view tests/test-http-branchmap.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

#require killdaemons

  $ hgserve() {
  >     hg serve -a localhost -p $HGPORT1 -d --pid-file=hg.pid \
  >       -E errors.log -v $@ > startup.log
  >     # Grepping hg serve stdout would hang on Windows
  >     grep -v 'listening at' startup.log
  >     cat hg.pid >> "$DAEMON_PIDS"
  > }
  $ hg init a
  $ hg --encoding utf-8 -R a branch æ
  marked working directory as branch \xc3\xa6 (esc)
  (branches are permanent and global, did you want a bookmark?)
  $ echo foo > a/foo
  $ hg -R a ci -Am foo
  adding foo
  $ hgserve -R a --config web.push_ssl=False --config web.allow_push=* --encoding latin1
  $ hg --encoding utf-8 clone http://localhost:$HGPORT1 b
  requesting all changes
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 1 changes to 1 files
  new changesets 867c11ce77b8
  updating to branch \xc3\xa6 (esc)
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ hg --encoding utf-8 -R b log
  changeset:   0:867c11ce77b8
  branch:      \xc3\xa6 (esc)
  tag:         tip
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     foo
  
  $ echo bar >> b/foo
  $ hg -R b ci -m bar
  $ hg --encoding utf-8 -R b push
  pushing to http://localhost:$HGPORT1/
  searching for changes
  remote: adding changesets
  remote: adding manifests
  remote: adding file changes
  remote: added 1 changesets with 1 changes to 1 files
  $ hg -R a --encoding utf-8 log
  changeset:   1:58e7c90d67cb
  branch:      \xc3\xa6 (esc)
  tag:         tip
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     bar
  
  changeset:   0:867c11ce77b8
  branch:      \xc3\xa6 (esc)
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     foo
  
  $ killdaemons.py hg.pid

verify 7e7d56fe4833 (encoding fallback in branchmap to maintain compatibility with 1.3.x)

  $ cat <<EOF > oldhg
  > import sys
  > from mercurial import ui, hg, commands
  > 
  > class StdoutWrapper(object):
  >     def __init__(self, stdout):
  >         self._file = stdout
  > 
  >     def write(self, data):
  >         if data == b'47\n':
  >             # latin1 encoding is one %xx (3 bytes) shorter
  >             data = b'44\n'
  >         elif data.startswith(b'%C3%A6 '):
  >             # translate to latin1 encoding
  >             data = b'%%E6 %s' % data[7:]
  >         self._file.write(data)
  > 
  >     def __getattr__(self, name):
  >         return getattr(self._file, name)
  > 
  > sys.stdout = StdoutWrapper(getattr(sys.stdout, 'buffer', sys.stdout))
  > sys.stderr = StdoutWrapper(getattr(sys.stderr, 'buffer', sys.stderr))
  > 
  > myui = ui.ui.load()
  > repo = hg.repository(myui, b'a')
  > commands.serve(myui, repo, stdio=True, cmdserver=False)
  > EOF
  $ echo baz >> b/foo
  $ hg -R b ci -m baz
  $ hg push -R b -e "\"$PYTHON\" oldhg" ssh://dummy/ --encoding latin1
  pushing to ssh://dummy/
  searching for changes
  remote: adding changesets
  remote: adding manifests
  remote: adding file changes
  remote: added 1 changesets with 1 changes to 1 files