feat: add log formatting

We introduce log formatting to support both text and json formats. This
can be configured through a CLI flag "log-format" or env var
"DCGM_EXPORTER_LOG_FORMAT".

Notably, the log format will capture any DCGM logging that is
configured.

We also move the automaxprocs call from an unused import to be
explicitly called when starting the dcgm exporter to ensure its logging
format honors the configuration.

cmd/dcgm-exporter/main.go

@@ -21,8 +21,6 @@ import (
 
 	"github.com/sirupsen/logrus"
 
-	_ "go.uber.org/automaxprocs"
-
 	"github.com/NVIDIA/dcgm-exporter/pkg/cmd"
 )
 

pkg/cmd/app.go

@@ -19,6 +19,7 @@ import (
 	"github.com/NVIDIA/go-dcgm/pkg/dcgm"
 	"github.com/sirupsen/logrus"
 	"github.com/urfave/cli/v2"
+	"go.uber.org/automaxprocs/maxprocs"
 
 	"github.com/NVIDIA/dcgm-exporter/pkg/dcgmexporter"
 	"github.com/NVIDIA/dcgm-exporter/pkg/stdout"
@@ -72,6 +73,7 @@ const (
 	CLIClockEventsCountWindowSize = "clock-events-count-window-size"
 	CLIEnableDCGMLog              = "enable-dcgm-log"
 	CLIDCGMLogLevel               = "dcgm-log-level"
+	CLILogFormat                  = "log-format"
 	CLIPodResourcesKubeletSocket  = "pod-resources-kubelet-socket"
 	CLIHPCJobMappingDir           = "hpc-job-mapping-dir"
 	CLINvidiaResourceNames        = "nvidia-resource-names"
@@ -226,6 +228,12 @@ func NewApp(buildVersion ...string) *cli.App {
 			Usage:   "Specify the DCGM log verbosity level. This parameter is effective only when the '--enable-dcgm-log' option is set to 'true'. Possible values: NONE, FATAL, ERROR, WARN, INFO, DEBUG and VERB",
 			EnvVars: []string{"DCGM_EXPORTER_DCGM_LOG_LEVEL"},
 		},
+		&cli.StringFlag{
+			Name:    CLILogFormat,
+			Value:   "text",
+			Usage:   "Specify the log output format. Possible values: text, json",
+			EnvVars: []string{"DCGM_EXPORTER_LOG_FORMAT"},
+		},
 		&cli.StringFlag{
 			Name:    CLIPodResourcesKubeletSocket,
 			Value:   "/var/lib/kubelet/pod-resources/kubelet.sock",
@@ -288,8 +296,27 @@ func action(c *cli.Context) (err error) {
 	})
 }
 
+func configureLogFormat(c *cli.Context) error {
+	logFormat := c.String(CLILogFormat)
+	switch logFormat {
+	case "text":
+		logrus.SetFormatter(&logrus.TextFormatter{})
+	case "json":
+		logrus.SetFormatter(&logrus.JSONFormatter{})
+	default:
+		return fmt.Errorf("invalid %s parameter values: %s", CLILogFormat, logFormat)
+	}
+	return nil
+}
+
 func startDCGMExporter(c *cli.Context, cancel context.CancelFunc) error {
 restart:
+	if err := configureLogFormat(c); err != nil {
+		return err
+	}
+
+	// Initialize automaxprocs with desired logging format.
+	maxprocs.Set(maxprocs.Logger(logrus.Infof))
 
 	logrus.Info("Starting dcgm-exporter")