Presently, the archiver process restarts when an archive callback
ERRORs. To avoid this, archive module authors can use sigsetjmp(),
manage a memory context, etc., but that requires a lot of extra
code that will likely look roughly the same between modules. This
commit adds basic archive callback ERROR handling to pgarch.c so
that module authors won't ordinarily need to worry about this.
While this built-in handler attempts to clean up anything that an
archive module could conceivably have left behind, it is possible
that some modules are doing unexpected things that require
additional cleanup. Module authors should be sure to do any extra
required cleanup in a PG_CATCH block within the archiving callback.
The archiving callback is now called in a short-lived memory
context that the archiver process resets between invocations. If a
module requires longer-lived storage, it must maintain its own
memory context.
Thanks to these changes, the basic_archive module can be greatly
simplified.
Suggested-by: Andres Freund
Reviewed-by: Andres Freund, Yong Li
Discussion: https://postgr.es/m/20230217215624.GA3131134%40nathanxps13
Previously, binaryheap didn't support updating a key and removing a
node in an efficient way. For example, in order to remove a node from
the binaryheap, the caller had to pass the node's position within the
array that the binaryheap internally has. Removing a node from the
binaryheap is done in O(log n) but searching for the key's position is
done in O(n).
This commit adds a hash table to binaryheap in order to track the
position of each nodes in the binaryheap. That way, by using newly
added functions such as binaryheap_update_up() etc., both updating a
key and removing a node can be done in O(1) on an average and O(log n)
in worst case. This is known as the indexed binary heap. The caller
can specify to use the indexed binaryheap by passing indexed = true.
The current code does not use the new indexing logic, but it will be
used by an upcoming patch.
Reviewed-by: Vignesh C, Peter Smith, Hayato Kuroda, Ajin Cherian,
Tomas Vondra, Shubham Khanna
Discussion: https://postgr.es/m/CAD21AoDffo37RC-eUuyHJKVEr017V2YYDLyn1xF_00ofptWbkg%40mail.gmail.com
Introduce new postmaster_child_launch() function that deals with the
differences in EXEC_BACKEND mode.
Refactor the mechanism of passing information from the parent to child
process. Instead of using different command-line arguments when
launching the child process in EXEC_BACKEND mode, pass a
variable-length blob of startup data along with all the global
variables. The contents of that blob depend on the kind of child
process being launched. In !EXEC_BACKEND mode, we use the same blob,
but it's simply inherited from the parent to child process.
Reviewed-by: Tristan Partin, Andres Freund
Discussion: https://www.postgresql.org/message-id/7a59b073-5b5b-151e-7ed3-8b01ff7ce9ef@iki.fi
Presently, if an archive module's check_configured_cb callback
returns false, a generic WARNING message is emitted, which
unfortunately provides no actionable details about the reason why
the module is not configured. This commit introduces a macro that
archive module authors can use to add a DETAIL line to this WARNING
message.
Co-authored-by: Tung Nguyen
Reviewed-by: Daniel Gustafsson, Álvaro Herrera
Discussion: https://postgr.es/m/4109578306242a7cd5661171647e11b2%40oss.nttdata.com
Now that BackendId was just another index into the proc array, it was
redundant with the 0-based proc numbers used in other places. Replace
all usage of backend IDs with proc numbers.
The only place where the term "backend id" remains is in a few pgstat
functions that expose backend IDs at the SQL level. Those IDs are now
in fact 0-based ProcNumbers too, but the documentation still calls
them "backend ids". That term still seems appropriate to describe what
the numbers are, so I let it be.
One user-visible effect is that pg_temp_0 is now a valid temp schema
name, for backend with ProcNumber 0.
Reviewed-by: Andres Freund
Discussion: https://www.postgresql.org/message-id/8171f1aa-496f-46a6-afc3-c46fe7a9b407@iki.fi
Commit bd5132db55 introduced new atomic read/write functions with
full barrier semantics, which are intended to simplify converting
non-performance-critical code to use atomic variables. This commit
demonstrates one such conversion.
