*
* checkpointer.cpp
*
* The checkpointer is new as of Postgres 9.2. It handles all checkpoints.
* Checkpoints are automatically dispatched after a certain amount of time has
* elapsed since the last one, and it can be signaled to perform requested
* checkpoints as well. (The GUC parameter that mandates a checkpoint every
* so many WAL segments is implemented by having backends signal when they
* fill WAL segments; the checkpointer itself doesn't watch for the
* condition.)
*
* The checkpointer is started by the postmaster as soon as the startup
* subprocess finishes, or as soon as recovery begins if we are doing archive
* recovery. It remains alive until the postmaster commands it to terminate.
* Normal termination is by SIGUSR2, which instructs the checkpointer to
* execute a shutdown checkpoint and then exit(0). (All backends must be
* stopped before SIGUSR2 is issued!) Emergency termination is by SIGQUIT;
* like any backend, the checkpointer will simply abort and exit on SIGQUIT.
*
* If the checkpointer exits unexpectedly, the postmaster treats that the same
* as a backend crash: shared memory may be corrupted, so remaining backends
* should be killed by SIGQUIT and then a recovery cycle started. (Even if
* shared memory isn't corrupted, we have lost information about which
* files need to be fsync'd for the next checkpoint, and so a system
* restart needs to be forced.)
*
* Portions Copyright (c) 2020 Huawei Technologies Co.,Ltd.
* Portions Copyright (c) 1996-2012, PostgreSQL Global Development Group
*
* IDENTIFICATION
* src/gausskernel/process/postmaster/checkpointer.cpp
*
* -------------------------------------------------------------------------
*/
#include "postgres.h"
#include "knl/knl_variable.h"
#include <signal.h>
#include <sys/time.h>
#include "access/xlog_internal.h"
#include "access/xlog.h"
#include "libpq/pqsignal.h"
#include "miscadmin.h"
#include "pgstat.h"
#include "postmaster/bgwriter.h"
#include "postmaster/pagewriter.h"
#include "replication/syncrep.h"
#include "replication/ss_disaster_cluster.h"
#include "storage/buf/bufmgr.h"
#include "storage/ipc.h"
#include "storage/lock/lwlock.h"
#include "storage/smgr/knl_usync.h"
#include "storage/smgr/relfilenode_hash.h"
#include "storage/proc.h"
#include "storage/shmem.h"
#include "storage/smgr/smgr.h"
#include "storage/spin.h"
#include "utils/guc.h"
#include "utils/memutils.h"
#include "utils/resowner.h"
#include "gssignal/gs_signal.h"
#include "postmaster/pagewriter.h"
* Shared memory area for communication between checkpointer and backends
*
* The ckpt counters allow backends to watch for completion of a checkpoint
* request they send. Here's how it works:
* * At start of a checkpoint, checkpointer reads (and clears) the request
* flags and increments ckpt_started, while holding ckpt_lck.
* * On completion of a checkpoint, checkpointer sets ckpt_done to
* equal ckpt_started.
* * On failure of a checkpoint, checkpointer increments ckpt_failed
* and sets ckpt_done to equal ckpt_started.
*
* The algorithm for backends is:
* 1. Record current values of ckpt_failed and ckpt_started, and
* set request flags, while holding ckpt_lck.
* 2. Send signal to request checkpoint.
* 3. Sleep until ckpt_started changes. Now you know a checkpoint has
* begun since you started this algorithm (although *not* that it was
* specifically initiated by your signal), and that it is using your flags.
* 4. Record new value of ckpt_started.
* 5. Sleep until ckpt_done >= saved value of ckpt_started. (Use modulo
* arithmetic here in case counters wrap around.) Now you know a
* checkpoint has started and completed, but not whether it was
* successful.
* 6. If ckpt_failed is different from the originally saved value,
* assume request failed; otherwise it was definitely successful.
*
* ckpt_flags holds the OR of the checkpoint request flags sent by all
* requesting backends since the last checkpoint start. The flags are
* chosen so that OR'ing is the correct way to combine multiple requests.
*
* num_backend_writes is used to count the number of buffer writes performed
* by user backend processes. This counter should be wide enough that it
* can't overflow during a single processing cycle. num_backend_fsync
* counts the subset of those writes that also had to do their own fsync,
* because the checkpointer failed to absorb their request.
*
* The requests array holds fsync requests sent by backends and not yet
* absorbed by the checkpointer.
*
* Unlike the checkpoint fields, num_backend_writes, num_backend_fsync, and
* the requests fields are protected by CheckpointerCommLock.
*
* fsync_request_launched, fsync_request_absorbed and fsync_request_finished are
* used for communication between main pagewriter and checkpointer as following:
* 1. main pagewriter sets fsync_request_launched to be true when it finds dw file is out of space.
* 2. main pagewriter waits in a loop for fsync_request_finished to be set
* 3. Before ckpt performs a smgrsync, it sets fsync_request_absorbed to be true and resets fsync_request_launched.
* 4. After ckpt successfully finishes a smgrsync, it sets fsync_request_finished and resets fsync_request_absorbed.
* 5. main pagewriter quits the above loop and resets fsync_request_finished.
* Note: if multiple pagewriters are to be allowed to reset dw file, then each of them needs such three flags.
* In the future, we may change dw file into a ring. Pagewriter will only wait for vaccant dw file space while dw file
* is truncated solely by checkpointer through its smgrsync.
* ----------
*/
typedef struct CheckpointerShmemStruct {
ThreadId checkpointer_pid;
slock_t ckpt_lck;
int64 fsync_start;
int64 fsync_done;
int64 fsync_request;
int ckpt_started;
int ckpt_done;
int ckpt_failed;
int ckpt_flags;
uint32 num_backend_writes;
uint32 num_backend_fsync;
int num_requests;
int max_requests;
CheckpointerRequest requests[1];
} CheckpointerShmemStruct;
#ifdef ENABLE_MOT
typedef struct CheckpointCallbackItem {
struct CheckpointCallbackItem* next;
CheckpointCallback callback;
void* arg;
} CheckpointCallbackItem;
#endif
extern volatile PMState pmState;
#define WRITES_PER_ABSORB 1000
static void CheckArchiveTimeout(void);
static bool IsCheckpointOnSchedule(double progress);
static bool ImmediateCheckpointRequested(void);
static bool CompactCheckpointerRequestQueue(void);
static void UpdateSharedMemoryConfig(void);
static void chkpt_quickdie(SIGNAL_ARGS);
static void ChkptSigHupHandler(SIGNAL_ARGS);
static void ReqCheckpointHandler(SIGNAL_ARGS);
static void chkpt_sigusr1_handler(SIGNAL_ARGS);
static void ReqShutdownHandler(SIGNAL_ARGS);
* Main entry point for checkpointer process
*
* This is invoked from AuxiliaryProcessMain, which has already created the
* basic execution environment, but not enabled signals yet.
