view tests/test-exchange-obsmarkers-case-C4.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

============================================
Testing obsolescence markers push: Cases C.4
============================================

Mercurial pushes obsolescences markers relevant to the "pushed-set", the set of
all changesets that requested to be "in sync" after the push (even if they are
already on both side).

This test belongs to a series of tests checking such set is properly computed
and applied. This does not tests "obsmarkers" discovery capabilities.

Category C: advanced case
TestCase 4: multiple successors, one is pruned

C.4 multiple successors, one is pruned
======================================

.. (A similarish situation can appends with split markers see the Z section)
..
.. {{{
..        A
..    B ○⇢ø⇠⊗ C
..       \|/
..        ● O
.. }}}
..
.. Marker exist from:
..
..  * `A ø⇠○ B`
..  * `A ø⇠○ C`
..  * C (prune)
..
.. Command run:
..
..  * hg push -r O
..
.. Expected exchange:
..
..  * `A ø⇠○ C`
..  * C (prune)
..
.. Expected exclude:
..
..  * `A ø⇠○ B`

Setup
-----

  $ . $TESTDIR/testlib/exchange-obsmarker-util.sh

Implemented as the non-split version

  $ setuprepos C.4
  creating test repo for test case C.4
  - pulldest
  - main
  - pushdest
  cd into `main` and proceed with env setup
  $ cd main
  $ mkcommit A
  $ hg update -q 0
  $ mkcommit B
  created new head
  $ hg update -q 0
  $ mkcommit C
  created new head
  $ hg debugobsolete --hidden `getid 'desc(A)'` `getid 'desc(B)'`
  obsoleted 1 changesets
  $ hg debugobsolete --hidden `getid 'desc(A)'` `getid 'desc(C)'`
  2 new content-divergent changesets
  $ hg prune -qd '0 0' .
  $ hg log -G --hidden
  x  7f7f229b13a6 (draft): C
  |
  | o  35b183996678 (draft): B
  |/
  | x  f5bc6836db60 (draft): A
  |/
  @  a9bdc8b26820 (public): O
  
  $ inspect_obsmarkers
  obsstore content
  ================
  f5bc6836db60e308a17ba08bf050154ba9c4fad7 35b1839966785d5703a01607229eea932db42f87 0 (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'}
  f5bc6836db60e308a17ba08bf050154ba9c4fad7 7f7f229b13a629a5b20581c6cb723f4e2ca54bed 0 (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'}
  7f7f229b13a629a5b20581c6cb723f4e2ca54bed 0 {a9bdc8b26820b1b87d585b82eb0ceb4a2ecdbc04} (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'}
  $ cd ..
  $ cd ..

Actual Test
-----------

  $ dotest C.4 O
  ## Running testcase C.4
  # testing echange of "O" (a9bdc8b26820)
  ## initial state
  # obstore: main
  7f7f229b13a629a5b20581c6cb723f4e2ca54bed 0 {a9bdc8b26820b1b87d585b82eb0ceb4a2ecdbc04} (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'}
  f5bc6836db60e308a17ba08bf050154ba9c4fad7 35b1839966785d5703a01607229eea932db42f87 0 (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'}
  f5bc6836db60e308a17ba08bf050154ba9c4fad7 7f7f229b13a629a5b20581c6cb723f4e2ca54bed 0 (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'}
  # obstore: pushdest
  # obstore: pulldest
  ## pushing "O" from main to pushdest
  pushing to pushdest
  searching for changes
  no changes found
  remote: 2 new obsolescence markers
  ## post push state
  # obstore: main
  7f7f229b13a629a5b20581c6cb723f4e2ca54bed 0 {a9bdc8b26820b1b87d585b82eb0ceb4a2ecdbc04} (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'}
  f5bc6836db60e308a17ba08bf050154ba9c4fad7 35b1839966785d5703a01607229eea932db42f87 0 (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'}
  f5bc6836db60e308a17ba08bf050154ba9c4fad7 7f7f229b13a629a5b20581c6cb723f4e2ca54bed 0 (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'}
  # obstore: pushdest
  7f7f229b13a629a5b20581c6cb723f4e2ca54bed 0 {a9bdc8b26820b1b87d585b82eb0ceb4a2ecdbc04} (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'}
  f5bc6836db60e308a17ba08bf050154ba9c4fad7 7f7f229b13a629a5b20581c6cb723f4e2ca54bed 0 (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'}
  # obstore: pulldest
  ## pulling "a9bdc8b26820" from main into pulldest
  pulling from main
  no changes found
  2 new obsolescence markers
  ## post pull state
  # obstore: main
  7f7f229b13a629a5b20581c6cb723f4e2ca54bed 0 {a9bdc8b26820b1b87d585b82eb0ceb4a2ecdbc04} (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'}
  f5bc6836db60e308a17ba08bf050154ba9c4fad7 35b1839966785d5703a01607229eea932db42f87 0 (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'}
  f5bc6836db60e308a17ba08bf050154ba9c4fad7 7f7f229b13a629a5b20581c6cb723f4e2ca54bed 0 (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'}
  # obstore: pushdest
  7f7f229b13a629a5b20581c6cb723f4e2ca54bed 0 {a9bdc8b26820b1b87d585b82eb0ceb4a2ecdbc04} (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'}
  f5bc6836db60e308a17ba08bf050154ba9c4fad7 7f7f229b13a629a5b20581c6cb723f4e2ca54bed 0 (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'}
  # obstore: pulldest
  7f7f229b13a629a5b20581c6cb723f4e2ca54bed 0 {a9bdc8b26820b1b87d585b82eb0ceb4a2ecdbc04} (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'}
  f5bc6836db60e308a17ba08bf050154ba9c4fad7 7f7f229b13a629a5b20581c6cb723f4e2ca54bed 0 (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'}