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Introduce replication slots.

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Replication slots are a crash-safe data structure which can be created
on either a master or a standby to prevent premature removal of
write-ahead log segments needed by a standby, as well as (with
hot_standby_feedback=on) pruning of tuples whose removal would cause
replication conflicts.  Slots have some advantages over existing
techniques, as explained in the documentation.

In a few places, we refer to the type of replication slots introduced
by this patch as "physical" slots, because forthcoming patches for
logical decoding will also have slots, but with somewhat different
properties.

Andres Freund and Robert Haas
This commit is contained in:
Robert Haas
2014-01-31 22:45:17 -05:00
parent 5bdef38b89
commit 858ec11858
42 changed files with 2356 additions and 62 deletions
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49
src/bin/pg_basebackup/receivelog.c
View File

@ -31,6 +31,8 @@
/* fd and filename for currently open WAL file */
static int walfile = -1;
static char current_walfile_name[MAXPGPATH] = "";
static bool reportFlushPosition = false;
static XLogRecPtr lastFlushPosition = InvalidXLogRecPtr;
static PGresult *HandleCopyStream(PGconn *conn, XLogRecPtr startpos,
uint32 timeline, char *basedir,
@ -133,7 +135,7 @@ open_walfile(XLogRecPtr startpoint, uint32 timeline, char *basedir,
* and returns false, otherwise returns true.
*/
static bool
close_walfile(char *basedir, char *partial_suffix)
close_walfile(char *basedir, char *partial_suffix, XLogRecPtr pos)
{
off_t currpos;
@ -187,6 +189,7 @@ close_walfile(char *basedir, char *partial_suffix)
_("%s: not renaming \"%s%s\", segment is not complete\n"),
progname, current_walfile_name, partial_suffix);
lastFlushPosition = pos;
return true;
}
@ -421,7 +424,10 @@ sendFeedback(PGconn *conn, XLogRecPtr blockpos, int64 now, bool replyRequested)
len += 1;
sendint64(blockpos, &replybuf[len]); /* write */
len += 8;
sendint64(InvalidXLogRecPtr, &replybuf[len]); /* flush */
if (reportFlushPosition)
sendint64(lastFlushPosition, &replybuf[len]); /* flush */
else
sendint64(InvalidXLogRecPtr, &replybuf[len]); /* flush */
len += 8;
sendint64(InvalidXLogRecPtr, &replybuf[len]); /* apply */
len += 8;
@ -511,6 +517,7 @@ ReceiveXlogStream(PGconn *conn, XLogRecPtr startpos, uint32 timeline,
int standby_message_timeout, char *partial_suffix)
{
char query[128];
char slotcmd[128];
PGresult *res;
XLogRecPtr stoppos;
@ -521,6 +528,29 @@ ReceiveXlogStream(PGconn *conn, XLogRecPtr startpos, uint32 timeline,
if (!CheckServerVersionForStreaming(conn))
return false;
if (replication_slot != NULL)
{
/*
* Report the flush position, so the primary can know what WAL we'll
* possibly re-request, and remove older WAL safely.
*
* We only report it when a slot has explicitly been used, because
* reporting the flush position makes one elegible as a synchronous
* replica. People shouldn't include generic names in
* synchronous_standby_names, but we've protected them against it so
* far, so let's continue to do so in the situations when possible.
* If they've got a slot, though, we need to report the flush position,
* so that the master can remove WAL.
*/
reportFlushPosition = true;
sprintf(slotcmd, "SLOT \"%s\" ", replication_slot);
}
else
{
reportFlushPosition = false;
slotcmd[0] = 0;
}
if (sysidentifier != NULL)
{
/* Validate system identifier hasn't changed */
@ -560,6 +590,12 @@ ReceiveXlogStream(PGconn *conn, XLogRecPtr startpos, uint32 timeline,
PQclear(res);
}
/*
* initialize flush position to starting point, it's the caller's
* responsibility that that's sane.
*/
lastFlushPosition = startpos;
while (1)
{
/*
@ -606,7 +642,8 @@ ReceiveXlogStream(PGconn *conn, XLogRecPtr startpos, uint32 timeline,
return true;
/* Initiate the replication stream at specified location */
snprintf(query, sizeof(query), "START_REPLICATION %X/%X TIMELINE %u",
snprintf(query, sizeof(query), "START_REPLICATION %s%X/%X TIMELINE %u",
slotcmd,
(uint32) (startpos >> 32), (uint32) startpos,
timeline);
res = PQexec(conn, query);
@ -810,7 +847,7 @@ HandleCopyStream(PGconn *conn, XLogRecPtr startpos, uint32 timeline,
*/
if (still_sending && stream_stop(blockpos, timeline, false))
{
if (!close_walfile(basedir, partial_suffix))
if (!close_walfile(basedir, partial_suffix, blockpos))
{
/* Potential error message is written by close_walfile */
goto error;
@ -909,7 +946,7 @@ HandleCopyStream(PGconn *conn, XLogRecPtr startpos, uint32 timeline,
*/
if (still_sending)
{
if (!close_walfile(basedir, partial_suffix))
if (!close_walfile(basedir, partial_suffix, blockpos))
{
/* Error message written in close_walfile() */
goto error;
@ -1074,7 +1111,7 @@ HandleCopyStream(PGconn *conn, XLogRecPtr startpos, uint32 timeline,
/* Did we reach the end of a WAL segment? */
if (blockpos % XLOG_SEG_SIZE == 0)
{
if (!close_walfile(basedir, partial_suffix))
if (!close_walfile(basedir, partial_suffix, blockpos))
/* Error message written in close_walfile() */
goto error;