From 5132a1c7864acf9283fea5761c5290a7ba986ca1 Mon Sep 17 00:00:00 2001
From: Felix Hamme <felix.hamme@ionos.com>
Date: Mon, 13 Sep 2021 14:34:33 +0200
Subject: [PATCH] fix mysql_slave_hosts_info for mysql 5.5 and mariadb 10.5,
 add unit test

The "show slave hosts" command on mysql 5.5 and mariadb 10.5 returns neither a "Slave_UUID" nor a "Rpl_recovery_rank" column. Set the slave_uuid metric label to "" in this case.

Signed-off-by: Felix Hamme <felix.hamme@ionos.com>
---
 collector/slave_hosts.go      | 35 +++++++++++++++++++++++---------
 collector/slave_hosts_test.go | 38 +++++++++++++++++++++++++++++++++++
 2 files changed, 64 insertions(+), 9 deletions(-)

diff --git a/collector/slave_hosts.go b/collector/slave_hosts.go
index 536d4b78..26678dc5 100644
--- a/collector/slave_hosts.go
+++ b/collector/slave_hosts.go
@@ -80,25 +80,42 @@ func (ScrapeSlaveHosts) Scrape(ctx context.Context, db *sql.DB, ch chan<- promet
 	var masterId string
 	var slaveUuid string
 
+	columnNames, err := slaveHostsRows.Columns()
+	if err != nil {
+		return err
+	}
+
 	for slaveHostsRows.Next() {
 		// Newer versions of mysql have the following
 		// 		Server_id, Host, Port, Master_id, Slave_UUID
 		// Older versions of mysql have the following
 		// 		Server_id, Host, Port, Rpl_recovery_rank, Master_id
-		err := slaveHostsRows.Scan(&serverId, &host, &port, &rrrOrMasterId, &slaveUuidOrMasterId)
+		// MySQL 5.5 and MariaDB 10.5 have the following
+		// 		Server_id, Host, Port, Master_id
+		if len(columnNames) == 5 {
+			err = slaveHostsRows.Scan(&serverId, &host, &port, &rrrOrMasterId, &slaveUuidOrMasterId)
+		} else {
+			err = slaveHostsRows.Scan(&serverId, &host, &port, &rrrOrMasterId)
+		}
 		if err != nil {
 			return err
 		}
 
-		// Check to see if slaveUuidOrMasterId resembles a UUID or not
-		// to find out if we are using an old version of MySQL
-		if _, err = uuid.FromString(slaveUuidOrMasterId); err != nil {
-			// We are running an older version of MySQL with no slave UUID
-			slaveUuid = ""
-			masterId = slaveUuidOrMasterId
+		// if a Slave_UUID or Rpl_recovery_rank field is present
+		if len(columnNames) == 5 {
+			// Check to see if slaveUuidOrMasterId resembles a UUID or not
+			// to find out if we are using an old version of MySQL
+			if _, err = uuid.FromString(slaveUuidOrMasterId); err != nil {
+				// We are running an older version of MySQL with no slave UUID
+				slaveUuid = ""
+				masterId = slaveUuidOrMasterId
+			} else {
+				// We are running a more recent version of MySQL
+				slaveUuid = slaveUuidOrMasterId
+				masterId = rrrOrMasterId
+			}
 		} else {
-			// We are running a more recent version of MySQL
-			slaveUuid = slaveUuidOrMasterId
+			slaveUuid = ""
 			masterId = rrrOrMasterId
 		}
 
diff --git a/collector/slave_hosts_test.go b/collector/slave_hosts_test.go
index 08b1612b..9f3f3848 100644
--- a/collector/slave_hosts_test.go
+++ b/collector/slave_hosts_test.go
@@ -99,3 +99,41 @@ func TestScrapeSlaveHostsNewFormat(t *testing.T) {
 		t.Errorf("there were unfulfilled exceptions: %s", err)
 	}
 }
+
+func TestScrapeSlaveHostsWithoutSlaveUuid(t *testing.T) {
+	db, mock, err := sqlmock.New()
+	if err != nil {
+		t.Fatalf("error opening a stub database connection: %s", err)
+	}
+	defer db.Close()
+
+	columns := []string{"Server_id", "Host", "Port", "Master_id"}
+	rows := sqlmock.NewRows(columns).
+		AddRow("192168010", "iconnect2", "3306", "192168012").
+		AddRow("1921680101", "athena", "3306", "192168012")
+	mock.ExpectQuery(sanitizeQuery("SHOW SLAVE HOSTS")).WillReturnRows(rows)
+
+	ch := make(chan prometheus.Metric)
+	go func() {
+		if err = (ScrapeSlaveHosts{}).Scrape(context.Background(), db, ch, log.NewNopLogger()); err != nil {
+			t.Errorf("error calling function on test: %s", err)
+		}
+		close(ch)
+	}()
+
+	counterExpected := []MetricResult{
+		{labels: labelMap{"server_id": "192168010", "slave_host": "iconnect2", "port": "3306", "master_id": "192168012", "slave_uuid": ""}, value: 1, metricType: dto.MetricType_GAUGE},
+		{labels: labelMap{"server_id": "1921680101", "slave_host": "athena", "port": "3306", "master_id": "192168012", "slave_uuid": ""}, value: 1, metricType: dto.MetricType_GAUGE},
+	}
+	convey.Convey("Metrics comparison", t, func() {
+		for _, expect := range counterExpected {
+			got := readMetric(<-ch)
+			convey.So(got, convey.ShouldResemble, expect)
+		}
+	})
+
+	// Ensure all SQL queries were executed
+	if err := mock.ExpectationsWereMet(); err != nil {
+		t.Errorf("there were unfulfilled exceptions: %s", err)
+	}
+}