Use it at level 4, a bit more restrictive than the default level, and
tweak our commanding comments to FALLTHROUGH.
(However, leave zic.c alone, since it's external code; to avoid the
warnings that would appear there, change CFLAGS for that file in the
Makefile.)
Author: Julien Rouhaud <rjuju123@gmail.com>
Author: Álvaro Herrera <alvherre@alvh.no-ip.org>
Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Discussion: https://postgr.es/m/20200412081825.qyo5vwwco3fv4gdo@nol
Discussion: https://postgr.es/m/flat/E1fDenm-0000C8-IJ@gemulon.postgresql.org
If the client is compiled with GSSAPI support and tries to start up GSS
with the server, but the server is not compiled with GSSAPI support, we
would mistakenly end up falling through to call ProcessStartupPacket
with secure_done = true, but the client might then try to perform SSL,
which the backend wouldn't understand and we'd end up failing the
connection with:
FATAL: unsupported frontend protocol 1234.5679: server supports 2.0 to 3.0
Fix by arranging to track ssl_done independently from gss_done, instead
of trying to use the same boolean for both.
Author: Andrew Gierth
Discussion: https://postgr.es/m/87h82kzwqn.fsf@news-spur.riddles.org.uk
Backpatch: 12-, where GSSAPI encryption was added.
Checkpointer uses its MyLatch to wake up when a checkpoint request is
received. But before commit c655077639 the latch was not used for
anything else, so the code could just go to sleep after each loop
without rechecking the sleeping condition. That commit added a separate
ResetLatch in its code path[1], which can cause a checkpoint to go
unnoticed for potentially a long time.
Fix by skipping sleep if any checkpoint flags are set. Also add a test
to verify this; authored by Kyotaro Horiguchi.
[1] CreateCheckPoint -> InvalidateObsoleteReplicationSlots ->
ConditionVariableTimeSleep
Report and diagnosis by Kyotaro Horiguchi.
Co-authored-by: Kyotaro Horiguchi <horikyota.ntt@gmail.com>
Co-authored-by: Álvaro Herrera <alvherre@alvh.no-ip.org>
Discussion: https://postgr.es/m/20200408.141956.891237856186513376.horikyota.ntt@gmail.com
This is for the benefit of running postgres under the rr
debugger. When using rr signal handlers running while a syscall is
active use an alternative stack. As e.g. bgworkers are started from
within signal handlers, the forked backend then has a different stack
base than postmaster. Previously that subsequently lead to those
processes triggering spurious "stack depth limit exceeded" errors.
Discussion: https://postgr.es/m/20200327182217.ubrrl32lyfhxfwk5@alap3.anarazel.de
This commit introduces new wait events RecoveryConflictSnapshot and
RecoveryConflictTablespace. The former is reported while waiting for
recovery conflict resolution on a vacuum cleanup. The latter is reported
while waiting for recovery conflict resolution on dropping tablespace.
Also this commit changes the code so that the wait event Lock is reported
while waiting in ResolveRecoveryConflictWithVirtualXIDs() for recovery
conflict resolution on a lock. Basically the wait event Lock is reported
during that wait, but previously was not reported only when that wait
happened in ResolveRecoveryConflictWithVirtualXIDs().
Author: Masahiko Sawada
Reviewed-by: Fujii Masao
Discussion: https://postgr.es/m/CA+fd4k4mXWTwfQLS3RPwGr4xnfAEs1ysFfgYHvmmoUgv6Zxvmg@mail.gmail.com
There's a number of SLRU caches used to access important data like clog,
commit timestamps, multixact, asynchronous notifications, etc. Until now
we had no easy way to monitor these shared caches, compute hit ratios,
number of reads/writes etc.
This commit extends the statistics collector to track this information
for a predefined list of SLRUs, and also introduces a new system view
pg_stat_slru displaying the data.
