Document and add support to input plugins for logging alias (#6357)

plugins/inputs/prometheus/kubernetes.go

@@ -68,7 +68,7 @@ func (p *Prometheus) start(ctx context.Context) error {
 			case <-time.After(time.Second):
 				err := p.watch(ctx, client)
 				if err != nil {
-					log.Printf("E! [inputs.prometheus] unable to watch resources: %v", err)
+					p.Log.Errorf("Unable to watch resources: %s", err.Error())
 				}
 			}
 		}
@@ -144,7 +144,7 @@ func registerPod(pod *corev1.Pod, p *Prometheus) {
 		return
 	}
 
-	log.Printf("D! [inputs.prometheus] will scrape metrics from %s", *targetURL)
+	log.Printf("D! [inputs.prometheus] will scrape metrics from %q", *targetURL)
 	// add annotation as metrics tags
 	tags := pod.GetMetadata().GetAnnotations()
 	if tags == nil {
@@ -158,7 +158,7 @@ func registerPod(pod *corev1.Pod, p *Prometheus) {
 	}
 	URL, err := url.Parse(*targetURL)
 	if err != nil {
-		log.Printf("E! [inputs.prometheus] could not parse URL %s: %v", *targetURL, err)
+		log.Printf("E! [inputs.prometheus] could not parse URL %q: %s", *targetURL, err.Error())
 		return
 	}
 	podURL := p.AddressToURL(URL, URL.Hostname())
@@ -211,13 +211,13 @@ func unregisterPod(pod *corev1.Pod, p *Prometheus) {
 		return
 	}
 
-	log.Printf("D! [inputs.prometheus] registered a delete request for %s in namespace %s",
+	log.Printf("D! [inputs.prometheus] registered a delete request for %q in namespace %q",
 		pod.GetMetadata().GetName(), pod.GetMetadata().GetNamespace())
 
 	p.lock.Lock()
 	defer p.lock.Unlock()
 	if _, ok := p.kubernetesPods[*url]; ok {
 		delete(p.kubernetesPods, *url)
-		log.Printf("D! [inputs.prometheus] will stop scraping for %s", *url)
+		log.Printf("D! [inputs.prometheus] will stop scraping for %q", *url)
 	}
 }

plugins/inputs/prometheus/kubernetes_test.go

@@ -3,6 +3,7 @@ package prometheus
 import (
 	"testing"
 
+	"github.com/influxdata/telegraf/testutil"
 	"github.com/stretchr/testify/assert"
 
 	v1 "github.com/ericchiang/k8s/apis/core/v1"
@@ -53,7 +54,7 @@ func TestScrapeURLAnnotationsCustomPathWithSep(t *testing.T) {
 }
 
 func TestAddPod(t *testing.T) {
-	prom := &Prometheus{}
+	prom := &Prometheus{Log: testutil.Logger{}}
 
 	p := pod()
 	p.Metadata.Annotations = map[string]string{"prometheus.io/scrape": "true"}
@@ -62,7 +63,7 @@ func TestAddPod(t *testing.T) {
 }
 
 func TestAddMultipleDuplicatePods(t *testing.T) {
-	prom := &Prometheus{}
+	prom := &Prometheus{Log: testutil.Logger{}}
 
 	p := pod()
 	p.Metadata.Annotations = map[string]string{"prometheus.io/scrape": "true"}
@@ -73,7 +74,7 @@ func TestAddMultipleDuplicatePods(t *testing.T) {
 }
 
 func TestAddMultiplePods(t *testing.T) {
-	prom := &Prometheus{}
+	prom := &Prometheus{Log: testutil.Logger{}}
 
 	p := pod()
 	p.Metadata.Annotations = map[string]string{"prometheus.io/scrape": "true"}
@@ -85,7 +86,7 @@ func TestAddMultiplePods(t *testing.T) {
 }
 
 func TestDeletePods(t *testing.T) {
-	prom := &Prometheus{}
+	prom := &Prometheus{Log: testutil.Logger{}}
 
 	p := pod()
 	p.Metadata.Annotations = map[string]string{"prometheus.io/scrape": "true"}

plugins/inputs/prometheus/prometheus.go

@@ -5,7 +5,6 @@ import (
 	"errors"
 	"fmt"
 	"io/ioutil"
-	"log"
 	"net"
 	"net/http"
 	"net/url"
@@ -42,6 +41,8 @@ type Prometheus struct {
 
 	tls.ClientConfig
 
+	Log telegraf.Logger
+
 	client *http.Client
 
 	// Should we scrape Kubernetes services for prometheus annotations
@@ -136,7 +137,7 @@ func (p *Prometheus) GetAllURLs() (map[string]URLAndAddress, error) {
 	for _, u := range p.URLs {
 		URL, err := url.Parse(u)
 		if err != nil {
-			log.Printf("prometheus: Could not parse %s, skipping it. Error: %s", u, err.Error())
+			p.Log.Errorf("Could not parse %q, skipping it. Error: %s", u, err.Error())
 			continue
 		}
 		allURLs[URL.String()] = URLAndAddress{URL: URL, OriginalURL: URL}
@@ -157,7 +158,7 @@ func (p *Prometheus) GetAllURLs() (map[string]URLAndAddress, error) {
 
 		resolvedAddresses, err := net.LookupHost(URL.Hostname())
 		if err != nil {
-			log.Printf("prometheus: Could not resolve %s, skipping it. Error: %s", URL.Host, err.Error())
+			p.Log.Errorf("Could not resolve %q, skipping it. Error: %s", URL.Host, err.Error())
 			continue
 		}
 		for _, resolved := range resolvedAddresses {

plugins/inputs/prometheus/prometheus_test.go

@@ -37,6 +37,7 @@ func TestPrometheusGeneratesMetrics(t *testing.T) {
 	defer ts.Close()
 
 	p := &Prometheus{
+		Log:  testutil.Logger{},
 		URLs: []string{ts.URL},
 	}
 
@@ -60,6 +61,7 @@ func TestPrometheusGeneratesMetricsWithHostNameTag(t *testing.T) {
 	defer ts.Close()
 
 	p := &Prometheus{
+		Log:                testutil.Logger{},
 		KubernetesServices: []string{ts.URL},
 	}
 	u, _ := url.Parse(ts.URL)
@@ -89,6 +91,7 @@ func TestPrometheusGeneratesMetricsAlthoughFirstDNSFails(t *testing.T) {
 	defer ts.Close()
 
 	p := &Prometheus{
+		Log:                testutil.Logger{},
 		URLs:               []string{ts.URL},
 		KubernetesServices: []string{"http://random.telegraf.local:88/metrics"},
 	}