Fix es.log-level behaviour (#3664)

pkg/es/config/config.go

@@ -32,6 +32,7 @@ import (
 	"github.com/olivere/elastic"
 	"github.com/uber/jaeger-lib/metrics"
 	"go.uber.org/zap"
+	"go.uber.org/zap/zapcore"
 	"go.uber.org/zap/zapgrpc"
 
 	"github.com/jaegertracing/jaeger/pkg/bearertoken"
@@ -458,26 +459,38 @@ func addLoggerOptions(options []elastic.ClientOptionFunc, logLevel string) ([]el
 	// e.g. --log-level=info and --es.log-level=debug would mute ES's debug logging and would require --log-level=debug
 	// to show ES debug logs.
 	prodConfig := zap.NewProductionConfig()
-	prodConfig.Level.SetLevel(zap.DebugLevel)
 
-	esLogger, err := prodConfig.Build()
-	if err != nil {
-		return options, err
-	}
+	var lvl zapcore.Level
+	var loggerOpts []zapgrpc.Option
+	var setLogger func(logger elastic.Logger) elastic.ClientOptionFunc
 
-	// Elastic client requires a "Printf"-able logger.
-	l := zapgrpc.NewLogger(esLogger)
 	switch logLevel {
 	case "debug":
-		l = zapgrpc.NewLogger(esLogger, zapgrpc.WithDebug())
-		options = append(options, elastic.SetTraceLog(l))
+		lvl = zap.DebugLevel
+		setLogger = elastic.SetTraceLog
+
+		// Enables the "level":"debug" log field. Without this,
+		// the "level" field defaults to "info".
+		loggerOpts = append(loggerOpts, zapgrpc.WithDebug())
 	case "info":
-		options = append(options, elastic.SetInfoLog(l))
+		lvl = zap.InfoLevel
+		setLogger = elastic.SetInfoLog
 	case "error":
-		options = append(options, elastic.SetErrorLog(l))
+		lvl = zap.ErrorLevel
+		setLogger = elastic.SetErrorLog
 	default:
 		return options, fmt.Errorf("unrecognized log-level: \"%s\"", logLevel)
 	}
+
+	prodConfig.Level.SetLevel(lvl)
+	esLogger, err := prodConfig.Build()
+	if err != nil {
+		return options, err
+	}
+
+	// Elastic client requires a "Printf"-able logger.
+	l := zapgrpc.NewLogger(esLogger, loggerOpts...)
+	options = append(options, setLogger(l))
 	return options, nil
 }