appinit

Overview ¶

Package appinit wires common service start-up concerns: logging setup, the metrics pipeline and optional CPU profiling. It defines the Flags and LogConfig structs (tagged for github.com/alecthomas/kong CLI parsing) that services embed in their command line definitions.

Each initializer returns an io.Closer (possibly nil) that the caller should close on shutdown, typically in reverse order:

logCloser, err := appinit.Logs(&flags.LogConfig, "myservice")
if err != nil {
	return err
}
if logCloser != nil {
	defer logCloser.Close()
}

prof, err := appinit.CPUProfiler(flags.CPUProfile) // nil closer when empty
if err != nil {
	return err
}
if prof != nil {
	defer prof.Close()
}

mc, err := appinit.Metrics(&cfg.Metrics, "myservice", "cluster-1", version, commit, myMetrics)
if err != nil {
	return err
}
if mc != nil {
	defer mc.Close()
}

Metrics and Logs mutate process-global state (xlog formatter, the global metrics sink, the default Prometheus registry) and are meant to be called once per process. Metrics also registers an xlog error hook that counts logged errors in metricskey.HealthLogErrors. Prometheus binds synchronously, returns bind errors to the caller, and uses bounded HTTP read deadlines. Closing the metrics closer stops its endpoint, the runtime stats collector and the CloudWatch publisher, after the publisher's final publish.