*/
void CheckpointerMain(void)
{
sigjmp_buf local_sigjmp_buf;
MemoryContext checkpointer_context;
bool bgwriter_first_startup = true;
t_thrd.checkpoint_cxt.CheckpointerShmem->checkpointer_pid = t_thrd.proc_cxt.MyProcPid;
u_sess->attr.attr_storage.CheckPointTimeout = ENABLE_INCRE_CKPT
? u_sess->attr.attr_storage.incrCheckPointTimeout
: u_sess->attr.attr_storage.fullCheckPointTimeout;
ereport(
LOG, (errmsg("checkpointer started, CheckPointTimeout is %d", u_sess->attr.attr_storage.CheckPointTimeout)));
* Properly accept or ignore signals the postmaster might send us
*
* Note: we deliberately ignore SIGTERM, because during a standard Unix
* system shutdown cycle, init will SIGTERM all processes at once. We
* want to wait for the backends to exit, whereupon the postmaster will
* tell us it's okay to shut down (via SIGUSR2).
*/
(void)gspqsignal(SIGURG, print_stack);
(void)gspqsignal(SIGHUP, ChkptSigHupHandler);
* file */
(void)gspqsignal(SIGINT, ReqCheckpointHandler);
(void)gspqsignal(SIGTERM, SIG_IGN);
(void)gspqsignal(SIGQUIT, chkpt_quickdie);
(void)gspqsignal(SIGALRM, SIG_IGN);
(void)gspqsignal(SIGPIPE, SIG_IGN);
(void)gspqsignal(SIGUSR1, chkpt_sigusr1_handler);
(void)gspqsignal(SIGUSR2, ReqShutdownHandler);
* Reset some signals that are accepted by postmaster but not here
*/
(void)gspqsignal(SIGCHLD, SIG_DFL);
(void)gspqsignal(SIGTTIN, SIG_DFL);
(void)gspqsignal(SIGTTOU, SIG_DFL);
(void)gspqsignal(SIGCONT, SIG_DFL);
(void)gspqsignal(SIGWINCH, SIG_DFL);
sigdelset(&t_thrd.libpq_cxt.BlockSig, SIGQUIT);
* Initialize so that first time-driven event happens at the correct time.
*/
t_thrd.checkpoint_cxt.last_checkpoint_time = t_thrd.checkpoint_cxt.last_truncate_log_time =
t_thrd.checkpoint_cxt.last_xlog_switch_time = (pg_time_t)time(NULL);
* Create a resource owner to keep track of our resources (currently only
* buffer pins).
*/
t_thrd.utils_cxt.CurrentResourceOwner = ResourceOwnerCreate(NULL, "Checkpointer",
THREAD_GET_MEM_CXT_GROUP(MEMORY_CONTEXT_STORAGE));
* Create a memory context that we will do all our work in. We do this so
* that we can reset the context during error recovery and thereby avoid
* possible memory leaks. Formerly this code just ran in
* t_thrd.top_mem_cxt, but resetting that would be a really bad idea.
*/
checkpointer_context = AllocSetContextCreate(t_thrd.top_mem_cxt,
"Checkpointer",
ALLOCSET_DEFAULT_MINSIZE,
ALLOCSET_DEFAULT_INITSIZE,
ALLOCSET_DEFAULT_MAXSIZE);
MemoryContextSwitchTo(checkpointer_context);
* If an exception is encountered, processing resumes here.
*
* See notes in postgres.c about the design of this coding.
*/
int curTryCounter;
int* oldTryCounter = NULL;
if (sigsetjmp(local_sigjmp_buf, 1) != 0) {
gstrace_tryblock_exit(true, oldTryCounter);
* Close all open files after any error. This is helpful on Windows,
* where holding deleted files open causes various strange errors.
* It's not clear we need it elsewhere, but shouldn't hurt.
*/
t_thrd.log_cxt.error_context_stack = NULL;
t_thrd.log_cxt.call_stack = NULL;
HOLD_INTERRUPTS();
EmitErrorReport();
AbortAsyncListIO();
#ifdef ENABLE_MOT
CallCheckpointCallback(EVENT_CHECKPOINT_ABORT, 0);
#endif
AtEOXact_SysDBCache(false);
* These operations are really just a minimal subset of
* AbortTransaction(). We don't have very many resources to worry
* about in checkpointer, but we do have LWLocks, buffers, and temp
* files.
*/
LWLockReleaseAll();
pgstat_report_waitevent(WAIT_EVENT_END);
AbortBufferIO();
UnlockBuffers();
ResourceOwnerRelease(t_thrd.utils_cxt.CurrentResourceOwner, RESOURCE_RELEASE_BEFORE_LOCKS, false, true);
AtEOXact_Buffers(false);
AtEOXact_SMgr();
AtEOXact_Files();
AtEOXact_HashTables(false);
crps_destory_ctxs();
if (t_thrd.checkpoint_cxt.ckpt_active) {
volatile CheckpointerShmemStruct* cps = t_thrd.checkpoint_cxt.CheckpointerShmem;
SpinLockAcquire(&cps->ckpt_lck);
cps->ckpt_failed++;
cps->ckpt_done = cps->ckpt_started;
SpinLockRelease(&cps->ckpt_lck);
t_thrd.checkpoint_cxt.ckpt_active = false;
}
* Now return to normal top-level context and clear ErrorContext for
* next time.
*/
MemoryContextSwitchTo(checkpointer_context);
FlushErrorState();
MemoryContextResetAndDeleteChildren(checkpointer_context);
RESUME_INTERRUPTS();
* Sleep at least 1 second after any error. A write error is likely
* to be repeated, and we don't want to be filling the error logs as
* fast as we can.
