procutil: make stream detection in make_line_buffered more correct and strict
In make_line_buffered(), we don’t want to wrap the stream if we know that lines
get flushed to the underlying raw stream already.
Previously, the heuristic was too optimistic. It assumed that any stream which
is not an instance of io.BufferedIOBase doesn’t need wrapping. However, there
are buffered streams that aren’t instances of io.BufferedIOBase, like
Mercurial’s own winstdout.
The new logic is different in two ways:
First, only for the check, if unwraps any combination of WriteAllWrapper and
winstdout.
Second, it skips wrapping the stream only if it is an instance of io.RawIOBase
(or already wrapped). If it is an instance of io.BufferedIOBase, it gets
wrapped. In any other case, the function raises an exception. This ensures
that, if an unknown stream is passed or we add another wrapper in the future,
we don’t wrap the stream if it’s already line buffered or not wrap the stream
if it’s not line buffered. In fact, this was already helpful during development
of this change. Without it, I possibly would have forgot that WriteAllWrapper
needs to be ignored for the check, leading to unnecessary wrapping if stdout is
unbuffered.
The alternative would have been to always wrap unknown streams. However, I
don’t think that anyone would benefit from being less strict. We can expect
streams from the standard library to be subclassing either io.RawIOBase or
io.BufferedIOBase, so running Mercurial in the standard way should not regress
by this change. Py2exe might replace sys.stdout and sys.stderr, but that
currently breaks Mercurial anyway and also these streams don’t claim to be
interactive, so this function is not called for them.
Test that, when an hg push is interrupted and the remote side receives SIGPIPE,
the remote hg is able to successfully roll back the transaction.
$ hg init -q remote
$ hg clone -q ssh://user@dummy/`pwd`/remote local
$ SIGPIPE_REMOTE_DEBUG_FILE="$TESTTMP/DEBUGFILE"
$ SYNCFILE1="$TESTTMP/SYNCFILE1"
$ SYNCFILE2="$TESTTMP/SYNCFILE2"
$ export SIGPIPE_REMOTE_DEBUG_FILE
$ export SYNCFILE1
$ export SYNCFILE2
$ PYTHONUNBUFFERED=1
$ export PYTHONUNBUFFERED
On the remote end, run hg, piping stdout and stderr through processes that we
know the PIDs of. We will later kill these to simulate an ssh client
disconnecting.
$ remotecmd="$RUNTESTDIR/testlib/sigpipe-remote.py"
In the pretxnchangegroup hook, kill the PIDs recorded above to simulate ssh
disconnecting. Then exit nonzero, to force a transaction rollback.
$ cat >remote/.hg/hgrc <<EOF
> [hooks]
> pretxnchangegroup.00-break-things=sh "$RUNTESTDIR/testlib/wait-on-file" 10 "$SYNCFILE2" "$SYNCFILE1"
> pretxnchangegroup.01-output-things=echo "some remote output to be forward to the closed pipe"
> pretxnchangegroup.02-output-things=echo "some more remote output"
> EOF
$ hg --cwd ./remote tip -T '{node|short}\n'
000000000000
$ cd local
$ echo foo > foo ; hg commit -qAm "commit"
(use quiet to avoid flacky output from the server)
$ hg push --quiet --remotecmd "$remotecmd"
abort: stream ended unexpectedly (got 0 bytes, expected 4)
[255]
$ cat $SIGPIPE_REMOTE_DEBUG_FILE
SIGPIPE-HELPER: Starting
SIGPIPE-HELPER: Redirection in place
SIGPIPE-HELPER: pipes closed in main
SIGPIPE-HELPER: SYNCFILE1 detected
SIGPIPE-HELPER: worker killed
SIGPIPE-HELPER: creating SYNCFILE2
SIGPIPE-HELPER: Shutting down
SIGPIPE-HELPER: Server process terminated with status 255 (no-windows !)
SIGPIPE-HELPER: Server process terminated with status 1 (windows !)
SIGPIPE-HELPER: Shut down
The remote should be left in a good state
$ hg --cwd ../remote tip -T '{node|short}\n'
000000000000
#if windows
XXX-Windows Broken behavior to be fixed
Behavior on Windows is broken and should be fixed. However this is a fairly
corner case situation and no data are being corrupted. This would affect
central repository being hosted on a Windows machine and accessed using ssh.
This was catch as we setup new CI for Windows. Making the test pass on Windows
was enough of a pain that fixing the behavior set aside for now. Dear and
honorable reader, feel free to fix it.
$ hg --cwd ../remote recover
rolling back interrupted transaction
(verify step skipped, run `hg verify` to check your repository content)
#else
$ hg --cwd ../remote recover
no interrupted transaction available
[1]
#endif