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

plugins/inputs/docker/docker.go

@@ -6,7 +6,6 @@ import (
 	"encoding/json"
 	"fmt"
 	"io"
-	"log"
 	"net/http"
 	"regexp"
 	"strconv"
@@ -45,6 +44,8 @@ type Docker struct {
 	ContainerStateInclude []string `toml:"container_state_include"`
 	ContainerStateExclude []string `toml:"container_state_exclude"`
 
+	Log telegraf.Logger
+
 	tlsint.ClientConfig
 
 	newEnvClient func() (Client, error)
@@ -107,8 +108,10 @@ var sampleConfig = `
   ## Whether to report for each container per-device blkio (8:0, 8:1...) and
   ## network (eth0, eth1, ...) stats or not
   perdevice = true
+
   ## Whether to report for each container total blkio and network stats or not
   total = false
+
   ## Which environment variables should we use as a tag
   ##tag_env = ["JAVA_HOME", "HEAP_SIZE"]
 
@@ -274,7 +277,7 @@ func (d *Docker) gatherSwarmInfo(acc telegraf.Accumulator) error {
 				fields["tasks_running"] = running[service.ID]
 				fields["tasks_desired"] = tasksNoShutdown[service.ID]
 			} else {
-				log.Printf("E! Unknow Replicas Mode")
+				d.Log.Error("Unknown replica mode")
 			}
 			// Add metrics
 			acc.AddFields("docker_swarm",

plugins/inputs/docker/docker_test.go

@@ -252,6 +252,7 @@ func TestDocker_WindowsMemoryContainerStats(t *testing.T) {
 	var acc testutil.Accumulator
 
 	d := Docker{
+		Log: testutil.Logger{},
 		newClient: func(string, *tls.Config) (Client, error) {
 			return &MockClient{
 				InfoF: func(ctx context.Context) (types.Info, error) {
@@ -390,6 +391,7 @@ func TestContainerLabels(t *testing.T) {
 			}
 
 			d := Docker{
+				Log:          testutil.Logger{},
 				newClient:    newClientFunc,
 				LabelInclude: tt.include,
 				LabelExclude: tt.exclude,
@@ -511,6 +513,7 @@ func TestContainerNames(t *testing.T) {
 			}
 
 			d := Docker{
+				Log:              testutil.Logger{},
 				newClient:        newClientFunc,
 				ContainerInclude: tt.include,
 				ContainerExclude: tt.exclude,
@@ -625,7 +628,10 @@ func TestContainerStatus(t *testing.T) {
 
 					return &client, nil
 				}
-				d = Docker{newClient: newClientFunc}
+				d = Docker{
+					Log:       testutil.Logger{},
+					newClient: newClientFunc,
+				}
 			)
 
 			// mock time
@@ -675,6 +681,7 @@ func TestContainerStatus(t *testing.T) {
 func TestDockerGatherInfo(t *testing.T) {
 	var acc testutil.Accumulator
 	d := Docker{
+		Log:       testutil.Logger{},
 		newClient: newClient,
 		TagEnvironment: []string{"ENVVAR1", "ENVVAR2", "ENVVAR3", "ENVVAR5",
 			"ENVVAR6", "ENVVAR7", "ENVVAR8", "ENVVAR9"},
@@ -824,6 +831,7 @@ func TestDockerGatherInfo(t *testing.T) {
 func TestDockerGatherSwarmInfo(t *testing.T) {
 	var acc testutil.Accumulator
 	d := Docker{
+		Log:       testutil.Logger{},
 		newClient: newClient,
 	}
 
@@ -931,6 +939,7 @@ func TestContainerStateFilter(t *testing.T) {
 			}
 
 			d := Docker{
+				Log:                   testutil.Logger{},
 				newClient:             newClientFunc,
 				ContainerStateInclude: tt.include,
 				ContainerStateExclude: tt.exclude,
@@ -992,6 +1001,7 @@ func TestContainerName(t *testing.T) {
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
 			d := Docker{
+				Log:       testutil.Logger{},
 				newClient: tt.clientFunc,
 			}
 			var acc testutil.Accumulator