Reviewed-by: Yong Li
Discussion: https://postgr.es/m/20231110205128.GB1315705%40nathanxps13
Presently, we rely on each individual signal handler to save the
initial value of errno and then restore it before returning if
needed. This is easily forgotten and, if missed, often goes
undetected for a long time.
In commit 3b00fdba9f, we introduced a wrapper signal handler
function that checks whether MyProcPid matches getpid(). This
commit moves the aforementioned errno restoration code from the
individual signal handlers to the new wrapper handler so that we no
longer need to worry about missing it.
Reviewed-by: Andres Freund, Noah Misch
Discussion: https://postgr.es/m/20231121212008.GA3742740%40nathanxps13
Quotes are applied to GUCs in a very inconsistent way across the code
base, with a mix of double quotes or no quotes used. This commit
removes double quotes around all the GUC names that are obviously
referred to as parameters with non-English words (use of underscore,
mixed case, etc).
This is the result of a discussion with Álvaro Herrera, Nathan Bossart,
Laurenz Albe, Peter Eisentraut, Tom Lane and Daniel Gustafsson.
Author: Peter Smith
Discussion: https://postgr.es/m/CAHut+Pv-kSN8SkxSdoHano_wPubqcg5789ejhCDZAcLFceBR-w@mail.gmail.com
A new callback named startup_cb, called shortly after a module is
loaded, is added. This makes possible the initialization of any
additional state data required by a module. This initial state data can
be saved in a ArchiveModuleState, that is now passed down to all the
callbacks that can be defined in a module. With this design, it is
possible to have a per-module state, aimed at opening the door to the
support of more than one archive module.
The initialization of the callbacks is changed so as
_PG_archive_module_init() does not anymore give in input a
ArchiveModuleCallbacks that a module has to fill in with callback
definitions. Instead, a module now needs to return a const
ArchiveModuleCallbacks.
All the structure and callback definitions of archive modules are moved
into their own header, named archive_module.h, from pgarch.h.
Command-based archiving follows the same line, with a new set of files
named shell_archive.{c,h}.
There are a few more items that are under discussion to improve the
design of archive modules, like the fact that basic_archive calls
sigsetjmp() by itself to define its own error handling flow. These will
be adjusted later, the changes done here cover already a good portion
of what has been discussed.
Any modules created for v15 will need to be adjusted to this new
design.
Author: Nathan Bossart
Reviewed-by: Andres Freund
Discussion: https://postgr.es/m/20230130194810.6fztfgbn32e7qarj@awork3.anarazel.de
In the 90s we needed to deal with computers that still had the
pre-standard signal masking APIs. That hasn't been relevant for a very
long time on Unix systems, and c94ae9d8 got rid of a remaining
dependency in our Windows porting code. PG_SETMASK didn't expose
save/restore functionality, so we'd already started using sigprocmask()
directly in places, creating the visual distraction of having two ways
to spell it. It's not part of the API that extensions are expected to
be using (but if they are, the change will be trivial). It seems like a
good time to drop the old macro and just call the standard POSIX
function.
Reviewed-by: Nathan Bossart <nathandbossart@gmail.com>
Discussion: https://postgr.es/m/CA%2BhUKG%2BKfQgrhHP2DLTohX1WwubaCBHmTzGnAEDPZ-Gug-Xskg%40mail.gmail.com
As coded, the timeout given to WaitLatch() was always equal to
PGARCH_AUTOWAKE_INTERVAL, as time() was called two times repeatedly.
This simplification could have been done in d75288f.
While on it, this adjusts a comment in pgarch.c to describe the archiver
in a more neutral way.
Author: Sravan Kumar, Nathan Bossart
Reviewed-by: Kyotaro Horiguchi
Discussion: https://postgr.es/m/CA+=NbjjqYE9-Lnw7H7DAiS5jebmoMikwZQb_sBP7kgBCn9q6Hg@mail.gmail.com
Setting archive_library and archive_command at the same time is now an
error. Before, archive_library would take precedence over
archive_command.
