Enable the mysqld_exporter without any required user changes

Signed-off-by: Matt Lord <mattalord@gmail.com>

Author: mattlord

pkg/operator/vttablet/constants.go

@@ -32,6 +32,7 @@ const (
 
 	mysqldExporterContainerName      = "mysqld-exporter"
 	mysqldExporterCommand            = "/bin/mysqld_exporter"
+	mysqldExporterMySQLCnf           = "client.cnf"
 	mysqldExporterUser               = "vt_dba"
 	mysqldExporterPort               = 9104
 	mysqldExporterPortName           = "metrics"

pkg/operator/vttablet/mysqlctld.go

@@ -40,6 +40,7 @@ ln -sf /dev/stderr /mnt/vt/config/stderr.symlink
 echo "log-error = /vt/config/stderr.symlink" > /mnt/vt/config/mycnf/log-error.cnf
 echo "binlog_format=row" > /mnt/vt/config/mycnf/rbr.cnf
 echo "socket = ` + mysqlSocketPath + `" > /mnt/vt/config/mycnf/socket.cnf
+echo -n "[client]\nuser=` + mysqldExporterUser + `\nsocket=` + mysqlSocketPath + `\n" > /mnt/vt/config/mycnf/` + mysqldExporterMySQLCnf + `
 `
 
 	mysqlSocketInitScript = `set -ex

pkg/operator/vttablet/pod.go

@@ -17,6 +17,7 @@ limitations under the License.
 package vttablet
 
 import (
+	"path/filepath"
 	"strconv"
 	"strings"
 
@@ -210,6 +211,9 @@ func UpdatePod(obj *corev1.Pod, spec *Spec) {
 				key = strings.TrimLeft(key, "-")
 				mysqldExporterAllFlags[key] = value
 			}
+			if _, ok := mysqldExporterAllFlags["config.my-cnf"]; !ok {
+				mysqldExporterAllFlags["config.my-cnf"] = filepath.Join(vtMycnfPath, mysqldExporterMySQLCnf)
+			}
 		}
 
 		// TODO: Can/should we still run mysqld_exporter pointing at external mysql?