improved session recovery when outbound tcp connection breaks, reduces

probability of message loss at the price of a highly unlikely potential
    (single) message duplication

ChangeLog

@@ -37,6 +37,9 @@ Version 3.12.1 (rgerhards), 2008-03-06
 - added ability to compile on HP UX; verified that imudp worked on HP UX;
   however, we are still in need of people trying out rsyslogd on HP UX,
   so it can not yet be assumed it runs there
+- improved session recovery when outbound tcp connection breaks, reduces
+  probability of message loss at the price of a highly unlikely potential
+  (single) message duplication
 ---------------------------------------------------------------------------
 Version 3.12.0 (rgerhards), 2008-02-28
 - added full expression support for filters; filters can now contain

omfwd.c

@@ -259,12 +259,13 @@ static rsRetVal TCPSendFrame(void *pvData, char *msg, size_t len)
  */
 static rsRetVal TCPSendPrepRetry(void *pvData)
 {
+	DEFiRet;
 	instanceData *pData = (instanceData *) pvData;
 
 	assert(pData != NULL);
 	close(pData->sock);
 	pData->sock = -1;
-	return RS_RET_OK;
+	RETiRet;
 }
 
 

tcpclt.c

@@ -303,12 +303,39 @@ Send(tcpclt_t *pThis, void *pData, char *msg, size_t len)
 		CHKiRet(pThis->initFunc(pData));
 		iRet = pThis->sendFunc(pData, msg, len);
 
-		if(iRet == RS_RET_OK || retry > 0) {
-			/* we are done - either we succeeded or the retry failed */
+		if(iRet == RS_RET_OK) {
+			/* we are done, we also use this as indication that the previous
+			 * message was succesfully received (it's not always the case, but its at 
+			 * least our best shot at it -- rgerhards, 2008-03-12
+			 */
+			if(pThis->prevMsg != NULL)
+				free(pThis->prevMsg);
+			/* if we can not alloc a new buffer, we silently ignore it. The worst that
+			 * happens is that we lose our message recovery buffer - anything else would
+			 * be worse, so don't try anything ;) -- rgerhards, 2008-03-12
+			 */
+			if((pThis->prevMsg = malloc(len)) != NULL) {
+				memcpy(pThis->prevMsg, msg, len);
+				pThis->lenPrevMsg = len;
+			}
+
+			/* we are done with this record */
 			bDone = 1;
-		} else { /* OK, one retry */
-			++retry;
-			CHKiRet(pThis->prepRetryFunc(pData)); /* try to recover */
+		} else {
+			if(retry == 0) { /* OK, one retry */
+				++retry;
+				CHKiRet(pThis->prepRetryFunc(pData)); /* try to recover */
+				/* now try to send our stored previous message (which most probably
+				 * didn't make it
+				 */
+				if(pThis->prevMsg != NULL) {
+					CHKiRet(pThis->initFunc(pData));
+					CHKiRet(pThis->sendFunc(pData, pThis->prevMsg, pThis->lenPrevMsg));
+				}
+			} else {
+				/* OK, max number of retries reached, nothing we can do */
+				bDone = 1;
+			}
 		}
 	}
 
@@ -414,7 +441,6 @@ ENDobjQueryInterface(tcpclt)
 BEGINObjClassExit(tcpclt, OBJ_IS_LOADABLE_MODULE) /* CHANGE class also in END MACRO! */
 CODESTARTObjClassExit(tcpclt)
 	/* release objects we no longer need */
-//objRelease(net, LM_NET_FILENAME);
 ENDObjClassExit(tcpclt)
 
 
@@ -424,7 +450,6 @@ ENDObjClassExit(tcpclt)
  */
 BEGINObjClassInit(tcpclt, 1, OBJ_IS_LOADABLE_MODULE) /* class, version - CHANGE class also in END MACRO! */
 	/* request objects we use */
-//CHKiRet(objUse(net, LM_NET_FILENAME));
 
 	/* set our own handlers */
 	OBJSetMethodHandler(objMethod_CONSTRUCTION_FINALIZER, tcpcltConstructFinalize);

tcpclt.h

@@ -33,6 +33,8 @@
 typedef struct tcpclt_s {
 	BEGINobjInstance;	/**< Data to implement generic object - MUST be the first data element! */
 	TCPFRAMINGMODE tcp_framing;
+	char *prevMsg;
+	size_t lenPrevMsg;
 	/* session specific callbacks */
 	rsRetVal (*initFunc)(void*);
 	rsRetVal (*sendFunc)(void*, char*, size_t);