view tests/test-convert-clonebranches.t @ 39561:d06834e0f48e

wireprotov2peer: stream decoded responses

Previously, wire protocol version 2 would buffer all response data.
Only once all data was received did we CBOR decode it and resolve
the future associated with the command. This was obviously not
desirable. In future commits that introduce large response payloads,
this caused significant memory bloat and slowed down client
operations due to waiting on the server.

This commit refactors the response handling code so that response
data can be streamed.

Command response objects now contain a buffered CBOR decoder. As
new data arrives, it is fed into the decoder. Decoded objects are
made available to the generator as they are decoded.

Because there is a separate thread processing incoming frames and
feeding data into the response object, there is the potential for
race conditions when mutating response objects. So a lock has been
added to guard access to critical state variables.

Because the generator emitting decoded objects needs to wait on
those objects to become available, we've added an Event for the
generator to wait on so it doesn't busy loop. This does mean
there is the potential for deadlocks. And I'm pretty sure they can
occur in some scenarios. We already have a handful of TODOs around
this. But I've added some more. Fixing this will likely require
moving the background thread receiving frames into clienthandler.
We likely would have done this anyway when implementing the client
bits for the SSH transport.

Test output changes because the initial CBOR map holding the overall
response state is now always handled internally by the response
object.

Differential Revision: https://phab.mercurial-scm.org/D4474

  $ cat <<EOF >> $HGRCPATH
  > [extensions]
  > convert =
  > [convert]
  > hg.tagsbranch = 0
  > EOF
  $ hg init source
  $ cd source
  $ echo a > a
  $ hg ci -qAm adda

Add a merge with one parent in the same branch

  $ echo a >> a
  $ hg ci -qAm changea
  $ hg up -qC 0
  $ hg branch branch0
  marked working directory as branch branch0
  (branches are permanent and global, did you want a bookmark?)
  $ echo b > b
  $ hg ci -qAm addb
  $ hg up -qC
  $ hg merge default
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  $ hg ci -qm mergeab
  $ hg tag -ql mergeab
  $ cd ..

Miss perl... sometimes

  $ cat > filter.py <<EOF
  > from __future__ import absolute_import
  > import re
  > import sys
  > 
  > r = re.compile(r'^(?:\d+|pulling from)')
  > sys.stdout.writelines([l for l in sys.stdin if r.search(l)])
  > EOF

convert

  $ hg convert -v --config convert.hg.clonebranches=1 source dest |
  >     $PYTHON filter.py
  3 adda
  2 changea
  1 addb
  pulling from default into branch0
  1 changesets found
  0 mergeab
  pulling from default into branch0
  1 changesets found

Add a merge with both parents and child in different branches

  $ cd source
  $ hg branch branch1
  marked working directory as branch branch1
  $ echo a > file1
  $ hg ci -qAm c1
  $ hg up -qC mergeab
  $ hg branch branch2
  marked working directory as branch branch2
  $ echo a > file2
  $ hg ci -qAm c2
  $ hg merge branch1
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  $ hg branch branch3
  marked working directory as branch branch3
  $ hg ci -qAm c3
  $ cd ..

incremental conversion

  $ hg convert -v --config convert.hg.clonebranches=1 source dest |
  >     $PYTHON filter.py
  2 c1
  pulling from branch0 into branch1
  4 changesets found
  1 c2
  pulling from branch0 into branch2
  4 changesets found
  0 c3
  pulling from branch1 into branch3
  5 changesets found
  pulling from branch2 into branch3
  1 changesets found