The list of built-in SLRUs is fixed, but additional SLRUs may be defined
in extensions. Unfortunately, there's no suitable registry of SLRUs, so
this patch simply defines a fixed list of SLRUs with entries for the
built-in ones and one entry for all additional SLRUs. Extensions adding
their own SLRU are fairly rare, so this seems acceptable.
This patch only allows monitoring of SLRUs, not tuning. The SLRU sizes
are still fixed (hard-coded in the code) and it's not entirely clear
which of the SLRUs might need a GUC to tune size. In a way, allowing us
to determine that is one of the goals of this patch.
Bump catversion as the patch introduces new functions and system view.
Author: Tomas Vondra
Reviewed-by: Alvaro Herrera
Discussion: https://www.postgresql.org/message-id/flat/20200119143707.gyinppnigokesjok@development
Traditionally autovacuum has only ever invoked a worker based on the
estimated number of dead tuples in a table and for anti-wraparound
purposes. For the latter, with certain classes of tables such as
insert-only tables, anti-wraparound vacuums could be the first vacuum that
the table ever receives. This could often lead to autovacuum workers being
busy for extended periods of time due to having to potentially freeze
every page in the table. This could be particularly bad for very large
tables. New clusters, or recently pg_restored clusters could suffer even
more as many large tables may have the same relfrozenxid, which could
result in large numbers of tables requiring an anti-wraparound vacuum all
at once.
Here we aim to reduce the work required by anti-wraparound and aggressive
vacuums in general, by triggering autovacuum when the table has received
enough INSERTs. This is controlled by adding two new GUCs and reloptions;
autovacuum_vacuum_insert_threshold and
autovacuum_vacuum_insert_scale_factor. These work exactly the same as the
existing scale factor and threshold controls, only base themselves off the
number of inserts since the last vacuum, rather than the number of dead
tuples. New controls were added rather than reusing the existing
controls, to allow these new vacuums to be tuned independently and perhaps
even completely disabled altogether, which can be done by setting
autovacuum_vacuum_insert_threshold to -1.
We make no attempt to skip index cleanup operations on these vacuums as
they may trigger for an insert-mostly table which continually doesn't have
enough dead tuples to trigger an autovacuum for the purpose of removing
those dead tuples. If we were to skip cleaning the indexes in this case,
then it is possible for the index(es) to become bloated over time.
There are additional benefits to triggering autovacuums based on inserts,
as tables which never contain enough dead tuples to trigger an autovacuum
are now more likely to receive a vacuum, which can mark more of the table
as "allvisible" and encourage the query planner to make use of Index Only
Scans.
Currently, we still obey vacuum_freeze_min_age when triggering these new
autovacuums based on INSERTs. For large insert-only tables, it may be
beneficial to lower the table's autovacuum_freeze_min_age so that tuples
are eligible to be frozen sooner. Here we've opted not to zero that for
these types of vacuums, since the table may just be insert-mostly and we
may otherwise freeze tuples that are still destined to be updated or
removed in the near future.
There was some debate to what exactly the new scale factor and threshold
should default to. For now, these are set to 0.2 and 1000, respectively.
There may be some motivation to adjust these before the release.
Author: Laurenz Albe, Darafei Praliaskouski
Reviewed-by: Alvaro Herrera, Masahiko Sawada, Chris Travers, Andres Freund, Justin Pryzby
Discussion: https://postgr.es/m/CAC8Q8t%2Bj36G_bLF%3D%2B0iMo6jGNWnLnWb1tujXuJr-%2Bx8ZCCTqoQ%40mail.gmail.com
The parameters primary_conninfo, primary_slot_name and
wal_receiver_create_temp_slot can now be changed with a simple "reload"
signal, no longer requiring a server restart. This is achieved by
signalling the walreceiver process to terminate and having it start
again with the new values.
Thanks to Andres Freund, Kyotaro Horiguchi, Fujii Masao for discussion.
