view tests/test-bookmarks-merge.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

# init

  $ hg init
  $ echo a > a
  $ hg add a
  $ hg commit -m'a'
  $ echo b > b
  $ hg add b
  $ hg commit -m'b'
  $ hg up -C 0
  0 files updated, 0 files merged, 1 files removed, 0 files unresolved
  $ echo c > c
  $ hg add c
  $ hg commit -m'c'
  created new head

# test merging of diverged bookmarks
  $ hg bookmark -r 1 "c@diverge"
  $ hg bookmark -r 1 b
  $ hg bookmark c
  $ hg bookmarks
     b                         1:d2ae7f538514
   * c                         2:d36c0562f908
     c@diverge                 1:d2ae7f538514
  $ hg merge "c@diverge"
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  $ hg commit -m'merge'
  $ hg bookmarks
     b                         1:d2ae7f538514
   * c                         3:b8f96cf4688b

  $ hg up -C 3
  0 files updated, 0 files merged, 0 files removed, 0 files unresolved
  (leaving bookmark c)
  $ echo d > d
  $ hg add d
  $ hg commit -m'd'

  $ hg up -C 3
  0 files updated, 0 files merged, 1 files removed, 0 files unresolved
  $ echo e > e
  $ hg add e
  $ hg commit -m'e'
  created new head
  $ hg up -C 5
  0 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ hg bookmark e
  $ hg bookmarks
     b                         1:d2ae7f538514
     c                         3:b8f96cf4688b
   * e                         5:26bee9c5bcf3

# the picked side is bookmarked

  $ hg up -C 4
  1 files updated, 0 files merged, 1 files removed, 0 files unresolved
  (leaving bookmark e)
  $ hg merge
  abort: heads are bookmarked - please merge with an explicit rev
  (run 'hg heads' to see all heads)
  [255]

# our revision is bookmarked

  $ hg up -C e
  1 files updated, 0 files merged, 1 files removed, 0 files unresolved
  (activating bookmark e)
  $ hg merge
  abort: no matching bookmark to merge - please merge with an explicit rev or bookmark
  (run 'hg heads' to see all heads)
  [255]

# merge bookmark heads

  $ hg up -C 4
  1 files updated, 0 files merged, 1 files removed, 0 files unresolved
  (leaving bookmark e)
  $ echo f > f
  $ hg commit -Am "f"
  adding f
  $ hg bookmarks -r 4 "e@diverged"
  $ hg up -q -C "e@diverged"
  $ hg merge
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  $ hg parents
  changeset:   4:a0546fcfe0fb
  bookmark:    e@diverged
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     d
  
  changeset:   5:26bee9c5bcf3
  bookmark:    e
  parent:      3:b8f96cf4688b
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     e
  
  $ hg up -C e
  1 files updated, 0 files merged, 1 files removed, 0 files unresolved
  (activating bookmark e)
  $ hg bookmarks
     b                         1:d2ae7f538514
     c                         3:b8f96cf4688b
   * e                         5:26bee9c5bcf3
     e@diverged                4:a0546fcfe0fb
  $ hg merge
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  $ hg commit -m'merge'
  $ hg bookmarks
     b                         1:d2ae7f538514
     c                         3:b8f96cf4688b
   * e                         7:ca784329f0ba

# test warning when all heads are inactive bookmarks

  $ hg up -C 6
  1 files updated, 0 files merged, 1 files removed, 0 files unresolved
  (leaving bookmark e)
  $ echo g > g
  $ hg commit -Am 'g'
  adding g
  $ hg bookmark -i g
  $ hg bookmarks
     b                         1:d2ae7f538514
     c                         3:b8f96cf4688b
     e                         7:ca784329f0ba
     g                         8:04dd21731d95
  $ hg heads
  changeset:   8:04dd21731d95
  bookmark:    g
  tag:         tip
  parent:      6:be381d1126a0
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     g
  
  changeset:   7:ca784329f0ba
  bookmark:    e
  parent:      5:26bee9c5bcf3
  parent:      4:a0546fcfe0fb
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     merge
  
  $ hg merge
  abort: heads are bookmarked - please merge with an explicit rev
  (run 'hg heads' to see all heads)
  [255]