Standardize API error logs

api/cmd/api/main.go

@@ -1,13 +1,12 @@
 package main
 
 import (
-	"log"
-
 	"github.com/julsemaan/anyfile-notepad/api/internal/app"
+	"github.com/julsemaan/anyfile-notepad/api/internal/logging"
 )
 
 func main() {
 	if err := app.Run(app.LoadConfigFromEnv()); err != nil {
-		log.Fatal(err)
+		logging.Fatalf("%v", err)
 	}
 }

api/internal/app/email.go

@@ -2,12 +2,13 @@ package app
 
 import (
 	"crypto/tls"
-	"fmt"
 	"net"
 	"net/smtp"
 	"os"
 	"strconv"
 	"strings"
+
+	"github.com/julsemaan/anyfile-notepad/api/internal/logging"
 )
 
 var smtpSendMail = smtp.SendMail
@@ -37,7 +38,7 @@ func sendEmailWithOptionalTLS(to []string, msg []byte) error {
 		err = smtpSendMail(addr, auth, from, to, msg)
 	}
 	if err != nil {
-		fmt.Println("ERROR: Unable to send email:", err)
+		logging.Error("Unable to send email:", err)
 		return err
 	}
 

api/internal/app/run.go

@@ -7,6 +7,7 @@ import (
 
 	"github.com/julsemaan/anyfile-notepad/api/internal/contact"
 	"github.com/julsemaan/anyfile-notepad/api/internal/httpapi"
+	"github.com/julsemaan/anyfile-notepad/api/internal/logging"
 	"github.com/julsemaan/anyfile-notepad/api/internal/resources"
 	"github.com/julsemaan/anyfile-notepad/api/internal/stats"
 	cache "github.com/patrickmn/go-cache"
@@ -22,7 +23,7 @@ func Run(cfg Config) error {
 
 	statsConn, err := statsd.New(statsd.Address(cfg.StatsdAddress))
 	if err != nil {
-		log.Printf("warning: statsd initialization failed: %v", err)
+		logging.Errorf("statsd initialization failed: %v", err)
 	}
 	if statsConn != nil {
 		defer statsConn.Close()

api/internal/contact/service.go

@@ -5,10 +5,10 @@ import (
 	"context"
 	"errors"
 	"fmt"
-	"log"
 	"strings"
 	"text/template"
 
+	"github.com/julsemaan/anyfile-notepad/api/internal/logging"
 	"github.com/rs/rest-layer/resource"
 )
 
@@ -58,11 +58,11 @@ func (s *Service) BeforeInsert(_ context.Context, items []*resource.Item) error
 	for _, item := range items {
 		msg, buildErr := buildMessage(recipients, item)
 		if buildErr != nil {
-			log.Printf("Unable to build contact request email: %v", buildErr)
+			logging.Errorf("Unable to build contact request email: %v", buildErr)
 			return errUnableToSendEmail
 		}
 		if sendErr := s.sendEmail(recipients, msg); sendErr != nil {
-			log.Printf("Unable to send contact request email: %v", sendErr)
+			logging.Errorf("Unable to send contact request email: %v", sendErr)
 			return errUnableToSendEmail
 		}
 	}
@@ -72,7 +72,7 @@ func (s *Service) BeforeInsert(_ context.Context, items []*resource.Item) error
 
 func (s *Service) AfterInsert(_ context.Context, items []*resource.Item, err *error) {
 	if err != nil && *err != nil {
-		log.Println("Not sending contact request email because there was an error saving the contact request")
+		logging.Error("Not sending contact request email because there was an error saving the contact request")
 		return
 	}
 

api/internal/logging/logging.go

@@ -0,0 +1,33 @@
+package logging
+
+import (
+	"fmt"
+	"log"
+	"os"
+	"strings"
+)
+
+const errorPrefix = "ERROR:"
+
+func output(message string) {
+	_ = log.Default().Output(3, message)
+}
+
+func Error(args ...interface{}) {
+	msg := strings.TrimSuffix(fmt.Sprintln(args...), "\n")
+	if msg == "" {
+		output(errorPrefix)
+		return
+	}
+
+	output(errorPrefix + " " + msg)
+}
+
+func Errorf(format string, args ...interface{}) {
+	output(errorPrefix + " " + fmt.Sprintf(format, args...))
+}
+
+func Fatalf(format string, args ...interface{}) {
+	output(errorPrefix + " " + fmt.Sprintf(format, args...))
+	os.Exit(1)
+}

api/internal/logging/logging_test.go

@@ -0,0 +1,81 @@
+package logging
+
+import (
+	"bytes"
+	"errors"
+	"log"
+	"os"
+	"os/exec"
+	"strings"
+	"testing"
+)
+
+func captureLogOutput(t *testing.T) *bytes.Buffer {
+	t.Helper()
+
+	buf := &bytes.Buffer{}
+	originalWriter := log.Writer()
+	originalFlags := log.Flags()
+	originalPrefix := log.Prefix()
+
+	log.SetOutput(buf)
+	log.SetFlags(0)
+	log.SetPrefix("")
+
+	t.Cleanup(func() {
+		log.SetOutput(originalWriter)
+		log.SetFlags(originalFlags)
+		log.SetPrefix(originalPrefix)
+	})
+
+	return buf
+}
+
+func TestErrorAddsPrefix(t *testing.T) {
+	buf := captureLogOutput(t)
+
+	Error("unable to send email", 42)
+
+	if got := buf.String(); !strings.Contains(got, "ERROR: unable to send email 42") {
+		t.Fatalf("expected ERROR prefix in output, got %q", got)
+	}
+}
+
+func TestErrorfAddsPrefix(t *testing.T) {
+	buf := captureLogOutput(t)
+
+	Errorf("unable to send email %d", 42)
+
+	if got := buf.String(); !strings.Contains(got, "ERROR: unable to send email 42") {
+		t.Fatalf("expected ERROR prefix in output, got %q", got)
+	}
+}
+
+func TestFatalfAddsPrefixAndExits(t *testing.T) {
+	if os.Getenv("LOGGING_FATALF_TEST") == "1" {
+		log.SetOutput(os.Stderr)
+		log.SetFlags(0)
+		log.SetPrefix("")
+		Fatalf("unable to send email %d", 42)
+		return
+	}
+
+	cmd := exec.Command(os.Args[0], "-test.run=TestFatalfAddsPrefixAndExits")
+	cmd.Env = append(os.Environ(), "LOGGING_FATALF_TEST=1")
+
+	var stderr bytes.Buffer
+	cmd.Stderr = &stderr
+
+	err := cmd.Run()
+	var exitErr *exec.ExitError
+	if !errors.As(err, &exitErr) {
+		t.Fatalf("expected process exit error, got %v", err)
+	}
+	if exitErr.ExitCode() != 1 {
+		t.Fatalf("expected exit code 1, got %d", exitErr.ExitCode())
+	}
+
+	if got := stderr.String(); !strings.Contains(got, "ERROR: unable to send email 42") {
+		t.Fatalf("expected ERROR prefix in fatal output, got %q", got)
+	}
+}