Author: Nathan Bossart <nathandbossart@gmail.com>
Reviewed-by: Peter Eisentraut <peter.eisentraut@enterprisedb.com>
Reviewed-by: Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com>
Discussion: https://www.postgresql.org/message-id/20220914222736.GA3042279%40nathanxps13
As currently designed, with a callback registered in a ERROR_CLEANUP
block, the shutdown callback would get called twice when updating
archive_library on SIGHUP, which is something that we want to avoid to
ease the life of extension writers.
Anyway, an ERROR in the archiver process is treated as a FATAL, stopping
it immediately, hence there is no need for a ERROR_CLEANUP block.
Instead of that, the shutdown callback is not called upon
before_shmem_exit(), giving to the modules the opportunity to do any
cleanup actions before the server shuts down its subsystems.
While on it, this commit adds some testing coverage for the shutdown
callback. Neither shell_archive nor basic_archive have been using it,
and one is added to shell_archive, whose trigger is checked in a TAP
test through a shutdown sequence.
Author: Nathan Bossart, Bharath Rupireddy
Reviewed-by: Kyotaro Horiguchi, Michael Paquier
Discussion: https://postgr.es/m/20221015221328.GB1821022@nathanxps13
Backpatch-through: 15
Presently, archive status files are durably renamed from .ready to
.done to indicate that a file has been archived. Persisting this
rename to disk accounts for a significant amount of the overhead
associated with archiving. While durably renaming the file
prevents re-archiving in most cases, archive commands and libraries
must already gracefully handle attempts to re-archive the last
archived file after a crash (e.g., a crash immediately after
archive_command exits but before the server renames the status
file).
This change reduces the amount of overhead associated with
archiving by using rename() instead of durable_rename() to rename
the archive status files. As a consequence, the server is more
likely to attempt to re-archive files after a crash, but as noted
above, archive commands and modules are already expected to handle
this. It is also possible that the server will attempt to re-
archive files that have been removed or recycled, but the archiver
already handles this, too.
Author: Nathan Bossart
Reviewed-by: Kyotaro Horiguchi, Fujii Masao
Discussion: https://postgr.es/m/20220222011948.GA3850532@nathanxps13
The code for unloading a library has been commented-out for over 12
years, ever since commit 602a9ef5a7, and we're
no closer to supporting it now than we were back then.
Nathan Bossart, reviewed by Michael Paquier and by me.
Discussion: http://postgr.es/m/Ynsc9bRL1caUSBSE@paquier.xyz
Only the pgstat_send_* functions that are called from outside pgstat*.c are
renamed (the rest will go away). This is done separately from the - quite
large - shared memory statistics patch to make review easier.
Author: Andres Freund <andres@anarazel.de>
Reviewed-By: Kyotaro Horiguchi <horikyota.ntt@gmail.com>
Discussion: https://postgr.es/m/20220404041516.cctrvpadhuriawlq@alap3.anarazel.de
Soon the stats collector will be no more, with statistics instead getting
stored in shared memory. There are a lot of references to the stats collector
in comments. This commit replaces most of these references with "cumulative
statistics system", with the remaining ones getting replaced as part of
subsequent commits.
This is done separately from the - quite large - shared memory statistics
patch to make review easier.
Author: Andres Freund <andres@anarazel.de>
Reviewed-By: Justin Pryzby <pryzby@telsasoft.com>
Reviewed-By: Thomas Munro <thomas.munro@gmail.com>
Reviewed-By: Kyotaro Horiguchi <horikyota.ntt@gmail.com>
Discussion: https://postgr.es/m/20220303021600.hs34ghqcw6zcokdh@alap3.anarazel.de
Discussion: https://postgr.es/m/20220308205351.2xcn6k4x5yivcxyd@alap3.anarazel.de
Running a shell command for each file to be archived has a lot of
overhead and may not offer as much error checking as you want, or the
exact semantics that you want. So, offer the option to call a loadable
module for each file to be archived, rather than running a shell command.