*/
pg_usleep(1000000L);
}
oldTryCounter = gstrace_tryblock_entry(&curTryCounter);
t_thrd.log_cxt.PG_exception_stack = &local_sigjmp_buf;
* Unblock signals (they were blocked when the postmaster forked us)
*/
gs_signal_setmask(&t_thrd.libpq_cxt.UnBlockSig, NULL);
(void)gs_signal_unblock_sigusr2();
* Use the recovery target timeline ID during recovery
*/
if (RecoveryInProgress())
t_thrd.xlog_cxt.ThisTimeLineID = GetRecoveryTargetTLI();
* Ensure all shared memory values are set correctly for the config. Doing
* this here ensures no race conditions from other concurrent updaters.
*/
UpdateSharedMemoryConfig();
* Advertise our latch that backends can use to wake us up while we're
* sleeping.
*/
g_instance.proc_base->checkpointerLatch = &t_thrd.proc->procLatch;
crps_create_ctxs(CHECKPOINT_THREAD);
pgstat_report_appname("CheckPointer");
pgstat_report_activity(STATE_IDLE, NULL);
* Loop forever
*/
for (;;) {
bool do_checkpoint = false;
bool do_dirty_flush = false;
int flags = 0;
pg_time_t now;
int elapsed_secs;
int cur_timeout;
int rc;
ResetLatch(&t_thrd.proc->procLatch);
pgstat_report_activity(STATE_RUNNING, NULL);
* Process any requests or signals received recently.
*/
CkptAbsorbFsyncRequests();
if (t_thrd.checkpoint_cxt.got_SIGHUP) {
t_thrd.checkpoint_cxt.got_SIGHUP = false;
ProcessConfigFile(PGC_SIGHUP);
u_sess->attr.attr_storage.CheckPointTimeout = ENABLE_INCRE_CKPT
? u_sess->attr.attr_storage.incrCheckPointTimeout
: u_sess->attr.attr_storage.fullCheckPointTimeout;
most_available_sync = (volatile bool) u_sess->attr.attr_storage.guc_most_available_sync;
* Checkpointer is the last process to shut down, so we ask it to
* hold the keys for a range of other tasks required most of which
* have nothing to do with checkpointing at all.
*
* For various reasons, some config values can change dynamically
* so the primary copy of them is held in shared memory to make
* sure all backends see the same value. We make Checkpointer
* responsible for updating the shared memory copy if the
* parameter setting changes because of SIGHUP.
*/
UpdateSharedMemoryConfig();
}
if (bgwriter_first_startup && !RecoveryInProgress()) {
t_thrd.checkpoint_cxt.checkpoint_requested = true;
flags = CHECKPOINT_IMMEDIATE;
bgwriter_first_startup = false;
ereport(LOG, (errmsg("database first startup and recovery finish, so do checkpointer.")));
}
if (t_thrd.checkpoint_cxt.checkpoint_requested) {
t_thrd.checkpoint_cxt.checkpoint_requested = false;
do_checkpoint = true;
u_sess->stat_cxt.BgWriterStats->m_requested_checkpoints++;
}
if (t_thrd.checkpoint_cxt.shutdown_requested || pmState == PM_SHUTDOWN) {
* From here on, elog(ERROR) should end with exit(1), not send
* control back to the sigsetjmp block above
*/
u_sess->attr.attr_common.ExitOnAnyError = true;
ShutdownXLOG(0, 0);
crps_destory_ctxs();
proc_exit(0);
}
* Force a checkpoint if too much time has elapsed since the last one.
* Note that we count a timed checkpoint in stats only when this
* occurs without an external request, but we set the CAUSE_TIME flag
* bit even if there is also an external request.
*/
now = (pg_time_t)time(NULL);
elapsed_secs = now - t_thrd.checkpoint_cxt.last_checkpoint_time;
if (elapsed_secs >= u_sess->attr.attr_storage.CheckPointTimeout) {
if (!do_checkpoint)
u_sess->stat_cxt.BgWriterStats->m_timed_checkpoints++;
do_checkpoint = true;
flags |= CHECKPOINT_CAUSE_TIME;
}
* Do a checkpoint if requested.
*/
if (do_checkpoint) {
bool ckpt_performed = false;
bool do_restartpoint = false;
volatile CheckpointerShmemStruct* cps = t_thrd.checkpoint_cxt.CheckpointerShmem;
* Check if we should perform a checkpoint or a restartpoint. As a
* side-effect, RecoveryInProgress() initializes TimeLineID if
* it's not set yet.
*/
do_restartpoint = RecoveryInProgress();
* Atomically fetch the request flags to figure out what kind of a
* checkpoint we should perform, and increase the started-counter
* to acknowledge that we've started a new checkpoint.
*/
SpinLockAcquire(&cps->ckpt_lck);
flags |= cps->ckpt_flags;
cps->ckpt_flags = 0;
cps->ckpt_started++;
SpinLockRelease(&cps->ckpt_lck);
* The end-of-recovery checkpoint is a real checkpoint that's
* performed while we're still in recovery.
*/
if (flags & CHECKPOINT_END_OF_RECOVERY) {
do_restartpoint = false;
}
* We will warn if (a) too soon since last checkpoint (whatever
* caused it) and (b) somebody set the CHECKPOINT_CAUSE_XLOG flag
* since the last checkpoint start. Note in particular that this
* implementation will not generate warnings caused by
* CheckPointTimeout < CheckPointWarning.
*/
if (!do_restartpoint && (flags & CHECKPOINT_CAUSE_XLOG) &&
elapsed_secs < u_sess->attr.attr_storage.CheckPointWarning)
ereport(LOG,
(errmsg_plural("checkpoints are occurring too frequently (%d second apart)",
"checkpoints are occurring too frequently (%d seconds apart)",
elapsed_secs,
elapsed_secs),
errhint("Consider increasing the configuration parameter \"checkpoint_segments\".")));
* Initialize checkpointer-private variables used during
* checkpoint
*/
t_thrd.checkpoint_cxt.ckpt_active = true;
if (!do_restartpoint)
t_thrd.checkpoint_cxt.ckpt_start_recptr = GetInsertRecPtr();
t_thrd.checkpoint_cxt.ckpt_start_time = now;
t_thrd.checkpoint_cxt.ckpt_cached_elapsed = 0;
if (flags & CHECKPOINT_FLUSH_DIRTY) {
do_dirty_flush = true;
}
* Do a normal checkpoint/restartpoint.
