Merge pull request #69 from BetaXOi/output-qmp-err

qmp: Output error detail when execute QMP command failed

qemu/qmp.go

@@ -313,7 +313,7 @@ func (q *QMP) finaliseCommandWithResponse(cmdEl *list.Element, cmdQueue *list.Li
 		if succeeded {
 			cmd.res <- qmpResult{response: response}
 		} else {
-			cmd.res <- qmpResult{err: fmt.Errorf("QMP command failed")}
+			cmd.res <- qmpResult{err: fmt.Errorf("QMP command failed: %v", response)}
 		}
 	}
 	if cmdQueue.Len() > 0 {
@@ -325,6 +325,23 @@ func (q *QMP) finaliseCommand(cmdEl *list.Element, cmdQueue *list.List, succeede
 	q.finaliseCommandWithResponse(cmdEl, cmdQueue, succeeded, nil)
 }
 
+func (q *QMP) errorDesc(errorData interface{}) (string, error) {
+	// convert error to json
+	data, err := json.Marshal(errorData)
+	if err != nil {
+		return "", fmt.Errorf("Unable to extract error information: %v", err)
+	}
+
+	// see: https://github.com/qemu/qemu/blob/stable-2.12/qapi/qmp-dispatch.c#L125
+	var qmpErr map[string]string
+	// convert json to qmpError
+	if err = json.Unmarshal(data, &qmpErr); err != nil {
+		return "", fmt.Errorf("Unable to convert json to qmpError: %v", err)
+	}
+
+	return qmpErr["desc"], nil
+}
+
 func (q *QMP) processQMPInput(line []byte, cmdQueue *list.List) {
 	var vmData map[string]interface{}
 	err := json.Unmarshal(line, &vmData)
@@ -339,7 +356,7 @@ func (q *QMP) processQMPInput(line []byte, cmdQueue *list.List) {
 	}
 
 	response, succeeded := vmData["return"]
-	_, failed := vmData["error"]
+	errData, failed := vmData["error"]
 
 	if !succeeded && !failed {
 		return
@@ -353,6 +370,14 @@ func (q *QMP) processQMPInput(line []byte, cmdQueue *list.List) {
 	}
 	cmd := cmdEl.Value.(*qmpCommand)
 	if failed || cmd.filter == nil {
+		if errData != nil {
+			desc, err := q.errorDesc(errData)
+			if err != nil {
+				q.cfg.Logger.Infof("Get error description failed: %v", err)
+			} else {
+				response = desc
+			}
+		}
 		q.finaliseCommandWithResponse(cmdEl, cmdQueue, succeeded, response)
 	} else {
 		cmd.resultReceived = true

qemu/qmp_test.go

@@ -1403,3 +1403,86 @@ func TestExecuteBalloon(t *testing.T) {
 	q.Shutdown()
 	<-disconnectedCh
 }
+
+func TestErrorDesc(t *testing.T) {
+	errDesc := "Somthing err messages"
+	errData := map[string]string{
+		"class": "GenericError",
+		"desc":  errDesc,
+	}
+
+	connectedCh := make(chan *QMPVersion)
+	disconnectedCh := make(chan struct{})
+	buf := newQMPTestCommandBuffer(t)
+	cfg := QMPConfig{Logger: qmpTestLogger{}}
+	q := startQMPLoop(buf, cfg, connectedCh, disconnectedCh)
+	checkVersion(t, connectedCh)
+
+	desc, err := q.errorDesc(errData)
+	if err != nil {
+		t.Fatalf("Unexpected error '%v'", err)
+	}
+	if desc != errDesc {
+		t.Fatalf("expected '%v'\n got '%v'", errDesc, desc)
+	}
+
+	q.Shutdown()
+	<-disconnectedCh
+}
+
+func TestExecCommandFailed(t *testing.T) {
+	errDesc := "unable to map backing store for guest RAM: Cannot allocate memory"
+	errData := map[string]string{
+		"class": "GenericError",
+		"desc":  errDesc,
+	}
+
+	connectedCh := make(chan *QMPVersion)
+	disconnectedCh := make(chan struct{})
+	buf := newQMPTestCommandBuffer(t)
+	buf.AddCommand("object-add", nil, "error", errData)
+	cfg := QMPConfig{Logger: qmpTestLogger{}}
+	q := startQMPLoop(buf, cfg, connectedCh, disconnectedCh)
+	checkVersion(t, connectedCh)
+
+	_, err := q.executeCommandWithResponse(context.Background(), "object-add", nil, nil, nil)
+	if err == nil {
+		t.Fatalf("expected error but got nil")
+	}
+
+	expectedString := "QMP command failed: " + errDesc
+	if err.Error() != expectedString {
+		t.Fatalf("expected '%v' but got '%v'", expectedString, err)
+	}
+
+	q.Shutdown()
+	<-disconnectedCh
+}
+
+func TestExecCommandFailedWithInnerError(t *testing.T) {
+	errData := map[string]string{
+		"class":            "GenericError",
+		"descFieldInvalid": "Invalid",
+	}
+
+	connectedCh := make(chan *QMPVersion)
+	disconnectedCh := make(chan struct{})
+	buf := newQMPTestCommandBuffer(t)
+	buf.AddCommand("object-add", nil, "error", errData)
+	cfg := QMPConfig{Logger: qmpTestLogger{}}
+	q := startQMPLoop(buf, cfg, connectedCh, disconnectedCh)
+	checkVersion(t, connectedCh)
+
+	_, err := q.executeCommandWithResponse(context.Background(), "object-add", nil, nil, nil)
+	if err == nil {
+		t.Fatalf("expected error but got nil")
+	}
+
+	expectedString := "QMP command failed: "
+	if err.Error() != expectedString {
+		t.Fatalf("expected '%v' but got '%v'", expectedString, err)
+	}
+
+	q.Shutdown()
+	<-disconnectedCh
+}