view tests/test-narrow-patch.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

#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 ..

  $ hg 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

Can show patch touching paths outside

  $ hg log -p
  changeset:   2:* (glob)
  tag:         tip
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     modify outside
  
  
  changeset:   1:* (glob)
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     modify inside
  
  diff -r * -r * inside/f1 (glob)
  --- a/inside/f1	Thu Jan 01 00:00:00 1970 +0000
  +++ b/inside/f1	Thu Jan 01 00:00:00 1970 +0000
  @@ -1,1 +1,1 @@
  -inside
  +modified
  
  changeset:   0:* (glob)
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     initial
  
  diff -r 000000000000 -r * inside/f1 (glob)
  --- /dev/null	Thu Jan 01 00:00:00 1970 +0000
  +++ b/inside/f1	Thu Jan 01 00:00:00 1970 +0000
  @@ -0,0 +1,1 @@
  +inside
  

  $ hg status --rev 1 --rev 2

Can show copies inside the narrow clone

  $ hg cp inside/f1 inside/f2
  $ hg diff --git
  diff --git a/inside/f1 b/inside/f2
  copy from inside/f1
  copy to inside/f2