--- rsyslog-8.2102.0-ori/action.c	2021-02-15 12:06:16.000000000 +0100
+++ rsyslog-8.2102.0-changes/action.c	2022-03-10 11:00:11.027242300 +0100
@@ -198,6 +198,7 @@
 	{ "name", eCmdHdlrGetWord, 0 }, /* legacy: actionname */
 	{ "type", eCmdHdlrString, CNFPARAM_REQUIRED }, /* legacy: actionname */
 	{ "action.errorfile", eCmdHdlrString, 0 },
+	{ "action.errorfile.maxsize", eCmdHdlrInt, 0 },
 	{ "action.writeallmarkmessages", eCmdHdlrBinary, 0 }, /* legacy: actionwriteallmarkmessages */
 	{ "action.execonlyeverynthtime", eCmdHdlrInt, 0 }, /* legacy: actionexeconlyeverynthtime */
 	{ "action.execonlyeverynthtimetimeout", eCmdHdlrInt, 0 }, /* legacy: actionexeconlyeverynthtimetimeout */
@@ -400,6 +401,8 @@
 	pThis->iResumeRetryCount = 0;
 	pThis->pszName = NULL;
 	pThis->pszErrFile = NULL;
+	pThis->maxErrFileSize = 0;
+	pThis->errFileWritten = 0;
 	pThis->pszExternalStateFile = NULL;
 	pThis->fdErrFile = -1;
 	pThis->bWriteAllMarkMsgs = 1;
@@ -1436,6 +1439,14 @@
 				pThis->pszName, pThis->pszErrFile);
 			goto done;
 		}
+		if (pThis->maxErrFileSize > 0) {
+			struct stat statbuf;
+			if (fstat(pThis->fdErrFile, &statbuf) == -1) {
+				LogError(errno, RS_RET_ERR, "failed to fstat %s", pThis->pszErrFile);
+				goto done;
+			}
+			pThis->errFileWritten += statbuf.st_size;
+		}
 	}
 
 	for(int i = 0 ; i < nparams ; ++i) {
@@ -1454,16 +1465,26 @@
 		char *const rendered = strdup((char*)fjson_object_to_json_string(etry));
 		if(rendered == NULL)
 			goto done;
-		const size_t toWrite = strlen(rendered) + 1;
-		/* note: we use the '\0' inside the string to store a LF - we do not
-		 * otherwise need it and it safes us a copy/realloc.
-		 */
-		rendered[toWrite-1] = '\n'; /* NO LONGER A STRING! */
-		const ssize_t wrRet = write(pThis->fdErrFile, rendered, toWrite);
-		if(wrRet != (ssize_t) toWrite) {
-			LogError(errno, RS_RET_IO_ERROR,
-				"action %s: error writing errorFile %s, write returned %lld",
-				pThis->pszName, pThis->pszErrFile, (long long) wrRet);
+		size_t toWrite = strlen(rendered) + 1;
+		// Check if need to truncate the amount of bytes to write
+		if (pThis->maxErrFileSize > 0) {
+			if (pThis->errFileWritten + toWrite > pThis->maxErrFileSize) {
+				// Truncate to the pending available
+				toWrite = pThis->maxErrFileSize - pThis->errFileWritten;
+			}
+			pThis->errFileWritten += toWrite;
+		}
+		if(toWrite > 0) {
+			/* note: we use the '\0' inside the string to store a LF - we do not
+			 * otherwise need it and it safes us a copy/realloc.
+			 */
+			rendered[toWrite-1] = '\n'; /* NO LONGER A STRING! */
+			const ssize_t wrRet = write(pThis->fdErrFile, rendered, toWrite);
+			if(wrRet != (ssize_t) toWrite) {
+				LogError(errno, RS_RET_IO_ERROR,
+					"action %s: error writing errorFile %s, write returned %lld",
+					pThis->pszName, pThis->pszErrFile, (long long) wrRet);
+			}
 		}
 		free(rendered);
 
@@ -2048,6 +2069,8 @@
 			continue; /* this is handled seperately during module select! */
 		} else if(!strcmp(pblk.descr[i].name, "action.errorfile")) {
 			pAction->pszErrFile = es_str2cstr(pvals[i].val.d.estr, NULL);
+		} else if(!strcmp(pblk.descr[i].name, "action.errorfile.maxsize")) {
+			pAction->maxErrFileSize = pvals[i].val.d.n;
 		} else if(!strcmp(pblk.descr[i].name, "action.externalstate.file")) {
 			pAction->pszExternalStateFile = es_str2cstr(pvals[i].val.d.estr, NULL);
 		} else if(!strcmp(pblk.descr[i].name, "action.writeallmarkmessages")) {
--- rsyslog-8.2102.0-ori/action.h	2020-10-03 19:06:47.000000000 +0200
+++ rsyslog-8.2102.0-changes/action.h	2022-03-04 11:36:47.024588972 +0100
@@ -77,6 +77,8 @@
 	/* error file */
 	const char *pszErrFile;
 	int fdErrFile;
+	size_t maxErrFileSize;
+	size_t errFileWritten;
 	pthread_mutex_t mutErrFile;
 	/* external stat file system */
 	const char *pszExternalStateFile;
--- rsyslog-8.2102.0-ori/tests/Makefile.am	2021-02-15 12:06:16.000000000 +0100
+++ rsyslog-8.2102.0-changes/tests/Makefile.am	2022-03-04 11:38:01.625095709 +0100
@@ -695,7 +695,8 @@
 	mysql-actq-mt.sh \
 	mysql-actq-mt-withpause.sh \
 	action-tx-single-processing.sh \
-	action-tx-errfile.sh
+	action-tx-errfile.sh \
+	action-tx-errfile-maxsize.sh
 
