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walwriter.h File Reference
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Functions

void WalWriterMain (void) pg_attribute_noreturn()
 

Variables

int WalWriterDelay
 
int WalWriterFlushAfter
 

Function Documentation

◆ WalWriterMain()

void WalWriterMain ( void  )

Definition at line 98 of file walwriter.c.

References AbortBufferIO(), ALLOCSET_DEFAULT_SIZES, AllocSetContextCreate, AtEOXact_Buffers(), AtEOXact_Files(), AtEOXact_HashTables(), AtEOXact_SMgr(), BlockSig, ConditionVariableCancelSleep(), EmitErrorReport(), error_context_stack, FlushErrorState(), got_SIGHUP, HIBERNATE_FACTOR, HOLD_INTERRUPTS, LOOPS_UNTIL_HIBERNATE, LWLockReleaseAll(), MemoryContextResetAndDeleteChildren, MemoryContextSwitchTo(), MyLatch, MyProc, PG_exception_stack, PG_SETMASK, pg_usleep(), PGC_SIGHUP, pgstat_report_wait_end(), pqsignal(), proc_exit(), ProcessConfigFile(), ProcGlobal, PGPROC::procLatch, procsignal_sigusr1_handler(), ReleaseAuxProcessResources(), ResetLatch(), RESUME_INTERRUPTS, SetWalWriterSleeping(), shutdown_requested, SIG_DFL, SIG_IGN, SIGALRM, SIGCHLD, SIGHUP, SIGPIPE, SIGQUIT, SIGUSR1, SIGUSR2, smgrcloseall(), TopMemoryContext, UnBlockSig, UnlockBuffers(), WAIT_EVENT_WAL_WRITER_MAIN, WaitLatch(), wal_quickdie(), WalShutdownHandler(), WalSigHupHandler(), WalWriterDelay, PROC_HDR::walwriterLatch, WL_EXIT_ON_PM_DEATH, WL_LATCH_SET, WL_TIMEOUT, and XLogBackgroundFlush().

Referenced by AuxiliaryProcessMain().