Also, add a 'basic_archive' contrib module as an example implementation
that archives to a local directory.
Nathan Bossart, with a little bit of kibitzing by me.
Discussion: http://postgr.es/m/20220202224433.GA1036711@nathanxps13
Previously pg_log_backend_memory_contexts() could request to
log the memory contexts of backends, but not of auxiliary processes
such as checkpointer. This commit enhances the function so that
it can also send the request to auxiliary processes. It's useful to
look at the memory contexts of those processes for debugging purpose
and better understanding of the memory usage pattern of them.
Note that pg_log_backend_memory_contexts() cannot send the request
to logger or statistics collector. Because this logging request
mechanism is based on shared memory but those processes aren't
connected to that.
Author: Bharath Rupireddy
Reviewed-by: Vignesh C, Kyotaro Horiguchi, Fujii Masao
Discussion: https://postgr.es/m/CALj2ACU1nBzpacOK2q=a65S_4+Oaz_rLTsU1Ri0gf7YUmnmhfQ@mail.gmail.com
The arch_filenames[] array elements were one byte too small, so that
a maximum-length filename would get corrupted if another entry
were made after it. (Noted by Thomas Munro, fix by Nathan Bossart.)
Move these arrays into a palloc'd struct, so that we aren't wasting
a few kilobytes of static data in each non-archiver process.
Add a binaryheap_reset() call to make it plain that we start the
directory scan with an empty heap. I don't think there's any live
bug of that sort, but it seems fragile, and this is very cheap
insurance.
Cleanup for commit beb4e9ba1, so no back-patch needed.
Discussion: https://postgr.es/m/CA+hUKGLHAjHuKuwtzsW7uMJF4BVPcQRL-UMZG_HM-g0y7yLkUg@mail.gmail.com
Presently, the archive_status directory was scanned for each file to
archive. When there are many status files, say because archive_command
has been failing for a long time, these directory scans can get very
slow. With this change, the archiver remembers several files to archive
during each directory scan, speeding things up.
To ensure timeline history files are archived as quickly as possible,
XLogArchiveNotify() forces the archiver to do a new directory scan as
soon as the .ready file for one is created.
Nathan Bossart, per a long discussion involving many people. It is
not clear to me exactly who out of all those people reviewed this
particular patch.
Discussion: http://postgr.es/m/CA+TgmobhAbs2yabTuTRkJTq_kkC80-+jw=pfpypdOJ7+gAbQbw@mail.gmail.com
Discussion: http://postgr.es/m/620F3CE1-0255-4D66-9D87-0EADE866985A@amazon.com
This commit changes WAL archiver process so that it's treated as
an auxiliary process and can use shared memory. This is an infrastructure
patch required for upcoming shared-memory based stats collector patch
series. These patch series basically need any processes including archiver
that can report the statistics to access to shared memory. Since this patch
itself is useful to simplify the code and when users monitor the status of
archiver, it's committed separately in advance.
This commit simplifies the code for WAL archiving. For example, previously
backends need to signal to archiver via postmaster when they notify
archiver that there are some WAL files to archive. On the other hand,
this commit removes that signal to postmaster and enables backends to
notify archier directly using shared latch.
Also, as the side of this change, the information about archiver process
becomes viewable at pg_stat_activity view.
Author: Kyotaro Horiguchi
Reviewed-by: Andres Freund, Álvaro Herrera, Julien Rouhaud, Tomas Vondra, Arthur Zakirov, Fujii Masao
Discussion: https://postgr.es/m/20180629.173418.190173462.horiguchi.kyotaro@lab.ntt.co.jp
We decided that the policy established in commit 7634bd4f6 for
the bgwriter, checkpointer, walwriter, and walreceiver processes,
namely that they should accept SIGQUIT at all times, really ought
to apply uniformly to all postmaster children. Therefore, get
rid of the duplicative and inconsistent per-process code for
establishing that signal handler and removing SIGQUIT from BlockSig.
