Introduce replication progress tracking infrastructure.

When implementing a replication solution ontop of logical decoding, two
related problems exist:
* How to safely keep track of replication progress
* How to change replication behavior, based on the origin of a row;
  e.g. to avoid loops in bi-directional replication setups

The solution to these problems, as implemented here, consist out of
three parts:

1) 'replication origins', which identify nodes in a replication setup.
2) 'replication progress tracking', which remembers, for each
   replication origin, how far replay has progressed in a efficient and
   crash safe manner.
3) The ability to filter out changes performed on the behest of a
   replication origin during logical decoding; this allows complex
   replication topologies. E.g. by filtering all replayed changes out.

Most of this could also be implemented in "userspace", e.g. by inserting
additional rows contain origin information, but that ends up being much
less efficient and more complicated.  We don't want to require various
replication solutions to reimplement logic for this independently. The
infrastructure is intended to be generic enough to be reusable.

This infrastructure also replaces the 'nodeid' infrastructure of commit
timestamps. It is intended to provide all the former capabilities,
except that there's only 2^16 different origins; but now they integrate
with logical decoding. Additionally more functionality is accessible via
SQL.  Since the commit timestamp infrastructure has also been introduced
in 9.5 (commit 73c986add) changing the API is not a problem.

For now the number of origins for which the replication progress can be
tracked simultaneously is determined by the max_replication_slots
GUC. That GUC is not a perfect match to configure this, but there
doesn't seem to be sufficient reason to introduce a separate new one.

Bumps both catversion and wal page magic.

Author: Andres Freund, with contributions from Petr Jelinek and Craig Ringer
Reviewed-By: Heikki Linnakangas, Petr Jelinek, Robert Haas, Steve Singer
Discussion: 20150216002155.GI15326@awork2.anarazel.de,
    20140923182422.GA15776@alap3.anarazel.de,
    20131114172632.GE7522@alap2.anarazel.de

1 files changed, 59 insertions, 17 deletions

diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index 1495bb499f5..511bcbbc519 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -40,8 +40,10 @@
 #include "libpq/pqsignal.h"
 #include "miscadmin.h"
 #include "pgstat.h"
+#include "replication/logical.h"
 #include "replication/walsender.h"
 #include "replication/syncrep.h"
+#include "replication/origin.h"
 #include "storage/fd.h"
 #include "storage/lmgr.h"
 #include "storage/predicate.h"
@@ -1073,21 +1075,27 @@ RecordTransactionCommit(void)
 							nmsgs, invalMessages,
 							RelcacheInitFileInval, forceSyncCommit,
 							InvalidTransactionId /* plain commit */);
-	}
 
-	/*
-	 * We only need to log the commit timestamp separately if the node
-	 * identifier is a valid value; the commit record above already contains
-	 * the timestamp info otherwise, and will be used to load it.
-	 */
-	if (markXidCommitted)
-	{
-		CommitTsNodeId		node_id;
+		/*
+		 * Record plain commit ts if not replaying remote actions, or if no
+		 * timestamp is configured.
+		 */
+		if (replorigin_sesssion_origin == InvalidRepOriginId ||
+			replorigin_sesssion_origin == DoNotReplicateId ||
+			replorigin_sesssion_origin_timestamp == 0)
+			replorigin_sesssion_origin_timestamp = xactStopTimestamp;
+		else
+			replorigin_session_advance(replorigin_sesssion_origin_lsn,
+									   XactLastRecEnd);
 
-		node_id = CommitTsGetDefaultNodeId();
+		/*
+		 * We don't need to WAL log origin or timestamp here, the commit
+		 * record contains all the necessary information and will redo the SET
+		 * action during replay.
+		 */
 		TransactionTreeSetCommitTsData(xid, nchildren, children,
-									   xactStopTimestamp,
-									   node_id, node_id != InvalidCommitTsNodeId);
+									   replorigin_sesssion_origin_timestamp,
+									   replorigin_sesssion_origin, false);
 	}
 
 	/*
@@ -1176,9 +1184,11 @@ RecordTransactionCommit(void)
 	if (wrote_xlog && markXidCommitted)
 		SyncRepWaitForLSN(XactLastRecEnd);
 
