view tests/test-merge-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

Check that renames are correctly saved by a commit after a merge

Test with the merge on 3 having the rename on the local parent

  $ hg init a
  $ cd a

  $ echo line1 > foo
  $ hg add foo
  $ hg ci -m '0: add foo'

  $ echo line2 >> foo
  $ hg ci -m '1: change foo'

  $ hg up -C 0
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved

  $ hg mv foo bar
  $ rm bar
  $ echo line0 > bar
  $ echo line1 >> bar
  $ hg ci -m '2: mv foo bar; change bar'
  created new head

  $ hg merge 1
  merging bar and foo to bar
  0 files updated, 1 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)

  $ cat bar
  line0
  line1
  line2

  $ hg ci -m '3: merge with local rename'

  $ hg debugindex bar
     rev linkrev nodeid       p1           p2
       0       2 d35118874825 000000000000 000000000000
       1       3 5345f5ab8abd 000000000000 d35118874825

  $ hg debugrename bar
  bar renamed from foo:9e25c27b87571a1edee5ae4dddee5687746cc8e2

  $ hg debugindex foo
     rev linkrev nodeid       p1           p2
       0       0 690b295714ae 000000000000 000000000000
       1       1 9e25c27b8757 690b295714ae 000000000000


Revert the content change from rev 2:

  $ hg up -C 2
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ rm bar
  $ echo line1 > bar
  $ hg ci -m '4: revert content change from rev 2'
  created new head

  $ hg log --template '{rev}:{node|short} {parents}\n'
  4:2263c1be0967 2:0f2ff26688b9 
  3:0555950ead28 2:0f2ff26688b9 1:5cd961e4045d 
  2:0f2ff26688b9 0:2665aaee66e9 
  1:5cd961e4045d 
  0:2665aaee66e9 

This should use bar@rev2 as the ancestor:

  $ hg --debug merge 3
    searching for copies back to rev 1
  resolving manifests
   branchmerge: True, force: False, partial: False
   ancestor: 0f2ff26688b9, local: 2263c1be0967+, remote: 0555950ead28
   preserving bar for resolve of bar
  starting 4 threads for background file closing (?)
   bar: versions differ -> m (premerge)
  picked tool ':merge' for bar (binary False symlink False changedelete False)
  merging bar
  my bar@2263c1be0967+ other bar@0555950ead28 ancestor bar@0f2ff26688b9
   premerge successful
  0 files updated, 1 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)

  $ cat bar
  line1
  line2

  $ hg ci -m '5: merge'

  $ hg debugindex bar
     rev linkrev nodeid       p1           p2
       0       2 d35118874825 000000000000 000000000000
       1       3 5345f5ab8abd 000000000000 d35118874825
       2       4 ff4b45017382 d35118874825 000000000000
       3       5 3701b4893544 ff4b45017382 5345f5ab8abd


Same thing, but with the merge on 3 having the rename
on the remote parent:

  $ cd ..
  $ hg clone -U -r 1 -r 2 a b
  adding changesets
  adding manifests
  adding file changes
  added 3 changesets with 3 changes to 2 files (+1 heads)
  new changesets 2665aaee66e9:0f2ff26688b9
  $ cd b

  $ hg up -C 1
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved

  $ hg merge 2
  merging foo and bar to bar
  0 files updated, 1 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)

  $ cat bar
  line0
  line1
  line2

  $ hg ci -m '3: merge with remote rename'

  $ hg debugindex bar
     rev linkrev nodeid       p1           p2
       0       2 d35118874825 000000000000 000000000000
       1       3 5345f5ab8abd 000000000000 d35118874825

  $ hg debugrename bar
  bar renamed from foo:9e25c27b87571a1edee5ae4dddee5687746cc8e2

  $ hg debugindex foo
     rev linkrev nodeid       p1           p2
       0       0 690b295714ae 000000000000 000000000000
       1       1 9e25c27b8757 690b295714ae 000000000000


Revert the content change from rev 2:

  $ hg up -C 2
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ rm bar
  $ echo line1 > bar
  $ hg ci -m '4: revert content change from rev 2'
  created new head

  $ hg log --template '{rev}:{node|short} {parents}\n'
  4:2263c1be0967 2:0f2ff26688b9 
  3:3ffa6b9e35f0 1:5cd961e4045d 2:0f2ff26688b9 
  2:0f2ff26688b9 0:2665aaee66e9 
  1:5cd961e4045d 
  0:2665aaee66e9 

This should use bar@rev2 as the ancestor:

  $ hg --debug merge 3
    searching for copies back to rev 1
  resolving manifests
   branchmerge: True, force: False, partial: False
   ancestor: 0f2ff26688b9, local: 2263c1be0967+, remote: 3ffa6b9e35f0
   preserving bar for resolve of bar
  starting 4 threads for background file closing (?)
   bar: versions differ -> m (premerge)
  picked tool ':merge' for bar (binary False symlink False changedelete False)
  merging bar
  my bar@2263c1be0967+ other bar@3ffa6b9e35f0 ancestor bar@0f2ff26688b9
   premerge successful
  0 files updated, 1 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)

  $ cat bar
  line1
  line2

  $ hg ci -m '5: merge'

  $ hg debugindex bar
     rev linkrev nodeid       p1           p2
       0       2 d35118874825 000000000000 000000000000
       1       3 5345f5ab8abd 000000000000 d35118874825
       2       4 ff4b45017382 d35118874825 000000000000
       3       5 3701b4893544 ff4b45017382 5345f5ab8abd

  $ cd ..