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
This test test the low-level definition of stack, agnostic from all formatting
Initial setup
$ cat << EOF >> $HGRCPATH
> [ui]
> logtemplate = {rev} {branch} {phase} {desc|firstline}\n
> [extensions]
> rebase=
> [experimental]
> evolution=createmarkers,exchange,allowunstable
> EOF
$ hg init main
$ cd main
$ hg branch other
marked working directory as branch other
(branches are permanent and global, did you want a bookmark?)
$ echo aaa > aaa
$ hg add aaa
$ hg commit -m c_a
$ echo aaa > bbb
$ hg add bbb
$ hg commit -m c_b
$ hg branch foo
marked working directory as branch foo
$ echo aaa > ccc
$ hg add ccc
$ hg commit -m c_c
$ echo aaa > ddd
$ hg add ddd
$ hg commit -m c_d
$ echo aaa > eee
$ hg add eee
$ hg commit -m c_e
$ echo aaa > fff
$ hg add fff
$ hg commit -m c_f
$ hg log -G
@ 5 foo draft c_f
|
o 4 foo draft c_e
|
o 3 foo draft c_d
|
o 2 foo draft c_c
|
o 1 other draft c_b
|
o 0 other draft c_a
Check that stack doesn't include public changesets
--------------------------------------------------
$ hg up other
0 files updated, 0 files merged, 4 files removed, 0 files unresolved
$ hg log -G -r "stack()"
@ 1 other draft c_b
|
o 0 other draft c_a
$ hg phase --public 'branch("other")'
$ hg log -G -r "stack()"
$ hg up foo
4 files updated, 0 files merged, 0 files removed, 0 files unresolved
Simple test
-----------
'stack()' list all changeset in the branch
$ hg branch
foo
$ hg log -G -r "stack()"
@ 5 foo draft c_f
|
o 4 foo draft c_e
|
o 3 foo draft c_d
|
o 2 foo draft c_c
|
~
Case with some of the branch unstable
------------------------------------
$ hg up 3
0 files updated, 0 files merged, 2 files removed, 0 files unresolved
$ echo bbb > ddd
$ hg commit --amend
2 new orphan changesets
$ hg log -G
@ 6 foo draft c_d
|
| * 5 foo draft c_f
| |
| * 4 foo draft c_e
| |
| x 3 foo draft c_d
|/
o 2 foo draft c_c
|
o 1 other public c_b
|
o 0 other public c_a
$ hg log -G -r "stack()"
@ 6 foo draft c_d
|
~
$ hg up -r "desc(c_e)"
2 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ hg log -G -r "stack()"
@ 4 foo draft c_e
|
x 3 foo draft c_d
|
~
$ hg up -r "desc(c_d)"
1 files updated, 0 files merged, 1 files removed, 0 files unresolved
$ hg log -G -r "stack()"
@ 6 foo draft c_d
|
~
Case with multiple topological heads
------------------------------------
Make things linear again
$ hg rebase -s 'desc(c_e)' -d 'desc(c_d) - obsolete()'
rebasing 4:4f2a69f6d380 "c_e"
rebasing 5:913c298d8b0a "c_f"
$ hg log -G
o 8 foo draft c_f
|
o 7 foo draft c_e
|
@ 6 foo draft c_d
|
o 2 foo draft c_c
|
o 1 other public c_b
|
o 0 other public c_a
Create the second branch
$ hg up 'desc(c_d)'
0 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ echo aaa > ggg
$ hg add ggg
$ hg commit -m c_g
created new head
$ echo aaa > hhh
$ hg add hhh
$ hg commit -m c_h
$ hg log -G
@ 10 foo draft c_h
|
o 9 foo draft c_g
|
| o 8 foo draft c_f
| |
| o 7 foo draft c_e
|/
o 6 foo draft c_d
|
o 2 foo draft c_c
|
o 1 other public c_b
|
o 0 other public c_a
Test output
$ hg log -G -r "stack(10)"
@ 10 foo draft c_h
|
o 9 foo draft c_g
|
~
$ hg log -G -r "stack(8)"
o 8 foo draft c_f
|
o 7 foo draft c_e
|
~
$ hg log -G -r "stack(head())"
@ 10 foo draft c_h
|
o 9 foo draft c_g
|
~
o 8 foo draft c_f
|
o 7 foo draft c_e
|
~
Check the stack order
$ hg log -r "first(stack())"
9 foo draft c_g
$ hg log -r "first(stack(10))"
9 foo draft c_g
$ hg log -r "first(stack(8))"
7 foo draft c_e
$ hg log -r "first(stack(head()))"
7 foo draft c_e
Case with multiple heads with unstability involved
--------------------------------------------------
We amend the message to make sure the display base pick the right changeset
$ hg up 'desc(c_d)'
0 files updated, 0 files merged, 2 files removed, 0 files unresolved
$ echo ccc > ddd
$ hg commit --amend -m 'c_D'
4 new orphan changesets
$ hg rebase -d . -s 'desc(c_g)'
rebasing 9:2ebb6e48ab8a "c_g"
rebasing 10:634f38e27a1d "c_h"
$ hg log -G
o 13 foo draft c_h
|
o 12 foo draft c_g
|
@ 11 foo draft c_D
|
| * 8 foo draft c_f
| |
| * 7 foo draft c_e
| |
| x 6 foo draft c_d
|/
o 2 foo draft c_c
|
o 1 other public c_b
|
o 0 other public c_a
We should improve stack definition to also show 12 and 13 here
$ hg log -G -r "stack()"
@ 11 foo draft c_D
|
~