+	/* remember end of last commit record */
+	XactLastCommitEnd = XactLastRecEnd;
+
 	/* Reset XactLastRecEnd until the next transaction writes something */
 	XactLastRecEnd = 0;
-
 cleanup:
 	/* Clean up local data */
 	if (rels)
@@ -4611,6 +4621,7 @@ XactLogCommitRecord(TimestampTz commit_time,
 	xl_xact_relfilenodes xl_relfilenodes;
 	xl_xact_invals		xl_invals;
 	xl_xact_twophase	xl_twophase;
+	xl_xact_origin		xl_origin;
 
 	uint8				info;
 
@@ -4668,6 +4679,15 @@ XactLogCommitRecord(TimestampTz commit_time,
 		xl_twophase.xid = twophase_xid;
 	}
 
+	/* dump transaction origin information */
+	if (replorigin_sesssion_origin != InvalidRepOriginId)
+	{
+		xl_xinfo.xinfo |= XACT_XINFO_HAS_ORIGIN;
+
+		xl_origin.origin_lsn = replorigin_sesssion_origin_lsn;
+		xl_origin.origin_timestamp = replorigin_sesssion_origin_timestamp;
+	}
+
 	if (xl_xinfo.xinfo != 0)
 		info |= XLOG_XACT_HAS_INFO;
 
@@ -4709,6 +4729,12 @@ XactLogCommitRecord(TimestampTz commit_time,
 	if (xl_xinfo.xinfo & XACT_XINFO_HAS_TWOPHASE)
 		XLogRegisterData((char *) (&xl_twophase), sizeof(xl_xact_twophase));
 
+	if (xl_xinfo.xinfo & XACT_XINFO_HAS_ORIGIN)
+		XLogRegisterData((char *) (&xl_origin), sizeof(xl_xact_origin));
+
+	/* we allow filtering by xacts */
+	XLogIncludeOrigin();
+
 	return XLogInsert(RM_XACT_ID, info);
 }
 
@@ -4806,10 +4832,12 @@ XactLogAbortRecord(TimestampTz abort_time,
 static void
 xact_redo_commit(xl_xact_parsed_commit *parsed,
 				 TransactionId xid,
-				 XLogRecPtr lsn)
+				 XLogRecPtr lsn,
+				 RepOriginId origin_id)
 {
 	TransactionId max_xid;
 	int			i;
+	TimestampTz	commit_time;
 
 	max_xid = TransactionIdLatest(xid, parsed->nsubxacts, parsed->subxacts);
 
@@ -4829,9 +4857,16 @@ xact_redo_commit(xl_xact_parsed_commit *parsed,
 		LWLockRelease(XidGenLock);
 	}
 
+	Assert(!!(parsed->xinfo & XACT_XINFO_HAS_ORIGIN) == (origin_id != InvalidRepOriginId));
+
+	if (parsed->xinfo & XACT_XINFO_HAS_ORIGIN)
+		commit_time = parsed->origin_timestamp;
+	else
+		commit_time = parsed->xact_time;
+
 	/* Set the transaction commit timestamp and metadata */
 	TransactionTreeSetCommitTsData(xid, parsed->nsubxacts, parsed->subxacts,
-								   parsed->xact_time, InvalidCommitTsNodeId,
+								   commit_time, origin_id,
 								   false);
 
 	if (standbyState == STANDBY_DISABLED)
@@ -4892,6 +4927,13 @@ xact_redo_commit(xl_xact_parsed_commit *parsed,
 		StandbyReleaseLockTree(xid, 0, NULL);
 	}
 
+	if (parsed->xinfo & XACT_XINFO_HAS_ORIGIN)
+	{
+		/* recover apply progress */
+		replorigin_advance(origin_id, parsed->origin_lsn, lsn,
+						   false /* backward */, false /* WAL */);
+	}
+
 	/* Make sure files supposed to be dropped are dropped */
 	if (parsed->nrels > 0)
 	{
@@ -5047,13 +5089,13 @@ xact_redo(XLogReaderState *record)
 		{
 			Assert(!TransactionIdIsValid(parsed.twophase_xid));
 			xact_redo_commit(&parsed, XLogRecGetXid(record),
-							 record->EndRecPtr);
+							 record->EndRecPtr, XLogRecGetOrigin(record));
 		}
 		else
 		{
 			Assert(TransactionIdIsValid(parsed.twophase_xid));
 			xact_redo_commit(&parsed, parsed.twophase_xid,
-							 record->EndRecPtr);
+							 record->EndRecPtr, XLogRecGetOrigin(record));
 			RemoveTwoPhaseFile(parsed.twophase_xid, false);
 		}
 	}