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Commit361bd16

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Allow Hot Standby to begin from a shutdown checkpoint.
Patch by Simon Riggs & me
1 parentea9c103 commit361bd16

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3 files changed

+224
-62
lines changed

3 files changed

+224
-62
lines changed

‎src/backend/access/transam/twophase.c‎

Lines changed: 84 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -7,7 +7,7 @@
77
* Portions Copyright (c) 1994, Regents of the University of California
88
*
99
* IDENTIFICATION
10-
*$PostgreSQL: pgsql/src/backend/access/transam/twophase.c,v 1.59 2010/02/26 02:00:34 momjian Exp $
10+
*$PostgreSQL: pgsql/src/backend/access/transam/twophase.c,v 1.60 2010/04/13 14:17:46 heikki Exp $
1111
*
1212
* NOTES
1313
*Each global transaction is associated with a global transaction
@@ -1718,6 +1718,89 @@ PrescanPreparedTransactions(TransactionId **xids_p, int *nxids_p)
17181718
returnresult;
17191719
}
17201720

1721+
/*
1722+
* StandbyRecoverPreparedTransactions
1723+
*
1724+
* Scan the pg_twophase directory and setup all the required information to
1725+
* allow standby queries to treat prepared transactions as still active.
1726+
* This is never called at the end of recovery - we use
1727+
* RecoverPreparedTransactions() at that point.
1728+
*
1729+
* Currently we simply call SubTransSetParent() for any subxids of prepared
1730+
* transactions. If overwriteOK is true, it's OK if some XIDs have already
1731+
* been marked in pg_subtrans.
1732+
*/
1733+
void
1734+
StandbyRecoverPreparedTransactions(booloverwriteOK)
1735+
{
1736+
DIR*cldir;
1737+
structdirent*clde;
1738+
1739+
cldir=AllocateDir(TWOPHASE_DIR);
1740+
while ((clde=ReadDir(cldir,TWOPHASE_DIR))!=NULL)
1741+
{
1742+
if (strlen(clde->d_name)==8&&
1743+
strspn(clde->d_name,"0123456789ABCDEF")==8)
1744+
{
1745+
TransactionIdxid;
1746+
char*buf;
1747+
TwoPhaseFileHeader*hdr;
1748+
TransactionId*subxids;
1749+
inti;
1750+
1751+
xid= (TransactionId)strtoul(clde->d_name,NULL,16);
1752+
1753+
/* Already processed? */
1754+
if (TransactionIdDidCommit(xid)||TransactionIdDidAbort(xid))
1755+
{
1756+
ereport(WARNING,
1757+
(errmsg("removing stale two-phase state file \"%s\"",
1758+
clde->d_name)));
1759+
RemoveTwoPhaseFile(xid, true);
1760+
continue;
1761+
}
1762+
1763+
/* Read and validate file */
1764+
buf=ReadTwoPhaseFile(xid, true);
1765+
if (buf==NULL)
1766+
{
1767+
ereport(WARNING,
1768+
(errmsg("removing corrupt two-phase state file \"%s\"",
1769+
clde->d_name)));
1770+
RemoveTwoPhaseFile(xid, true);
1771+
continue;
1772+
}
1773+
1774+
/* Deconstruct header */
1775+
hdr= (TwoPhaseFileHeader*)buf;
1776+
if (!TransactionIdEquals(hdr->xid,xid))
1777+
{
1778+
ereport(WARNING,
1779+
(errmsg("removing corrupt two-phase state file \"%s\"",
1780+
clde->d_name)));
1781+
RemoveTwoPhaseFile(xid, true);
1782+
pfree(buf);
1783+
continue;
1784+
}
1785+
1786+
/*
1787+
* Examine subtransaction XIDs ... they should all follow main
1788+
* XID.
1789+
*/
1790+
subxids= (TransactionId*)
1791+
(buf+MAXALIGN(sizeof(TwoPhaseFileHeader)));
1792+
for (i=0;i<hdr->nsubxacts;i++)
1793+
{
1794+
TransactionIdsubxid=subxids[i];
1795+
1796+
Assert(TransactionIdFollows(subxid,xid));
1797+
SubTransSetParent(xid,subxid,overwriteOK);
1798+
}
1799+
}
1800+
}
1801+
FreeDir(cldir);
1802+
}
1803+
17211804
/*
17221805
* RecoverPreparedTransactions
17231806
*