*/
if (do_dirty_flush) {
ereport(LOG, (errmsg("[file repair] request checkpoint, flush all dirty page.")));
Assert(RecoveryInProgress());
if (ENABLE_INCRE_CKPT) {
g_instance.ckpt_cxt_ctl->full_ckpt_expected_flush_loc = get_dirty_page_queue_tail();
pg_memory_barrier();
if (get_dirty_page_num() > 0) {
g_instance.ckpt_cxt_ctl->flush_all_dirty_page = true;
ereport(LOG, (errmsg("[file repair] need flush %ld pages.", get_dirty_page_num())));
CheckPointBuffers(flags, true);
}
} else {
CheckPointBuffers(flags, true);
}
} else if (!do_restartpoint && !SS_DISASTER_STANDBY_CLUSTER) {
CreateCheckPoint(flags);
ckpt_performed = true;
if (!bgwriter_first_startup && CheckFpwBeforeFirstCkpt()) {
DisableFpwBeforeFirstCkpt();
}
} else {
ckpt_performed = CreateRestartPoint(flags);
}
* After any checkpoint, close all smgr files. This is so we
* won't hang onto smgr references to deleted files indefinitely.
*/
smgrcloseall();
* Indicate checkpoint completion to any waiting backends.
*/
SpinLockAcquire(&cps->ckpt_lck);
cps->ckpt_done = cps->ckpt_started;
SpinLockRelease(&cps->ckpt_lck);
if (ckpt_performed) {
* Note we record the checkpoint start time not end time as
* t_thrd.checkpoint_cxt.last_checkpoint_time. This is so that time-driven
* checkpoints happen at a predictable spacing.
*/
t_thrd.checkpoint_cxt.last_checkpoint_time = now;
} else if (!do_dirty_flush) {
* We were not able to perform the restartpoint (checkpoints
* throw an ERROR in case of error). Most likely because we
* have not received any new checkpoint WAL records since the
* last restartpoint. Try again in 15 s.
*/
t_thrd.checkpoint_cxt.last_checkpoint_time = now - u_sess->attr.attr_storage.CheckPointTimeout + 15;
}
t_thrd.checkpoint_cxt.ckpt_active = false;
}
CheckArchiveTimeout();
* Send off activity statistics to the stats collector. (The reason
* why we re-use bgwriter-related code for this is that the bgwriter
* and checkpointer used to be just one process. It's probably not
* worth the trouble to split the stats support into two independent
* stats message types.)
*/
pgstat_send_bgwriter();
* Sleep until we are signaled or it's time for another checkpoint or
* xlog file switch.
*/
now = (pg_time_t)time(NULL);
elapsed_secs = now - t_thrd.checkpoint_cxt.last_checkpoint_time;
elapsed_secs = (elapsed_secs < 0) ? 0 : elapsed_secs;
if (elapsed_secs >= u_sess->attr.attr_storage.CheckPointTimeout)
continue;
cur_timeout = u_sess->attr.attr_storage.CheckPointTimeout - elapsed_secs;
if (u_sess->attr.attr_common.XLogArchiveTimeout > 0 && !RecoveryInProgress()) {
elapsed_secs = now - t_thrd.checkpoint_cxt.last_xlog_switch_time;
if (elapsed_secs >= u_sess->attr.attr_common.XLogArchiveTimeout)
continue;
cur_timeout = Min(cur_timeout, u_sess->attr.attr_common.XLogArchiveTimeout - elapsed_secs);
}
pgstat_report_activity(STATE_IDLE, NULL);
rc = WaitLatch(&t_thrd.proc->procLatch,
WL_LATCH_SET | WL_TIMEOUT | WL_POSTMASTER_DEATH,
cur_timeout * 1000L );
* Emergency bailout if postmaster has died. This is to avoid the
* necessity for manual cleanup of all postmaster children.
*/
if (rc & WL_POSTMASTER_DEATH) {
crps_destory_ctxs();
gs_thread_exit(1);
}
}
}
* CheckArchiveTimeout -- check for archive_timeout and switch xlog files
*
* This will switch to a new WAL file and force an archive file write
* if any activity is recorded in the current WAL file, including just
* a single checkpoint record.
*/
static void CheckArchiveTimeout(void)
{
pg_time_t now;
pg_time_t last_time;
if (u_sess->attr.attr_common.XLogArchiveTimeout <= 0 || RecoveryInProgress())
return;
now = (pg_time_t)time(NULL);
if ((int)(now - t_thrd.checkpoint_cxt.last_xlog_switch_time) < u_sess->attr.attr_common.XLogArchiveTimeout)
return;
* Update local state ... note that t_thrd.checkpoint_cxt.last_xlog_switch_time is the last time
* a switch was performed *or requested*.
*/
last_time = GetLastSegSwitchTime();
t_thrd.checkpoint_cxt.last_xlog_switch_time = Max(t_thrd.checkpoint_cxt.last_xlog_switch_time, last_time);
if ((int)(now - t_thrd.checkpoint_cxt.last_xlog_switch_time) >= u_sess->attr.attr_common.XLogArchiveTimeout) {
XLogRecPtr switchpoint;
switchpoint = RequestXLogSwitch();
* If the returned pointer points exactly to a segment boundary,
* assume nothing happened.
*/
if ((switchpoint % XLogSegSize) != 0)
ereport(DEBUG1,
(errmsg("transaction log switch forced (archive_timeout=%d)",
u_sess->attr.attr_common.XLogArchiveTimeout)));
* Update state in any case, so we don't retry constantly when the
* system is idle.
*/
t_thrd.checkpoint_cxt.last_xlog_switch_time = now;
}
}
* Returns true if an immediate checkpoint request is pending. (Note that
* this does not check the *current* checkpoint's IMMEDIATE flag, but whether
* there is one pending behind it.)
*/
static bool ImmediateCheckpointRequested(void)
{
if (t_thrd.checkpoint_cxt.checkpoint_requested) {
volatile CheckpointerShmemStruct* cps = t_thrd.checkpoint_cxt.CheckpointerShmem;
* We don't need to acquire the ckpt_lck in this case because we're
* only looking at a single flag bit.
*/
if (cps->ckpt_flags & CHECKPOINT_IMMEDIATE)
return true;
}
return false;
}
* CheckpointWriteDelay -- control rate of checkpoint
*
* This function is called after each page write performed by BufferSync().
* It is responsible for throttling BufferSync()'s write rate to hit
* checkpoint_completion_target.
*
* The checkpoint request flags should be passed in; currently the only one
* examined is CHECKPOINT_IMMEDIATE, which disables delays between writes.
