Creating a DB2 client container as Prometheus scraping target in K8s

I need to mine some business metrics from a DB2 database and present it in the Grafana dashboard. A Prometheus scraping target is to be developed.

I published a Medium paper about 3 years ago to run DB2 queries in Golang by using the DB2 ODBC/CLI driver. Following that, let's create a container image as a Prometheus scraping target and run it in Kubernetes.

The app as a scraping target

Some Golang code excerpts to describe how the data collection works,

The DB and metric struct

type MetricConfig struct {
 Name      string `yaml:"name"`
 Desc      string `yaml:"desc"`
 Sql       string `yaml:"sql"`
 Frequency string `yaml:"frequency"`
}
type DBMetricsConfig struct {
 Dsn      string         `yaml:"dsn,omitempty"`
 User     string         `yaml:"user,omitempty"`
 Password string         `yaml:"password,omitempty"`
 Metrics  []MetricConfig `yaml:"metrics,omitempty"`
}

The Dsn is the DB2’s ODBC Data Source Name. The metric is a type of Prometheus Gauge. The metric value will be set from a SQL query that returns a single row and a single column. We run the data collection as a cron job using the jobrunner library.

The initialization function,

func ScheduleDBMetricJob(mc DBMetricsConfig) error {
 user := os.Getenv(mc.User)
 password := os.Getenv(mc.Password)
 db, err := sqlx.Open("odbc", fmt.Sprintf("DSN=%s;uid=%s;pwd=%s", mc.Dsn, user, password))
 if err != nil {
  logrus.Errorf("Error opening database: %v", err)
  return err
 }
 db.SetMaxIdleConns(5)
 db.SetMaxOpenConns(5)
 for _, met := range mc.Metrics {
  gauge := prometheus.NewGauge(prometheus.GaugeOpts{
   Namespace: "db2",
   Subsystem: "mon",
   Name:      met.Name,
   Help:      met.Desc,
  })
  prometheus.MustRegister(gauge)
  jobrunner.Schedule(fmt.Sprintf("@every %s", met.Frequency), DBMetricJob{
   db:    db,
   sql:   met.Sql,
   gauge: gauge,
  })
 }
 return nil
}

The actual data collection function shown below is straightforward, thanks to the sqlx helper function.

type DBMetricJob struct {
 db…