‎src/backend/access/transam/xlog.c‎

Lines changed: 138 additions & 60 deletions
Original file line numberDiff line numberDiff line change
@@ -7,7 +7,7 @@
77
* Portions Copyright (c) 1996-2010, PostgreSQL Global Development Group
88
* Portions Copyright (c) 1994, Regents of the University of California
99
*
10-
* $PostgreSQL: pgsql/src/backend/access/transam/xlog.c,v 1.393 2010/04/12 10:40:42 heikki Exp $
10+
* $PostgreSQL: pgsql/src/backend/access/transam/xlog.c,v 1.394 2010/04/13 14:17:46 heikki Exp $
1111
*
1212
*-------------------------------------------------------------------------
1313
*/
@@ -496,6 +496,7 @@ static TimeLineID lastPageTLI = 0;
496496
staticXLogRecPtrminRecoveryPoint;/* local copy of
497497
* ControlFile->minRecoveryPoint */
498498
staticboolupdateMinRecoveryPoint= true;
499+
staticboolreachedMinRecoveryPoint= false;
499500

500501
staticboolInRedo= false;
501502

@@ -551,6 +552,7 @@ static void ValidateXLOGDirectoryStructure(void);
551552
staticvoidCleanupBackupHistory(void);
552553
staticvoidUpdateMinRecoveryPoint(XLogRecPtrlsn,boolforce);
553554
staticXLogRecord*ReadRecord(XLogRecPtr*RecPtr,intemode,boolfetching_ckpt);
555+
staticvoidCheckRecoveryConsistency(void);
554556
staticboolValidXLOGHeader(XLogPageHeaderhdr,intemode);
555557
staticXLogRecord*ReadCheckpointRecord(XLogRecPtrRecPtr,intwhichChkpt);
556558
staticList*readTimeLineHistory(TimeLineIDtargetTLI);
@@ -5591,7 +5593,6 @@ StartupXLOG(void)
55915593
uint32freespace;
55925594
TransactionIdoldestActiveXID;
55935595
boolbgwriterLaunched= false;
5594-
boolbackendsAllowed= false;
55955596

55965597
/*
55975598
* Read control file and check XLOG status looks valid.
@@ -5838,6 +5839,8 @@ StartupXLOG(void)
58385839
if (InRecovery)
58395840
{
58405841
intrmid;
5842+
/* use volatile pointer to prevent code rearrangement */
5843+
volatileXLogCtlData*xlogctl=XLogCtl;
58415844

58425845
/*
58435846
* Update pg_control to show that we are recovering and to show the
@@ -5930,6 +5933,33 @@ StartupXLOG(void)
59305933
StartupMultiXact();
59315934

59325935
ProcArrayInitRecoveryInfo(oldestActiveXID);
5936+
5937+
/*
5938+
* If we're beginning at a shutdown checkpoint, we know that
5939+
* nothing was running on the master at this point. So fake-up
5940+
* an empty running-xacts record and use that here and now.
5941+
* Recover additional standby state for prepared transactions.
5942+
*/
5943+
if (wasShutdown)
5944+
{
5945+
RunningTransactionsDatarunning;
5946+
5947+
/*
5948+
* Construct a RunningTransactions snapshot representing a shut
5949+
* down server, with only prepared transactions still alive.
5950+
* We're never overflowed at this point because all subxids
5951+
* are listed with their parent prepared transactions.
5952+
*/
5953+
running.xcnt=nxids;
5954+
running.subxid_overflow= false;
5955+
running.nextXid=checkPoint.nextXid;
5956+
running.oldestRunningXid=oldestActiveXID;
5957+
running.xids=xids;
5958+
5959+
ProcArrayApplyRecoveryInfo(&running);
5960+
5961+
StandbyRecoverPreparedTransactions(false);
5962+
}
59335963
}
59345964

59355965
/* Initialize resource managers */
@@ -5939,6 +5969,46 @@ StartupXLOG(void)
59395969
RmgrTable[rmid].rm_startup();
59405970
}
59415971

