tests/test-bundle2-multiple-changegroups.t

py3: make stdout line-buffered if connected to a TTY

Status messages that are to be shown on the terminal should be written to the
file descriptor before anything further is done, to keep the user updated.

One common way to achieve this is to make stdout line-buffered if it is
connected to a TTY. This is done on Python 2 (except on Windows, where libc,
which the CPython 2 streams depend on, does not properly support this).

Python 3 rolls it own I/O streams. On Python 3, buffered binary streams can't be
set line-buffered. The previous code (added in 227ba1afcb65) incorrectly
assumed that on Python 3, pycompat.stdout (sys.stdout.buffer) is already
line-buffered. However the interpreter initializes it with a block-buffered
stream or an unbuffered stream (when the -u option or the PYTHONUNBUFFERED
environment variable is set), never with a line-buffered stream.

One example where the current behavior is unacceptable is when running
`hg pull https://www.mercurial-scm.org/repo/hg` on Python 3, where the line
"pulling from https://www.mercurial-scm.org/repo/hg" does not appear on the
terminal before the hg process blocks while waiting for the server.

Various approaches to fix this problem are possible, including:

1. Weaken the contract of procutil.stdout to not give any guarantees about
   buffering behavior. In this case, users of procutil.stdout need to be
   changed to do enough flushes. In particular,
  1. either ui must insert enough flushes for ui.write() and friends, or
  2. ui.write() and friends get split into flushing and fully buffered
     methods, or
  3. users of ui.write() and friends must flush explicitly.
2. Make stdout unbuffered.
3. Make stdout line-buffered. Since Python 3 does not natively support that for
   binary streams, we must implement it ourselves.

(2.) is problematic because using unbuffered I/O changes the performance
characteristics significantly compared to line-buffered (which is used on
Python 2) and this would be a regression.

(1.2.) and (1.3) are a substantial amount of work. It’s unclear whether the
added complexity would be justified, given that raw performance doesn’t matter
that much when writing to a terminal much faster than the user could read it.

(1.1.) pushes complexity into the ui class instead of separating the concern of
how stdout is buffered. Other users of procutil.stdout would still need to take
care of the flushes.

This patch implements (3.). The general performance considerations are very
similar to (1.1.). The extra method invocation and method forwarding add a
little more overhead if the class is used. In exchange, it doesn’t add overhead
if not used.


For the benchmarks, I compared the previous implementation (incorrect on Python
3), (1.1.), (3.) and (2.). The command was chosen so that the streams were
configured as if they were writing to a TTY, but actually write to a pager,
which is also the default:
HGRCPATH=/dev/null python3 ./hg --cwd ~/vcs/mozilla-central --time --pager yes --config pager.pager='cat > /dev/null' status --all

previous:
time: real 7.880 secs (user 7.290+0.050 sys 0.580+0.170)
time: real 7.830 secs (user 7.220+0.070 sys 0.590+0.140)
time: real 7.800 secs (user 7.210+0.050 sys 0.570+0.170)

(1.1.) using Yuya Nishihara’s patch:
time: real 9.860 secs (user 8.670+0.350 sys 1.160+0.830)
time: real 9.540 secs (user 8.430+0.370 sys 1.100+0.770)
time: real 9.830 secs (user 8.630+0.370 sys 1.180+0.840)

(3.) using this patch:
time: real 9.580 secs (user 8.480+0.350 sys 1.090+0.770)
time: real 9.670 secs (user 8.480+0.330 sys 1.170+0.860)
time: real 9.640 secs (user 8.500+0.350 sys 1.130+0.810)

(2.) using a previous patch by me:
time: real 10.480 secs (user 8.850+0.720 sys 1.590+1.500)
time: real 10.490 secs (user 8.750+0.750 sys 1.710+1.470)
time: real 10.240 secs (user 8.600+0.700 sys 1.590+1.510)


As expected, there’s no difference on Python 2, as exactly the same code paths
are used:

previous:
time: real 6.950 secs (user 5.870+0.330 sys 1.070+0.770)
time: real 7.040 secs (user 6.040+0.360 sys 0.980+0.750)
time: real 7.070 secs (user 5.950+0.360 sys 1.100+0.760)

this patch:
time: real 7.010 secs (user 5.900+0.390 sys 1.070+0.730)
time: real 7.000 secs (user 5.850+0.350 sys 1.120+0.760)
time: real 7.000 secs (user 5.790+0.380 sys 1.170+0.710)

