Improve logging

log/logging.go

@@ -90,7 +90,7 @@ var (
 	startedSignal = make(chan struct{})
 )
 
-// SetPkgLevels sets individual log levels for packages.
+// SetPkgLevels sets individual log levels for packages. Only effective after Start().
 func SetPkgLevels(levels map[string]Severity) {
 	pkgLevelsLock.Lock()
 	pkgLevels = levels
@@ -103,7 +103,7 @@ func UnSetPkgLevels() {
 	pkgLevelsActive.UnSet()
 }
 
-// SetLogLevel sets a new log level.
+// SetLogLevel sets a new log level. Only effective after Start().
 func SetLogLevel(level Severity) {
 	atomic.StoreUint32(logLevel, uint32(level))
 }
@@ -138,7 +138,7 @@ func Start() (err error) {
 
 	initialLogLevel := ParseLevel(logLevelFlag)
 	if initialLogLevel > 0 {
-		atomic.StoreUint32(logLevel, uint32(initialLogLevel))
+		SetLogLevel(initialLogLevel)
 	} else {
 		err = fmt.Errorf("log warning: invalid log level \"%s\", falling back to level info", logLevelFlag)
 		fmt.Fprintf(os.Stderr, "%s\n", err.Error())

log/output.go

@@ -2,6 +2,8 @@ package log
 
 import (
 	"fmt"
+	"os"
+	"runtime/debug"
 	"time"
 )
 
@@ -39,16 +41,51 @@ func writeLine(line *logLine, duplicates uint64) {
 }
 
 func startWriter() {
-	shutdownWaitGroup.Add(1)
 	fmt.Println(fmt.Sprintf("%s%s %s BOF%s", InfoLevel.color(), time.Now().Format(timeFormat), rightArrow, endColor()))
-	go writer()
+
+	shutdownWaitGroup.Add(1)
+	go writerManager()
 }
 
-func writer() {
+func writerManager() {
+	defer shutdownWaitGroup.Done()
+
+	for {
+		err := writer()
+		if err != nil {
+			Errorf("log: writer failed: %s", err)
+		} else {
+			return
+		}
+	}
+}
+
+func writer() (err error) {
+	defer func() {
+		// recover from panic
+		panicVal := recover()
+		if panicVal != nil {
+			err = fmt.Errorf("%s", panicVal)
+
+			// write stack to stderr
+			fmt.Fprintf(
+				os.Stderr,
+				`===== Error Report =====
+Message: %s
+StackTrace:
+
+%s
+===== End of Report =====
+`,
+				err,
+				string(debug.Stack()),
+			)
+		}
+	}()
+
 	var currentLine *logLine
 	var nextLine *logLine
 	var duplicates uint64
-	defer shutdownWaitGroup.Done()
 
 	for {
 		// reset
@@ -106,7 +143,9 @@ func writer() {
 		}
 
 		// write final line
-		writeLine(currentLine, duplicates)
+		if currentLine != nil {
+			writeLine(currentLine, duplicates)
+		}
 		// reset state
 		currentLine = nil //nolint:ineffassign
 		nextLine = nil