Author: Sergei Kornilov <sk@zsrv.org>
Reviewed-by: Michael Paquier <michael@paquier.xyz>
Reviewed-by: Álvaro Herrera <alvherre@alvh.no-ip.org>
Discussion: https://postgr.es/m/19513901543181143@sas1-19a94364928d.qloud-c.yandex.net
The default hook function sets the default password callback function.
In order to allow preloaded libraries to have an opportunity to override
the default, TLS initialization if now delayed slightly until after
shared preloaded libraries have been loaded.
A test module is provided which contains a trivial example that decodes
an obfuscated password for an SSL certificate.
Author: Andrew Dunstan
Reviewed By: Andreas Karlsson, Asaba Takanori
Discussion: https://postgr.es/m/04116472-818b-5859-1d74-3d995aab2252@2ndQuadrant.com
Previously if a promotion was triggered while recovery was paused,
the paused state continued. Also recovery could be paused by executing
pg_wal_replay_pause() even while a promotion was ongoing. That is,
recovery pause had higher priority over a standby promotion.
But this behavior was not desirable because most users basically wanted
the recovery to complete as soon as possible and the server to become
the master when they requested a promotion.
This commit changes recovery so that it prefers a promotion over
recovery pause. That is, if a promotion is triggered while recovery
is paused, the paused state ends and a promotion continues. Also
this commit makes recovery pause functions like pg_wal_replay_pause()
throw an error if they are executed while a promotion is ongoing.
Internally, this commit adds new internal function PromoteIsTriggered()
that returns true if a promotion is triggered. Since the name of
this function and the existing function IsPromoteTriggered() are
confusingly similar, the commit changes the name of IsPromoteTriggered()
to IsPromoteSignaled, as more appropriate name.
Author: Fujii Masao
Reviewed-by: Atsushi Torikoshi, Sergei Kornilov
Discussion: https://postgr.es/m/00c194b2-dbbb-2e8a-5b39-13f14048ef0a@oss.nttdata.com
This commit introduces new wait events BackupWaitWalArchive and
RecoveryPause. The former is reported while waiting for the WAL files
required for the backup to be successfully archived. The latter is
reported while waiting for recovery in pause state to be resumed.
Author: Fujii Masao
Reviewed-by: Michael Paquier, Atsushi Torikoshi, Robert Haas
Discussion: https://postgr.es/m/f0651f8c-9c96-9f29-0ff9-80414a15308a@oss.nttdata.com
This commit renames RecoveryWalAll and RecoveryWalStream wait events to
RecoveryWalStream and RecoveryRetrieveRetryInterval, respectively,
in order to make the names and what they are more consistent. For example,
previously RecoveryWalAll was reported as a wait event while the recovery
was waiting for WAL from a stream, and which was confusing because the name
was very different from the situation where the wait actually could happen.
The names of macro variables for those wait events also are renamed
accordingly.
This commit also changes the category of RecoveryRetrieveRetryInterval to
Timeout from Activity because the wait event is reported while waiting based
on wal_retrieve_retry_interval.
Author: Fujii Masao
Reviewed-by: Kyotaro Horiguchi, Atsushi Torikoshi
Discussion: https://postgr.es/m/124997ee-096a-5d09-d8da-2c7a57d0816e@oss.nttdata.com
Use the new MyBackendType instead. More similar changes for other "am
something" variables are possible. This one was just particularly
simple.
Reviewed-by: Julien Rouhaud <rjuju123@gmail.com>
Reviewed-by: Kuntal Ghosh <kuntalghosh.2007@gmail.com>
Reviewed-by: Alvaro Herrera <alvherre@2ndquadrant.com>
Discussion: https://www.postgresql.org/message-id/flat/c65e5196-4f04-4ead-9353-6088c19615a3@2ndquadrant.com
Add a new global variable MyBackendType that uses the same BackendType
enum that was previously only used by the stats collector. That way
several duplicate ways of checking what type a particular process is
can be simplified. Since it's no longer just for stats, move to
miscinit.c and rename existing functions to match the expanded
purpose.
