add -hostname-override

cmd/node_problem_detector.go

@@ -26,6 +26,7 @@ import (
 	"k8s.io/node-problem-detector/pkg/version"
 
 	"github.com/golang/glog"
+	"fmt"
 )
 
 // TODO: Move flags to options directory.
@@ -33,6 +34,7 @@ var (
 	kernelMonitorConfigPath = flag.String("kernel-monitor", "/config/kernel-monitor.json", "The path to the kernel monitor config file")
 	apiServerOverride       = flag.String("apiserver-override", "", "Custom URI used to connect to Kubernetes ApiServer")
 	printVersion            = flag.Bool("version", false, "Print version information and quit")
+	hostnameOverride        = flag.String("hostname-override", "", "Custom node name used to override hostname")
 )
 
 func validateCmdParams() {
@@ -41,6 +43,36 @@ func validateCmdParams() {
 	}
 }
 
+func getNodeNameOrDie() string {
+	var nodeName string
+
+	// Check hostname override first for customized node name.
+	if *hostnameOverride != "" {
+		return *hostnameOverride
+	}
+
+	// Get node name from environment variable NODE_NAME
+	// By default, assume that the NODE_NAME env should have been set with
+	// downward api or user defined exported environment variable. We prefer it because sometimes
+	// the hostname returned by os.Hostname is not right because:
+	// 1. User may override the hostname.
+	// 2. For some cloud providers, os.Hostname is different from the real hostname.
+	nodeName = os.Getenv("NODE_NAME")
+	if nodeName != "" {
+		return nodeName
+	}
+
+	// For backward compatibility. If the env is not set, get the hostname
+	// from os.Hostname(). This may not work for all configurations and
+	// environments.
+	nodeName, err := os.Hostname()
+	if err != nil {
+		panic(fmt.Sprintf("Failed to get host name: %v", err))
+	}
+
+	return nodeName
+}
+
 func main() {
 	flag.Parse()
 	validateCmdParams()
@@ -50,7 +82,9 @@ func main() {
 		os.Exit(0)
 	}
 
+	nodeName := getNodeNameOrDie()
+
 	k := kernelmonitor.NewKernelMonitorOrDie(*kernelMonitorConfigPath)
-	p := problemdetector.NewProblemDetector(k, *apiServerOverride)
+	p := problemdetector.NewProblemDetector(k, *apiServerOverride, nodeName)
 	p.Run()
 }