view tests/test-wireproto-command-manifestdata.t @ 44950:f9734b2d59cc

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)

  $ . $TESTDIR/wireprotohelpers.sh

  $ hg init server
  $ enablehttpv2 server
  $ cd server
  $ echo a0 > a
  $ echo b0 > b
  $ mkdir -p dir0/child0 dir0/child1 dir1
  $ echo c0 > dir0/c
  $ echo d0 > dir0/d
  $ echo e0 > dir0/child0/e
  $ echo f0 > dir0/child1/f
  $ hg -q commit -A -m 'commit 0'

  $ echo a1 > a
  $ echo d1 > dir0/d
  $ hg commit -m 'commit 1'
  $ echo f0 > dir0/child1/f
  $ hg commit -m 'commit 2'
  nothing changed
  [1]

  $ hg -q up -r 0
  $ echo a2 > a
  $ hg commit -m 'commit 3'
  created new head

  $ hg log -G -T '{rev}:{node} {desc}\n'
  @  2:c8757a2ffe552850d1e0dfe60d295ebf64c196d9 commit 3
  |
  | o  1:650165e803375748a94df471e5b58d85763e0b29 commit 1
  |/
  o  0:6d85ca1270b377d320098556ba5bfad34a9ee12d commit 0
  

  $ hg --debug debugindex -m
     rev linkrev nodeid                                   p1                                       p2
       0       0 1b175b595f022cfab5b809cc0ed551bd0b3ff5e4 0000000000000000000000000000000000000000 0000000000000000000000000000000000000000
       1       1 91e0bdbfb0dde0023fa063edc1445f207a22eac7 1b175b595f022cfab5b809cc0ed551bd0b3ff5e4 0000000000000000000000000000000000000000
       2       2 46a6721b5edaf0ea04b79a5cb3218854a4d2aba0 1b175b595f022cfab5b809cc0ed551bd0b3ff5e4 0000000000000000000000000000000000000000

  $ hg serve -p $HGPORT -d --pid-file hg.pid -E error.log
  $ cat hg.pid > $DAEMON_PIDS

Missing arguments is an error

  $ sendhttpv2peer << EOF
  > command manifestdata
  > EOF
  creating http peer for wire protocol version 2
  sending manifestdata command
  abort: missing required arguments: nodes, tree!
  [255]

  $ sendhttpv2peer << EOF
  > command manifestdata
  >     nodes eval:[]
  > EOF
  creating http peer for wire protocol version 2
  sending manifestdata command
  abort: missing required arguments: tree!
  [255]

Unknown node is an error

  $ sendhttpv2peer << EOF
  > command manifestdata
  >     nodes eval:[b'\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa']
  >     tree eval:b''
  > EOF
  creating http peer for wire protocol version 2
  sending manifestdata command
  abort: unknown node: \xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa! (esc)
  [255]

Fetching a single revision returns just metadata by default

  $ sendhttpv2peer << EOF
  > command manifestdata
  >     nodes eval:[b'\x46\xa6\x72\x1b\x5e\xda\xf0\xea\x04\xb7\x9a\x5c\xb3\x21\x88\x54\xa4\xd2\xab\xa0']
  >     tree eval:b''
  > EOF
  creating http peer for wire protocol version 2
  sending manifestdata command
  response: gen[
    {
      b'totalitems': 1
    },
    {
      b'node': b'F\xa6r\x1b^\xda\xf0\xea\x04\xb7\x9a\\\xb3!\x88T\xa4\xd2\xab\xa0'
    }
  ]

Requesting parents works

  $ sendhttpv2peer << EOF
  > command manifestdata
  >     nodes eval:[b'\x46\xa6\x72\x1b\x5e\xda\xf0\xea\x04\xb7\x9a\x5c\xb3\x21\x88\x54\xa4\xd2\xab\xa0']
  >     tree eval:b''
  >     fields eval:[b'parents']
  > EOF
  creating http peer for wire protocol version 2
  sending manifestdata command
  response: gen[
    {
      b'totalitems': 1
    },
    {
      b'node': b'F\xa6r\x1b^\xda\xf0\xea\x04\xb7\x9a\\\xb3!\x88T\xa4\xd2\xab\xa0',
      b'parents': [
        b'\x1b\x17[Y_\x02,\xfa\xb5\xb8\t\xcc\x0e\xd5Q\xbd\x0b?\xf5\xe4',
        b'\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00'
      ]
    }
  ]