Reviewed-by: Julien Rouhaud <rjuju123@gmail.com>
Reviewed-by: Kuntal Ghosh <kuntalghosh.2007@gmail.com>
Reviewed-by: Alvaro Herrera <alvherre@2ndquadrant.com>
Discussion: https://www.postgresql.org/message-id/flat/c65e5196-4f04-4ead-9353-6088c19615a3@2ndquadrant.com
The init_ps_display() arguments were mostly lies by now, so to match
typical usage, just use one argument and let the caller assemble it
from multiple sources if necessary. The only user of the additional
arguments is BackendInitialize(), which was already doing string
assembly on the caller side anyway.
Remove the second argument of set_ps_display() ("force") and just
handle that in init_ps_display() internally.
BackendInitialize() also used to set the initial status as
"authentication", but that was very far from where authentication
actually happened. So now it's set to "initializing" and then
"authentication" just before the actual call to
ClientAuthentication().
Reviewed-by: Julien Rouhaud <rjuju123@gmail.com>
Reviewed-by: Kuntal Ghosh <kuntalghosh.2007@gmail.com>
Reviewed-by: Alvaro Herrera <alvherre@2ndquadrant.com>
Discussion: https://www.postgresql.org/message-id/flat/c65e5196-4f04-4ead-9353-6088c19615a3@2ndquadrant.com
Such an access became possible when commit 246a6c8f7 added more
aggressive cleanup of orphaned temp relations by autovacuum.
Since autovacuum's snapshot might be slightly stale, it could
attempt to access an already-dropped temp namespace, resulting in
an assertion failure or null-pointer dereference. (In practice,
since we don't drop temp namespaces automatically but merely
recycle them, this situation could only arise if a superuser does
a manual drop of a temp namespace. Still, that should be allowed.)
The core of the bug, IMO, is that isTempNamespaceInUse and its callers
failed to think hard about whether to treat "temp namespace isn't there"
differently from "temp namespace isn't in use". In hopes of forestalling
future mistakes of the same ilk, replace that function with a new one
checkTempNamespaceStatus, which makes the same tests but returns a
three-way enum rather than just a bool. isTempNamespaceInUse is gone
entirely in HEAD; but just in case some external code is relying on it,
keep it in the back branches, as a bug-compatible wrapper around the
new function.
Per report originally from Prabhat Kumar Sahu, investigated by Mahendra
Singh and Michael Paquier; the final form of the patch is my fault.
This replaces the failed fix attempt in a052f6cbb.
Backpatch as far as v11, as 246a6c8f7 was.
Discussion: https://postgr.es/m/CAKYtNAr9Zq=1-ww4etHo-VCC-k120YxZy5OS01VkaLPaDbv2tg@mail.gmail.com
The comments in fd.c have long claimed that all file allocations should
go through that module, but in reality that's not always practical.
fd.c doesn't supply APIs for invoking some FD-producing syscalls like
pipe() or epoll_create(); and the APIs it does supply for non-virtual
FDs are mostly insistent on releasing those FDs at transaction end;
and in some cases the actual open() call is in code that can't be made
to use fd.c, such as libpq.
This has led to a situation where, in a modern server, there are likely
to be seven or so long-lived FDs per backend process that are not known
to fd.c. Since NUM_RESERVED_FDS is only 10, that meant we had *very*
few spare FDs if max_files_per_process is >= the system ulimit and
fd.c had opened all the files it thought it safely could. The
contrib/postgres_fdw regression test, in particular, could easily be
made to fall over by running it under a restrictive ulimit.
To improve matters, invent functions Acquire/Reserve/ReleaseExternalFD
that allow outside callers to tell fd.c that they have or want to allocate
a FD that's not directly managed by fd.c. Add calls to track all the
fixed FDs in a standard backend session, so that we are honestly
guaranteeing that NUM_RESERVED_FDS FDs remain unused below the EMFILE
limit in a backend's idle state. The coding rules for these functions say
that there's no need to call them in code that just allocates one FD over
a fairly short interval; we can dip into NUM_RESERVED_FDS for such cases.
