enable configuring several log outputs

setup.go

@@ -5,6 +5,7 @@ import (
 	"fmt"
 	"os"
 	"regexp"
+	"strings"
 	"sync"
 
 	"go.uber.org/zap"
@@ -29,6 +30,7 @@ const (
 	envLoggingFmt = "GOLOG_LOG_FMT"
 
 	envLoggingFile = "GOLOG_FILE" // /path/to/file
+	envLoggingOutput = "GOLOG_OUTPUT" // possible values: stdout|stderr|file combine multiple values with '+'
 )
 
 type LogFormat int
@@ -263,5 +265,20 @@ func configFromEnv() Config {
 		cfg.Stderr = false
 	}
 
+	output := os.Getenv(envLoggingOutput)
+	outputOptions := strings.Split(output, "+")
+	for _, opt := range outputOptions {
+		switch opt {
+		case "stdout":
+			cfg.Stdout = true
+		case "stderr":
+			cfg.Stderr = true
+		case "file":
+			if cfg.File == "" {
+				fmt.Fprint(os.Stderr, "please specify a GOLOG_FILE value to write to")
+			}
+		}
+	}
+
 	return cfg
 }

setup_test.go

@@ -3,6 +3,7 @@ package log
 import (
 	"bytes"
 	"io"
+	"io/ioutil"
 	"os"
 	"strings"
 	"testing"
@@ -37,3 +38,87 @@ func TestGetLoggerDefault(t *testing.T) {
 	}
 
 }
+
+func TestLogToFileAndStderr(t *testing.T) {
+	// setup stderr
+	r, w, err := os.Pipe()
+	if err != nil {
+		t.Fatalf("failed to open pipe: %v", err)
+	}
+
+	stderr := os.Stderr
+	os.Stderr = w
+	defer func() {
+		os.Stderr = stderr
+	}()
+
+	// setup file
+	logfile, err := ioutil.TempFile("", "go-log-test")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer os.Remove(logfile.Name())
+
+	os.Setenv(envLoggingFile, logfile.Name())
+
+	// set log output env var
+	os.Setenv(envLoggingOutput, "file+stderr")
+
+	SetupLogging(configFromEnv())
+
+	log := getLogger("test")
+
+	want := "scooby"
+	log.Error(want)
+	w.Close()
+
+	buf := &bytes.Buffer{}
+	if _, err := io.Copy(buf, r); err != nil && err != io.ErrClosedPipe {
+		t.Fatalf("unexpected error: %v", err)
+	}
+
+	if !strings.Contains(buf.String(), want) {
+		t.Errorf("got %q, wanted it to contain log output", buf.String())
+	}
+
+	content, err := ioutil.ReadFile(logfile.Name())
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if !strings.Contains(string(content), want) {
+		t.Logf("want: '%s', got: '%s'", want, string(content))
+		t.Fail()
+	}
+}
+
+func TestLogToFile(t *testing.T) {
+	// get tmp log file
+	logfile, err := ioutil.TempFile("", "go-log-test")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer os.Remove(logfile.Name())
+
+	// set the go-log file env var
+	os.Setenv(envLoggingFile, logfile.Name())
+
+	SetupLogging(configFromEnv())
+
+	log := getLogger("test")
+
+	// write log to file
+	want := "grokgrokgrok"
+	log.Error(want)
+
+	// read log file and check contents
+	content, err := ioutil.ReadFile(logfile.Name())
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if !strings.Contains(string(content), want) {
+		t.Logf("want: '%s', got: '%s'", want, string(content))
+		t.Fail()
+	}
+}