Requesting revision data works
(haveparents defaults to false, so fulltext is emitted)

  $ sendhttpv2peer << EOF
  > command manifestdata
  >     nodes eval:[b'\x46\xa6\x72\x1b\x5e\xda\xf0\xea\x04\xb7\x9a\x5c\xb3\x21\x88\x54\xa4\xd2\xab\xa0']
  >     tree eval:b''
  >     fields eval:[b'revision']
  > EOF
  creating http peer for wire protocol version 2
  sending manifestdata command
  response: gen[
    {
      b'totalitems': 1
    },
    {
      b'fieldsfollowing': [
        [
          b'revision',
          292
        ]
      ],
      b'node': b'F\xa6r\x1b^\xda\xf0\xea\x04\xb7\x9a\\\xb3!\x88T\xa4\xd2\xab\xa0'
    },
    b'a\x000879345e39377229634b420c639454156726c6b6\nb\x00819e258d31a5e1606629f365bb902a1b21ee4216\ndir0/c\x00914445346a0ca0629bd47ceb5dfe07e4d4cf2501\ndir0/child0/e\x00bbba6c06b30f443d34ff841bc985c4d0827c6be4\ndir0/child1/f\x0012fc7dcd773b5a0a929ce195228083c6ddc9cec4\ndir0/d\x00538206dc971e521540d6843abfe6d16032f6d426\n'
  ]

haveparents=False yields same output

  $ sendhttpv2peer << EOF
  > command manifestdata
  >     nodes eval:[b'\x46\xa6\x72\x1b\x5e\xda\xf0\xea\x04\xb7\x9a\x5c\xb3\x21\x88\x54\xa4\xd2\xab\xa0']
  >     tree eval:b''
  >     fields eval:[b'revision']
  >     haveparents eval:False
  > EOF
  creating http peer for wire protocol version 2
  sending manifestdata command
  response: gen[
    {
      b'totalitems': 1
    },
    {
      b'fieldsfollowing': [
        [
          b'revision',
          292
        ]
      ],
      b'node': b'F\xa6r\x1b^\xda\xf0\xea\x04\xb7\x9a\\\xb3!\x88T\xa4\xd2\xab\xa0'
    },
    b'a\x000879345e39377229634b420c639454156726c6b6\nb\x00819e258d31a5e1606629f365bb902a1b21ee4216\ndir0/c\x00914445346a0ca0629bd47ceb5dfe07e4d4cf2501\ndir0/child0/e\x00bbba6c06b30f443d34ff841bc985c4d0827c6be4\ndir0/child1/f\x0012fc7dcd773b5a0a929ce195228083c6ddc9cec4\ndir0/d\x00538206dc971e521540d6843abfe6d16032f6d426\n'
  ]

haveparents=True will emit delta

  $ sendhttpv2peer << EOF
  > command manifestdata
  >     nodes eval:[b'\x46\xa6\x72\x1b\x5e\xda\xf0\xea\x04\xb7\x9a\x5c\xb3\x21\x88\x54\xa4\xd2\xab\xa0']
  >     tree eval:b''
  >     fields eval:[b'revision']
  >     haveparents eval:True
  > EOF
  creating http peer for wire protocol version 2
  sending manifestdata command
  response: gen[
    {
      b'totalitems': 1
    },
    {
      b'deltabasenode': b'\x1b\x17[Y_\x02,\xfa\xb5\xb8\t\xcc\x0e\xd5Q\xbd\x0b?\xf5\xe4',
      b'fieldsfollowing': [
        [
          b'delta',
          55
        ]
      ],
      b'node': b'F\xa6r\x1b^\xda\xf0\xea\x04\xb7\x9a\\\xb3!\x88T\xa4\xd2\xab\xa0'
    },
    b'\x00\x00\x00\x00\x00\x00\x00+\x00\x00\x00+a\x000879345e39377229634b420c639454156726c6b6\n'
  ]

Requesting multiple revisions works
(haveparents defaults to false, so fulltext is emitted unless a parent
has been emitted)