That means that there aren't all that many places where we need to worry.
But postgres_fdw and dblink must use this facility to account for
long-lived FDs consumed by libpq connections. There may be other places
where it's worth doing such accounting, too, but this seems like enough
to solve the immediate problem.
Internally to fd.c, "external" FDs are limited to max_safe_fds/3 FDs.
(Callers can choose to ignore this limit, but of course it's unwise
to do so except for fixed file allocations.) I also reduced the limit
on "allocated" files to max_safe_fds/3 FDs (it had been max_safe_fds/2).
Conceivably a smarter rule could be used here --- but in practice,
on reasonable systems, max_safe_fds should be large enough that this
isn't much of an issue, so KISS for now. To avoid possible regression
in the number of external or allocated files that can be opened,
increase FD_MINFREE and the lower limit on max_files_per_process a
little bit; we now insist that the effective "ulimit -n" be at least 64.
This seems like pretty clearly a bug fix, but in view of the lack of
field complaints, I'll refrain from risking a back-patch.
Discussion: https://postgr.es/m/E1izCmM-0005pV-Co@gemulon.postgresql.org
This commit also updates wait event enum into alphabetical order.
Previously the enum entry for GSSOpenServer was added out-of-order.
Back-patch to v12 where commit b0b39f72b9 introduced
GSSOpenServer wait event. In v12, the commit doesn't include
the update of wait event enum, not to break ABI.
Author: Fujii Masao
Reviewed-by: Michael Paquier
Discussion: https://postgr.es/m/949931aa-4ed4-d867-a7b5-de9c02b2292b@oss.nttdata.com
We used to strategically place newlines after some function call left
parentheses to make pgindent move the argument list a few chars to the
left, so that the whole line would fit under 80 chars. However,
pgindent no longer does that, so the newlines just made the code
vertically longer for no reason. Remove those newlines, and reflow some
of those lines for some extra naturality.
Reviewed-by: Michael Paquier, Tom Lane
Discussion: https://postgr.es/m/20200129200401.GA6303@alvherre.pgsql
The leaks have been detected by a Coverity run on Windows. No backpatch
is done as the leaks are minor.
While on it, make restricted token creation more consistent in its error
handling by logging an error instead of a warning if missing
advapi32.dll, which was missing in the NT4 days. Any modern platform
should have this DLL around. Now, if the library is not there, an error
is still reported back to the caller, and nothing is done do there is no
behavior change done in this commit.
Author: Ranier Vilela
Discussion: https://postgr.es/m/CAEudQApa9MG0foPkgPX87fipk=vhnF2Xfg+CfUyR08h4R7Mywg@mail.gmail.com
This feature allows the vacuum to leverage multiple CPUs in order to
process indexes. This enables us to perform index vacuuming and index
cleanup with background workers. This adds a PARALLEL option to VACUUM
command where the user can specify the number of workers that can be used
to perform the command which is limited by the number of indexes on a
table. Specifying zero as a number of workers will disable parallelism.
This option can't be used with the FULL option.
Each index is processed by at most one vacuum process. Therefore parallel
vacuum can be used when the table has at least two indexes.
The parallel degree is either specified by the user or determined based on
the number of indexes that the table has, and further limited by
max_parallel_maintenance_workers. The index can participate in parallel
vacuum iff it's size is greater than min_parallel_index_scan_size.
Author: Masahiko Sawada and Amit Kapila
Reviewed-by: Dilip Kumar, Amit Kapila, Robert Haas, Tomas Vondra,
Mahendra Singh and Sergei Kornilov
Tested-by: Mahendra Singh and Prabhat Sahu
Discussion:
https://postgr.es/m/CAD21AoDTPMgzSkV4E3SFo1CH_x50bf5PqZFQf4jmqjk-C03BWg@mail.gmail.comhttps://postgr.es/m/CAA4eK1J-VoR9gzS5E75pcD-OH0mEyCdp8RihcwKrcuw7J-Q0+w@mail.gmail.com
A new function EmitProcSignalBarrier() can be used to emit a global
barrier which all backends that participate in the ProcSignal
mechanism must absorb, and a new function WaitForProcSignalBarrier()
can be used to wait until all relevant backends have in fact
absorbed the barrier.