Instead, make InitPostmasterChild do it.
The handler set up by InitPostmasterChild is SignalHandlerForCrashExit,
which just summarily does _exit(2). In interactive backends, we
almost immediately replace that with quickdie, since we would prefer
to try to tell the client that we're dying. However, this patch is
changing the behavior of autovacuum (both launcher and workers), as
well as walsenders. Those processes formerly also used quickdie,
but AFAICS that was just mindless copy-and-paste: they don't have
any interactive client that's likely to benefit from being told this.
The stats collector continues to be an outlier, in that it thinks
SIGQUIT means normal exit. That should probably be changed for
consistency, but there's another patch set where that's being
dealt with, so I didn't do so here.
Discussion: https://postgr.es/m/644875.1599933441@sss.pgh.pa.us
Commit 8e19a8264 changed the SIGQUIT handlers of almost all server
processes not to run atexit callbacks. The archiver process was
skipped, perhaps because it's not connected to shared memory; but
it's just as true here that running atexit callbacks in a signal
handler is unsafe. So let's make it work like the rest.
In HEAD and v13, we can use the common SignalHandlerForCrashExit
handler. Before that, just tweak pgarch_exit to use _exit(2)
explicitly.
Like the previous commit, back-patch to all supported branches.
Kyotaro Horiguchi, back-patching by me
Discussion: https://postgr.es/m/1850884.1599601164@sss.pgh.pa.us
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
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
At the end of recovery for the post-promotion process, a new history
file is created followed by the last partial segment of the previous
timeline. Based on the timing, the archiver would first try to archive
the last partial segment and then the history file. This can delay the
detection of a new timeline taken, particularly depending on the time it
takes to transfer the last partial segment as it delays the moment the
history file of the new timeline gets archived. This can cause promoted
standbys to use the same timeline as one already taken depending on the
circumstances if multiple instances look at archives at the same
location.
This commit changes the order of archiving so as history files are
archived in priority over other file types, which reduces the likelihood
of the same timeline being taken (still not reducing the window to
zero), and it makes the archiver behave more consistently with the
startup process doing its post-promotion business.
Author: David Steele
Reviewed-by: Michael Paquier, Kyotaro Horiguchi
Discussion: https://postgr.es/m/929068cf-69e1-bba2-9dc0-e05986aed471@pgmasters.net
Backpatch-through: 9.5
At least as far back as the 2008 spec, POSIX has defined strsignal(3)
for looking up descriptive strings for signal numbers. We hadn't gotten
the word though, and were still using the crufty old sys_siglist array,
which is in no standard even though most Unixen provide it.
Aside from not being formally standards-compliant, this was just plain
ugly because it involved #ifdef's at every place using the code.
To eliminate the #ifdef's, create a portability function pg_strsignal,
which wraps strsignal(3) if available and otherwise falls back to
sys_siglist[] if available. The set of Unixen with neither API is
probably empty these days, but on any platform with neither, you'll
just get "unrecognized signal". All extant callers print the numeric
signal number too, so no need to work harder than that.
Along the way, upgrade pg_basebackup's child-error-exit reporting
to match the rest of the system.
Discussion: https://postgr.es/m/25758.1544983503@sss.pgh.pa.us
Commit ffa4cbd62 added logic to detect SIGPIPE failure of a COPY child
process, but it only worked correctly if the SIGPIPE occurred in the
immediate child process. Depending on the shell in use and the
complexity of the shell command string, we might instead get back
an exit code of 128 + SIGPIPE, representing a shell error exit
reporting SIGPIPE in the child process.
