send plugin error stack traces over gRPC and log error locations

Signed-off-by: Steve Kriss <krisss@vmware.com>

pkg/plugin/framework/server_errors.go

@@ -0,0 +1,85 @@
+/*
+Copyright 2019 the Velero contributors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package framework
+
+import (
+	goproto "github.com/golang/protobuf/proto"
+	"github.com/pkg/errors"
+	"google.golang.org/grpc/codes"
+	"google.golang.org/grpc/status"
+
+	proto "github.com/heptio/velero/pkg/plugin/generated"
+	"github.com/heptio/velero/pkg/util/logging"
+)
+
+// newGRPCErrorWithCode wraps err in a gRPC status error with the error's stack trace
+// included in the details if it exists. This provides an easy way to send
+// stack traces from plugin servers across the wire to the plugin client.
+//
+// This function should be used in the internal plugin server code to wrap
+// all errors before they're returned.
+func newGRPCErrorWithCode(err error, code codes.Code, details ...goproto.Message) error {
+	// if it's already a gRPC status error, use it; otherwise, create a new one
+	statusErr, ok := status.FromError(err)
+	if !ok {
+		statusErr = status.New(code, err.Error())
+	}
+
+	// get a Stack for the error and add it to details
+	if stack := errorStack(err); stack != nil {
+		details = append(details, stack)
+	}
+
+	statusErr, err = statusErr.WithDetails(details...)
+	if err != nil {
+		return status.Errorf(codes.Unknown, "error adding details to the gRPC error: %v", err)
+	}
+
+	return statusErr.Err()
+}
+
+// newGRPCError is a convenience functino for creating a new gRPC error
+// with code = codes.Unknown
+func newGRPCError(err error, details ...goproto.Message) error {
+	return newGRPCErrorWithCode(err, codes.Unknown, details...)
+}
+
+// errorStack gets a stack trace, if it exists, from the provided error, and
+// returns it as a *proto.Stack.
+func errorStack(err error) *proto.Stack {
+	stackTracer, ok := err.(stackTracer)
+	if !ok {
+		return nil
+	}
+
+	stackTrace := new(proto.Stack)
+	for _, frame := range stackTracer.StackTrace() {
+		location := logging.GetFrameLocationInfo(frame)
+
+		stackTrace.Frames = append(stackTrace.Frames, &proto.StackFrame{
+			File:     location.File,
+			Line:     int32(location.Line),
+			Function: location.Function,
+		})
+	}
+
+	return stackTrace
+}
+
+type stackTracer interface {
+	StackTrace() errors.StackTrace
+}