This can be used to coordinate global state changes, such as turning
checksums on while the system is running.
There's no real client of this mechanism yet, although two are
proposed, but an enum has to have at least one element, so this
includes a placeholder type (PROCSIGNAL_BARRIER_PLACEHOLDER) which
should be replaced by the first real client of this mechanism to
get committed.
Andres Freund and Robert Haas, reviewed by Daniel Gustafsson and,
in earlier versions, by Magnus Hagander.
Discussion: http://postgr.es/m/CA+TgmoZwDk=BguVDVa+qdA6SBKef=PKbaKDQALTC_9qoz1mJqg@mail.gmail.com
Commit 7dbfea3c45 thought it could get
away with removing this, but Thomas Munro reports, on behalf of the
buildfarm, that it's still needed at least on Windows to avoid
compiler warnings.
Where possible, share signal handler code and main loop interrupt
checking. This saves quite a bit of code and should simplify
maintenance, too.
This commit intends not to change the way anything works, even
though that might allow more code to be unified. It does unify
a bunch of individual variables into a ShutdownRequestPending
flag that has is now used by a bunch of different process types,
though.
Patch by me, reviewed by Andres Freund and Daniel Gustafsson.
Discussion: http://postgr.es/m/CA+TgmoZwDk=BguVDVa+qdA6SBKef=PKbaKDQALTC_9qoz1mJqg@mail.gmail.com
There seems to be no reason for every background process to have
its own flag indicating that a config-file reload is needed.
Instead, let's just use ConfigFilePending for that purpose
everywhere.
Patch by me, reviewed by Andres Freund and Daniel Gustafsson.
Discussion: http://postgr.es/m/CA+TgmoZwDk=BguVDVa+qdA6SBKef=PKbaKDQALTC_9qoz1mJqg@mail.gmail.com
Some auxiliary processes, as well as the autovacuum launcher,
have interrupt handling code directly in their main loops.
Try to abstract things a little better by moving it into
separate functions.
This doesn't make any functional difference, and leaves
in place relatively large differences among processes in how
interrupts are handled, but hopefully it at least makes it
easier to see the commonalities and differences across
process types.
Patch by me, reviewed by Andres Freund and Daniel Gustafsson.
Discussion: http://postgr.es/m/CA+TgmoZwDk=BguVDVa+qdA6SBKef=PKbaKDQALTC_9qoz1mJqg@mail.gmail.com
AuxiliaryProcessMain does ProcSignalInit, so one might expect that
auxiliary processes would need to respond to SendProcSignal, but none
of the auxiliary processes do that. Change them to use
procsignal_sigusr1_handler instead of their own private handlers so
that they do. Besides seeming more correct, this is also less code. It
shouldn't make any functional difference right now because, as far as
we know, there are no current cases where SendProcSignal targets an
auxiliary process, but there are plans to change that in the future.
Andres Freund
Discussion: http://postgr.es/m/20181030051643.elbxjww5jjgnjaxg@alap3.anarazel.de
This gets rid of our former behavior of forcibly downcasing
the postmaster's hostname list and truncating the elements to
NAMEDATALEN. In principle, DNS hostnames are case-insensitive
so the first behavior should be harmless, and server hostnames
are seldom long enough for the second behavior to be an issue.
But it's still dubious, and an easy fix is available: just use
SplitGUCList instead.
AFAICT, all other SplitIdentifierString calls in the backend are
OK: either the items actually are SQL identifiers, or they are
keywords that are short and case-insensitive.
Per thinking about bug #16106. While this has been wrong for
a very long time, the lack of field complaints means there's
little reason to back-patch.