We could just hack up ClosePipeToProgram() to add the extra case,
but it seems like this is a fairly general issue deserving a more
general and better-documented solution. I chose to add a couple
of functions in src/common/wait_error.c, which is a natural place
to know about wait-result encodings, that will test for either a
specific child-process signal type or any child-process signal failure.
Then, adjust other places that were doing ad-hoc tests of this type
to use the common functions.
In RestoreArchivedFile, this fixes a race condition affecting whether
the process will report an error or just silently proc_exit(1): before,
that depended on whether the intermediate shell got SIGTERM'd itself
or reported a child process failing on SIGTERM.
Like the previous patch, back-patch to v10; we could go further
but there seems no real need to.
Per report from Erik Rijkers.
Discussion: https://postgr.es/m/f3683f87ab1701bea5d86a7742b22432@xs4all.nl
When a WAL segment is recycled, its ".ready" and ".done" status files
get also automatically removed, however this is not done in a durable
manner. Hence, in a subsequent crash, it could be possible that a
".ready" status file is still around with its corresponding segment
already gone.
If the backend reaches such a state, the archive command would most
likely complain about a segment non-existing and would keep retrying,
causing WAL segments to bloat pg_wal/, potentially making Postgres crash
hard when running out of space.
As status files are removed after each individual segment, using
durable_unlink() does not completely close the window either, as a crash
could happen between the moment the WAL segment is recycled and the
moment its status files are removed. This has also some performance
impact with the additional fsync() calls needed to make the removal in a
durable manner. Doing the cleanup at recovery is not cost-free either
as this makes crash recovery potentially take longer than necessary.
So, instead, as per an idea of Stephen Frost, make the archiver aware of
orphan status files and remove them on-the-fly if the corresponding
segment goes missing. Removal failures follow a model close to what
happens for WAL segments, where multiple attempts are done before giving
up temporarily, and where a successful orphan removal makes the archiver
move immediately to the next WAL segment thought as ready to be
archived.
Author: Michael Paquier
Reviewed-by: Nathan Bossart, Andres Freund, Stephen Frost, Kyotaro
Horiguchi
Discussion: https://postgr.es/m/20180928032827.GF1500@paquier.xyz
Users of the WaitEventSet and WaitLatch() APIs can now choose between
asking for WL_POSTMASTER_DEATH and then handling it explicitly, or asking
for WL_EXIT_ON_PM_DEATH to trigger immediate exit on postmaster death.
This reduces code duplication, since almost all callers want the latter.
Repair all code that was previously ignoring postmaster death completely,
or requesting the event but ignoring it, or requesting the event but then
doing an unconditional PostmasterIsAlive() call every time through its
event loop (which is an expensive syscall on platforms for which we don't
have USE_POSTMASTER_DEATH_SIGNAL support).
Assert that callers of WaitLatchXXX() under the postmaster remember to
ask for either WL_POSTMASTER_DEATH or WL_EXIT_ON_PM_DEATH, to prevent
future bugs.
The only process that doesn't handle postmaster death is syslogger. It
waits until all backends holding the write end of the syslog pipe
(including the postmaster) have closed it by exiting, to be sure to
capture any parting messages. By using the WaitEventSet API directly
it avoids the new assertion, and as a by-product it may be slightly
more efficient on platforms that have epoll().
Author: Thomas Munro
Reviewed-by: Kyotaro Horiguchi, Heikki Linnakangas, Tom Lane
Discussion: https://postgr.es/m/CAEepm%3D1TCviRykkUb69ppWLr_V697rzd1j3eZsRMmbXvETfqbQ%40mail.gmail.com,
https://postgr.es/m/CAEepm=2LqHzizbe7muD7-2yHUbTOoF7Q+qkSD5Q41kuhttRTwA@mail.gmail.com
For reasons lost in the mists of time, most postmaster child processes
reset SIGTTIN/SIGTTOU signal handling to SIG_DFL, with the major exception
that backend sessions do not. It seems like a pretty bad idea for any
postmaster children to do that: if stderr is connected to the terminal,
and the user has put the postmaster in background, any log output would
result in the child process freezing up. Hence, switch them all to
doing what backends do, ie, nothing. This allows them to inherit the
postmaster's SIG_IGN setting. On the other hand, manually-launched
processes such as standalone backends will have default processing,
which seems fine.