Create an extension to test bundle2 with multiple changegroups

  $ cat > bundle2.py <<EOF
  > """
  > """
  > from mercurial import changegroup, discovery, exchange
  > 
  > def _getbundlechangegrouppart(bundler, repo, source, bundlecaps=None,
  >                               b2caps=None, heads=None, common=None,
  >                               **kwargs):
  >     # Create two changegroups given the common changesets and heads for the
  >     # changegroup part we are being requested. Use the parent of each head
  >     # in 'heads' as intermediate heads for the first changegroup.
  >     intermediates = [repo[r].p1().node() for r in heads]
  >     outgoing = discovery.outgoing(repo, common, intermediates)
  >     cg = changegroup.makechangegroup(repo, outgoing, b'01',
  >                                      source, bundlecaps=bundlecaps)
  >     bundler.newpart(b'output', data=b'changegroup1')
  >     bundler.newpart(b'changegroup', data=cg.getchunks())
  >     outgoing = discovery.outgoing(repo, common + intermediates, heads)
  >     cg = changegroup.makechangegroup(repo, outgoing, b'01',
  >                                      source, bundlecaps=bundlecaps)
  >     bundler.newpart(b'output', data=b'changegroup2')
  >     bundler.newpart(b'changegroup', data=cg.getchunks())
  > 
  > def _pull(repo, *args, **kwargs):
  >   pullop = _orig_pull(repo, *args, **kwargs)
  >   repo.ui.write(b'pullop.cgresult is %d\n' % pullop.cgresult)
  >   return pullop
  > 
  > _orig_pull = exchange.pull
  > exchange.pull = _pull
  > exchange.getbundle2partsmapping[b'changegroup'] = _getbundlechangegrouppart
  > EOF

  $ cat >> $HGRCPATH << EOF
  > [ui]
  > logtemplate={rev}:{node|short} {phase} {author} {bookmarks} {desc|firstline}
  > EOF

Start with a simple repository with a single commit

  $ hg init repo
  $ cd repo
  $ cat > .hg/hgrc << EOF
  > [extensions]
  > bundle2=$TESTTMP/bundle2.py
  > EOF

  $ echo A > A
  $ hg commit -A -m A -q
  $ cd ..

Clone

  $ hg clone -q repo clone

Add two linear commits

  $ cd repo
  $ echo B > B
  $ hg commit -A -m B -q
  $ echo C > C
  $ hg commit -A -m C -q

  $ cd ../clone
  $ cat >> .hg/hgrc <<EOF
  > [hooks]
  > pretxnchangegroup = sh -c "printenv.py --line pretxnchangegroup"
  > changegroup = sh -c "printenv.py --line changegroup"
  > incoming = sh -c "printenv.py --line incoming"
  > EOF

Pull the new commits in the clone

  $ hg pull
  pulling from $TESTTMP/repo
  searching for changes
  remote: changegroup1
  adding changesets
  adding manifests
  adding file changes
  pretxnchangegroup hook: HG_HOOKNAME=pretxnchangegroup
  HG_HOOKTYPE=pretxnchangegroup
  HG_NODE=27547f69f25460a52fff66ad004e58da7ad3fb56
  HG_NODE_LAST=27547f69f25460a52fff66ad004e58da7ad3fb56
  HG_PENDING=$TESTTMP/clone
  HG_SOURCE=pull
  HG_TXNID=TXN:$ID$
  HG_TXNNAME=pull
  file:/*/$TESTTMP/repo (glob)
  HG_URL=file:$TESTTMP/repo
  
  remote: changegroup2
  adding changesets
  adding manifests
  adding file changes
  pretxnchangegroup hook: HG_HOOKNAME=pretxnchangegroup
  HG_HOOKTYPE=pretxnchangegroup
  HG_NODE=f838bfaca5c7226600ebcfd84f3c3c13a28d3757
  HG_NODE_LAST=f838bfaca5c7226600ebcfd84f3c3c13a28d3757
  HG_PENDING=$TESTTMP/clone
  HG_PHASES_MOVED=1
  HG_SOURCE=pull
  HG_TXNID=TXN:$ID$
  HG_TXNNAME=pull
  file:/*/$TESTTMP/repo (glob)
  HG_URL=file:$TESTTMP/repo
  
  added 2 changesets with 2 changes to 2 files
  new changesets 27547f69f254:f838bfaca5c7
  changegroup hook: HG_HOOKNAME=changegroup
  HG_HOOKTYPE=changegroup
  HG_NODE=27547f69f25460a52fff66ad004e58da7ad3fb56
  HG_NODE_LAST=27547f69f25460a52fff66ad004e58da7ad3fb56
  HG_SOURCE=pull
  HG_TXNID=TXN:$ID$
  HG_TXNNAME=pull
  file:/*/$TESTTMP/repo (glob)
  HG_URL=file:$TESTTMP/repo
  
