Enable ErrCheck (#5386)

* Enable ErrCheck

.golangci.yml

@@ -16,6 +16,12 @@ run:
     - pkg/network
 
 issues:
+  # Do not limit the number of issues per linter.
+  max-issues-per-linter: 0
+
+  # Do not limit the number of times a same issue is reported.
+  max-same-issues: 0
+
   exclude:
     - "`eventContext` is unused"
     - "`\\(\\*DatadogLogger\\).changeLogLevel` is unused"
@@ -34,7 +40,11 @@ issues:
     # ignore warning on linux about fields used only on windows
     - "`context` is unused"
     - "`id` is unused"
-
+  exclude-rules:
+    # Exclude some linters from running on tests files.
+    - path: _test\.go
+      linters:
+        - errcheck
 
 linters:
   disable-all: true
@@ -47,3 +57,9 @@ linters:
     - misspell    # Finds commonly misspelled English words in comments
     - gofmt       # Gofmt checks whether code was gofmt-ed
     - golint      # Golint differs from gofmt. Gofmt reformats Go source code, whereas golint prints out style mistakes
+    - errcheck    # errcheck is a program for checking for unchecked errors in go programs.
+
+linters-settings:
+  errcheck:
+    # Disable warnings for `fmt` and `log` packages. Also ignore `Write` functions from `net/http` package.
+    ignore: fmt:.*,github.com/DataDog/datadog-agent/pkg/util/log:.*,net/http:Write

cmd/agent/api/agent/agent.go

@@ -321,7 +321,7 @@ func setRuntimeConfig(w http.ResponseWriter, r *http.Request) {
 	vars := mux.Vars(r)
 	setting := vars["setting"]
 	log.Infof("Got a request to change a setting: %s", setting)
-	r.ParseForm()
+	r.ParseForm() //nolint:errcheck
 	value := html.UnescapeString(r.Form.Get("value"))
 
 	if err := config.SetRuntimeSetting(setting, value); err != nil {

cmd/agent/api/agent/agent_jmx.go

@@ -81,7 +81,7 @@ func getJMXConfigs(w http.ResponseWriter, r *http.Request) {
 		http.Error(w, err.Error(), 500)
 		return
 	}
-	w.Write(jsonPayload)
+	w.Write(jsonPayload) //nolint:errcheck
 }
 
 func setJMXStatus(w http.ResponseWriter, r *http.Request) {

cmd/agent/api/server.go

@@ -89,7 +89,7 @@ func StartServer() error {
 	}
 	tlsListener := tls.NewListener(listener, &tlsConfig)
 
-	go srv.Serve(tlsListener)
+	go srv.Serve(tlsListener) //nolint:errcheck
 	return nil
 }
 

cmd/agent/app/check.go

@@ -69,7 +69,7 @@ func init() {
 	checkCmd.Flags().StringVarP(&breakPoint, "breakpoint", "b", "", "set a breakpoint at a particular line number (Python checks only)")
 	checkCmd.Flags().BoolVarP(&profileMemory, "profile-memory", "m", false, "run the memory profiler (Python checks only)")
 	checkCmd.Flags().BoolVar(&fullSketches, "full-sketches", false, "output sketches with bins information")
-	config.Datadog.BindPFlag("cmd.check.fullsketches", checkCmd.Flags().Lookup("full-sketches"))
+	config.Datadog.BindPFlag("cmd.check.fullsketches", checkCmd.Flags().Lookup("full-sketches")) //nolint:errcheck
 
 	// Power user flags - mark as hidden
 	createHiddenStringFlag(&profileMemoryDir, "m-dir", "", "an existing directory in which to store memory profiling data, ignoring clean-up")
@@ -104,7 +104,7 @@ var checkCmd = &cobra.Command{
 		if len(args) != 0 {
 			checkName = args[0]
 		} else {
-			cmd.Help()
+			cmd.Help() //nolint:errcheck
 			return nil
 		}
 
@@ -460,7 +460,7 @@ func getMetricsData(agg *aggregator.BufferedAggregator) map[string]interface{} {
 		// https://github.com/DataDog/datadog-agent/blob/b2d9527ec0ec0eba1a7ae64585df443c5b761610/pkg/metrics/series.go#L109-L122
 		var data map[string]interface{}
 		sj, _ := json.Marshal(series)
-		json.Unmarshal(sj, &data)
+		json.Unmarshal(sj, &data) //nolint:errcheck
 
 		aggData["metrics"] = data["series"]
 	}
@@ -487,7 +487,7 @@ func singleCheckRun() bool {
 
 func createHiddenStringFlag(p *string, name string, value string, usage string) {
 	checkCmd.Flags().StringVar(p, name, value, usage)
-	checkCmd.Flags().MarkHidden(name)
+	checkCmd.Flags().MarkHidden(name) //nolint:errcheck
 }
 
