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
$ cat >> $HGRCPATH << EOF
> [extensions]
> show =
> EOF
$ hg init repo0
$ cd repo0
Command works on an empty repo
$ hg show work
Single draft changeset shown
$ echo 0 > foo
$ hg -q commit -A -m 'commit 0'
$ hg show work
@ 9f17 commit 0
Even when it isn't the wdir
$ hg -q up null
$ hg show work
o 9f17 commit 0
Single changeset is still there when public because it is a head
$ hg phase --public -r 0
$ hg show work
o 9f17 commit 0
A draft child will show both it and public parent
$ hg -q up 0
$ echo 1 > foo
$ hg commit -m 'commit 1'
$ hg show work
@ 181c commit 1
o 9f17 commit 0
Multiple draft children will be shown
$ echo 2 > foo
$ hg commit -m 'commit 2'
$ hg show work
@ 128c commit 2
o 181c commit 1
o 9f17 commit 0
Bumping first draft changeset to public will hide its parent
$ hg phase --public -r 1
$ hg show work
@ 128c commit 2
o 181c commit 1
|
~
Multiple DAG heads will be shown
$ hg -q up -r 1
$ echo 3 > foo
$ hg commit -m 'commit 3'
created new head
$ hg show work
@ f0ab commit 3
| o 128c commit 2
|/
o 181c commit 1
|
~
Even when wdir is something else
$ hg -q up null
$ hg show work
o f0ab commit 3
| o 128c commit 2
|/
o 181c commit 1
|
~
Draft child shows public head (multiple heads)
$ hg -q up 0
$ echo 4 > foo
$ hg commit -m 'commit 4'
created new head
$ hg show work
@ 668c commit 4
| o f0ab commit 3
| | o 128c commit 2
| |/
| o 181c commit 1
|/
o 9f17 commit 0
$ cd ..
Branch name appears in output
$ hg init branches
$ cd branches
$ echo 0 > foo
$ hg -q commit -A -m 'commit 0'
$ echo 1 > foo
$ hg commit -m 'commit 1'
$ echo 2 > foo
$ hg commit -m 'commit 2'
$ hg phase --public -r .
$ hg -q up -r 1
$ hg branch mybranch
marked working directory as branch mybranch
(branches are permanent and global, did you want a bookmark?)
$ echo 3 > foo
$ hg commit -m 'commit 3'
$ echo 4 > foo
$ hg commit -m 'commit 4'
$ hg show work
@ f8dd (mybranch) commit 4
o 90cf (mybranch) commit 3
| o 128c commit 2
|/
o 181c commit 1
|
~
$ cd ..
Bookmark name appears in output
$ hg init bookmarks
$ cd bookmarks
$ echo 0 > foo
$ hg -q commit -A -m 'commit 0'
$ echo 1 > foo
$ hg commit -m 'commit 1'
$ echo 2 > foo
$ hg commit -m 'commit 2'
$ hg phase --public -r .
$ hg bookmark @
$ hg -q up -r 1
$ echo 3 > foo
$ hg commit -m 'commit 3'
created new head
$ echo 4 > foo
$ hg commit -m 'commit 4'
$ hg bookmark mybook
$ hg show work
@ cac8 (mybook) commit 4
o f0ab commit 3
| o 128c (@) commit 2
|/
o 181c commit 1
|
~
$ cd ..
Tags are rendered
$ hg init tags
$ cd tags
$ echo 0 > foo
$ hg -q commit -A -m 'commit 1'
$ echo 1 > foo
$ hg commit -m 'commit 2'
$ hg tag 0.1
$ hg phase --public -r .
$ echo 2 > foo
$ hg commit -m 'commit 3'
$ hg tag 0.2
$ hg show work
@ 3758 Added tag 0.2 for changeset 6379c25b76f1
o 6379 (0.2) commit 3
o a2ad Added tag 0.1 for changeset 6a75536ea0b1
|
~
$ cd ..
Multiple names on same changeset render properly
$ hg init multiplenames
$ cd multiplenames
$ echo 0 > foo
$ hg -q commit -A -m 'commit 1'
$ hg phase --public -r .
$ hg branch mybranch
marked working directory as branch mybranch
(branches are permanent and global, did you want a bookmark?)
$ hg bookmark mybook
$ echo 1 > foo
$ hg commit -m 'commit 2'
$ hg show work
@ 3483 (mybook) (mybranch) commit 2
o 97fc commit 1
Multiple bookmarks on same changeset render properly
$ hg book mybook2
$ hg show work
@ 3483 (mybook mybook2) (mybranch) commit 2
o 97fc commit 1
$ cd ..
Extra namespaces are rendered
$ hg init extranamespaces
$ cd extranamespaces
$ echo 0 > foo
$ hg -q commit -A -m 'commit 1'
$ hg phase --public -r .
$ echo 1 > foo
$ hg commit -m 'commit 2'
$ echo 2 > foo
$ hg commit -m 'commit 3'
$ hg --config extensions.revnames=$TESTDIR/revnamesext.py show work
@ 32f3 (r2) commit 3
o 6a75 (r1) commit 2
o 97fc (r0) commit 1
Obsolescence information appears in labels.
$ cat >> .hg/hgrc << EOF
> [experimental]
> evolution=createmarkers
> EOF
$ hg debugobsolete `hg log -r 'desc("commit 2")' -T "{node}"`
obsoleted 1 changesets
1 new orphan changesets
$ hg show work --color=debug
@ [log.changeset changeset.draft changeset.unstable instability.orphan|32f3] [log.description|commit 3]
x [log.changeset changeset.draft changeset.obsolete|6a75] [log.description|commit 2]
|
~
$ cd ..
Prefix collision on hashes increases shortest node length
$ hg init hashcollision
$ cd hashcollision
$ echo 0 > a
$ hg -q commit -Am 0
$ for i in 17 1057 2857 4025; do
> hg -q up 0
> echo $i > a
> hg -q commit -m $i
> echo 0 > a
> hg commit -m "$i commit 2"
> done
$ hg show work
@ cfd04 4025 commit 2
o c562d 4025
| o 08048 2857 commit 2
| o c5623 2857
|/
| o 6a6b6 1057 commit 2
| o c5625 1057
|/
| o 96b4e 17 commit 2
| o 11424 17
|/
o b4e73 0
$ cd ..