Support providing a log level to empire

Fixes remind101#929

cmd/empire/factories.go

@@ -40,7 +40,10 @@ func newRootContext(c *cli.Context) (context.Context, error) {
 	if err != nil {
 		return nil, err
 	}
-	l := newLogger()
+	l, err := newLogger(c)
+	if err != nil {
+		return nil, err
+	}
 
 	ctx := context.Background()
 	if r != nil {
@@ -367,11 +370,17 @@ func newRunRecorder(c *cli.Context) (empire.RunRecorder, error) {
 
 // Logger ==============================
 
-func newLogger() log15.Logger {
+func newLogger(c *cli.Context) (log15.Logger, error) {
 	l := log15.New()
-	h := log15.StreamHandler(os.Stdout, log15.LogfmtFormat())
+	lvl := c.String(FlagLogLevel)
+	log.Println(fmt.Sprintf("Using log level %s", lvl))
+	v, err := log15.LvlFromString(c.String(FlagLogLevel))
+	if err != nil {
+		return l, err
+	}
+	h := log15.LvlFilterHandler(v, log15.StreamHandler(os.Stdout, log15.LogfmtFormat()))
 	l.SetHandler(log15.LazyHandler(h))
-	return l
+	return l, err
 }
 
 // Reporter ============================

cmd/empire/main.go

@@ -16,6 +16,7 @@ const (
 	FlagEventsBackend    = "events.backend"
 	FlagRunLogsBackend   = "runlogs.backend"
 	FlagMessagesRequired = "messages.required"
+	FlagLogLevel         = "log.level"
 
 	FlagGithubClient       = "github.client.id"
 	FlagGithubClientSecret = "github.client.secret"
@@ -334,6 +335,12 @@ var EmpireFlags = []cli.Flag{
 		Usage:  "If true, attached runs will be shown in `emp ps` output.",
 		EnvVar: "EMPIRE_X_SHOW_ATTACHED",
 	},
+	cli.StringFlag{
+		Name:   FlagLogLevel,
+		Value:  "info",
+		Usage:  "Specify the log level for the empire server. You can use this to enable debug logs by specifying `debug`.",
+		EnvVar: "EMPIRE_LOG_LEVEL",
+	},
 }
 
 func main() {