Discussion: https://postgr.es/m/16106-7d319e4295d08e70@postgresql.org
When maintaining or merging patches, one of the most common sources
for conflicts are the list of objects in makefiles. Especially when
the split across lines has been changed on both sides, which is
somewhat common due to attempting to stay below 80 columns, those
conflicts are unnecessarily laborious to resolve.
By splitting, and alphabetically sorting, OBJS style lines into one
object per line, conflicts should be less frequent, and easier to
resolve when they still occur.
Author: Andres Freund
Discussion: https://postgr.es/m/20191029200901.vww4idgcxv74cwes@alap3.anarazel.de
Any callback set would have no meaning in the context of an exception.
As an autovacuum worker exits quickly in this context, this could be
only an issue within EmitErrorReport(), where the elog hook is for
example called. That's unlikely to going to be a problem, but let's be
clean and consistent with other code paths handling exceptions. This is
present since 2909419, which introduced autovacuum.
Author: Ashwin Agrawal
Reviewed-by: Tom Lane, Michael Paquier
Discussion: https://postgr.es/m/CALfoeisM+_+dgmAdAOHAu0k-ZpEHHqSSG=GRf3pKJGm8OqWX0w@mail.gmail.com
Backpatch-through: 9.4
POSIX sigaction(2) can be told to block a set of signals while a
signal handler executes. Make use of that instead of manually
blocking and unblocking signals in the postmaster's signal handlers.
This should save a few cycles, and it also prevents recursive
invocation of signal handlers when many signals arrive in close
succession. We have seen buildfarm failures that seem to be due to
postmaster stack overflow caused by such recursion (exacerbated by
a Linux PPC64 kernel bug).
This doesn't change anything about the way that it works on Windows.
Somebody might consider adjusting port/win32/signal.c to let it work
similarly, but I'm not in a position to do that.
For the moment, just apply to HEAD. Possibly we should consider
back-patching this, but it'd be good to let it age awhile first.
Discussion: https://postgr.es/m/14878.1570820201@sss.pgh.pa.us
The postmaster's code path for spawning a bgworker neglected to check
whether we already have the max number of live child processes. That's
a bit hard to hit, since it would necessarily be a transient condition;
but if we do, AssignPostmasterChildSlot() fails causing a postmaster
crash, as seen in a report from Bhargav Kamineni.
To fix, invoke canAcceptConnections() in the bgworker code path, as we
do in the other code paths that spawn children. Since we don't want
the same pmState tests in this case, add a child-process-type parameter
to canAcceptConnections() so that it can know what to do.
Back-patch to 9.5. In principle the same hazard exists in 9.4, but the
code is enough different that this patch wouldn't quite fix it there.
Given the tiny usage of bgworkers in that branch it doesn't seem worth
creating a variant patch for it.
Discussion: https://postgr.es/m/18733.1570382257@sss.pgh.pa.us
This is a second try at what commit 57431a911 tried to do, namely,
launch the syslogger before we open postmaster sockets so that our
messages about the sockets end up in the syslogger files. That
commit fell foul of a bunch of subtle issues caused by trying to
launch a postmaster child process before creating shared memory.
Rather than messing with that interaction, let's postpone opening
the sockets till after we launch the syslogger.
This would not have been terribly safe before commit 7de19fbc0,
because we relied on socket opening to detect whether any competing
postmasters were using the same port number. But now that we choose
IPC keys without regard to the port number, there's no interaction
to worry about.
Also delay creation of the external PID file (if requested) till after
the sockets are open, since external code could plausibly be relying
on that ordering of events. And postpone most of the work of
RemovePgTempFiles() so that that potentially-slow processing still
happens after we make the external PID file. We have to be a bit
careful about that last though: as noted in the discussion subsequent to
bug #15804, EXEC_BACKEND builds still have to clear the parameter-file
temp dir before launching the syslogger.
Patch by me; thanks to Michael Paquier for review/testing.