99 {
100  sigjmp_buf local_sigjmp_buf;
101  MemoryContext walwriter_context;
102  int left_till_hibernate;
103  bool hibernating;
104 
105  /*
106  * Properly accept or ignore signals the postmaster might send us
107  *
108  * We have no particular use for SIGINT at the moment, but seems
109  * reasonable to treat like SIGTERM.
110  */
111  pqsignal(SIGHUP, WalSigHupHandler); /* set flag to read config file */
112  pqsignal(SIGINT, WalShutdownHandler); /* request shutdown */
113  pqsignal(SIGTERM, WalShutdownHandler); /* request shutdown */
114  pqsignal(SIGQUIT, wal_quickdie); /* hard crash time */
118  pqsignal(SIGUSR2, SIG_IGN); /* not used */
119 
120  /*
121  * Reset some signals that are accepted by postmaster but not here
122  */
124 
125  /* We allow SIGQUIT (quickdie) at all times */
126  sigdelset(&BlockSig, SIGQUIT);
127 
128  /*
129  * Create a memory context that we will do all our work in. We do this so
130  * that we can reset the context during error recovery and thereby avoid
131  * possible memory leaks. Formerly this code just ran in
132  * TopMemoryContext, but resetting that would be a really bad idea.
133  */
134  walwriter_context = AllocSetContextCreate(TopMemoryContext,
135  "Wal Writer",
137  MemoryContextSwitchTo(walwriter_context);
138 
139  /*
140  * If an exception is encountered, processing resumes here.
141  *
142  * This code is heavily based on bgwriter.c, q.v.
143  */
144  if (sigsetjmp(local_sigjmp_buf, 1) != 0)
145  {
146  /* Since not using PG_TRY, must reset error stack by hand */
147  error_context_stack = NULL;
148 
149  /* Prevent interrupts while cleaning up */
150  HOLD_INTERRUPTS();
151 
152  /* Report the error to the server log */
153  EmitErrorReport();
154 
155  /*
156  * These operations are really just a minimal subset of
157  * AbortTransaction(). We don't have very many resources to worry
158  * about in walwriter, but we do have LWLocks, and perhaps buffers?
159  */
163  AbortBufferIO();
164  UnlockBuffers();
166  AtEOXact_Buffers(false);
167  AtEOXact_SMgr();
168  AtEOXact_Files(false);
169  AtEOXact_HashTables(false);
170 
171  /*
172  * Now return to normal top-level context and clear ErrorContext for
173  * next time.
174  */
175  MemoryContextSwitchTo(walwriter_context);
176  FlushErrorState();
177 
178  /* Flush any leaked data in the top-level context */
179  MemoryContextResetAndDeleteChildren(walwriter_context);
180 
181  /* Now we can allow interrupts again */
183 
184  /*
185  * Sleep at least 1 second after any error. A write error is likely
186  * to be repeated, and we don't want to be filling the error logs as
187  * fast as we can.
188  */
189  pg_usleep(1000000L);
190 
191  /*
192  * Close all open files after any error. This is helpful on Windows,
193  * where holding deleted files open causes various strange errors.
194  * It's not clear we need it elsewhere, but shouldn't hurt.
195  */
196  smgrcloseall();
197  }
198 
199  /* We can now handle ereport(ERROR) */
200  PG_exception_stack = &local_sigjmp_buf;
201 
202  /*
203  * Unblock signals (they were blocked when the postmaster forked us)
204  */
206 
207  /*
208  * Reset hibernation state after any error.
209  */
210  left_till_hibernate = LOOPS_UNTIL_HIBERNATE;
211  hibernating = false;
212  SetWalWriterSleeping(false);
213 
214  /*
215  * Advertise our latch that backends can use to wake us up while we're
216  * sleeping.
217  */
219 
220  /*
221  * Loop forever
222  */
223  for (;;)
224  {
225  long cur_timeout;
226 
227  /*
228  * Advertise whether we might hibernate in this cycle. We do this
229  * before resetting the latch to ensure that any async commits will
230  * see the flag set if they might possibly need to wake us up, and
231  * that we won't miss any signal they send us. (If we discover work
232  * to do in the last cycle before we would hibernate, the global flag
233  * will be set unnecessarily, but little harm is done.) But avoid
234  * touching the global flag if it doesn't need to change.
235  */
236  if (hibernating != (left_till_hibernate <= 1))
237  {
238  hibernating = (left_till_hibernate <= 1);
239  SetWalWriterSleeping(hibernating);
240  }
241 
242  /* Clear any already-pending wakeups */
244 
245  /*
246  * Process any requests or signals received recently.
247  */
248  if (got_SIGHUP)
249  {
250  got_SIGHUP = false;
252  }
253  if (shutdown_requested)
254  {
