database/postgres
1
0
Fork 0
mirror of https://github.com/postgres/postgres.git synced 2025-07-30 11:03:19 +03:00
Code Activity

checkpointer: Request checkpoint via latch instead of signal

Browse Source 
The motivation for this change is that a future commit will use SIGINT for
another purpose (postmaster requesting WAL access to be shut down) and that
there no other signals that we could readily use (see code comment for the
reason why SIGTERM shouldn't be used). But it's also a tad nicer / more
efficient to use SetLatch(), as it avoids sending signals when checkpointer
already is busy.

Reviewed-by: Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
Reviewed-by: Nazir Bilal Yavuz <byavuz81@gmail.com>
Discussion: https://postgr.es/m/kgng5nrvnlv335evmsuvpnh354rw7qyazl73kdysev2cr2v5zu@m3cfzxicm5kp
This commit is contained in:
Andres Freund
2025-01-24 17:00:10 -05:00
parent a5579a90af
commit 4d271e3ec2
1 changed files with 19 additions and 41 deletions
Download Patch File Download Diff File Expand all files Collapse all files

60
src/backend/postmaster/checkpointer.c
View File

@ -159,9 +159,6 @@ static bool ImmediateCheckpointRequested(void);
static bool CompactCheckpointerRequestQueue(void); static bool CompactCheckpointerRequestQueue(void);
static void UpdateSharedMemoryConfig(void); static void UpdateSharedMemoryConfig(void);
/* Signal handlers */
static void ReqCheckpointHandler(SIGNAL_ARGS);
/* /*
* Main entry point for checkpointer process * Main entry point for checkpointer process
@ -191,7 +188,7 @@ CheckpointerMain(char *startup_data, size_t startup_data_len)
* tell us it's okay to shut down (via SIGUSR2). * tell us it's okay to shut down (via SIGUSR2).
*/ */
pqsignal(SIGHUP, SignalHandlerForConfigReload); pqsignal(SIGHUP, SignalHandlerForConfigReload);
pqsignal(SIGINT, ReqCheckpointHandler); /* request checkpoint */ pqsignal(SIGINT, SIG_IGN);
pqsignal(SIGTERM, SIG_IGN); /* ignore SIGTERM */ pqsignal(SIGTERM, SIG_IGN); /* ignore SIGTERM */
/* SIGQUIT handler was already set up by InitPostmasterChild */ /* SIGQUIT handler was already set up by InitPostmasterChild */
pqsignal(SIGALRM, SIG_IGN); pqsignal(SIGALRM, SIG_IGN);
@ -860,23 +857,6 @@ IsCheckpointOnSchedule(double progress)
} }
/* --------------------------------
* signal handler routines
* --------------------------------
*/
/* SIGINT: set flag to run a normal checkpoint right away */
static void
ReqCheckpointHandler(SIGNAL_ARGS)
{
/*
* The signaling process should have set ckpt_flags nonzero, so all we
* need do is ensure that our main loop gets kicked out of any wait.
*/
SetLatch(MyLatch);
}
/* -------------------------------- /* --------------------------------
* communication with backends * communication with backends
* -------------------------------- * --------------------------------
@ -990,38 +970,36 @@ RequestCheckpoint(int flags)
SpinLockRelease(&CheckpointerShmem->ckpt_lck); SpinLockRelease(&CheckpointerShmem->ckpt_lck);
/* /*
* Send signal to request checkpoint. It's possible that the checkpointer * Set checkpointer's latch to request checkpoint. It's possible that the
* hasn't started yet, or is in process of restarting, so we will retry a * checkpointer hasn't started yet, so we will retry a few times if
* few times if needed. (Actually, more than a few times, since on slow * needed. (Actually, more than a few times, since on slow or overloaded
* or overloaded buildfarm machines, it's been observed that the * buildfarm machines, it's been observed that the checkpointer can take
* checkpointer can take several seconds to start.) However, if not told * several seconds to start.) However, if not told to wait for the
* to wait for the checkpoint to occur, we consider failure to send the * checkpoint to occur, we consider failure to set the latch to be
* signal to be nonfatal and merely LOG it. The checkpointer should see * nonfatal and merely LOG it. The checkpointer should see the request
* the request when it does start, with or without getting a signal. * when it does start, with or without the SetLatch().
*/ */
#define MAX_SIGNAL_TRIES 600 /* max wait 60.0 sec */ #define MAX_SIGNAL_TRIES 600 /* max wait 60.0 sec */
for (ntries = 0;; ntries++) for (ntries = 0;; ntries++)
{ {
if (CheckpointerShmem->checkpointer_pid == 0) volatile PROC_HDR *procglobal = ProcGlobal;
ProcNumber checkpointerProc = procglobal->checkpointerProc;
if (checkpointerProc == INVALID_PROC_NUMBER)
{ {
if (ntries >= MAX_SIGNAL_TRIES || !(flags & CHECKPOINT_WAIT)) if (ntries >= MAX_SIGNAL_TRIES || !(flags & CHECKPOINT_WAIT))
{ {
elog((flags & CHECKPOINT_WAIT) ? ERROR : LOG, elog((flags & CHECKPOINT_WAIT) ? ERROR : LOG,
"could not signal for checkpoint: checkpointer is not running"); "could not notify checkpoint: checkpointer is not running");
break;
}
}
else if (kill(CheckpointerShmem->checkpointer_pid, SIGINT) != 0)
{
if (ntries >= MAX_SIGNAL_TRIES || !(flags & CHECKPOINT_WAIT))
{
elog((flags & CHECKPOINT_WAIT) ? ERROR : LOG,
"could not signal for checkpoint: %m");
break; break;
} }
} }
else else
break; /* signal sent successfully */ {
SetLatch(&GetPGProcByNumber(checkpointerProc)->procLatch);
/* notified successfully */
break;
}
CHECK_FOR_INTERRUPTS(); CHECK_FOR_INTERRUPTS();
pg_usleep(100000L); /* wait 0.1 sec, then retry */ pg_usleep(100000L); /* wait 0.1 sec, then retry */