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Efficient transaction-controlled synchronous replication.

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If a standby is broadcasting reply messages and we have named
one or more standbys in synchronous_standby_names then allow
users who set synchronous_replication to wait for commit, which
then provides strict data integrity guarantees. Design avoids
sending and receiving transaction state information so minimises
bookkeeping overheads. We synchronize with the highest priority
standby that is connected and ready to synchronize. Other standbys
can be defined to takeover in case of standby failure.

This version has very strict behaviour; more relaxed options
may be added at a later date.

Simon Riggs and Fujii Masao, with reviews by Yeb Havinga, Jaime
Casanova, Heikki Linnakangas and Robert Haas, plus the assistance
of many other design reviewers.
This commit is contained in:
Simon Riggs
2011-03-06 22:49:16 +00:00
parent 149b2673c2
commit a8a8a3e096
21 changed files with 507 additions and 22 deletions
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12
src/backend/storage/lmgr/proc.c
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@ -39,6 +39,7 @@
#include "access/xact.h"
#include "miscadmin.h"
#include "postmaster/autovacuum.h"
#include "replication/syncrep.h"
#include "storage/ipc.h"
#include "storage/lmgr.h"
#include "storage/pmsignal.h"
@ -196,6 +197,7 @@ InitProcGlobal(void)
PGSemaphoreCreate(&(procs[i].sem));
procs[i].links.next = (SHM_QUEUE *) ProcGlobal->freeProcs;
ProcGlobal->freeProcs = &procs[i];
InitSharedLatch(&procs[i].waitLatch);
}
/*
@ -214,6 +216,7 @@ InitProcGlobal(void)
PGSemaphoreCreate(&(procs[i].sem));
procs[i].links.next = (SHM_QUEUE *) ProcGlobal->autovacFreeProcs;
ProcGlobal->autovacFreeProcs = &procs[i];
InitSharedLatch(&procs[i].waitLatch);
}
/*
@ -224,6 +227,7 @@ InitProcGlobal(void)
{
AuxiliaryProcs[i].pid = 0; /* marks auxiliary proc as not in use */
PGSemaphoreCreate(&(AuxiliaryProcs[i].sem));
InitSharedLatch(&procs[i].waitLatch);
}
/* Create ProcStructLock spinlock, too */
@ -326,6 +330,13 @@ InitProcess(void)
SHMQueueInit(&(MyProc->myProcLocks[i]));
MyProc->recoveryConflictPending = false;
/* Initialise for sync rep */
MyProc->waitLSN.xlogid = 0;
MyProc->waitLSN.xrecoff = 0;
MyProc->syncRepState = SYNC_REP_NOT_WAITING;
SHMQueueElemInit(&(MyProc->syncRepLinks));
OwnLatch((Latch *) &MyProc->waitLatch);
/*
* We might be reusing a semaphore that belonged to a failed process. So
* be careful and reinitialize its value here. (This is not strictly
@ -365,6 +376,7 @@ InitProcessPhase2(void)
/*
* Arrange to clean that up at backend exit.
*/
on_shmem_exit(SyncRepCleanupAtProcExit, 0);
on_shmem_exit(RemoveProcFromArray, 0);
}