In passing, also remove useless resets of SIGCONT and SIGWINCH signal
processing. Perhaps the postmaster once changed those to something
besides SIG_DFL, but it doesn't now, so these are just wasted (and
confusing) syscalls.
Basically, this propagates the changes made in commit 8e2998d8a from
backends to other postmaster children. Probably the only reason these
calls now exist elsewhere is that I missed changing pgstat.c along with
postgres.c at the time.
Given the lack of field complaints that can be traced to this, I don't
presently feel a need to back-patch.
Discussion: https://postgr.es/m/5627.1542477392@sss.pgh.pa.us
This patch fixes a couple of low-probability bugs that could lead to
reporting an irrelevant errno value (and hence possibly a wrong SQLSTATE)
concerning directory-open or file-open failures. It also fixes places
where we took shortcuts in reporting such errors, either by using elog
instead of ereport or by using ereport but forgetting to specify an
errcode. And it eliminates a lot of just plain redundant error-handling
code.
In service of all this, export fd.c's formerly-static function
ReadDirExtended, so that external callers can make use of the coding
pattern
dir = AllocateDir(path);
while ((de = ReadDirExtended(dir, path, LOG)) != NULL)
if they'd like to treat directory-open failures as mere LOG conditions
rather than errors. Also fix FreeDir to be a no-op if we reach it
with dir == NULL, as such a coding pattern would cause.
Then, remove code at many call sites that was throwing an error or log
message for AllocateDir failure, as ReadDir or ReadDirExtended can handle
that job just fine. Aside from being a net code savings, this gets rid of
a lot of not-quite-up-to-snuff reports, as mentioned above. (In some
places these changes result in replacing a custom error message such as
"could not open tablespace directory" with more generic wording "could not
open directory", but it was agreed that the custom wording buys little as
long as we report the directory name.) In some other call sites where we
can't just remove code, change the error reports to be fully
project-style-compliant.
Also reorder code in restoreTwoPhaseData that was acquiring a lock
between AllocateDir and ReadDir; in the unlikely but surely not
impossible case that LWLockAcquire changes errno, AllocateDir failures
would be misreported. There is no great value in opening the directory
before acquiring TwoPhaseStateLock, so just do it in the other order.
Also fix CheckXLogRemoved to guarantee that it preserves errno,
as quite a number of call sites are implicitly assuming. (Again,
it's unlikely but I think not impossible that errno could change
during a SpinLockAcquire. If so, this function was broken for its
own purposes as well as breaking callers.)
And change a few places that were using not-per-project-style messages,
such as "could not read directory" when "could not open directory" is
more correct.
Back-patch the exporting of ReadDirExtended, in case we have occasion
to back-patch some fix that makes use of it; it's not needed right now
but surely making it global is pretty harmless. Also back-patch the
restoreTwoPhaseData and CheckXLogRemoved fixes. The rest of this is
essentially cosmetic and need not get back-patched.
Michael Paquier, with a bit of additional work by me
Discussion: https://postgr.es/m/CAB7nPqRpOCxjiirHmebEFhXVTK7V5Jvw4bz82p7Oimtsm3TyZA@mail.gmail.com
Remove gratuitous differences in the process names shown in
pg_stat_activity.backend_type and the ps output.
Reviewed-by: Takayuki Tsunakawa <tsunakawa.takay@jp.fujitsu.com>
Nathan Bossart
Masahiko Sawada
Heikki Linnakangas
Bruce Momjian
Michael Paquier
Thomas Munro
Peter Eisentraut
Fujii Masao
Tom Lane
Robert Haas
Andres Freund
Peter Eisentraut