  $ sendhttpv2peer << EOF
  > command manifestdata
  >     nodes eval:[b'\x1b\x17\x5b\x59\x5f\x02\x2c\xfa\xb5\xb8\x09\xcc\x0e\xd5\x51\xbd\x0b\x3f\xf5\xe4', b'\x46\xa6\x72\x1b\x5e\xda\xf0\xea\x04\xb7\x9a\x5c\xb3\x21\x88\x54\xa4\xd2\xab\xa0']
  >     tree eval:b''
  >     fields eval:[b'revision']
  > EOF
  creating http peer for wire protocol version 2
  sending manifestdata command
  response: gen[
    {
      b'totalitems': 2
    },
    {
      b'fieldsfollowing': [
        [
          b'revision',
          292
        ]
      ],
      b'node': b'\x1b\x17[Y_\x02,\xfa\xb5\xb8\t\xcc\x0e\xd5Q\xbd\x0b?\xf5\xe4'
    },
    b'a\x002b4eb07319bfa077a40a2f04913659aef0da42da\nb\x00819e258d31a5e1606629f365bb902a1b21ee4216\ndir0/c\x00914445346a0ca0629bd47ceb5dfe07e4d4cf2501\ndir0/child0/e\x00bbba6c06b30f443d34ff841bc985c4d0827c6be4\ndir0/child1/f\x0012fc7dcd773b5a0a929ce195228083c6ddc9cec4\ndir0/d\x00538206dc971e521540d6843abfe6d16032f6d426\n',
    {
      b'deltabasenode': b'\x1b\x17[Y_\x02,\xfa\xb5\xb8\t\xcc\x0e\xd5Q\xbd\x0b?\xf5\xe4',
      b'fieldsfollowing': [
        [
          b'delta',
          55
        ]
      ],
      b'node': b'F\xa6r\x1b^\xda\xf0\xea\x04\xb7\x9a\\\xb3!\x88T\xa4\xd2\xab\xa0'
    },
    b'\x00\x00\x00\x00\x00\x00\x00+\x00\x00\x00+a\x000879345e39377229634b420c639454156726c6b6\n'
  ]

With haveparents=True, first revision is a delta instead of fulltext

  $ sendhttpv2peer << EOF
  > command manifestdata
  >     nodes eval:[b'\x1b\x17\x5b\x59\x5f\x02\x2c\xfa\xb5\xb8\x09\xcc\x0e\xd5\x51\xbd\x0b\x3f\xf5\xe4', b'\x46\xa6\x72\x1b\x5e\xda\xf0\xea\x04\xb7\x9a\x5c\xb3\x21\x88\x54\xa4\xd2\xab\xa0']
  >     tree eval:b''
  >     fields eval:[b'revision']
  >     haveparents eval:True
  > EOF
  creating http peer for wire protocol version 2
  sending manifestdata command
  response: gen[
    {
      b'totalitems': 2
    },
    {
      b'fieldsfollowing': [
        [
          b'revision',
          292
        ]
      ],
      b'node': b'\x1b\x17[Y_\x02,\xfa\xb5\xb8\t\xcc\x0e\xd5Q\xbd\x0b?\xf5\xe4'
    },
    b'a\x002b4eb07319bfa077a40a2f04913659aef0da42da\nb\x00819e258d31a5e1606629f365bb902a1b21ee4216\ndir0/c\x00914445346a0ca0629bd47ceb5dfe07e4d4cf2501\ndir0/child0/e\x00bbba6c06b30f443d34ff841bc985c4d0827c6be4\ndir0/child1/f\x0012fc7dcd773b5a0a929ce195228083c6ddc9cec4\ndir0/d\x00538206dc971e521540d6843abfe6d16032f6d426\n',
    {
      b'deltabasenode': b'\x1b\x17[Y_\x02,\xfa\xb5\xb8\t\xcc\x0e\xd5Q\xbd\x0b?\xf5\xe4',
      b'fieldsfollowing': [
        [
          b'delta',
          55
        ]
      ],
      b'node': b'F\xa6r\x1b^\xda\xf0\xea\x04\xb7\x9a\\\xb3!\x88T\xa4\xd2\xab\xa0'
    },
    b'\x00\x00\x00\x00\x00\x00\x00+\x00\x00\x00+a\x000879345e39377229634b420c639454156726c6b6\n'
  ]