*
* 'progress' is an estimate of how much of the work has been done, as a
* fraction between 0.0 meaning none, and 1.0 meaning all done.
*/
void CheckpointWriteDelay(int flags, double progress)
{
if (!AmCheckpointerProcess())
return;
* Perform the usual duties and take a nap, unless we're behind schedule,
* in which case we just try to catch up as quickly as possible.
*/
if (!((uint32)flags & CHECKPOINT_IMMEDIATE) && !t_thrd.checkpoint_cxt.shutdown_requested &&
!ImmediateCheckpointRequested() && IsCheckpointOnSchedule(progress)) {
if (t_thrd.checkpoint_cxt.got_SIGHUP) {
t_thrd.checkpoint_cxt.got_SIGHUP = false;
ProcessConfigFile(PGC_SIGHUP);
most_available_sync = (volatile bool)u_sess->attr.attr_storage.guc_most_available_sync;
UpdateSharedMemoryConfig();
}
CkptAbsorbFsyncRequests();
t_thrd.checkpoint_cxt.absorbCounter = WRITES_PER_ABSORB;
CheckArchiveTimeout();
* Report interim activity statistics to the stats collector.
*/
pgstat_send_bgwriter();
* This sleep used to be connected to bgwriter_delay, typically 200ms.
* That resulted in more frequent wakeups if not much work to do.
* Checkpointer and bgwriter are no longer related so take the Big
* Sleep.
*/
pg_usleep(100000L);
} else if (--t_thrd.checkpoint_cxt.absorbCounter <= 0) {
* Absorb pending fsync requests after each WRITES_PER_ABSORB write
* operations even when we don't sleep, to prevent overflow of the
* fsync request queue.
*/
CkptAbsorbFsyncRequests();
t_thrd.checkpoint_cxt.absorbCounter = WRITES_PER_ABSORB;
}
}
* IsCheckpointOnSchedule -- are we on schedule to finish this checkpoint
* in time?
*
* Compares the current progress against the time/segments elapsed since last
* checkpoint, and returns true if the progress we've made this far is greater
* than the elapsed time/segments.
*/
static bool IsCheckpointOnSchedule(double progress)
{
XLogRecPtr recptr;
struct timeval now;
double elapsed_xlogs, elapsed_time;
Assert(t_thrd.checkpoint_cxt.ckpt_active);
u_sess->attr.attr_storage.CheckPointTimeout = ENABLE_INCRE_CKPT
? u_sess->attr.attr_storage.incrCheckPointTimeout
: u_sess->attr.attr_storage.fullCheckPointTimeout;
progress *= u_sess->attr.attr_storage.CheckPointCompletionTarget;
* Check against the cached value first. Only do the more expensive
* calculations once we reach the target previously calculated. Since
* neither time or WAL insert pointer moves backwards, a freshly
* calculated value can only be greater than or equal to the cached value.
*/
if (progress < t_thrd.checkpoint_cxt.ckpt_cached_elapsed)
return false;
* Check progress against WAL segments written and checkpoint_segments.
*
* We compare the current WAL insert location against the location
* computed before calling CreateCheckPoint. The code in XLogInsert that
* actually triggers a checkpoint when checkpoint_segments is exceeded
* compares against RedoRecptr, so this is not completely accurate.
* However, it's good enough for our purposes, we're only calculating an
* estimate anyway.
*/
if (!RecoveryInProgress()) {
recptr = GetInsertRecPtr();
elapsed_xlogs = (((double)(recptr - t_thrd.checkpoint_cxt.ckpt_start_recptr)) / XLogSegSize) /
(u_sess->attr.attr_storage.CheckPointSegments);
if (progress < elapsed_xlogs) {
t_thrd.checkpoint_cxt.ckpt_cached_elapsed = elapsed_xlogs;
return false;
}
}
* Check progress against time elapsed and checkpoint_timeout.
*/
gettimeofday(&now, NULL);
elapsed_time = ((double)((pg_time_t)now.tv_sec - t_thrd.checkpoint_cxt.ckpt_start_time) + now.tv_usec / 1000000.0) /
u_sess->attr.attr_storage.CheckPointTimeout;
if (progress < elapsed_time) {
t_thrd.checkpoint_cxt.ckpt_cached_elapsed = elapsed_time;
return false;
}
return true;
}
* signal handler routines
* --------------------------------
*/
* chkpt_quickdie() occurs when signalled SIGQUIT by the postmaster.
*
* Some backend has bought the farm,
* so we need to stop what we're doing and exit.
*/
static void chkpt_quickdie(SIGNAL_ARGS)
{
gs_signal_setmask(&t_thrd.libpq_cxt.BlockSig, NULL);
* We DO NOT want to run proc_exit() callbacks -- we're here because
* shared memory may be corrupted, so we don't want to try to clean up our
* transaction. Just nail the windows shut and get out of town. Now that
* there's an atexit callback to prevent third-party code from breaking
* things by calling exit() directly, we have to reset the callbacks
* explicitly to make this work as intended.
*/
on_exit_reset();
* Note we do exit(2) not exit(0). This is to force the postmaster into a
* system reset cycle if some idiot DBA sends a manual SIGQUIT to a random
* backend. This is necessary precisely because we don't clean up our
* shared memory state. (The "dead man switch" mechanism in pmsignal.c
* should ensure the postmaster sees this as a crash, too, but no harm in
* being doubly sure.)
*/
crps_destory_ctxs();
exit(2);
}
static void ChkptSigHupHandler(SIGNAL_ARGS)
{
int save_errno = errno;
t_thrd.checkpoint_cxt.got_SIGHUP = true;
if (t_thrd.proc)
SetLatch(&t_thrd.proc->procLatch);
errno = save_errno;
}
static void ReqCheckpointHandler(SIGNAL_ARGS)
{
int save_errno = errno;
t_thrd.checkpoint_cxt.checkpoint_requested = true;
if (t_thrd.proc)
SetLatch(&t_thrd.proc->procLatch);
errno = save_errno;
}
static void chkpt_sigusr1_handler(SIGNAL_ARGS)
{
int save_errno = errno;
latch_sigusr1_handler();
errno = save_errno;
}
static void ReqShutdownHandler(SIGNAL_ARGS)
{
int save_errno = errno;
t_thrd.checkpoint_cxt.shutdown_requested = true;
if (t_thrd.proc)
SetLatch(&t_thrd.proc->procLatch);
errno = save_errno;
}
* communication with backends
* --------------------------------
*/
* CheckpointerShmemSize
* Compute space needed for checkpointer-related shared memory
*/
const uint DDL_REQUEST_MAX = 100000;
Size CheckpointerShmemSize(void)
{
Size size;
* Currently, the size of the requests[] array is arbitrarily set equal to
* NBuffers. This may prove too large or small ...
