Locate panic line

pkg/graceful/graceful.go

@@ -6,8 +6,11 @@ package graceful
 
 import (
 	"context"
+	"fmt"
 	"os"
 	"os/signal"
+	"runtime/debug"
+	"strings"
 	"sync"
 	"syscall"
 	"time"
@@ -60,7 +63,7 @@ func (p *Process) AddStarter(ctx context.Context, fn func(ctx context.Context) e
 	go func() {
 		defer func() {
 			if r := recover(); r != nil {
-				p.logger.Error().Interface("panic", r).Msg("panic in service")
+				p.logger.Error().Err(panicToErr(r, 10)).Msg("panic in service")
 				p.ShutdownNow()
 			}
 		}()
@@ -123,7 +126,7 @@ func (p *Process) ShutdownNow() {
 	go func() {
 		defer func() {
 			if r := recover(); r != nil {
-				p.logger.Error().Interface("panic", r).Msg("panic during shutdown")
+				p.logger.Error().Err(panicToErr(r, 10)).Msg("panic during shutdown")
 			}
 
 			// complete shutdown
@@ -144,6 +147,20 @@ func (p *Process) ShutdownNow() {
 	}
 }
 
+// panicToErr converts panic to error WITH exact line of panic.
+// Note the offset should be determined empirically.
+func panicToErr(panic any, offset int) error {
+	stack := string(debug.Stack())
+	lines := strings.Split(stack, "\n")
+	line := ""
+
+	if len(lines) > offset {
+		line = strings.TrimSpace(lines[offset])
+	}
+
+	return fmt.Errorf("panic: %v at %s", panic, line)
+}
+
 // NewSigChan creates a new signal channel.
 func NewSigChan(signals ...os.Signal) chan os.Signal {
 	out := make(chan os.Signal, 1)

pkg/graceful/graceful_test.go

@@ -135,7 +135,7 @@ func TestProcess(t *testing.T) {
 		assert.Contains(t, ts.logBuffer.String(), "failed to start service")
 	})
 
-	t.Run("Panic handling", func(t *testing.T) {
+	t.Run("Panic handling during startup", func(t *testing.T) {
 		t.Parallel()
 
 		// ARRANGE
@@ -153,6 +153,31 @@ func TestProcess(t *testing.T) {
 		// Check that service had errors and was stopped
 		assert.Contains(t, ts.logBuffer.String(), "Shutdown completed")
 		assert.Contains(t, ts.logBuffer.String(), "panic in service")
+
+		// Check that error contains exact line of panic
+		assert.Contains(t, ts.logBuffer.String(), "graceful_test.go:145")
+	})
+
+	t.Run("Panic handling during shutdown", func(t *testing.T) {
+		t.Parallel()
+
+		// ARRANGE
+		ts := newTestSuite(t, defaultTimeout, false)
+
+		ts.process.AddStopper(func() {
+			panic("bombarda maxima")
+		})
+
+		// ACT
+		ts.process.ShutdownNow()
+
+		// ASSERT
+		// Check that service had errors and was stopped
+		assert.Contains(t, ts.logBuffer.String(), "Shutdown completed")
+		assert.Contains(t, ts.logBuffer.String(), "panic during shutdown")
+
+		// Check that error contains exact line of panic
+		assert.Contains(t, ts.logBuffer.String(), "graceful_test.go:168")
 	})
 
 	t.Run("WaitForShutdown noop", func(t *testing.T) {