log api panic with a stack trace

http/router.go

@@ -3,9 +3,14 @@ package http
 import (
 	"fmt"
 	"net/http"
+	"os"
+	"runtime/debug"
+	"sync"
 
 	platform "github.com/influxdata/influxdb"
+	influxlogger "github.com/influxdata/influxdb/logger"
 	"github.com/julienschmidt/httprouter"
+	"go.uber.org/zap"
 )
 
 // NewRouter returns a new router with a 404 handler, a 405 handler, and a panic handler.
@@ -50,5 +55,25 @@ func panicHandler(w http.ResponseWriter, r *http.Request, rcv interface{}) {
 		Err:  fmt.Errorf("%v", rcv),
 	}
 
+	l := getPanicLogger()
+	l.Error(
+		pe.Msg,
+		zap.String("err", pe.Err.Error()),
+		zap.String("stack", fmt.Sprintf("%s", debug.Stack())),
+	)
+
 	EncodeError(ctx, pe, w)
 }
+
+var panicLogger *zap.Logger
+var panicLoggerOnce sync.Once
+
+// getPanicLogger returns a logger for panicHandler.
+func getPanicLogger() *zap.Logger {
+	panicLoggerOnce.Do(func() {
+		panicLogger = influxlogger.New(os.Stderr)
+		panicLogger = panicLogger.With(zap.String("handler", "panic"))
+	})
+
+	return panicLogger
+}