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87a6690cc6
The main motivation for this change is to have a process that can serialize stats after all other processes have terminated. Serializing stats already happens in checkpointer, even though walsenders can be active longer. The only reason the current shutdown sequence does not actively cause problems is that walsender currently does not generate any stats. However, there is an upcoming patch changing that. Another need for this change originates in the AIO patchset, where IO workers (which, in some edge cases, can emit stats of their own) need to run while the shutdown checkpoint is being written. This commit changes the shutdown sequence so checkpointer is signalled (via SIGINT) to trigger writing the shutdown checkpoint without also causing checkpointer to exit. Once checkpointer wrote the shutdown checkpoint it notifies postmaster via PMSIGNAL_XLOG_IS_SHUTDOWN and waits for the termination signal (SIGUSR2, as before). Checkpointer now is terminated after all children, other than dead-end children and logger, have been terminated, tracked using the new PM_WAIT_CHECKPOINTER PMState. Reviewed-by: Heikki Linnakangas <hlinnaka@iki.fi> Reviewed-by: Bertrand Drouvot <bertranddrouvot.pg@gmail.com> Reviewed-by: Nazir Bilal Yavuz <byavuz81@gmail.com> Discussion: https://postgr.es/m/kgng5nrvnlv335evmsuvpnh354rw7qyazl73kdysev2cr2v5zu@m3cfzxicm5kp
109 lines
3.5 KiB
C
109 lines
3.5 KiB
C
/*-------------------------------------------------------------------------
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*
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* pmsignal.h
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* routines for signaling between the postmaster and its child processes
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*
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*
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* Portions Copyright (c) 1996-2025, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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* src/include/storage/pmsignal.h
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*
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*-------------------------------------------------------------------------
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*/
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#ifndef PMSIGNAL_H
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#define PMSIGNAL_H
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#include <signal.h>
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#ifdef HAVE_SYS_PRCTL_H
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#include "sys/prctl.h"
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#endif
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#ifdef HAVE_SYS_PROCCTL_H
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#include "sys/procctl.h"
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#endif
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/*
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* Reasons for signaling the postmaster. We can cope with simultaneous
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* signals for different reasons. If the same reason is signaled multiple
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* times in quick succession, however, the postmaster is likely to observe
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* only one notification of it. This is okay for the present uses.
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*/
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typedef enum
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{
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PMSIGNAL_RECOVERY_STARTED, /* recovery has started */
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PMSIGNAL_BEGIN_HOT_STANDBY, /* begin Hot Standby */
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PMSIGNAL_ROTATE_LOGFILE, /* send SIGUSR1 to syslogger to rotate logfile */
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PMSIGNAL_START_AUTOVAC_LAUNCHER, /* start an autovacuum launcher */
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PMSIGNAL_START_AUTOVAC_WORKER, /* start an autovacuum worker */
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PMSIGNAL_BACKGROUND_WORKER_CHANGE, /* background worker state change */
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PMSIGNAL_START_WALRECEIVER, /* start a walreceiver */
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PMSIGNAL_ADVANCE_STATE_MACHINE, /* advance postmaster's state machine */
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PMSIGNAL_XLOG_IS_SHUTDOWN, /* ShutdownXLOG() completed */
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} PMSignalReason;
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#define NUM_PMSIGNALS (PMSIGNAL_XLOG_IS_SHUTDOWN+1)
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/*
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* Reasons why the postmaster would send SIGQUIT to its children.
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*/
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typedef enum
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{
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PMQUIT_NOT_SENT = 0, /* postmaster hasn't sent SIGQUIT */
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PMQUIT_FOR_CRASH, /* some other backend bought the farm */
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PMQUIT_FOR_STOP, /* immediate stop was commanded */
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} QuitSignalReason;
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/* PMSignalData is an opaque struct, details known only within pmsignal.c */
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typedef struct PMSignalData PMSignalData;
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#ifdef EXEC_BACKEND
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extern PGDLLIMPORT volatile PMSignalData *PMSignalState;
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#endif
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/*
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* prototypes for functions in pmsignal.c
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*/
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extern Size PMSignalShmemSize(void);
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extern void PMSignalShmemInit(void);
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extern void SendPostmasterSignal(PMSignalReason reason);
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extern bool CheckPostmasterSignal(PMSignalReason reason);
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extern void SetQuitSignalReason(QuitSignalReason reason);
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extern QuitSignalReason GetQuitSignalReason(void);
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extern void MarkPostmasterChildSlotAssigned(int slot);
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extern bool MarkPostmasterChildSlotUnassigned(int slot);
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extern bool IsPostmasterChildWalSender(int slot);
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extern void RegisterPostmasterChildActive(void);
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extern void MarkPostmasterChildWalSender(void);
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extern bool PostmasterIsAliveInternal(void);
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extern void PostmasterDeathSignalInit(void);
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/*
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* Do we have a way to ask for a signal on parent death?
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*
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* If we do, pmsignal.c will set up a signal handler, that sets a flag when
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* the parent dies. Checking the flag first makes PostmasterIsAlive() a lot
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* cheaper in usual case that the postmaster is alive.
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*/
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#if (defined(HAVE_SYS_PRCTL_H) && defined(PR_SET_PDEATHSIG)) || \
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(defined(HAVE_SYS_PROCCTL_H) && defined(PROC_PDEATHSIG_CTL))
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#define USE_POSTMASTER_DEATH_SIGNAL
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#endif
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#ifdef USE_POSTMASTER_DEATH_SIGNAL
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extern PGDLLIMPORT volatile sig_atomic_t postmaster_possibly_dead;
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static inline bool
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PostmasterIsAlive(void)
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{
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if (likely(!postmaster_possibly_dead))
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return true;
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return PostmasterIsAliveInternal();
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}
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#else
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#define PostmasterIsAlive() PostmasterIsAliveInternal()
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#endif
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#endif /* PMSIGNAL_H */
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