  incoming hook: HG_HOOKNAME=incoming
  HG_HOOKTYPE=incoming
  HG_NODE=27547f69f25460a52fff66ad004e58da7ad3fb56
  HG_SOURCE=pull
  HG_TXNID=TXN:$ID$
  HG_TXNNAME=pull
  file:/*/$TESTTMP/repo (glob)
  HG_URL=file:$TESTTMP/repo
  
  changegroup hook: HG_HOOKNAME=changegroup
  HG_HOOKTYPE=changegroup
  HG_NODE=f838bfaca5c7226600ebcfd84f3c3c13a28d3757
  HG_NODE_LAST=f838bfaca5c7226600ebcfd84f3c3c13a28d3757
  HG_PHASES_MOVED=1
  HG_SOURCE=pull
  HG_TXNID=TXN:$ID$
  HG_TXNNAME=pull
  file:/*/$TESTTMP/repo (glob)
  HG_URL=file:$TESTTMP/repo
  
  incoming hook: HG_HOOKNAME=incoming
  HG_HOOKTYPE=incoming
  HG_NODE=f838bfaca5c7226600ebcfd84f3c3c13a28d3757
  HG_PHASES_MOVED=1
  HG_SOURCE=pull
  HG_TXNID=TXN:$ID$
  HG_TXNNAME=pull
  file:/*/$TESTTMP/repo (glob)
  HG_URL=file:$TESTTMP/repo
  
  pullop.cgresult is 1
  (run 'hg update' to get a working copy)
  $ hg update
  2 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ hg log -G
  @  2:f838bfaca5c7 public test  C
  |
  o  1:27547f69f254 public test  B
  |
  o  0:4a2df7238c3b public test  A
  
Add more changesets with multiple heads to the original repository

  $ cd ../repo
  $ echo D > D
  $ hg commit -A -m D -q
  $ hg up -r 1
  0 files updated, 0 files merged, 2 files removed, 0 files unresolved
  $ echo E > E
  $ hg commit -A -m E -q
  $ echo F > F
  $ hg commit -A -m F -q
  $ hg up -r 1
  0 files updated, 0 files merged, 2 files removed, 0 files unresolved
  $ echo G > G
  $ hg commit -A -m G -q
  $ hg up -r 3
  2 files updated, 0 files merged, 1 files removed, 0 files unresolved
  $ echo H > H
  $ hg commit -A -m H -q
  $ hg log -G
  @  7:5cd59d311f65 draft test  H
  |
  | o  6:1d14c3ce6ac0 draft test  G
  | |
  | | o  5:7f219660301f draft test  F
  | | |
  | | o  4:8a5212ebc852 draft test  E
  | |/
  o |  3:b3325c91a4d9 draft test  D
  | |
  o |  2:f838bfaca5c7 draft test  C
  |/
  o  1:27547f69f254 draft test  B
  |
  o  0:4a2df7238c3b draft test  A
  
New heads are reported during transfer and properly accounted for in
pullop.cgresult

  $ cd ../clone
  $ hg pull
  pulling from $TESTTMP/repo
  searching for changes
  remote: changegroup1
  adding changesets
  adding manifests
  adding file changes
  pretxnchangegroup hook: HG_HOOKNAME=pretxnchangegroup
  HG_HOOKTYPE=pretxnchangegroup
  HG_NODE=b3325c91a4d916bcc4cdc83ea3fe4ece46a42f6e
  HG_NODE_LAST=8a5212ebc8527f9fb821601504794e3eb11a1ed3
  HG_PENDING=$TESTTMP/clone
  HG_SOURCE=pull
  HG_TXNID=TXN:$ID$
  HG_TXNNAME=pull
  file:/*/$TESTTMP/repo (glob)
  HG_URL=file:$TESTTMP/repo
  
  remote: changegroup2
  adding changesets
  adding manifests
  adding file changes
  pretxnchangegroup hook: HG_HOOKNAME=pretxnchangegroup
  HG_HOOKTYPE=pretxnchangegroup
  HG_NODE=7f219660301fe4c8a116f714df5e769695cc2b46
  HG_NODE_LAST=5cd59d311f6508b8e0ed28a266756c859419c9f1
  HG_PENDING=$TESTTMP/clone
  HG_PHASES_MOVED=1
  HG_SOURCE=pull
  HG_TXNID=TXN:$ID$
  HG_TXNNAME=pull
  file:/*/$TESTTMP/repo (glob)
  HG_URL=file:$TESTTMP/repo
  