*/
size = offsetof(CheckpointerShmemStruct, requests);
if (ENABLE_INCRE_CKPT) {
size = add_size(size, mul_size(DDL_REQUEST_MAX, sizeof(CheckpointerRequest)));
} else {
size = add_size(size, mul_size(TOTAL_BUFFER_NUM, sizeof(CheckpointerRequest)));
}
return size;
}
* CheckpointerShmemInit
* Allocate and initialize checkpointer-related shared memory
*/
void CheckpointerShmemInit(void)
{
Size size = CheckpointerShmemSize();
bool found = false;
t_thrd.checkpoint_cxt.CheckpointerShmem =
(CheckpointerShmemStruct*)ShmemInitStruct("Checkpointer Data", size, &found);
if (!found) {
* First time through, so initialize. Note that we zero the whole
* requests array; this is so that CompactCheckpointerRequestQueue
* can assume that any pad bytes in the request structs are zeroes.
*/
MemSet((char*)t_thrd.checkpoint_cxt.CheckpointerShmem, 0, size);
SpinLockInit(&t_thrd.checkpoint_cxt.CheckpointerShmem->ckpt_lck);
t_thrd.checkpoint_cxt.CheckpointerShmem->max_requests = ENABLE_INCRE_CKPT ? DDL_REQUEST_MAX : TOTAL_BUFFER_NUM;
}
}
* Check wheter checkpoint proc is running while waiting request checkpoint to finish.
*/
static void CheckPointProcRunning(void)
{
if (g_instance.pid_cxt.CheckpointerPID == 0) {
ereport(FATAL,
(errcode(ERRCODE_WITH_CHECK_OPTION_VIOLATION),
errmsg("could not request checkpoint because checkpointer not running")));
}
}
* RequestCheckpoint
* Called in backend processes to request a checkpoint
*
* flags is a bitwise OR of the following:
* CHECKPOINT_IS_SHUTDOWN: checkpoint is for database shutdown.
* CHECKPOINT_END_OF_RECOVERY: checkpoint is for end of WAL recovery.
* CHECKPOINT_IMMEDIATE: finish the checkpoint ASAP,
* ignoring checkpoint_completion_target parameter.
* CHECKPOINT_FORCE: force a checkpoint even if no XLOG activity has occurred
* since the last one (implied by CHECKPOINT_IS_SHUTDOWN or
* CHECKPOINT_END_OF_RECOVERY).
* CHECKPOINT_WAIT: wait for completion before returning (otherwise,
* just signal checkpointer to do it, and return).
* CHECKPOINT_CAUSE_XLOG: checkpoint is requested due to xlog filling.
* (This affects logging, and in particular enables CheckPointWarning.)
*/
void RequestCheckpoint(int flags)
{
volatile CheckpointerShmemStruct* cps = t_thrd.checkpoint_cxt.CheckpointerShmem;
int ntries;
int old_failed, old_started;
* If in a standalone backend, just do it ourselves.
*/
if (!IsPostmasterEnvironment) {
* There's no point in doing slow checkpoints in a standalone backend,
* because there's no other backends the checkpoint could disrupt.
*/
CreateCheckPoint(flags | CHECKPOINT_IMMEDIATE);
* After any checkpoint, close all smgr files. This is so we won't
* hang onto smgr references to deleted files indefinitely.
*/
smgrcloseall();
return;
}
* Atomically set the request flags, and take a snapshot of the counters.
* When we see ckpt_started > old_started, we know the flags we set here
* have been seen by checkpointer.
*
* Note that we OR the flags with any existing flags, to avoid overriding
* a "stronger" request by another backend. The flag senses must be
* chosen to make this work!
*/
SpinLockAcquire(&cps->ckpt_lck);
old_failed = cps->ckpt_failed;
old_started = cps->ckpt_started;
cps->ckpt_flags |= flags;
SpinLockRelease(&cps->ckpt_lck);
* Send signal to request checkpoint. It's possible that the checkpointer
* hasn't started yet, or is in process of restarting, so we will retry a
* few times if needed. Also, if not told to wait for the checkpoint to
* occur, we consider failure to send the signal to be nonfatal and merely
* LOG it.
*/
for (ntries = 0;; ntries++) {
if (t_thrd.checkpoint_cxt.CheckpointerShmem->checkpointer_pid == 0) {
if (ntries >= (u_sess->attr.attr_storage.CheckPointWaitTimeOut * 10) || pmState == PM_SHUTDOWN_2) {
if (flags & CHECKPOINT_WAIT) {
ereport(ERROR,
(errcode(ERRCODE_WITH_CHECK_OPTION_VIOLATION),
errmsg("could not request checkpoint because checkpointer not running")));
} else {
ereport(LOG, (errmsg("could not request checkpoint because checkpointer not running")));
}
break;
}
} else if (gs_signal_send(t_thrd.checkpoint_cxt.CheckpointerShmem->checkpointer_pid, SIGINT) != 0) {
if (ntries >= (u_sess->attr.attr_storage.CheckPointWaitTimeOut * 10)) {
if (flags & CHECKPOINT_WAIT) {
ereport(ERROR,
(errcode(ERRCODE_WITH_CHECK_OPTION_VIOLATION), errmsg("could not signal for checkpoint: %m")));
} else {
ereport(LOG, (errmsg("could not signal for checkpoint: %m")));
}
break;
}
} else {
break;
}
CHECK_FOR_INTERRUPTS();
pg_usleep(100000L);
}
* If requested, wait for completion. We detect completion according to
* the algorithm given above.
*/
if (flags & CHECKPOINT_WAIT) {
int new_started, new_failed;
for (;;) {
SpinLockAcquire(&cps->ckpt_lck);
new_started = cps->ckpt_started;
SpinLockRelease(&cps->ckpt_lck);
if (new_started != old_started) {
break;
}
CHECK_FOR_INTERRUPTS();
CheckPointProcRunning();
pg_usleep(100000L);
}
* We are waiting for ckpt_done >= new_started, in a modulo sense.
