requesting all changes
  adding changesets
  adding manifests
  adding file changes
  added 3 changesets with 2 changes to 1 files
  new changesets *:* (glob)
  updating to branch default
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ cd narrow

  $ hg update -q 0

Can not modify dirstate outside

  $ mkdir outside
  $ touch outside/f1
  $ hg debugwalk -I 'relglob:f1'
  matcher: <includematcher includes='(?:(?:|.*/)f1(?:/|$))'>
  f  inside/f1  inside/f1
  $ hg add outside/f1
  abort: cannot track 'outside/f1' - it is outside the narrow clone
  [255]
  $ touch outside/f3
  $ hg add outside/f3
  abort: cannot track 'outside/f3' - it is outside the narrow clone
  [255]

But adding a truly excluded file shouldn't count

  $ hg add outside/f3 -X outside/f3

  $ rm -r outside

Can modify dirstate inside

  $ echo modified > inside/f1
  $ touch inside/f3
  $ hg add inside/f3
  $ hg status
  M inside/f1
  A inside/f3
  $ hg revert -qC .
  $ rm inside/f3

Can commit changes inside. Leaves outside unchanged.

  $ hg update -q 'desc("initial")'
  $ echo modified2 > inside/f1
  $ hg manifest --debug
  4d6a634d5ba06331a60c29ee0db8412490a54fcd 644   inside/f1
  7fb3bb6356d28d4dc352c5ba52d7350a81b6bd46 644   outside/f1 (flat !)
  d0f2f706468ab0e8bec7af87446835fb1b13511b 755 d outside/ (tree !)
  $ hg commit -m 'modify inside/f1'
  created new head
  $ hg files -r .
  inside/f1
  outside/f1 (flat !)
  outside/ (tree !)
  $ hg manifest --debug
  3f4197b4a11b9016e77ebc47fe566944885fd11b 644   inside/f1
  7fb3bb6356d28d4dc352c5ba52d7350a81b6bd46 644   outside/f1 (flat !)
  d0f2f706468ab0e8bec7af87446835fb1b13511b 755 d outside/ (tree !)
Some filesystems (notably FAT/exFAT only store timestamps with 2
seconds of precision, so by sleeping for 3 seconds, we can ensure that
the timestamps of files stored by dirstate will appear older than the
dirstate file, and therefore we'll be able to get stable output from
debugdirstate. If we don't do this, the test can be slightly flaky.
  $ sleep 3
  $ hg status
  $ hg debugdirstate --nodates
  n 644         10 set                 inside/f1