  added 5 changesets with 5 changes to 5 files (+2 heads)
  new changesets b3325c91a4d9:5cd59d311f65
  changegroup hook: HG_HOOKNAME=changegroup
  HG_HOOKTYPE=changegroup
  HG_NODE=b3325c91a4d916bcc4cdc83ea3fe4ece46a42f6e
  HG_NODE_LAST=8a5212ebc8527f9fb821601504794e3eb11a1ed3
  HG_SOURCE=pull
  HG_TXNID=TXN:$ID$
  HG_TXNNAME=pull
  file:/*/$TESTTMP/repo (glob)
  HG_URL=file:$TESTTMP/repo
  
  incoming hook: HG_HOOKNAME=incoming
  HG_HOOKTYPE=incoming
  HG_NODE=b3325c91a4d916bcc4cdc83ea3fe4ece46a42f6e
  HG_SOURCE=pull
  HG_TXNID=TXN:$ID$
  HG_TXNNAME=pull
  file:/*/$TESTTMP/repo (glob)
  HG_URL=file:$TESTTMP/repo
  
  incoming hook: HG_HOOKNAME=incoming
  HG_HOOKTYPE=incoming
  HG_NODE=8a5212ebc8527f9fb821601504794e3eb11a1ed3
  HG_SOURCE=pull
  HG_TXNID=TXN:$ID$
  HG_TXNNAME=pull
  file:/*/$TESTTMP/repo (glob)
  HG_URL=file:$TESTTMP/repo
  
  changegroup hook: HG_HOOKNAME=changegroup
  HG_HOOKTYPE=changegroup
  HG_NODE=7f219660301fe4c8a116f714df5e769695cc2b46
  HG_NODE_LAST=5cd59d311f6508b8e0ed28a266756c859419c9f1
  HG_PHASES_MOVED=1
  HG_SOURCE=pull
  HG_TXNID=TXN:$ID$
  HG_TXNNAME=pull
  file:/*/$TESTTMP/repo (glob)
  HG_URL=file:$TESTTMP/repo
  
  incoming hook: HG_HOOKNAME=incoming
  HG_HOOKTYPE=incoming
  HG_NODE=7f219660301fe4c8a116f714df5e769695cc2b46
  HG_PHASES_MOVED=1
  HG_SOURCE=pull
  HG_TXNID=TXN:$ID$
  HG_TXNNAME=pull
  file:/*/$TESTTMP/repo (glob)
  HG_URL=file:$TESTTMP/repo
  
  incoming hook: HG_HOOKNAME=incoming
  HG_HOOKTYPE=incoming
  HG_NODE=1d14c3ce6ac0582d2809220d33e8cd7a696e0156
  HG_PHASES_MOVED=1
  HG_SOURCE=pull
  HG_TXNID=TXN:$ID$
  HG_TXNNAME=pull
  file:/*/$TESTTMP/repo (glob)
  HG_URL=file:$TESTTMP/repo
  
  incoming hook: HG_HOOKNAME=incoming
  HG_HOOKTYPE=incoming
  HG_NODE=5cd59d311f6508b8e0ed28a266756c859419c9f1
  HG_PHASES_MOVED=1
  HG_SOURCE=pull
  HG_TXNID=TXN:$ID$
  HG_TXNNAME=pull
  file:/*/$TESTTMP/repo (glob)
  HG_URL=file:$TESTTMP/repo
  
  pullop.cgresult is 3
  (run 'hg heads' to see heads, 'hg merge' to merge)
  $ hg log -G
  o  7:5cd59d311f65 public test  H
  |
  | o  6:1d14c3ce6ac0 public test  G
  | |
  | | o  5:7f219660301f public test  F
  | | |
  | | o  4:8a5212ebc852 public test  E
  | |/
  o |  3:b3325c91a4d9 public test  D
  | |
  @ |  2:f838bfaca5c7 public test  C
  |/
  o  1:27547f69f254 public test  B
  |
  o  0:4a2df7238c3b public test  A
  
Removing a head from the original repository by merging it

  $ cd ../repo
  $ hg merge -r 6 -q
  $ hg commit -m Merge
  $ echo I > I
  $ hg commit -A -m H -q
  $ hg log -G
  @  9:9d18e5bd9ab0 draft test  H
  |
  o    8:71bd7b46de72 draft test  Merge
  |\
  | o  7:5cd59d311f65 draft test  H
  | |
  o |  6:1d14c3ce6ac0 draft test  G
  | |
  | | o  5:7f219660301f draft test  F
  | | |
  +---o  4:8a5212ebc852 draft test  E
  | |
  | o  3:b3325c91a4d9 draft test  D
  | |
  | o  2:f838bfaca5c7 draft test  C
  |/
  o  1:27547f69f254 draft test  B
  |
  o  0:4a2df7238c3b draft test  A
  