*/
for (;;) {
int new_done;
SpinLockAcquire(&cps->ckpt_lck);
new_done = cps->ckpt_done;
new_failed = cps->ckpt_failed;
SpinLockRelease(&cps->ckpt_lck);
if (new_done - new_started >= 0) {
break;
}
CHECK_FOR_INTERRUPTS();
CheckPointProcRunning();
pg_usleep(100000L);
}
if (new_failed != old_failed)
ereport(ERROR,
(errcode(ERRCODE_WITH_CHECK_OPTION_VIOLATION),
errmsg("checkpoint request failed"),
errhint("Consult recent messages in the server log for details.")));
}
}
* ForwardSyncRequest
* Forward a file-fsync request from a backend to the checkpointer
*
* Whenever a backend is compelled to write directly to a relation
* (which should be seldom, if the background writer is getting its job done),
* the backend calls this routine to pass over knowledge that the relation
* is dirty and must be fsync'd before next checkpoint. We also use this
* opportunity to count such writes for statistical purposes.
*
* To avoid holding the lock for longer than necessary, we normally write
* to the requests[] queue without checking for duplicates. The checkpointer
* will have to eliminate dups internally anyway. However, if we discover
* that the queue is full, we make a pass over the entire queue to compact
* it. This is somewhat expensive, but the alternative is for the backend
* to perform its own fsync, which is far more expensive in practice. It
* is theoretically possible a backend fsync might still be necessary, if
* the queue is full and contains no duplicate entries. In that case, we
* let the backend know by returning false.
*/
bool CkptForwardSyncRequest(const FileTag *ftag, SyncRequestType type)
{
CheckpointerRequest* request = NULL;
bool too_full = false;
if (!IsUnderPostmaster) {
return false;
}
if (AmCheckpointerProcess()) {
ereport(ERROR,
(errcode(ERRCODE_WITH_CHECK_OPTION_VIOLATION),
errmsg("ForwardFsyncRequest must not be called in checkpointer")));
}
LWLockAcquire(CheckpointerCommLock, LW_EXCLUSIVE);
if (!AmBackgroundWriterProcess() && !AmPageWriterProcess()) {
t_thrd.checkpoint_cxt.CheckpointerShmem->num_backend_writes++;
}
* If the checkpointer isn't running or the request queue is full, the
* backend will have to perform its own fsync request. But before forcing
* that to happen, we can try to compact the request queue.
*/
if (t_thrd.checkpoint_cxt.CheckpointerShmem->checkpointer_pid == 0 ||
(t_thrd.checkpoint_cxt.CheckpointerShmem->num_requests >=
t_thrd.checkpoint_cxt.CheckpointerShmem->max_requests &&
!CompactCheckpointerRequestQueue())) {
* Count the subset of writes where backends have to do their own
* fsync
*/
if (!AmBackgroundWriterProcess() && !AmPageWriterProcess()) {
t_thrd.checkpoint_cxt.CheckpointerShmem->num_backend_fsync++;
}
LWLockRelease(CheckpointerCommLock);
return false;
}
request =
&t_thrd.checkpoint_cxt.CheckpointerShmem->requests[t_thrd.checkpoint_cxt.CheckpointerShmem->num_requests++];
request->ftag = *ftag;
request->type = type;
too_full = (t_thrd.checkpoint_cxt.CheckpointerShmem->num_requests >=
t_thrd.checkpoint_cxt.CheckpointerShmem->max_requests / 2);
LWLockRelease(CheckpointerCommLock);
if (too_full && g_instance.proc_base->checkpointerLatch) {
SetLatch(g_instance.proc_base->checkpointerLatch);
}
return true;
}
int getDuplicateRequest(CheckpointerRequest *requests, int num_requests, bool *skip_slot)
{
struct CheckpointerSlotMapping {
CheckpointerRequest request;
int slot;
};
int n;
int num_skipped = 0;
HASHCTL ctl;
HTAB* htab = NULL;
errno_t rc = memset_s(&ctl, sizeof(ctl), 0, sizeof(ctl));
securec_check(rc, "\0", "\0");
ctl.keysize = sizeof(CheckpointerRequest);
ctl.entrysize = sizeof(struct CheckpointerSlotMapping);
ctl.hash = CheckpointerRequestHash;
ctl.match = CheckpointerRequestMatch;
ctl.hcxt = CurrentMemoryContext;
htab = hash_create("CompactRequestQueue", num_requests, &ctl,
HASH_ELEM | HASH_FUNCTION | HASH_CONTEXT | HASH_COMPARE);
* The basic idea here is that a request can be skipped if it's followed
* by a later, identical request. It might seem more sensible to work
* backwards from the end of the queue and check whether a request is
* *preceded* by an earlier, identical request, in the hopes of doing less
* copying. But that might change the semantics, if there's an
* intervening FORGET_RELATION_FSYNC or FORGET_DATABASE_FSYNC request, so
* we do it this way. It would be possible to be even smarter if we made
* the code below understand the specific semantics of such requests (it
* could blow away preceding entries that would end up being canceled
* anyhow), but it's not clear that the extra complexity would buy us
* anything.
*/
for (n = 0; n < num_requests; n++) {
CheckpointerRequest* request = NULL;
struct CheckpointerSlotMapping* slotmap;
bool found = false;
* We use the request struct directly as a hashtable key. This
* assumes that any padding bytes in the structs are consistently the
* same, which should be okay because we zeroed them in
* CheckpointerShmemInit. Note also that RelFileNode had better
* contain no pad bytes.
*/
request = &requests[n];
slotmap = (CheckpointerSlotMapping*)hash_search(htab, request, HASH_ENTER, &found);
if (found) {
skip_slot[slotmap->slot] = true;
num_skipped++;
}
slotmap->slot = n;
}
hash_destroy(htab);
if (!num_skipped) {
return 0;
}
return num_skipped;
}
* CompactCheckpointerRequestQueue
* Remove duplicates from the request queue to avoid backend fsyncs.
* Returns "true" if any entries were removed.
*
* Although a full fsync request queue is not common, it can lead to severe
* performance problems when it does happen. So far, this situation has
* only been observed to occur when the system is under heavy write load,
* and especially during the "sync" phase of a checkpoint. Without this
* logic, each backend begins doing an fsync for every block written, which
* gets very expensive and can slow down the whole system.