 func populateMemoryProfileConfig(initConfig map[string]interface{}) error {

cmd/agent/app/config.go

@@ -99,7 +99,7 @@ func requestConfig() (string, error) {
 	r, err := util.DoGet(c, apiConfigURL)
 	if err != nil {
 		var errMap = make(map[string]string)
-		json.Unmarshal(r, &errMap)
+		json.Unmarshal(r, &errMap) //nolint:errcheck
 		// If the error has been marshalled into a json object, check it and return it properly
 		if e, found := errMap["error"]; found {
 			return "", fmt.Errorf(e)
@@ -125,7 +125,7 @@ func listRuntimeConfigurableValue(cmd *cobra.Command, args []string) error {
 	r, err := util.DoGet(c, url)
 	if err != nil {
 		var errMap = make(map[string]string)
-		json.Unmarshal(r, &errMap)
+		json.Unmarshal(r, &errMap) //nolint:errcheck
 		// If the error has been marshalled into a json object, check it and return it properly
 		if e, found := errMap["error"]; found {
 			return fmt.Errorf(e)
@@ -162,7 +162,7 @@ func setConfigValue(cmd *cobra.Command, args []string) error {
 	r, err := util.DoPost(c, url, "application/x-www-form-urlencoded", bytes.NewBuffer([]byte(body)))
 	if err != nil {
 		var errMap = make(map[string]string)
-		json.Unmarshal(r, &errMap)
+		json.Unmarshal(r, &errMap) //nolint:errcheck
 		// If the error has been marshalled into a json object, check it and return it properly
 		if e, found := errMap["error"]; found {
 			return fmt.Errorf(e)
@@ -190,7 +190,7 @@ func getConfigValue(cmd *cobra.Command, args []string) error {
 	r, err := util.DoGet(c, url)
 	if err != nil {
 		var errMap = make(map[string]string)
-		json.Unmarshal(r, &errMap)
+		json.Unmarshal(r, &errMap) //nolint:errcheck
 		// If the error has been marshalled into a json object, check it and return it properly
 		if e, found := errMap["error"]; found {
 			return fmt.Errorf(e)

cmd/agent/app/dogstatsd_stats.go

@@ -78,7 +78,7 @@ func requestDogstatsdStats() error {
 	r, e := util.DoGet(c, urlstr)
 	if e != nil {
 		var errMap = make(map[string]string)
-		json.Unmarshal(r, &errMap)
+		json.Unmarshal(r, &errMap) //nolint:errcheck
 		// If the error has been marshalled into a json object, check it and return it properly
 		if err, found := errMap["error"]; found {
 			e = fmt.Errorf(err)
@@ -97,7 +97,7 @@ func requestDogstatsdStats() error {
 	// The rendering is done in the client so that the agent has less work to do
 	if prettyPrintJSON {
 		var prettyJSON bytes.Buffer
-		json.Indent(&prettyJSON, r, "", "  ")
+		json.Indent(&prettyJSON, r, "", "  ") //nolint:errcheck
 		s = prettyJSON.String()
 	} else if jsonStatus {
 		s = string(r)

cmd/agent/app/health.go

@@ -69,7 +69,7 @@ func requestHealth() error {
 	r, err := util.DoGet(c, urlstr)
 	if err != nil {
 		var errMap = make(map[string]string)
-		json.Unmarshal(r, &errMap)
+		json.Unmarshal(r, &errMap) //nolint:errcheck
 		// If the error has been marshalled into a json object, check it and return it properly
 		if e, found := errMap["error"]; found {
 			err = fmt.Errorf(e)

cmd/agent/app/integrations.go

@@ -75,7 +75,7 @@ func init() {
 	integrationCmd.PersistentFlags().StringVarP(&pythonMajorVersion, "python", "", "", "the version of Python to act upon (2 or 3). defaults to the python_version setting in datadog.yaml")
 
 	// Power user flags - mark as hidden
-	integrationCmd.PersistentFlags().MarkHidden("use-sys-python")
+	integrationCmd.PersistentFlags().MarkHidden("use-sys-python") //nolint:errcheck
 
 	showCmd.Flags().BoolVarP(&versionOnly, "show-version-only", "q", false, "only display version information")
 	installCmd.Flags().BoolVarP(

cmd/agent/app/launchgui.go

@@ -64,7 +64,7 @@ func launchGui(cmd *cobra.Command, args []string) error {
 	csrfToken, err := util.DoGet(c, urlstr)
 	if err != nil {
 		var errMap = make(map[string]string)
-		json.Unmarshal(csrfToken, &errMap)
+		json.Unmarshal(csrfToken, &errMap) //nolint:errcheck
 		if e, found := errMap["error"]; found {
 			err = fmt.Errorf(e)
 		}

cmd/agent/app/run.go

@@ -183,7 +183,7 @@ func StartAgent() error {
 	if config.Datadog.GetBool("telemetry.enabled") {
 		http.Handle("/telemetry", telemetry.Handler())
 	}
-	go http.ListenAndServe("127.0.0.1:"+port, http.DefaultServeMux)
+	go http.ListenAndServe("127.0.0.1:"+port, http.DefaultServeMux) //nolint:errcheck
 
