From 3929c5ac37a5b6c6ae0430c40438da087da07e1a Mon Sep 17 00:00:00 2001
From: Gerardo Malazdrewicz <36243997+GerMalaz@users.noreply.github.com>
Date: Sun, 31 Oct 2021 09:37:55 -0300
Subject: check_mysql.c: Detect running mysqldump

When checking a slave, if the IO Thread or the SQL Thread are stopped, check for running mysqldump threads, return STATE_OK if there is any.
Requires PROCESS privilege to work (else the mysqldump thread(s) would not be detected).

Enlarged SLAVERESULTSIZE to fit "Mysqldump: in progress" at the end of the string.
Got a NULL pointer in row[seconds_behind_field] instead of the "NULL" string when a mysqldump is running [mysql 5.7.34 + libmariadb3 10.3.31], so added a check for that.

diff --git a/plugins/check_mysql.c b/plugins/check_mysql.c
index 0cba50e..5b9a4fe 100644
--- a/plugins/check_mysql.c
+++ b/plugins/check_mysql.c
@@ -34,7 +34,7 @@ const char *progname = "check_mysql";
 const char *copyright = "1999-2011";
 const char *email = "devel@monitoring-plugins.org";
 
-#define SLAVERESULTSIZE 70
+#define SLAVERESULTSIZE 96
 
 #include "common.h"
 #include "utils.h"
@@ -89,6 +89,8 @@ static const char *metric_counter[LENGTH_METRIC_COUNTER] = {
 	"Uptime"
 };
 
+#define MYSQLDUMP_THREADS_QUERY "SELECT COUNT(1) mysqldumpThreads FROM information_schema.processlist WHERE info LIKE 'SELECT /*!40001 SQL_NO_CACHE */%'"
+
 thresholds *my_threshold = NULL;
 
 int process_arguments (int, char **);
@@ -275,11 +277,29 @@ main (int argc, char **argv)
 			/* Save slave status in slaveresult */
 			snprintf (slaveresult, SLAVERESULTSIZE, "Slave IO: %s Slave SQL: %s Seconds Behind Master: %s", row[slave_io_field], row[slave_sql_field], seconds_behind_field!=-1?row[seconds_behind_field]:"Unknown");
 
-			/* Raise critical error if SQL THREAD or IO THREAD are stopped */
+			/* Raise critical error if SQL THREAD or IO THREAD are stopped, but only if there are no mysqldump threads running */
 			if (strcmp (row[slave_io_field], "Yes") != 0 || strcmp (row[slave_sql_field], "Yes") != 0) {
-				mysql_free_result (res);
-				mysql_close (&mysql);
-				die (STATE_CRITICAL, "%s\n", slaveresult);
+				MYSQL_RES *res_mysqldump;
+				MYSQL_ROW row_mysqldump;
+				unsigned int mysqldump_threads = 0;
+
+				if (mysql_query (&mysql, MYSQLDUMP_THREADS_QUERY) == 0) {
+					/* store the result */
+					if ( (res_mysqldump = mysql_store_result (&mysql)) != NULL) {
+						if (mysql_num_rows(res_mysqldump) == 1) {
+							if ( (row_mysqldump = mysql_fetch_row (res_mysqldump)) != NULL) {
+								mysqldump_threads = atoi(row_mysqldump[0]);
+							}
+						}
+						/* free the result */
+						mysql_free_result (res_mysqldump);
+					}
+				}
+				if (mysqldump_threads == 0) {
+					die (STATE_CRITICAL, "%s\n", slaveresult);
+				} else {
+					strlcat (slaveresult, " Mysqldump: in progress", SLAVERESULTSIZE);
+				}
 			}
 
 			if (verbose >=3) {
@@ -291,7 +311,7 @@ main (int argc, char **argv)
 			}
 
 			/* Check Seconds Behind against threshold */
-			if ((seconds_behind_field != -1) && (strcmp (row[seconds_behind_field], "NULL") != 0)) {
+			if ((seconds_behind_field != -1) && (row[seconds_behind_field] != NULL && strcmp (row[seconds_behind_field], "NULL") != 0)) {
 				double value = atof(row[seconds_behind_field]);
 				int status;
 
-- 
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