a backend has done exit(0) or exit(1) without having disengaged itself
from shared memory. We are at risk for this whenever third-party code is
loaded into a backend, since such code might not know it's supposed to go
through proc_exit() instead. Also, it is reported that under Windows
there are ways to externally kill a process that cause the status code
returned to the postmaster to be indistinguishable from a voluntary exit
(thank you, Microsoft). If this does happen then the system is probably
hosed --- for instance, the dead session might still be holding locks.
So the best recovery method is to treat this like a backend crash.
The dead man switch is armed for a particular child process when it
acquires a regular PGPROC, and disarmed when the PGPROC is released;
these should be the first and last touches of shared memory resources
in a backend, or close enough anyway. This choice means there is no
coverage for auxiliary processes, but I doubt we need that, since they
shouldn't be executing any user-provided code anyway.
This patch also improves the management of the EXEC_BACKEND
ShmemBackendArray array a bit, by reducing search costs.
Although this problem is of long standing, the lack of field complaints
seems to mean it's not critical enough to risk back-patching; at least
not till we get some more testing of this mechanism.
error message if the installation directory layout is messed up (or at least,
something more useful than the behavior exhibited in bug #4787). During
postmaster startup, check that get_pkglib_path resolves as a readable
directory; and if ParseTzFile() fails to open the expected timezone
abbreviation file, check the possibility that the directory is missing rather
than just the specified file. In case of either failure, issue a hint
suggesting that the installation is broken. These two checks cover the lib/
and share/ trees of a full installation, which should take care of most
scenarios where a sysadmin decides to get cute.
are using our own ports of getopt or getopt_long, those will define
the variable for themselves; and if not, we don't need these, because
we never touch the variable anyway.
recovery: if background writer or pgstat process dies during recovery (or
any other child process, but those two are the only ones running), send
SIGQUIT to the startup process using correct pid.
its usual buffer cleaning duties during archive recovery, and it's responsible
for performing restartpoints.
This requires some changes in postmaster. When the startup process has done
all the initialization and is ready to start WAL redo, it signals the
postmaster to launch the background writer. The postmaster is signaled again
when the point in recovery is reached where we know that the database is in
consistent state. Postmaster isn't interested in that at the moment, but
that's the point where we could let other backends in to perform read-only
queries. The postmaster is signaled third time when the recovery has ended,
so that postmaster knows that it's safe to start accepting connections.
The startup process now traps SIGTERM, and performs a "clean" shutdown. If
you do a fast shutdown during recovery, a shutdown restartpoint is performed,
like a shutdown checkpoint, and postmaster kills the processes cleanly. You
still have to continue the recovery at next startup, though.
Currently, the background writer is only launched during archive recovery.
We could launch it during crash recovery as well, but it seems better to keep
that codepath as simple as possible, for the sake of robustness. And it
couldn't do any restartpoints during crash recovery anyway, so it wouldn't be
that useful.
log_restartpoints is gone. Use log_checkpoints instead. This is yet to be
documented.
This whole operation is a pre-requisite for Hot Standby, but has some value of
its own whether the hot standby patch makes 8.4 or not.
Simon Riggs, with lots of modifications by me.
initialization, to give loadable modules a reasonable place to perform
creation of any shared memory areas they need. This is the logical conclusion
of our previous creation of RequestAddinShmemSpace() and RequestAddinLWLocks().
We don't need an explicit shmem_shutdown_hook, because the existing
on_shmem_exit and on_proc_exit mechanisms serve that need.
Also, adjust SubPostmasterMain so that libraries that got loaded into the
postmaster will be loaded into all child processes, not only regular backends.
This improves consistency with the non-EXEC_BACKEND behavior, and might be
necessary for functionality for some types of add-ons.
ctype are now more like encoding, stored in new datcollate and datctype
columns in pg_database.
This is a stripped-down version of Radek Strnad's patch, with further
changes by me.
each connection. This makes it possible to catch errors in the pg_hba
file when it's being reloaded, instead of silently reloading a broken
file and failing only when a user tries to connect.
This patch also makes the "sameuser" argument to ident authentication
optional.
unnecessary cache resets. The major changes are:
* When the queue overflows, we only issue a cache reset to the specific
backend or backends that still haven't read the oldest message, rather
than resetting everyone as in the original coding.
* When we observe backend(s) falling well behind, we signal SIGUSR1
to only one backend, the one that is furthest behind and doesn't already
have a signal outstanding for it. When it finishes catching up, it will
in turn signal SIGUSR1 to the next-furthest-back guy, if there is one that
is far enough behind to justify a signal. The PMSIGNAL_WAKEN_CHILDREN
mechanism is removed.
* We don't attempt to clean out dead messages after every message-receipt
operation; rather, we do it on the insertion side, and only when the queue
fullness passes certain thresholds.
* Split SInvalLock into SInvalReadLock and SInvalWriteLock so that readers
don't block writers nor vice versa (except during the infrequent queue
cleanout operations).
* Transfer multiple sinval messages for each acquisition of a read or
write lock.
do CancelBackup at a sane place, fix some oversights in the state transitions,
allow only superusers to connect while we are waiting for backup mode to end.
have pg_ctl warn about this.
Cancel running online backups (by renaming the backup_label file,
thus rendering the backup useless) when shutting down in fast mode.