 	// Setup healthcheck port
 	var healthPort = config.Datadog.GetInt("health_port")
@@ -249,7 +249,7 @@ func StartAgent() error {
 	}
 	common.Forwarder = forwarder.NewDefaultForwarder(forwarder.NewOptions(keysPerDomain))
 	log.Debugf("Starting forwarder")
-	common.Forwarder.Start()
+	common.Forwarder.Start() //nolint:errcheck
 	log.Debugf("Forwarder started")
 
 	agentName := "agent"

cmd/agent/app/secret.go

@@ -69,7 +69,7 @@ func showSecretInfo() error {
 	r, err := util.DoGet(c, apiConfigURL)
 	if err != nil {
 		var errMap = make(map[string]string)
-		json.Unmarshal(r, &errMap)
+		json.Unmarshal(r, &errMap) //nolint:errcheck
 		// If the error has been marshalled into a json object, check it and return it properly
 		if e, found := errMap["error"]; found {
 			return fmt.Errorf("%s", e)

cmd/agent/app/standalone/jmx.go

@@ -108,9 +108,9 @@ func loadJMXConfigs(runner *jmxfetch.JMXFetch, selectedChecks []string) {
 			c.Instances = instances
 
 			jmx.AddScheduledConfig(c)
-			runner.ConfigureFromInitConfig(c.InitConfig)
+			runner.ConfigureFromInitConfig(c.InitConfig) //nolint:errcheck
 			for _, instance := range c.Instances {
-				runner.ConfigureFromInstance(instance)
+				runner.ConfigureFromInstance(instance) //nolint:errcheck
 			}
 		}
 	}

cmd/agent/app/status.go

@@ -112,7 +112,7 @@ func requestStatus() error {
 	// The rendering is done in the client so that the agent has less work to do
 	if prettyPrintJSON {
 		var prettyJSON bytes.Buffer
-		json.Indent(&prettyJSON, r, "", "  ")
+		json.Indent(&prettyJSON, r, "", "  ") //nolint:errcheck
 		s = prettyJSON.String()
 	} else if jsonStatus {
 		s = string(r)
@@ -125,7 +125,7 @@ func requestStatus() error {
 	}
 
 	if statusFilePath != "" {
-		ioutil.WriteFile(statusFilePath, []byte(s), 0644)
+		ioutil.WriteFile(statusFilePath, []byte(s), 0644) //nolint:errcheck
 	} else {
 		fmt.Println(s)
 	}
@@ -180,14 +180,14 @@ func componentStatus(component string) error {
 	// The rendering is done in the client so that the agent has less work to do
 	if prettyPrintJSON {
 		var prettyJSON bytes.Buffer
-		json.Indent(&prettyJSON, r, "", "  ")
+		json.Indent(&prettyJSON, r, "", "  ") //nolint:errcheck
 		s = prettyJSON.String()
 	} else {
 		s = string(r)
 	}
 
 	if statusFilePath != "" {
-		ioutil.WriteFile(statusFilePath, []byte(s), 0644)
+		ioutil.WriteFile(statusFilePath, []byte(s), 0644) //nolint:errcheck
 	} else {
 		fmt.Println(s)
 	}
@@ -208,7 +208,7 @@ func makeRequest(url string) ([]byte, error) {
 	r, e := util.DoGet(c, url)
 	if e != nil {
 		var errMap = make(map[string]string)
-		json.Unmarshal(r, &errMap)
+		json.Unmarshal(r, &errMap) //nolint:errcheck
 		// If the error has been marshalled into a json object, check it and return it properly
 		if err, found := errMap["error"]; found {
 			e = fmt.Errorf(err)

cmd/agent/clcrunnerapi/clc_runner_server.go

@@ -87,7 +87,7 @@ func StartCLCRunnerServer() error {
 	}
 	tlsListener := tls.NewListener(clcListener, &tlsConfig)
 
-	go srv.Serve(tlsListener)
+	go srv.Serve(tlsListener) //nolint:errcheck
 	return nil
 }
 

cmd/agent/common/import.go

@@ -252,7 +252,7 @@ func copyFile(src, dst string, overwrite bool, transformations []TransformationF
 		}
 	}
 
