Merge pull request #328 from pohly/fatal-backtrace-revert

klog.Fatal backtrace revert

integration_tests/klog_test.go

@@ -91,9 +91,10 @@ func TestDestinationsWithDifferentFlags(t *testing.T) {
 		notExpectedInDir map[int]res
 	}{
 		"default flags": {
-			// Everything, including the trace on fatal, goes to stderr
+			// Everything, EXCEPT the trace on fatal, goes to stderr
 
-			expectedOnStderr: allLogREs,
+			expectedOnStderr:    res{infoLogRE, warningLogRE, errorLogRE, fatalLogRE},
+			notExpectedOnStderr: res{stackTraceRE},
 		},
 		"everything disabled": {
 			// Nothing, including the trace on fatal, is showing anywhere
@@ -112,11 +113,12 @@ func TestDestinationsWithDifferentFlags(t *testing.T) {
 			notExpectedOnStderr: res{infoLogRE},
 		},
 		"with logtostderr only": {
-			// Everything, including the trace on fatal, goes to stderr
+			// Everything, EXCEPT the trace on fatal, goes to stderr
 
 			flags: []string{"-logtostderr=true", "-alsologtostderr=false", "-stderrthreshold=1000"},
 
-			expectedOnStderr: allLogREs,
+			expectedOnStderr:    res{infoLogRE, warningLogRE, errorLogRE, fatalLogRE},
+			notExpectedOnStderr: res{stackTraceRE},
 		},
 		"with log file only": {
 			// Everything, including the trace on fatal, goes to the single log file
@@ -154,13 +156,14 @@ func TestDestinationsWithDifferentFlags(t *testing.T) {
 			notExpectedInDir:    defaultNotExpectedInDirREs,
 		},
 		"with log dir and logtostderr": {
-			// Everything, including the trace on fatal, goes to stderr. The -log_dir is
+			// Everything, EXCEPT the trace on fatal, goes to stderr. The -log_dir is
 			// ignored, nothing goes to the log files in the log dir.
 
 			logdir: true,
 			flags:  []string{"-logtostderr=true", "-alsologtostderr=false", "-stderrthreshold=1000"},
 
-			expectedOnStderr: allLogREs,
+			expectedOnStderr:    res{infoLogRE, warningLogRE, errorLogRE, fatalLogRE},
+			notExpectedOnStderr: res{stackTraceRE},
 		},
 		"with log file and log dir": {
 			// Everything, including the trace on fatal, goes to the single log file.

klog.go

@@ -924,12 +924,15 @@ func (l *loggingT) output(s severity.Severity, log *logr.Logger, buf *buffer.Buf
 			OsExit(1)
 		}
 		// Dump all goroutine stacks before exiting.
-		trace := stacks(true)
-		// Write the stack trace for all goroutines to the stderr.
-		if l.toStderr || l.alsoToStderr || s >= l.stderrThreshold.get() || alsoToStderr {
-			os.Stderr.Write(trace)
+		// First, make sure we see the trace for the current goroutine on standard error.
+		// If -logtostderr has been specified, the loop below will do that anyway
+		// as the first stack in the full dump.
+		if !l.toStderr {
+			os.Stderr.Write(stacks(false))
 		}
+
 		// Write the stack trace for all goroutines to the files.
+		trace := stacks(true)
 		logExitFunc = func(error) {} // If we get a write error, we'll still exit below.
 		for log := severity.FatalLog; log >= severity.InfoLog; log-- {
 			if f := l.file[log]; f != nil { // Can be nil if -logtostderr is set.
@@ -1586,7 +1589,18 @@ func ErrorSDepth(depth int, err error, msg string, keysAndValues ...interface{})
 }
 
 // Fatal logs to the FATAL, ERROR, WARNING, and INFO logs,
-// including a stack trace of all running goroutines, then calls OsExit(255).
+// prints stack trace(s), then calls OsExit(255).
+//
+// Stderr only receives a dump of the current goroutine's stack trace. Log files,
+// if there are any, receive a dump of the stack traces in all goroutines.
+//
+// Callers who want more control over handling of fatal events may instead use a
+// combination of different functions:
+// - some info or error logging function, optionally with a stack trace
+//   value generated by github.com/go-logr/lib/dbg.Backtrace
+// - Flush to flush pending log data
+// - panic, os.Exit or returning to the caller with an error
+//
 // Arguments are handled in the manner of fmt.Print; a newline is appended if missing.
 func Fatal(args ...interface{}) {
 	logging.print(severity.FatalLog, logging.logger, logging.filter, args...)