Merge pull request #1521 from mxinden/errcheck

*.go: Introduce errcheck enforcing error handling

Makefile

@@ -15,6 +15,7 @@ include Makefile.common
 
 FRONTEND_DIR            = $(BIN_DIR)/ui/app
 DOCKER_IMAGE_NAME       ?= alertmanager
+ERRCHECK_BINARY         := $(FIRST_GOPATH)/bin/errcheck
 
 ifdef DEBUG
 	bindata_flags = -debug
@@ -59,3 +60,11 @@ clean:
 	rm template/internal/deftmpl/bindata.go
 	rm ui/bindata.go
 	cd $(FRONTEND_DIR) && $(MAKE) clean
+
+.PHONY: test
+test: common-test $(ERRCHECK_BINARY)
+	@echo ">> running errcheck with exclude file scripts/errcheck_excludes.txt"
+	$(ERRCHECK_BINARY) -verbose -exclude scripts/errcheck_excludes.txt -ignoretests ./...
+
+$(ERRCHECK_BINARY):
+	@go get github.com/kisielk/errcheck

api/api.go

@@ -770,7 +770,10 @@ func (api *API) respond(w http.ResponseWriter, data interface{}) {
 		level.Error(api.logger).Log("msg", "Error marshalling JSON", "err", err)
 		return
 	}
-	w.Write(b)
+
+	if _, err := w.Write(b); err != nil {
+		level.Error(api.logger).Log("msg", "failed to write data to connection", "err", err)
+	}
 }
 
 func (api *API) respondError(w http.ResponseWriter, apiErr apiError, data interface{}) {
@@ -796,7 +799,9 @@ func (api *API) respondError(w http.ResponseWriter, apiErr apiError, data interf
 	}
 	level.Error(api.logger).Log("msg", "API error", "err", apiErr.Error())
 
-	w.Write(b)
+	if _, err := w.Write(b); err != nil {
+		level.Error(api.logger).Log("msg", "failed to write data to connection", "err", err)
+	}
 }
 
 func (api *API) receive(r *http.Request, v interface{}) error {

cmd/alertmanager/main.go

@@ -407,7 +407,8 @@ func main() {
 		for {
 			select {
 			case <-hup:
-				reload()
+				// ignore error, already logged in `reload()`
+				_ = reload()
 			case errc := <-webReload:
 				errc <- reload()
 			}

notify/impl.go

@@ -280,7 +280,11 @@ func (n *Email) Notify(ctx context.Context, as ...*types.Alert) (bool, error) {
 			return true, err
 		}
 	}
-	defer c.Quit()
+	defer func() {
+		if err := c.Quit(); err != nil {
+			level.Error(n.logger).Log("msg", "failed to close SMTP connection", "err", err)
+		}
+	}()
 
 	if n.conf.Hello != "" {
 		err := c.Hello(n.conf.Hello)

provider/mem/mem.go

@@ -90,9 +90,8 @@ func (a *Alerts) runGC() {
 }
 
 // Close the alert provider.
-func (a *Alerts) Close() error {
+func (a *Alerts) Close() {
 	close(a.stopGC)
-	return nil
 }
 
 func max(a, b int) int {

scripts/errcheck_excludes.txt

@@ -0,0 +1,8 @@
+(io.Closer).Close
+(*os.File).Close
+fmt.Fprintf
+fmt.Fprintln
+
+(github.com/prometheus/alertmanager/vendor/github.com/go-kit/kit/log.Logger).Log
+// Allowed log levels are enforced via kingpin
+(*github.com/prometheus/alertmanager/vendor/github.com/prometheus/common/promlog.AllowedLevel).Set

test/acceptance.go

@@ -94,7 +94,11 @@ func freeAddress() string {
 	if err != nil {
 		panic(err)
 	}
-	defer l.Close()
+	defer func() {
+		if err := l.Close(); err != nil {
+			panic(err)
+		}
+	}()
 
 	return l.Addr().String()
 }

test/mock.go

@@ -257,7 +257,11 @@ func NewWebhook(c *Collector) *MockWebhook {
 		collector: c,
 		opts:      c.opts,
 	}
-	go http.Serve(l, wh)
+	go func() {
+		if err := http.Serve(l, wh); err != nil {
+			panic(err)
+		}
+	}()
 
 	return wh
 }