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Make standby server continuously retry restoring the next WAL segment with

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restore_command, if the connection to the primary server is lost. This
ensures that the standby can recover automatically, if the connection is
lost for a long time and standby falls behind so much that the required
WAL segments have been archived and deleted in the master.

This also makes standby_mode useful without streaming replication; the
server will keep retrying restore_command every few seconds until the
trigger file is found. That's the same basic functionality pg_standby
offers, but without the bells and whistles.

To implement that, refactor the ReadRecord/FetchRecord functions. The
FetchRecord() function introduced in the original streaming replication
patch is removed, and all the retry logic is now in a new function called
XLogReadPage(). XLogReadPage() is now responsible for executing
restore_command, launching walreceiver, and waiting for new WAL to arrive
from primary, as required.

This also changes the life cycle of walreceiver. When launched, it now only
tries to connect to the master once, and exits if the connection fails, or
is lost during streaming for any reason. The startup process detects the
death, and re-launches walreceiver if necessary.
This commit is contained in:
Heikki Linnakangas
2010-01-27 15:27:51 +00:00
parent ab13d1e925
commit 1bb2558046
6 changed files with 553 additions and 565 deletions
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182
src/backend/replication/walreceiver.c
View File

@@ -29,7 +29,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/replication/walreceiver.c,v 1.1 2010/01/20 09:16:24 heikki Exp $
* $PostgreSQL: pgsql/src/backend/replication/walreceiver.c,v 1.2 2010/01/27 15:27:51 heikki Exp $
*
*-------------------------------------------------------------------------
*/
@@ -134,8 +134,7 @@ static void WalRcvShutdownHandler(SIGNAL_ARGS);
static void WalRcvQuickDieHandler(SIGNAL_ARGS);
/* Prototypes for private functions */
static void InitWalRcv(void);
static void WalRcvKill(int code, Datum arg);
static void WalRcvDie(int code, Datum arg);
static void XLogWalRcvWrite(char *buf, Size nbytes, XLogRecPtr recptr);
static void XLogWalRcvFlush(void);
@@ -153,21 +152,57 @@ static struct
void
WalReceiverMain(void)
{
sigjmp_buf local_sigjmp_buf;
MemoryContext walrcv_context;
char conninfo[MAXCONNINFO];
XLogRecPtr startpoint;
/* use volatile pointer to prevent code rearrangement */
volatile WalRcvData *walrcv = WalRcv;
/* Load the libpq-specific functions */
load_file("libpqwalreceiver", false);
if (walrcv_connect == NULL || walrcv_receive == NULL ||
walrcv_disconnect == NULL)
elog(ERROR, "libpqwalreceiver didn't initialize correctly");
/*
* WalRcv should be set up already (if we are a backend, we inherit
* this by fork() or EXEC_BACKEND mechanism from the postmaster).
*/
Assert(walrcv != NULL);
/* Mark walreceiver in progress */
InitWalRcv();
/*
* Mark walreceiver as running in shared memory.
*
* Do this as early as possible, so that if we fail later on, we'll
* set state to STOPPED. If we die before this, the startup process
* will keep waiting for us to start up, until it times out.
*/
SpinLockAcquire(&walrcv->mutex);
Assert(walrcv->pid == 0);
switch(walrcv->walRcvState)
{
case WALRCV_STOPPING:
/* If we've already been requested to stop, don't start up. */
walrcv->walRcvState = WALRCV_STOPPED;
/* fall through */
case WALRCV_STOPPED:
SpinLockRelease(&walrcv->mutex);
proc_exit(1);
break;
case WALRCV_STARTING:
/* The usual case */
break;
case WALRCV_RUNNING:
/* Shouldn't happen */
elog(PANIC, "walreceiver still running according to shared memory state");
}
/* Advertise our PID so that the startup process can kill us */
walrcv->pid = MyProcPid;
walrcv->walRcvState = WALRCV_RUNNING;
/* Fetch information required to start streaming */
strlcpy(conninfo, (char *) walrcv->conninfo, MAXCONNINFO);
startpoint = walrcv->receivedUpto;
SpinLockRelease(&walrcv->mutex);
/* Arrange to clean up at walreceiver exit */
on_shmem_exit(WalRcvDie, 0);
