D2720: debugcommands: introduce actions to perform deterministic reads

[mharbison72 (Matt Harbison)]

mharbison72 added a comment.


  In https://phab.mercurial-scm.org/D2720#44350, @indygreg wrote:
  
  > In https://phab.mercurial-scm.org/D2720#44293, @mharbison72 wrote:
  >
  > > i> write(4) -> 4:
  > >  i>     426\n
  > >  i> write(426) -> 426:
  > >  i>     HG10UN\x00\x00\x00\x9eh\x98b\x13\xbdD\x85\xeaQS55\xe3\xfc\x9ex\x00zq\x1f\x00\x00\x00\x00\x00\x00\x00\x0
  > >  0\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\
  > >  x00\x00\x00\x00\x00h\x98b\x13\xbdD\x85\xeaQS55\xe3\xfc\x9ex\x00zq\x1f\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\
  > >  x00>cba485ca3678256e044428f70f58291196f6e9de\n
  > >  i>     test\n
  > >  i>     0 0\n
  > >  i>     foo\n
  > >  i>     \n
  > >  i>     initial\x00\x00\x00\x00\x00\x00\x00\x8d\xcb\xa4\x85\xca6x%n\x04D(\xf7\x0fX)\x11\x96\xf6\xe9\xde\x00\x00
  > >  \x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x
  > >  00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00h\x98b\x13\xbdD\x85\xeaQS55\xe3\xfc\x9ex\x00zq\x1f\x00\x00\x00\x00\x
  > >  00\x00\x00\x00\x00\x00\x00-foo\x00362fef284ce2ca02aecc8de6d5e8a1c3af0556fe\n
  > >  i>     \x00\x00\x00\x00\x00\x00\x00\x07foo\x00\x00\x00b6/\xef(L\xe2\xca\x02\xae\xcc\x8d\xe6\xd5\xe8\xa1\xc3\xa
  > >  f\x05V\xfe\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00
  > >  \x00\x00\x00\x00\x00\x00\x00\x00\
  > >
  > >  
  >
  >
  > This is a wonky place to hang! For context, this is processing a `command unbundle` line. The lines that follow should be:
  >
  >   i> write(2) -> 2:
  >   i>     0\n
  >   i> flush() -> None
  >   o> readline() -> 2:
  >   o>     0\n
  >   o> readline() -> 2:
  >   o>     1\n
  >   o> read(1) -> 1: 0
  >   result: 0
  >   remote output: 
  >   e> read(115) -> 115:
  >   e>     abort: incompatible Mercurial client; bundle2 required\n
  >   e>     (see https://www.mercurial-scm.org/wiki/IncompatibleClient)\n
  >   
  >
  > What happens under the hood during pushes is we send out chunks containing the bundle followed by an empty chunk. That code is:
  >
  >   for d in iter(lambda: fp.read(4096), ''):
  >       self._writeframed(d)
  >   self._writeframed("", flush=True)
  >
  >
  > That empty chunk is apparently not getting sent. Or its logging is not getting written/printed.
  >
  > This patch shouldn't have changed any behavior with regard to this part of the I/O. So I'm scratching my head over how this caused deadlock. Are you sure you can bisect it to this patch.
  
  
  Yep.  I imported this with `hg phapread --stack`, and can run the https://phab.mercurial-scm.org/D2719 in 50 seconds or so.  The debug run of this I let hang out for 20 minutes before killing it.
  
  Here's the neighboring failure from https://phab.mercurial-scm.org/D2719, because I can't explain the AWOL output.  (But that shouldn't have stopped stdout above mid stream.)
  
    --- e:/Projects/hg/tests/test-ssh-proto-unbundle.t
    +++ e:/Projects/hg/tests/test-ssh-proto-unbundle.t.err
    @@ -93,9 +93,6 @@
       o> read(1) -> 1: 0
       result: 0
       remote output:
    -  e> read(-1) -> 115:
    -  e>     abort: incompatible Mercurial client; bundle2 required\n
    -  e>     (see https://www.mercurial-scm.org/wiki/IncompatibleClient)\n
    
       testing ssh2
       creating ssh peer from handshake results
    @@ -143,9 +140,6 @@
       o> read(1) -> 1: 0
       result: 0
       remote output:
    -  e> read(-1) -> 115:
    -  e>     abort: incompatible Mercurial client; bundle2 required\n
    -  e>     (see https://www.mercurial-scm.org/wiki/IncompatibleClient)\n
    
       $ cd ..

REPOSITORY
  rHG Mercurial

REVISION DETAIL
  https://phab.mercurial-scm.org/D2720

To: indygreg, #hg-reviewers
Cc: mharbison72, mercurial-devel