Removed heads are reported during transfer and properly accounted for in
pullop.cgresult

  $ cd ../clone
  $ hg pull
  pulling from $TESTTMP/repo
  searching for changes
  remote: changegroup1
  adding changesets
  adding manifests
  adding file changes
  pretxnchangegroup hook: HG_HOOKNAME=pretxnchangegroup
  HG_HOOKTYPE=pretxnchangegroup
  HG_NODE=71bd7b46de72e69a32455bf88d04757d542e6cf4
  HG_NODE_LAST=71bd7b46de72e69a32455bf88d04757d542e6cf4
  HG_PENDING=$TESTTMP/clone
  HG_SOURCE=pull
  HG_TXNID=TXN:$ID$
  HG_TXNNAME=pull
  file:/*/$TESTTMP/repo (glob)
  HG_URL=file:$TESTTMP/repo
  
  remote: changegroup2
  adding changesets
  adding manifests
  adding file changes
  pretxnchangegroup hook: HG_HOOKNAME=pretxnchangegroup
  HG_HOOKTYPE=pretxnchangegroup
  HG_NODE=9d18e5bd9ab09337802595d49f1dad0c98df4d84
  HG_NODE_LAST=9d18e5bd9ab09337802595d49f1dad0c98df4d84
  HG_PENDING=$TESTTMP/clone
  HG_PHASES_MOVED=1
  HG_SOURCE=pull
  HG_TXNID=TXN:$ID$
  HG_TXNNAME=pull
  file:/*/$TESTTMP/repo (glob)
  HG_URL=file:$TESTTMP/repo
  
  added 2 changesets with 1 changes to 1 files (-1 heads)
  new changesets 71bd7b46de72:9d18e5bd9ab0
  changegroup hook: HG_HOOKNAME=changegroup
  HG_HOOKTYPE=changegroup
  HG_NODE=71bd7b46de72e69a32455bf88d04757d542e6cf4
  HG_NODE_LAST=71bd7b46de72e69a32455bf88d04757d542e6cf4
  HG_SOURCE=pull
  HG_TXNID=TXN:$ID$
  HG_TXNNAME=pull
  file:/*/$TESTTMP/repo (glob)
  HG_URL=file:$TESTTMP/repo
  
  incoming hook: HG_HOOKNAME=incoming
  HG_HOOKTYPE=incoming
  HG_NODE=71bd7b46de72e69a32455bf88d04757d542e6cf4
  HG_SOURCE=pull
  HG_TXNID=TXN:$ID$
  HG_TXNNAME=pull
  file:/*/$TESTTMP/repo (glob)
  HG_URL=file:$TESTTMP/repo
  
  changegroup hook: HG_HOOKNAME=changegroup
  HG_HOOKTYPE=changegroup
  HG_NODE=9d18e5bd9ab09337802595d49f1dad0c98df4d84
  HG_NODE_LAST=9d18e5bd9ab09337802595d49f1dad0c98df4d84
  HG_PHASES_MOVED=1
  HG_SOURCE=pull
  HG_TXNID=TXN:$ID$
  HG_TXNNAME=pull
  file:/*/$TESTTMP/repo (glob)
  HG_URL=file:$TESTTMP/repo
  
  incoming hook: HG_HOOKNAME=incoming
  HG_HOOKTYPE=incoming
  HG_NODE=9d18e5bd9ab09337802595d49f1dad0c98df4d84
  HG_PHASES_MOVED=1
  HG_SOURCE=pull
  HG_TXNID=TXN:$ID$
  HG_TXNNAME=pull
  file:/*/$TESTTMP/repo (glob)
  HG_URL=file:$TESTTMP/repo
  
  pullop.cgresult is -2
  (run 'hg update' to get a working copy)
  $ hg log -G
  o  9:9d18e5bd9ab0 public test  H
  |
  o    8:71bd7b46de72 public test  Merge
  |\
  | o  7:5cd59d311f65 public test  H
  | |
  o |  6:1d14c3ce6ac0 public test  G
  | |
  | | o  5:7f219660301f public test  F
  | | |
  +---o  4:8a5212ebc852 public test  E
  | |
  | o  3:b3325c91a4d9 public test  D
  | |
  | @  2:f838bfaca5c7 public test  C
  |/
  o  1:27547f69f254 public test  B
  |
  o  0:4a2df7238c3b public test  A