Send seqno in hansshake response

Author: knizhnik

arbiter.c

@@ -465,6 +465,7 @@ static int MtmConnectSocket(char const* host, int port, int timeout)
 
 	/* Some node considered that I am dead, so switch to recovery mode */
 	MtmLock(LW_EXCLUSIVE);
+	Mtm->nodes[resp.node-1].sendSeqNo = resp.seqno;
 	if (BIT_CHECK(resp.disabledNodeMask, MtmNodeId-1)) { 
 		elog(WARNING, "Node %d thinks that I was dead", resp.node);
 		BIT_SET(Mtm->disabledNodeMask, MtmNodeId-1);
@@ -576,6 +577,7 @@ static void MtmAcceptOneConnection()
 			resp.sxid = ShmemVariableCache->nextXid;
 			resp.csn  = MtmGetCurrentTime();
 			resp.node = MtmNodeId;
+			resp.seqno = Mtm->nodes[req.hdr.node-1].recvSeqNo;
 			MtmUpdateNodeConnectionInfo(&Mtm->nodes[req.hdr.node-1].con, req.connStr);
 			if (!MtmWriteSocket(fd, &resp, sizeof resp)) { 
 				elog(WARNING, "Arbiter failed to write response for handshake message to node %d", resp.node);

multimaster.c

@@ -663,6 +663,15 @@ MtmResetTransaction(MtmCurrentTrans* x)
 	x->status = TRANSACTION_STATUS_UNKNOWN;
 }
 
+
+static const char* const isoLevelStr[] = 
+{
+	"read uncommitted", 
+	"read committed", 
+	"repeatable read", 
+	"serializable"
+};
+
 static void 
 MtmBeginTransaction(MtmCurrentTrans* x)
 {
@@ -679,13 +688,16 @@ MtmBeginTransaction(MtmCurrentTrans* x)
 		x->isPrepared = false;
 		x->isTransactionBlock = IsTransactionBlock();
 		/* Application name can be changed usnig PGAPPNAME environment variable */
-		if (!IsBackgroundWorker && x->isDistributed && Mtm->status != MTM_ONLINE && strcmp(application_name, MULTIMASTER_ADMIN) != 0) { 
+		if (x->isDistributed && Mtm->status != MTM_ONLINE && strcmp(application_name, MULTIMASTER_ADMIN) != 0) { 
 			/* Reject all user's transactions at offline cluster. 
 			 * Allow execution of transaction by bg-workers to make it possible to perform recovery.
 			 */
 			MtmUnlock();			
 			elog(ERROR, "Multimaster node is not online: current status %s", MtmNodeStatusMnem[Mtm->status]);
 		}
+		if (x->isDistributed && XactIsoLevel != XACT_REPEATABLE_READ) { 
+			elog(LOG, "Isolation level %s is not supported by multimaster", isoLevelStr[XactIsoLevel]);
+		}
 		x->containsDML = false;
         x->snapshot = MtmAssignCSN();	
 		x->gtid.xid = InvalidTransactionId;
@@ -2163,6 +2175,13 @@ _PG_init(void)
 		NULL
 	);
 
+	if (DefaultXactIsoLevel != XACT_REPEATABLE_READ) { 
+		elog(ERROR, "Multimaster requires repeatable read default isolation level");
+	}
+	if (synchronous_commit != SYNCHRONOUS_COMMIT_ON) { 
+		elog(ERROR, "Multimaster requires synchronous commit on");
+	}
+
 	MtmSplitConnStrs();
     MtmStartReceivers();