Since we start the worker threads with _beginthreadex(), we should use
_endthreadex() to terminate them. We got this right in the normal-exit
code path, but not so much during an error exit from a worker.
In addition, be sure to apply CloseHandle to the thread handle after
each thread exits.
It's not clear that these oversights cause any user-visible problems,
since the pg_dump run is about to terminate anyway. Still, it's clearly
better to follow Microsoft's API specifications than ignore them.
Also a few cosmetic cleanups in WaitForTerminatingWorkers(), including
being a bit less random about where to cast between uintptr_t and HANDLE,
and being sure to clear the worker identity field for each dead worker
(not that false matches should be possible later, but let's be careful).
Original observation and patch by Armin Schöffmann, cosmetic improvements
by Michael Paquier and me. (Armin's patch also included closing sockets
in ShutdownWorkersHard(), but that's been dealt with already in commit
df8d2d8c4.) Back-patch to 9.3 where parallel pg_dump was introduced.
Discussion: <zarafa.570306bd.3418.074bf1420d8f2ba2@root.aegaeon.de>
In the original design for parallel dump, worker processes reported errors
by sending them up to the master process, which would print the messages.
This is unworkably fragile for a couple of reasons: it risks deadlock if a
worker sends an error at an unexpected time, and if the master has already
died for some reason, the user will never get to see the error at all.
Revert that idea and go back to just always printing messages to stderr.
This approach means that if all the workers fail for similar reasons (eg,
bad password or server shutdown), the user will see N copies of that
message, not only one as before. While that's slightly annoying, it's
certainly better than not seeing any message; not to mention that we
shouldn't assume that only the first failure is interesting.
An additional problem in the same area was that the master failed to
disable SIGPIPE (at least until much too late), which meant that sending a
command to an already-dead worker would cause the master to crash silently.
That was bad enough in itself but was made worse by the total reliance on
the master to print errors: even if the worker had reported an error, you
would probably not see it, depending on timing. Instead disable SIGPIPE
right after we've forked the workers, before attempting to send them
anything.
Additionally, the master relies on seeing socket EOF to realize that a
worker has exited prematurely --- but on Windows, there would be no EOF
since the socket is attached to the process that includes both the master
and worker threads, so it remains open. Make archive_close_connection()
close the worker end of the sockets so that this acts more like the Unix
case. It's not perfect, because if a worker thread exits without going
through exit_nicely() the closures won't happen; but that's not really
supposed to happen.
This has been wrong all along, so back-patch to 9.3 where parallel dump
was introduced.
Report: <2458.1450894615@sss.pgh.pa.us>
Most pg_dump.c global variables, which were passed down individually to
dumping routines, are now grouped as members of the new DumpOptions
struct, which is used as a local variable and passed down into routines
that need it. This helps future development efforts; in particular it
is said to enable a mode in which a parallel pg_dump run can output
multiple streams, and have them restored in parallel.
Also take the opportunity to clean up the pg_dump header files somewhat,
to avoid circularity.
Author: Joachim Wieland, revised by Álvaro Herrera
Reviewed by Peter Eisentraut
Move functions used only by pg_dump and pg_restore from dumputils.c to a new
file, pg_backup_utils.c. dumputils.c is linked into psql and some programs
in bin/scripts, so it seems good to keep it slim. The parallel functionality
is moved to parallel.c, as is exit_horribly, because the interesting code in
exit_horribly is parallel-related.
This refactoring gets rid of the on_exit_msg_func function pointer. It was
problematic, because a modern gcc version with -Wmissing-format-attribute
complained if it wasn't marked with PF_PRINTF_ATTRIBUTE, but the ancient gcc
version that Tom Lane's old HP-UX box has didn't accept that attribute on a
function pointer, and gave an error. We still use a similar function pointer
trick for getLocalPQBuffer() function, to use a thread-local version of that
in parallel mode on Windows, but that dodges the problem because it doesn't
take printf-like arguments.