5972+
/*
5973+
* Initialize shared replayEndRecPtr and recoveryLastRecPtr.
5974+
*
5975+
* This is slightly confusing if we're starting from an online
5976+
* checkpoint; we've just read and replayed the chekpoint record,
5977+
* but we're going to start replay from its redo pointer, which
5978+
* precedes the location of the checkpoint record itself. So even
5979+
* though the last record we've replayed is indeed ReadRecPtr, we
5980+
* haven't replayed all the preceding records yet. That's OK for
5981+
* the current use of these variables.
5982+
*/
5983+
SpinLockAcquire(&xlogctl->info_lck);
5984+
xlogctl->replayEndRecPtr=ReadRecPtr;
5985+
xlogctl->recoveryLastRecPtr=ReadRecPtr;
5986+
SpinLockRelease(&xlogctl->info_lck);
5987+
5988+
/*
5989+
* Let postmaster know we've started redo now, so that it can
5990+
* launch bgwriter to perform restartpoints. We don't bother
5991+
* during crash recovery as restartpoints can only be performed
5992+
* during archive recovery. And we'd like to keep crash recovery
5993+
* simple, to avoid introducing bugs that could you from
5994+
* recovering after crash.
5995+
*
5996+
* After this point, we can no longer assume that we're the only
5997+
* process in addition to postmaster! Also, fsync requests are
5998+
* subsequently to be handled by the bgwriter, not locally.
5999+
*/
6000+
if (InArchiveRecovery&&IsUnderPostmaster)
6001+
{
6002+
SetForwardFsyncRequests();
6003+
SendPostmasterSignal(PMSIGNAL_RECOVERY_STARTED);
6004+
bgwriterLaunched= true;
6005+
}
6006+
6007+
/*
6008+
* Allow read-only connections immediately if we're consistent already.
6009+
*/
6010+
CheckRecoveryConsistency();
6011+
59426012
/*
59436013
* Find the first record that logically follows the checkpoint --- it
59446014
* might physically precede it, though.
@@ -5958,43 +6028,14 @@ StartupXLOG(void)
59586028
{
59596029
boolrecoveryContinue= true;
59606030
boolrecoveryApply= true;
5961-
boolreachedMinRecoveryPoint= false;
59626031
ErrorContextCallbackerrcontext;
59636032

5964-
/* use volatile pointer to prevent code rearrangement */
5965-
volatileXLogCtlData*xlogctl=XLogCtl;
5966-
5967-
/* initialize shared replayEndRecPtr and recoveryLastRecPtr */
5968-
SpinLockAcquire(&xlogctl->info_lck);
5969-
xlogctl->replayEndRecPtr=ReadRecPtr;
5970-
xlogctl->recoveryLastRecPtr=ReadRecPtr;
5971-
SpinLockRelease(&xlogctl->info_lck);
5972-
59736033
InRedo= true;
59746034

59756035
ereport(LOG,
59766036
(errmsg("redo starts at %X/%X",
59776037
ReadRecPtr.xlogid,ReadRecPtr.xrecoff)));
59786038

5979-
/*
5980-
* Let postmaster know we've started redo now, so that it can
5981-
* launch bgwriter to perform restartpoints. We don't bother
5982-
* during crash recovery as restartpoints can only be performed
5983-
* during archive recovery. And we'd like to keep crash recovery
5984-
* simple, to avoid introducing bugs that could you from
5985-
* recovering after crash.
5986-
*
5987-
* After this point, we can no longer assume that we're the only
5988-
* process in addition to postmaster! Also, fsync requests are
5989-
* subsequently to be handled by the bgwriter, not locally.
5990-
*/
5991-
if (InArchiveRecovery&&IsUnderPostmaster)
5992-
{
5993-
SetForwardFsyncRequests();
5994-
SendPostmasterSignal(PMSIGNAL_RECOVERY_STARTED);
5995-
bgwriterLaunched= true;
5996-
}
5997-
59986039
/*
59996040
* main redo apply loop
60006041
*/
@@ -6024,32 +6065,8 @@ StartupXLOG(void)
60246065
/* Handle interrupt signals of startup process */
60256066
HandleStartupProcInterrupts();
60266067

