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Fix crash in WAL sender when starting physical replication

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Since database connections can be used with WAL senders in 9.4, it is
possible to use physical replication.  This commit fixes a crash when
starting physical replication with a WAL sender using a database
connection, caused by the refactoring done in 850196b.

There have been discussions about forbidding the use of physical
replication in a database connection, but this is left for later,
taking care only of the crash new to 13.

While on it, add a test to check for a failure when attempting logical
replication if the WAL sender does not have a database connection.  This
part is extracted from a larger patch by Kyotaro Horiguchi.

Reported-by: Vladimir Sitnikov
Author: Michael Paquier, Kyotaro Horiguchi
Reviewed-by: Kyotaro Horiguchi, Álvaro Herrera
Discussion: https://postgr.es/m/CAB=Je-GOWMj1PTPkeUhjqQp-4W3=nW-pXe2Hjax6rJFffB5_Aw@mail.gmail.com
Backpatch-through: 13
This commit is contained in:
Michael Paquier
2020-06-08 10:12:31 +09:00
parent 9b5f85fb0a
commit 10ffe0fa72
4 changed files with 31 additions and 26 deletions
Download Patch File Download Diff File Expand all files Collapse all files

4
src/backend/access/transam/xlogreader.c
View File

@ -44,6 +44,8 @@ static bool ValidXLogRecordHeader(XLogReaderState *state, XLogRecPtr RecPtr,
static bool ValidXLogRecord(XLogReaderState *state, XLogRecord *record,
XLogRecPtr recptr);
static void ResetDecoder(XLogReaderState *state);
static void WALOpenSegmentInit(WALOpenSegment *seg, WALSegmentContext *segcxt,
int segsize, const char *waldir);
/* size of the buffer allocated for error message. */
#define MAX_ERRORMSG_LEN 1000
@ -210,7 +212,7 @@ allocate_recordbuf(XLogReaderState *state, uint32 reclength)
/*
* Initialize the passed segment structs.
*/
void
static void
WALOpenSegmentInit(WALOpenSegment *seg, WALSegmentContext *segcxt,
int segsize, const char *waldir)
{

38
src/backend/replication/walsender.c
View File

@ -130,13 +130,11 @@ bool log_replication_commands = false;
bool wake_wal_senders = false;
/*
* Physical walsender does not use xlogreader to read WAL, but it does use a
* fake one to keep state. Logical walsender uses a proper xlogreader. Both
* keep the 'xlogreader' pointer to the right one, for the sake of common
* routines.
* xlogreader used for replication. Note that a WAL sender doing physical
* replication does not need xlogreader to read WAL, but it needs one to
* keep a state of its work.
*/
static XLogReaderState fake_xlogreader;
static XLogReaderState *xlogreader;
static XLogReaderState *xlogreader = NULL;
/*
* These variables keep track of the state of the timeline we're currently
@ -285,20 +283,6 @@ InitWalSender(void)
/* Initialize empty timestamp buffer for lag tracking. */
lag_tracker = MemoryContextAllocZero(TopMemoryContext, sizeof(LagTracker));
/*
* Prepare physical walsender's fake xlogreader struct. Logical walsender
* does this later.
*/
if (!am_db_walsender)
{
xlogreader = &fake_xlogreader;
xlogreader->routine =
*XL_ROUTINE(.segment_open = WalSndSegmentOpen,
.segment_close = wal_segment_close);
WALOpenSegmentInit(&xlogreader->seg, &xlogreader->segcxt,
wal_segment_size, NULL);
}
}
/*
@ -594,6 +578,18 @@ StartReplication(StartReplicationCmd *cmd)
(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
errmsg("IDENTIFY_SYSTEM has not been run before START_REPLICATION")));
/* create xlogreader for physical replication */
xlogreader =
XLogReaderAllocate(wal_segment_size, NULL,
XL_ROUTINE(.segment_open = WalSndSegmentOpen,
.segment_close = wal_segment_close),
NULL);
if (!xlogreader)
ereport(ERROR,
(errcode(ERRCODE_OUT_OF_MEMORY),
errmsg("out of memory")));
/*
* We assume here that we're logging enough information in the WAL for
* log-shipping, since this is checked in PostmasterMain().
@ -1643,6 +1639,8 @@ exec_replication_command(const char *cmd_string)
StartReplication(cmd);
else
StartLogicalReplication(cmd);
Assert(xlogreader != NULL);
break;
}