/*
* If possible, make this process a group leader, so that the postmaster
@@ -200,81 +235,21 @@ WalReceiverMain(void)
/* We allow SIGQUIT (quickdie) at all times */
sigdelset(&BlockSig, SIGQUIT);
/* Load the libpq-specific functions */
load_file("libpqwalreceiver", false);
if (walrcv_connect == NULL || walrcv_receive == NULL ||
walrcv_disconnect == NULL)
elog(ERROR, "libpqwalreceiver didn't initialize correctly");
/*
* Create a resource owner to keep track of our resources (not clear that
* we need this, but may as well have one).
*/
CurrentResourceOwner = ResourceOwnerCreate(NULL, "Wal Receiver");
/*
* 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.
*/
walrcv_context = AllocSetContextCreate(TopMemoryContext,
"Wal Receiver",
ALLOCSET_DEFAULT_MINSIZE,
ALLOCSET_DEFAULT_INITSIZE,
ALLOCSET_DEFAULT_MAXSIZE);
MemoryContextSwitchTo(walrcv_context);
/*
* If an exception is encountered, processing resumes here.
*
* This code is heavily based on bgwriter.c, q.v.
*/
if (sigsetjmp(local_sigjmp_buf, 1) != 0)
{
/* Since not using PG_TRY, must reset error stack by hand */
error_context_stack = NULL;
/* Reset WalRcvImmediateInterruptOK */
DisableWalRcvImmediateExit();
/* Prevent interrupts while cleaning up */
HOLD_INTERRUPTS();
/* Report the error to the server log */
EmitErrorReport();
/* Disconnect any previous connection. */
EnableWalRcvImmediateExit();
walrcv_disconnect();
DisableWalRcvImmediateExit();
/*
* Now return to normal top-level context and clear ErrorContext for
* next time.
*/
MemoryContextSwitchTo(walrcv_context);
FlushErrorState();
/* Flush any leaked data in the top-level context */
MemoryContextResetAndDeleteChildren(walrcv_context);
/* Now we can allow interrupts again */
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);
}
/* We can now handle ereport(ERROR) */
PG_exception_stack = &local_sigjmp_buf;
/* Unblock signals (they were blocked when the postmaster forked us) */
PG_SETMASK(&UnBlockSig);
/* Fetch connection information from shared memory */
SpinLockAcquire(&walrcv->mutex);
strlcpy(conninfo, (char *) walrcv->conninfo, MAXCONNINFO);
startpoint = walrcv->receivedUpto;
SpinLockRelease(&walrcv->mutex);
/* Establish the connection to the primary for XLOG streaming */
EnableWalRcvImmediateExit();
walrcv_connect(conninfo, startpoint);
@@ -330,63 +305,24 @@ WalReceiverMain(void)
}
}
/* Advertise our pid in shared memory, so that startup process can kill us. */
static void
InitWalRcv(void)
{
/* use volatile pointer to prevent code rearrangement */
volatile WalRcvData *walrcv = WalRcv;
/*
* WalRcv should be set up already (if we are a backend, we inherit
* this by fork() or EXEC_BACKEND mechanism from the postmaster).
*/
if (walrcv == NULL)
elog(PANIC, "walreceiver control data uninitialized");
/* If we've already been requested to stop, don't start up */
SpinLockAcquire(&walrcv->mutex);
Assert(walrcv->pid == 0);
if (walrcv->walRcvState == WALRCV_STOPPED ||
walrcv->walRcvState == WALRCV_STOPPING)
{
walrcv->walRcvState = WALRCV_STOPPED;
SpinLockRelease(&walrcv->mutex);
proc_exit(1);
}
walrcv->pid = MyProcPid;
SpinLockRelease(&walrcv->mutex);
/* Arrange to clean up at walreceiver exit */
on_shmem_exit(WalRcvKill, 0);
}
/*
* Clear our pid from shared memory at exit.
* Mark us as STOPPED in shared memory at exit.
*/
static void
WalRcvKill(int code, Datum arg)
WalRcvDie(int code, Datum arg)
{
/* use volatile pointer to prevent code rearrangement */
volatile WalRcvData *walrcv = WalRcv;
bool stopped = false;
SpinLockAcquire(&walrcv->mutex);
if (walrcv->walRcvState == WALRCV_STOPPING ||
walrcv->walRcvState == WALRCV_STOPPED)
{
walrcv->walRcvState = WALRCV_STOPPED;
stopped = true;
elog(LOG, "walreceiver stopped");
}
Assert(walrcv->walRcvState == WALRCV_RUNNING ||
walrcv->walRcvState == WALRCV_STOPPING);
walrcv->walRcvState = WALRCV_STOPPED;
walrcv->pid = 0;
SpinLockRelease(&walrcv->mutex);
/* Terminate the connection gracefully. */
walrcv_disconnect();
/* If requested to stop, tell postmaster to not restart us. */
if (stopped)
SendPostmasterSignal(PMSIGNAL_SHUTDOWN_WALRECEIVER);
}
/* SIGHUP: set flag to re-read config file at next convenient time */