Laurenz Albe
key files that are similar to the one for the postmaster's data directory
permissions check. (I chose to standardize on that one since it's the most
heavily used and presumably best-wordsmithed by now.) Also eliminate explicit
tests on file ownership in these places, since the ensuing read attempt must
fail anyway if it's wrong, and there seems no value in issuing the same error
message for distinct problems. (But I left in the explicit ownership test in
postmaster.c, since it had its own error message anyway.) Also be more
specific in the documentation's descriptions of these checks. Per a gripe
from Kevin Hunter.
With the addition of multiple autovacuum workers, our choices were to delete
the check, document the interaction with autovacuum_max_workers, or complicate
the check to try to hide that interaction. Since this restriction has never
been adequate to ensure backends can't run out of pinnable buffers, it doesn't
really have enough excuse to live to justify the second or third choices.
Per discussion of a complaint from Andreas Kling (see also bug #3888).
This commit also removes several documentation references to this restriction,
but I'm not sure I got them all.
finish archiving everything (when there's no error), and to eliminate various
hazards as best we can. This fixes a previous 8.3 patch that caused the
postmaster to kill and then restart the archiver during shutdown (!?).
The new behavior is that the archiver is allowed to run unmolested until
the bgwriter has exited; then it is sent SIGUSR2 to tell it to do a final
archiving cycle and quit. We only SIGQUIT the archiver if we want a panic
stop; this is important since SIGQUIT will also be sent to any active
archive_command. The postmaster also now doesn't SIGQUIT the stats collector
until the bgwriter is done, since the bgwriter can send stats messages in 8.3.
The postmaster will not exit until both the archiver and stats collector are
gone; this provides some defense (not too bulletproof) against conflicting
archiver or stats collector processes being started by a new postmaster
instance. We continue the prior practice that the archiver will check
for postmaster death immediately before issuing any archive_command; that
gives some additional protection against conflicting archivers.
Also, modify the archiver process to notice SIGTERM and refuse to issue any
more archive commands if it gets it. The postmaster doesn't ever send it
SIGTERM; we assume that any such signal came from init and is a notice of
impending whole-system shutdown. In this situation it seems imprudent to try
to start new archive commands --- if they aren't extremely quick they're
likely to get SIGKILL'd by init.
All per discussion.
childprocess deaths instead of using one thread per child. This drastastically
reduces the address space usage and should allow for more backends running.
Also change the win32_waitpid functionality to use an IO Completion Port for
queueing child death notices instead of using a fixed-size array.
- create a separate archive_mode GUC, on which archive_command is dependent
- %r option in recovery.conf sends last restartpoint to recovery command
- %r used in pg_standby, updated README
- minor other code cleanup in pg_standby
- doc on Warm Standby now mentions pg_standby and %r
- log_restartpoints recovery option emits LOG message at each restartpoint
- end of recovery now displays last transaction end time, as requested
by Warren Little; also shown at each restartpoint
- restart archiver if needed to carry away WAL files at shutdown
Simon Riggs
constant flow of new connection requests could prevent the postmaster from
completing a shutdown or crash restart. This is done by labeling child
processes that are "dead ends", that is, we know that they were launched only
to tell a client that it can't connect. These processes are managed
separately so that they don't confuse us into thinking that we can't advance
to the next stage of a shutdown or restart sequence, until the very end
where we must wait for them to drain out so we can delete the shmem segment.
Per discussion of a misbehavior reported by Keaton Adams.
Since this code was baroque already, and my first attempt at fixing the
problem made it entirely impenetrable, I took the opportunity to rewrite it
in a state-machine style. That eliminates some duplicated code sections and
hopefully makes everything a bit clearer.
as well as regular backends: if no regular backend launches before the autovac
launcher tries to start an autovac worker, the postmaster would get an Assert
fault due to calling PostmasterRandom before random_seed was initialized.
Cleanest solution seems to be to take the initialization of random_seed out
of ServerLoop and let PostmasterRandom do it for itself.
not bothering to initialize is_autovacuum for regular backends, meaning there
was a significant chance of the postmaster prematurely sending them SIGTERM
during database shutdown. Also, leaving the cancel key unset for an autovac
worker meant that any client could send it SIGINT, which doesn't sound
especially good either.
so that we will be able to create a cookie for all processes for CSVlogs.
It is set wherever MyProcPid is set. Take the opportunity to remove the now
unnecessary session-only restriction on the %s and %c escapes in log_line_prefix.
and fsync WAL at convenient intervals. For the moment it just tries to
offload this work from backends, but soon it will be responsible for
guaranteeing a maximum delay before asynchronously-committed transactions
will be flushed to disk.
This is a portion of Simon Riggs' async-commit patch, committed to CVS
separately because a background WAL writer seems like it might be a good idea
independently of the async-commit feature. I rebased walwriter.c on
bgwriter.c because it seemed like a more appropriate way of handling signals;
while the startup/shutdown logic in postmaster.c is more like autovac because
we want walwriter to quit before we start the shutdown checkpoint.
against a Unix server, and Windows-specific server-side authentication
using SSPI "negotiate" method (Kerberos or NTLM).
Only builds properly with MSVC for now.
Tom Lane
Alvaro Herrera
Heikki Linnakangas
Bruce Momjian
Peter Eisentraut
Magnus Hagander
Neil Conway
Andrew Dunstan