*
* Trying to do this every time the queue is full could lose if there
* aren't any removable entries. But that should be vanishingly rare in
* practice: there's one queue entry per shared buffer.
*/
static bool CompactCheckpointerRequestQueue(void)
{
int preserve_count;
bool* skip_slot = NULL;
int num_skipped = 0;
Assert(LWLockHeldByMe(CheckpointerCommLock));
skip_slot = (bool*)palloc0(sizeof(bool) * t_thrd.checkpoint_cxt.CheckpointerShmem->num_requests);
num_skipped = getDuplicateRequest(t_thrd.checkpoint_cxt.CheckpointerShmem->requests,
t_thrd.checkpoint_cxt.CheckpointerShmem->num_requests, skip_slot);
if (num_skipped == 0) {
pfree(skip_slot);
return false;
}
preserve_count = 0;
for (int n = 0; n < t_thrd.checkpoint_cxt.CheckpointerShmem->num_requests; n++) {
if (skip_slot[n])
continue;
t_thrd.checkpoint_cxt.CheckpointerShmem->requests[preserve_count++] =
t_thrd.checkpoint_cxt.CheckpointerShmem->requests[n];
}
ereport(DEBUG1,
(errmsg("compacted fsync request queue from %d entries to %d entries",
t_thrd.checkpoint_cxt.CheckpointerShmem->num_requests,
preserve_count)));
t_thrd.checkpoint_cxt.CheckpointerShmem->num_requests = preserve_count;
pfree(skip_slot);
return true;
}
* AbsorbFsyncRequests
* Retrieve queued fsync requests and pass them to local smgr.
*
* This is exported because it must be called during CreateCheckPoint;
* we have to be sure we have accepted all pending requests just before
* we start fsync'ing. Since CreateCheckPoint sometimes runs in
* non-checkpointer processes, do nothing if not checkpointer.
*/
void CkptAbsorbFsyncRequests(void)
{
CheckpointerRequest* requests = NULL;
CheckpointerRequest* request = NULL;
int n;
if (!AmCheckpointerProcess())
return;
* We have to PANIC if we fail to absorb all the pending requests (eg,
* because our hashtable runs out of memory). This is because the system
* cannot run safely if we are unable to fsync what we have been told to
* fsync. Fortunately, the hashtable is so small that the problem is
* quite unlikely to arise in practice.
*/
START_CRIT_SECTION();
* We try to avoid holding the lock for a long time by copying the request
* array.
*/
LWLockAcquire(CheckpointerCommLock, LW_EXCLUSIVE);
u_sess->stat_cxt.BgWriterStats->m_buf_written_backend +=
t_thrd.checkpoint_cxt.CheckpointerShmem->num_backend_writes;
u_sess->stat_cxt.BgWriterStats->m_buf_fsync_backend += t_thrd.checkpoint_cxt.CheckpointerShmem->num_backend_fsync;
t_thrd.checkpoint_cxt.CheckpointerShmem->num_backend_writes = 0;
t_thrd.checkpoint_cxt.CheckpointerShmem->num_backend_fsync = 0;
n = t_thrd.checkpoint_cxt.CheckpointerShmem->num_requests;
if (n > 0) {
errno_t rc;
requests = (CheckpointerRequest*)palloc(n * sizeof(CheckpointerRequest));
rc = memcpy_s(requests,
n * sizeof(CheckpointerRequest),
t_thrd.checkpoint_cxt.CheckpointerShmem->requests,
n * sizeof(CheckpointerRequest));
securec_check(rc, "\0", "\0");
}
t_thrd.checkpoint_cxt.CheckpointerShmem->num_requests = 0;
LWLockRelease(CheckpointerCommLock);
for (request = requests; n > 0; request++, n--) {
RememberSyncRequest(&request->ftag, request->type);
}
if (requests != NULL) {
pfree(requests);
}
END_CRIT_SECTION();
}
* Update any shared memory configurations based on config parameters
*/
static void UpdateSharedMemoryConfig(void)
{
SyncRepUpdateSyncStandbysDefined();
* If full_page_writes has been changed by SIGHUP, we update it in shared
* memory and write an XLOG_FPW_CHANGE record.
*/
UpdateFullPageWrites();
ereport(DEBUG2, (errmsg("checkpointer updated shared memory configuration values")));
}
* FirstCallSinceLastCheckpoint allows a process to take an action once
* per checkpoint cycle by asynchronously checking for checkpoint completion.
*/
bool FirstCallSinceLastCheckpoint(void)
{
volatile CheckpointerShmemStruct* cps = t_thrd.checkpoint_cxt.CheckpointerShmem;
int new_done;
bool FirstCall = false;
SpinLockAcquire(&cps->ckpt_lck);
new_done = cps->ckpt_done;
SpinLockRelease(&cps->ckpt_lck);
if (new_done != t_thrd.checkpoint_cxt.ckpt_done)
FirstCall = true;
t_thrd.checkpoint_cxt.ckpt_done = new_done;
return FirstCall;
}
bool CheckpointInProgress(void)
{
bool inProgress = false;
volatile CheckpointerShmemStruct* cps = t_thrd.checkpoint_cxt.CheckpointerShmem;
SpinLockAcquire(&cps->ckpt_lck);
if (cps->ckpt_done != cps->ckpt_started) {
inProgress = true;
}
SpinLockRelease(&cps->ckpt_lck);
ereport(LOG, (errmsg("CheckpointInProgress: ckpt_done=%d, ckpt_started=%d",
cps->ckpt_done, cps->ckpt_started)));
return inProgress;
}
#ifdef ENABLE_MOT
void RegisterCheckpointCallback(CheckpointCallback callback, void* arg)
{
CheckpointCallbackItem *item;
item = (CheckpointCallbackItem*)MemoryContextAlloc(
INSTANCE_GET_MEM_CXT_GROUP(MEMORY_CONTEXT_STORAGE), sizeof(CheckpointCallbackItem));
item->callback = callback;
item->arg = arg;
item->next = g_instance.ckpt_cxt_ctl->ckptCallback;
g_instance.ckpt_cxt_ctl->ckptCallback = item;
}
void CallCheckpointCallback(CheckpointEvent checkpointEvent, XLogRecPtr lsn)
{
CheckpointCallbackItem* item;
for (item = g_instance.ckpt_cxt_ctl->ckptCallback; item; item = item->next) {
(*item->callback) (checkpointEvent, lsn, item->arg);
}
}
#endif