-	ioutil.WriteFile(dst, data, 0640)
+	ioutil.WriteFile(dst, data, 0640) //nolint:errcheck
 
 	ddGroup, errGroup := user.LookupGroup("dd-agent")
 	ddUser, errUser := user.LookupId("dd-agent")

cmd/agent/gui/checks.go

@@ -71,7 +71,7 @@ func runCheck(w http.ResponseWriter, r *http.Request) {
 	instances := collector.GetChecksByNameForConfigs(name, common.AC.GetAllConfigs())
 
 	for _, ch := range instances {
-		common.Coll.RunCheck(ch)
+		common.Coll.RunCheck(ch) //nolint:errcheck
 	}
 	log.Infof("Scheduled new check: " + name)
 	w.Write([]byte("Scheduled new check:" + name))
@@ -223,13 +223,13 @@ func setCheckConfigFile(w http.ResponseWriter, r *http.Request) {
 
 		// Attempt to write new configs to custom checks directory
 		path := filepath.Join(checkConfFolderPath, fileName)
-		os.MkdirAll(checkConfFolderPath, os.FileMode(0755))
+		os.MkdirAll(checkConfFolderPath, os.FileMode(0755)) //nolint:errcheck
 		e = ioutil.WriteFile(path, data, 0600)
 
 		// If the write didn't work, try writing to the default checks directory
 		if e != nil && strings.Contains(e.Error(), "no such file or directory") {
 			path = filepath.Join(defaultCheckConfFolderPath, fileName)
-			os.MkdirAll(defaultCheckConfFolderPath, os.FileMode(0755))
+			os.MkdirAll(defaultCheckConfFolderPath, os.FileMode(0755)) //nolint:errcheck
 			e = ioutil.WriteFile(path, data, 0600)
 		}
 

cmd/agent/gui/gui.go

@@ -82,7 +82,7 @@ func StartGUIServer(port string) error {
 	if e != nil {
 		return e
 	}
-	go http.Serve(listener, router)
+	go http.Serve(listener, router) //nolint:errcheck
 	log.Infof("GUI server is listening at 127.0.0.1:" + port)
 
 	// Create a CSRF token (unique to each session)

cmd/agent/gui/render.go

@@ -35,7 +35,7 @@ type Data struct {
 func renderStatus(rawData []byte, request string) (string, error) {
 	var b = new(bytes.Buffer)
 	stats := make(map[string]interface{})
-	json.Unmarshal(rawData, &stats)
+	json.Unmarshal(rawData, &stats) //nolint:errcheck
 
 	data := Data{Stats: stats}
 	e := fillTemplate(b, data, request+"Status")
@@ -50,7 +50,7 @@ func renderRunningChecks() (string, error) {
 
 	runnerStatsJSON := []byte(expvar.Get("runner").String())
 	runnerStats := make(map[string]interface{})
-	json.Unmarshal(runnerStatsJSON, &runnerStats)
+	json.Unmarshal(runnerStatsJSON, &runnerStats) //nolint:errcheck
 	loaderErrs := collector.GetLoaderErrors()
 	configErrs := autodiscovery.GetConfigErrors()
 

cmd/cluster-agent-cloudfoundry/app/app.go

@@ -162,7 +162,7 @@ func run(cmd *cobra.Command, args []string) error {
 		log.Error("Misconfiguration of agent endpoints: ", err)
 	}
 	f := forwarder.NewDefaultForwarder(forwarder.NewOptions(keysPerDomain))
-	f.Start()
+	f.Start() //nolint:errcheck
 	s := serializer.NewSerializer(f)
 
 	aggregatorInstance := aggregator.InitAggregator(s, hostname, aggregator.ClusterAgentName)

cmd/cluster-agent/admission/server.go

@@ -44,7 +44,7 @@ func RunServer(mainCtx context.Context) error {
 	}
 	go func() error {
 		return log.Error(server.ListenAndServeTLS("", ""))
-	}()
+	}() //nolint:errcheck
 
 	<-mainCtx.Done()
 

cmd/cluster-agent/api/server.go

@@ -53,10 +53,10 @@ func StartServer(sc clusteragent.ServerContext) error {
 		return fmt.Errorf("Unable to create the api server: %v", err)
 	}
 	// Internal token
-	util.CreateAndSetAuthToken()
+	util.CreateAndSetAuthToken() //nolint:errcheck
 
 	// DCA client token
-	util.InitDCAAuthToken()
+	util.InitDCAAuthToken() //nolint:errcheck
 
 	// create cert
 	hosts := []string{"127.0.0.1", "localhost"}
@@ -90,7 +90,7 @@ func StartServer(sc clusteragent.ServerContext) error {
 
 	tlsListener := tls.NewListener(listener, &tlsConfig)
 
-	go srv.Serve(tlsListener)
+	go srv.Serve(tlsListener) //nolint:errcheck
 	return nil
 }