Revisions are sorted by DAG order, parents first

  $ sendhttpv2peer << EOF
  > command manifestdata
  >     nodes eval:[b'\x46\xa6\x72\x1b\x5e\xda\xf0\xea\x04\xb7\x9a\x5c\xb3\x21\x88\x54\xa4\xd2\xab\xa0', b'\x1b\x17\x5b\x59\x5f\x02\x2c\xfa\xb5\xb8\x09\xcc\x0e\xd5\x51\xbd\x0b\x3f\xf5\xe4']
  >     tree eval:b''
  >     fields eval:[b'revision']
  > EOF
  creating http peer for wire protocol version 2
  sending manifestdata command
  response: gen[
    {
      b'totalitems': 2
    },
    {
      b'fieldsfollowing': [
        [
          b'revision',
          292
        ]
      ],
      b'node': b'\x1b\x17[Y_\x02,\xfa\xb5\xb8\t\xcc\x0e\xd5Q\xbd\x0b?\xf5\xe4'
    },
    b'a\x002b4eb07319bfa077a40a2f04913659aef0da42da\nb\x00819e258d31a5e1606629f365bb902a1b21ee4216\ndir0/c\x00914445346a0ca0629bd47ceb5dfe07e4d4cf2501\ndir0/child0/e\x00bbba6c06b30f443d34ff841bc985c4d0827c6be4\ndir0/child1/f\x0012fc7dcd773b5a0a929ce195228083c6ddc9cec4\ndir0/d\x00538206dc971e521540d6843abfe6d16032f6d426\n',
    {
      b'deltabasenode': b'\x1b\x17[Y_\x02,\xfa\xb5\xb8\t\xcc\x0e\xd5Q\xbd\x0b?\xf5\xe4',
      b'fieldsfollowing': [
        [
          b'delta',
          55
        ]
      ],
      b'node': b'F\xa6r\x1b^\xda\xf0\xea\x04\xb7\x9a\\\xb3!\x88T\xa4\xd2\xab\xa0'
    },
    b'\x00\x00\x00\x00\x00\x00\x00+\x00\x00\x00+a\x000879345e39377229634b420c639454156726c6b6\n'
  ]

Requesting parents and revision data works

  $ sendhttpv2peer << EOF
  > command manifestdata
  >     nodes eval:[b'\x1b\x17\x5b\x59\x5f\x02\x2c\xfa\xb5\xb8\x09\xcc\x0e\xd5\x51\xbd\x0b\x3f\xf5\xe4', b'\x46\xa6\x72\x1b\x5e\xda\xf0\xea\x04\xb7\x9a\x5c\xb3\x21\x88\x54\xa4\xd2\xab\xa0']
  >     tree eval:b''
  >     fields eval:[b'parents', b'revision']
  > EOF
  creating http peer for wire protocol version 2
  sending manifestdata command
  response: gen[
    {
      b'totalitems': 2
    },
    {
      b'fieldsfollowing': [
        [
          b'revision',
          292
        ]
      ],
      b'node': b'\x1b\x17[Y_\x02,\xfa\xb5\xb8\t\xcc\x0e\xd5Q\xbd\x0b?\xf5\xe4',
      b'parents': [
        b'\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00',
        b'\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00'
      ]
    },
    b'a\x002b4eb07319bfa077a40a2f04913659aef0da42da\nb\x00819e258d31a5e1606629f365bb902a1b21ee4216\ndir0/c\x00914445346a0ca0629bd47ceb5dfe07e4d4cf2501\ndir0/child0/e\x00bbba6c06b30f443d34ff841bc985c4d0827c6be4\ndir0/child1/f\x0012fc7dcd773b5a0a929ce195228083c6ddc9cec4\ndir0/d\x00538206dc971e521540d6843abfe6d16032f6d426\n',
    {
      b'deltabasenode': b'\x1b\x17[Y_\x02,\xfa\xb5\xb8\t\xcc\x0e\xd5Q\xbd\x0b?\xf5\xe4',
      b'fieldsfollowing': [
        [
          b'delta',
          55
        ]
      ],
      b'node': b'F\xa6r\x1b^\xda\xf0\xea\x04\xb7\x9a\\\xb3!\x88T\xa4\xd2\xab\xa0',
      b'parents': [
        b'\x1b\x17[Y_\x02,\xfa\xb5\xb8\t\xcc\x0e\xd5Q\xbd\x0b?\xf5\xe4',
        b'\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00'
      ]
    },
    b'\x00\x00\x00\x00\x00\x00\x00+\x00\x00\x00+a\x000879345e39377229634b420c639454156726c6b6\n'
  ]

  $ cat error.log