 mysql-basic.log: mysqld-start.log
 mysql-basic-cnf6.log: mysqld-start.log
@@ -2156,6 +2157,8 @@
 	sndrcv_omudpspoof_nonstdpt.sh \
 	sndrcv_gzip.sh \
 	action-tx-single-processing.sh \
+	omfwd-errfile-maxsize.sh \
+	action-tx-errfile-maxsize.sh \
 	action-tx-errfile.sh \
 	testsuites/action-tx-errfile.result \
 	pipeaction.sh \
--- rsyslog-8.2102.0-ori/tests/omfwd-errfile-maxsize.sh	1970-01-01 01:00:00.000000000 +0100
+++ rsyslog-8.2102.0-changes/tests/omfwd-errfile-maxsize.sh	2022-03-04 11:39:02.060506234 +0100
@@ -0,0 +1,17 @@
+#!/bin/bash
+# part of the rsyslog project, released under ASL 2.0
+. ${srcdir:=.}/diag.sh init
+
+export MAX_ERROR_SIZE=1999
+
+generate_conf
+add_conf '
+action(type="omfwd" target="1.2.3.4" port="1234" Protocol="tcp" NetworkNamespace="doesNotExist"
+       action.errorfile="'$RSYSLOG2_OUT_LOG'" action.errorfile.maxsize="'$MAX_ERROR_SIZE'")
+'
+startup
+shutdown_when_empty
+wait_shutdown
+check_file_exists ${RSYSLOG2_OUT_LOG}
+file_size_check ${RSYSLOG2_OUT_LOG} ${MAX_ERROR_SIZE}
+exit_test
--- rsyslog-8.2102.0-ori/tests/action-tx-errfile-maxsize.sh	1970-01-01 01:00:00.000000000 +0100
+++ rsyslog-8.2102.0-changes/tests/action-tx-errfile-maxsize.sh	2022-03-04 11:59:22.592796989 +0100
@@ -0,0 +1,35 @@
+#!/bin/bash
+# part of the rsyslog project, released under ASL 2.0
+
+. ${srcdir:=.}/diag.sh init
+
+export NUMMESSAGES=50 # enough to generate big file
+export MAX_ERROR_SIZE=100
+
+generate_conf
+add_conf '
+$ModLoad ../plugins/ommysql/.libs/ommysql
+global(errormessagestostderr.maxnumber="5")
+
+template(type="string" name="tpl" string="insert into SystemEvents (Message, Facility) values (\"%msg%\", %$!facility%)" option.sql="on")
+
+if((not($msg contains "error")) and ($msg contains "msgnum:")) then {
+	set $.num = field($msg, 58, 2);
+	if $.num % 2 == 0 then {
+		set $!facility = $syslogfacility;
+	} else {
+		set $/cntr = 0;
+	}
+	action(type="ommysql" name="mysql_action_errfile_maxsize" server="127.0.0.1" template="tpl"
+	       db="'$RSYSLOG_DYNNAME'" uid="rsyslog" pwd="testbench" action.errorfile="'$RSYSLOG2_OUT_LOG'" action.errorfile.maxsize="'$MAX_ERROR_SIZE'")
+}
+'
+mysql_prep_for_test
+startup
+injectmsg
+shutdown_when_empty
+wait_shutdown
+mysql_get_data
+check_file_exists ${RSYSLOG2_OUT_LOG}
+file_size_check ${RSYSLOG2_OUT_LOG} ${MAX_ERROR_SIZE}
+exit_test
--- rsyslog-8.2102.0/tests/omfwd-errfile-maxsize-filled.sh	1970-01-01 01:00:00.000000000 +0100
+++ rsyslog-8.2102.0-changes/tests/omfwd-errfile-maxsize-filled.sh	2022-03-08 16:24:01.174365289 +0100
@@ -0,0 +1,19 @@
+#!/bin/bash
+# part of the rsyslog project, released under ASL 2.0
+. ${srcdir:=.}/diag.sh init
+ERRFILE=$(mktemp)
+export MAX_ERROR_SIZE=1999
+export INITIAL_FILE_SIZE=$((MAX_ERROR_SIZE - 100))
+dd if=/dev/urandom of=${ERRFILE}  bs=1 count=${INITIAL_FILE_SIZE}
+generate_conf
+add_conf '
+action(type="omfwd" target="1.2.3.4" port="1234" Protocol="tcp" NetworkNamespace="doesNotExist"
+       action.errorfile="'$ERRFILE'" action.errorfile.maxsize="'$MAX_ERROR_SIZE'")
+'
+startup
+shutdown_when_empty
+wait_shutdown
+check_file_exists ${ERRFILE}
+file_size_check ${ERRFILE} ${MAX_ERROR_SIZE}
+exit_test
+rm ${ERRFILE}