255  /* Normal exit from the walwriter is here */
256  proc_exit(0); /* done */
257  }
258 
259  /*
260  * Do what we're here for; then, if XLogBackgroundFlush() found useful
261  * work to do, reset hibernation counter.
262  */
263  if (XLogBackgroundFlush())
264  left_till_hibernate = LOOPS_UNTIL_HIBERNATE;
265  else if (left_till_hibernate > 0)
266  left_till_hibernate--;
267 
268  /*
269  * Sleep until we are signaled or WalWriterDelay has elapsed. If we
270  * haven't done anything useful for quite some time, lengthen the
271  * sleep time so as to reduce the server's idle power consumption.
272  */
273  if (left_till_hibernate > 0)
274  cur_timeout = WalWriterDelay; /* in ms */
275  else
276  cur_timeout = WalWriterDelay * HIBERNATE_FACTOR;
277 
278  (void) WaitLatch(MyLatch,
280  cur_timeout,
282  }
283 }
#define SIGQUIT
Definition: win32_port.h:155
#define AllocSetContextCreate
Definition: memutils.h:170
#define WL_TIMEOUT
Definition: latch.h:127
void ProcessConfigFile(GucContext context)
#define SIGUSR1
Definition: win32_port.h:166
#define SIGCHLD
Definition: win32_port.h:164
PGPROC * MyProc
Definition: proc.c:67
void AtEOXact_Buffers(bool isCommit)
Definition: bufmgr.c:2423
void ReleaseAuxProcessResources(bool isCommit)
Definition: resowner.c:855
static void WalSigHupHandler(SIGNAL_ARGS)
Definition: walwriter.c:319
static MemoryContext MemoryContextSwitchTo(MemoryContext context)
Definition: palloc.h:109
#define LOOPS_UNTIL_HIBERNATE
Definition: walwriter.c:77
void proc_exit(int code)
Definition: ipc.c:104
PROC_HDR * ProcGlobal
Definition: proc.c:80
#define SIGPIPE
Definition: win32_port.h:159
#define SIGUSR2
Definition: win32_port.h:167
void FlushErrorState(void)
Definition: elog.c:1678
void ResetLatch(Latch *latch)
Definition: latch.c:519
#define PG_SETMASK(mask)
Definition: pqsignal.h:19
void AtEOXact_Files(bool isCommit)
Definition: fd.c:2818
Latch procLatch
Definition: proc.h:104
int WaitLatch(Latch *latch, int wakeEvents, long timeout, uint32 wait_event_info)
Definition: latch.c:344
void smgrcloseall(void)
Definition: smgr.c:286
#define RESUME_INTERRUPTS()
Definition: miscadmin.h:118
ErrorContextCallback * error_context_stack
Definition: elog.c:91
void pg_usleep(long microsec)
Definition: signal.c:53
void AtEOXact_SMgr(void)
Definition: smgr.c:655
Latch * walwriterLatch
Definition: proc.h:265
void ConditionVariableCancelSleep(void)
static void WalShutdownHandler(SIGNAL_ARGS)
Definition: walwriter.c:331
#define ALLOCSET_DEFAULT_SIZES
Definition: memutils.h:192
bool XLogBackgroundFlush(void)
Definition: xlog.c:2994
#define SIGHUP
Definition: win32_port.h:154
static volatile sig_atomic_t got_SIGHUP
Definition: walwriter.c:83
static volatile sig_atomic_t shutdown_requested
Definition: walwriter.c:84
sigset_t UnBlockSig
Definition: pqsignal.c:22
static void pgstat_report_wait_end(void)
Definition: pgstat.h:1342
MemoryContext TopMemoryContext
Definition: mcxt.c:44
Definition: guc.h:72
static void wal_quickdie(SIGNAL_ARGS)
Definition: walwriter.c:298
#define SIG_IGN
Definition: win32_port.h:151
void UnlockBuffers(void)
Definition: bufmgr.c:3574
#define MemoryContextResetAndDeleteChildren(ctx)
Definition: memutils.h:67
sigset_t BlockSig
Definition: pqsignal.c:22
void EmitErrorReport(void)
Definition: elog.c:1533
pqsigfunc pqsignal(int signum, pqsigfunc handler)
Definition: signal.c:170
#define SIG_DFL
Definition: win32_port.h:149
#define SIGALRM
Definition: win32_port.h:160
void AbortBufferIO(void)
Definition: bufmgr.c:4030
void SetWalWriterSleeping(bool sleeping)
Definition: xlog.c:12288
int WalWriterDelay
Definition: walwriter.c:69
sigjmp_buf * PG_exception_stack
Definition: elog.c:93
#define HOLD_INTERRUPTS()
Definition: miscadmin.h:116
struct Latch * MyLatch
Definition: globals.c:54
void LWLockReleaseAll(void)
Definition: lwlock.c:1825
void procsignal_sigusr1_handler(SIGNAL_ARGS)
Definition: procsignal.c:260
void AtEOXact_HashTables(bool isCommit)
Definition: dynahash.c:1834
#define WL_LATCH_SET
Definition: latch.h:124
#define WL_EXIT_ON_PM_DEATH
Definition: latch.h:129
#define HIBERNATE_FACTOR
Definition: walwriter.c:78

Variable Documentation

◆ WalWriterDelay

int WalWriterDelay

Definition at line 69 of file walwriter.c.

Referenced by LogicalRepApplyLoop(), WalWriterMain(), and XLogBackgroundFlush().

◆ WalWriterFlushAfter

int WalWriterFlushAfter

Definition at line 70 of file walwriter.c.

Referenced by XLogBackgroundFlush().