Merge pull request #741 from jaffee/707-catch-panics

add recovery in top level handler

handler.go

@@ -29,6 +29,7 @@ import (
 	"net/http"
 	_ "net/http/pprof"
 	"os"
+	"runtime/debug"
 	"strconv"
 	"strings"
 	"time"
@@ -138,6 +139,16 @@ func (h *Handler) methodNotAllowedHandler(w http.ResponseWriter, r *http.Request
 
 // ServeHTTP handles an HTTP request.
 func (h *Handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	defer func() {
+		if err := recover(); err != nil {
+			w.WriteHeader(http.StatusInternalServerError)
+			stack := debug.Stack()
+			msg := "PANIC: %s\n%s"
+			fmt.Fprintf(h.LogOutput, msg, err, stack)
+			fmt.Fprintf(w, msg, err, stack)
+		}
+	}()
+
 	t := time.Now()
 	h.Router.ServeHTTP(w, r)
 	dif := time.Since(t)

handler_test.go

@@ -32,6 +32,30 @@ import (
 	"github.com/pilosa/pilosa/test"
 )
 
+func TestHandlerPanics(t *testing.T) {
+	h := test.NewHandler()
+	buf := &bytes.Buffer{}
+	h.Handler.LogOutput = buf
+
+	w := httptest.NewRecorder()
+	// will panic since Handler has no Holder set up
+	h.ServeHTTP(w, test.MustNewHTTPRequest("GET", "/index/taxi", nil))
+	bufbytes, err := ioutil.ReadAll(buf)
+	if err != nil {
+		t.Fatalf("reading all logoutput: %v", err)
+	}
+	if !bytes.Contains(bufbytes, []byte("PANIC: runtime error: invalid memory address or nil pointer dereference")) {
+		t.Fatalf("expected panic in log, but got: %s", bufbytes)
+	}
+	if w.Code != http.StatusInternalServerError {
+		t.Fatalf("expected internal server error, but got: %v", w.Code)
+	}
+	bodyBytes := w.Body.Bytes()
+	if !bytes.Contains(bodyBytes, []byte("PANIC: runtime error: invalid memory address or nil pointer dereference")) {
+		t.Fatalf("response to client should have panic, but got %s", bodyBytes)
+	}
+}
+
 // Ensure the handler returns "not found" for invalid paths.
 func TestHandler_NotFound(t *testing.T) {
 	hldr := test.MustOpenHolder()