6027-
/*
6028-
* Have we passed our safe starting point?
6029-
*/
6030-
if (!reachedMinRecoveryPoint&&
6031-
XLByteLE(minRecoveryPoint,EndRecPtr)&&
6032-
XLogRecPtrIsInvalid(ControlFile->backupStartPoint))
6033-
{
6034-
reachedMinRecoveryPoint= true;
6035-
ereport(LOG,
6036-
(errmsg("consistent recovery state reached at %X/%X",
6037-
EndRecPtr.xlogid,EndRecPtr.xrecoff)));
6038-
}
6039-
6040-
/*
6041-
* Have we got a valid starting snapshot that will allow
6042-
* queries to be run? If so, we can tell postmaster that the
6043-
* database is consistent now, enabling connections.
6044-
*/
6045-
if (standbyState==STANDBY_SNAPSHOT_READY&&
6046-
!backendsAllowed&&
6047-
reachedMinRecoveryPoint&&
6048-
IsUnderPostmaster)
6049-
{
6050-
backendsAllowed= true;
6051-
SendPostmasterSignal(PMSIGNAL_RECOVERY_CONSISTENT);
6052-
}
6068+
/* Allow read-only connections if we're consistent now */
6069+
CheckRecoveryConsistency();
60536070

60546071
/*
60556072
* Have we reached our recovery target?
@@ -6398,6 +6415,44 @@ StartupXLOG(void)
63986415
}
63996416
}
64006417

6418+
/*
6419+
* Checks if recovery has reached a consistent state. When consistency is
6420+
* reached and we have a valid starting standby snapshot, tell postmaster
6421+
* that it can start accepting read-only connections.
6422+
*/
6423+
staticvoid
6424+
CheckRecoveryConsistency(void)
6425+
{
6426+
staticboolbackendsAllowed= false;
6427+
6428+
/*
6429+
* Have we passed our safe starting point?
6430+
*/
6431+
if (!reachedMinRecoveryPoint&&
6432+
XLByteLE(minRecoveryPoint,EndRecPtr)&&
6433+
XLogRecPtrIsInvalid(ControlFile->backupStartPoint))
6434+
{
6435+
reachedMinRecoveryPoint= true;
6436+
ereport(LOG,
6437+
(errmsg("consistent recovery state reached at %X/%X",
6438+
EndRecPtr.xlogid,EndRecPtr.xrecoff)));
6439+
}
6440+
6441+
/*
6442+
* Have we got a valid starting snapshot that will allow
6443+
* queries to be run? If so, we can tell postmaster that the
6444+
* database is consistent now, enabling connections.
6445+
*/
6446+
if (standbyState==STANDBY_SNAPSHOT_READY&&
6447+
!backendsAllowed&&
6448+
reachedMinRecoveryPoint&&
6449+
IsUnderPostmaster)
6450+
{
6451+
backendsAllowed= true;
6452+
SendPostmasterSignal(PMSIGNAL_RECOVERY_CONSISTENT);
6453+
}
6454+
}
6455+
64016456
/*
64026457
* Is the system still in recovery?
64036458
*
@@ -7657,13 +7712,36 @@ xlog_redo(XLogRecPtr lsn, XLogRecord *record)
76577712
if (standbyState!=STANDBY_DISABLED)
76587713
CheckRequiredParameterValues(checkPoint);
76597714

7715+
/*
7716+
* If we see a shutdown checkpoint, we know that nothing was
7717+
* running on the master at this point. So fake-up an empty
7718+
* running-xacts record and use that here and now. Recover
7719+
* additional standby state for prepared transactions.
7720+
*/
76607721
if (standbyState >=STANDBY_INITIALIZED)
76617722
{
7723+
TransactionId*xids;
7724+
intnxids;
7725+
TransactionIdoldestActiveXID;
7726+
RunningTransactionsDatarunning;
7727+
7728+
oldestActiveXID=PrescanPreparedTransactions(&xids,&nxids);
7729+
76627730
/*
7663-
* Remove stale transactions, if any.
7731+
* Construct a RunningTransactions snapshot representing a shut
7732+
* down server, with only prepared transactions still alive.
7733+
* We're never overflowed at this point because all subxids
7734+
* are listed with their parent prepared transactions.
76647735
*/
7665-
ExpireOldKnownAssignedTransactionIds(checkPoint.nextXid);
7666-
StandbyReleaseOldLocks(checkPoint.nextXid);
7736+
running.xcnt=nxids;
7737+
running.subxid_overflow= false;
7738+
running.nextXid=checkPoint.nextXid;
7739+
running.oldestRunningXid=oldestActiveXID;
7740+
running.xids=xids;
7741+
7742+
ProcArrayApplyRecoveryInfo(&running);
7743+
7744+
StandbyRecoverPreparedTransactions(true);
76677745
}
76687746

76697747
/* ControlFile->checkPointCopy always tracks the latest ckpt XID */

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