Discussion: https://postgr.es/m/15804-3721117bf40fb654@postgresql.org
This approach provides a much tighter binding between a data directory
and the associated SysV shared memory block (and SysV or named-POSIX
semaphores, if we're using those). Key collisions are still possible,
but only between data directories stored on different filesystems,
so the situation should be negligible in practice. More importantly,
restarting the postmaster with a different port number no longer
risks failing to identify a relevant shared memory block, even when
postmaster.pid has been removed. A standalone backend is likewise
much more certain to detect conflicting leftover backends.
(In the longer term, we might now think about deprecating the port as
a cluster-wide value, so that one postmaster could support sockets
with varying port numbers. But that's for another day.)
The hazards fixed here apply only on Unix systems; our Windows code
paths already use identifiers derived from the data directory path
name rather than the port.
src/test/recovery/t/017_shm.pl, which intends to test key-collision
cases, has been substantially rewritten since it can no longer use
two postmasters with identical port numbers to trigger the case.
Instead, use Perl's IPC::SharedMem module to create a conflicting
shmem segment directly. The test script will be skipped if that
module is not available. (This means that some older buildfarm
members won't run it, but I don't think that that results in any
meaningful coverage loss.)
Patch by me; thanks to Noah Misch and Peter Eisentraut for discussion
and review.
Discussion: https://postgr.es/m/16908.1557521200@sss.pgh.pa.us
The logic ending progress reporting for a backend entry introduced by
b6fb647 causes callers of pgstat_progress_end_command() to do some extra
work when track_activities is enabled as the process fields are reset in
the backend entry even if no command were started for reporting.
This resets the fields only if a command is registered for progress
reporting, and only if track_activities is enabled.
Author: Masahiho Sawada
Discussion: https://postgr.es/m/CAD21AoCry_vJ0E-m5oxJXGL3pnos-xYGCzF95rK5Bbi3Uf-rpA@mail.gmail.com
Backpatch-through: 9.6
A report from Alvaro Herrera shows that if we're in PM_STARTUP
state, and we spawn a dead_end child to reject some incoming
connection request, and that child dies with an unexpected exit
code, the postmaster does not respond well. We correctly send
SIGQUIT to the startup process, but then:
* if the startup process exits with nonzero exit code, as expected,
we thought that that indicated a crash and aborted startup.
* if the startup process exits with zero exit code, which is possible
due to the inherent race condition, we'd advance to PM_RUN state
which is fine --- but the code forgot that AbortStartTime would be
nonzero in this situation. We'd either die on the Asserts saying
that it was zero, or perhaps misbehave later on. (A quick look
suggests that the only misbehavior might be busy-waiting due to
DetermineSleepTime doing the wrong thing.)
To fix the first point, adjust the state-machine logic to recognize
that a nonzero exit code is expected after sending SIGQUIT, and have
it transition to a state where we can restart the startup process.
To fix the second point, change the Asserts to clear the variable
rather than just claiming it should be clear already.
Perhaps we could improve this further by not treating a crash of
a dead_end child as a reason for panic'ing the database. However,
since those child processes are connected to shared memory, that
seems a bit risky. There are few good reasons for a dead_end child
to report failure anyway (the cause of this in Alvaro's report is
quite unclear). On balance, therefore, a minimal fix seems best.
This is an oversight in commit 45811be94. While that was back-patched,
I'm hesitant to back-patch this change. The lack of reasons for a
dead_end child to fail suggests that the case should be very rare in
the field, which squares with the lack of reports; so it seems like
this might not be worth the risk of introducing new issues. In any
case we can let it bake awhile in HEAD before considering a back-patch.
Discussion: https://postgr.es/m/20190615160950.GA31378@alvherre.pgsql
Alvaro Herrera
Stephen Frost
Tomas Vondra
Michael Paquier
Andres Freund
Fujii Masao
David Rowley
Andrew Dunstan
Peter Eisentraut
Tom Lane
Amit Kapila
Bruce Momjian
Robert Haas