Feature Request: "debug" flag should surface Prometheus scraper errors

[andersnm]

I assumed the agent surfaces Prometheus scraper errors in the agent logs, especifically when the agent { debug: true } is set. Turns out it doesn't. Would of been a time-saver if it did.

EDIT: There is an undocumented DEBUG environment variable to enable Prometheus debug logging in the CloudWatch Agent:

amazon-cloudwatch-agent/plugins/inputs/prometheus/start.go

Lines 82 to 90 in 71bdd66

	func Start(configFilePath string, receiver storage.Appendable, shutDownChan chan interface{}, wg *sync.WaitGroup, mth *metricsTypeHandler) {
	logLevel := &promslog.AllowedLevel{}
	logLevel.Set("info")
	if os.Getenv("DEBUG") != "" {
	runtime.SetBlockProfileRate(20)
	runtime.SetMutexProfileFraction(20)
	logLevel.Set("debug")
	}

[EDIT: removed confused bugreport caused by warning while expecting other errors in the logs]