add GDrive provider support (#118)

* GDrive provider support
* More reliable basedir ownership
* Fix mimetype

vendor/cloud.google.com/go/trace/grpc.go

@@ -0,0 +1,108 @@
+// Copyright 2017 Google LLC
+//
+// 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 trace
+
+import (
+	"encoding/hex"
+	"fmt"
+
+	"cloud.google.com/go/internal/tracecontext"
+	"golang.org/x/net/context"
+	"google.golang.org/grpc"
+	"google.golang.org/grpc/metadata"
+)
+
+const grpcMetadataKey = "grpc-trace-bin"
+
+// GRPCClientInterceptor returns a grpc.UnaryClientInterceptor that traces all outgoing requests from a gRPC client.
+// The calling context should already have a *trace.Span; a child span will be
+// created for the outgoing gRPC call. If the calling context doesn't have a span,
+// the call will not be traced. If the client is nil, then the interceptor just
+// passes through the request.
+//
+// The functionality in gRPC that this feature relies on is currently experimental.
+func (c *Client) GRPCClientInterceptor() grpc.UnaryClientInterceptor {
+	if c == nil {
+		return func(ctx context.Context, method string, req, reply interface{}, cc *grpc.ClientConn, invoker grpc.UnaryInvoker, opts ...grpc.CallOption) error {
+			return invoker(ctx, method, req, reply, cc, opts...)
+		}
+	}
+	return grpc.UnaryClientInterceptor(c.grpcUnaryInterceptor)
+}
+
+func (c *Client) grpcUnaryInterceptor(ctx context.Context, method string, req, reply interface{}, cc *grpc.ClientConn, invoker grpc.UnaryInvoker, opts ...grpc.CallOption) error {
+	// TODO: also intercept streams.
+	span := FromContext(ctx).NewChild(method)
+	if span == nil {
+		span = c.NewSpan(method)
+	}
+	defer span.Finish()
+
+	traceContext := make([]byte, tracecontext.Len)
+	// traceID is a hex-encoded 128-bit value.
+	// TODO(jbd): Decode trace IDs upon arrival and
+	// represent trace IDs with 16 bytes internally.
+	tid, err := hex.DecodeString(span.trace.traceID)
+	if err != nil {
+		return invoker(ctx, method, req, reply, cc, opts...)
+	}
+	tracecontext.Encode(traceContext, tid, span.span.SpanId, byte(span.trace.globalOptions))
+	md, ok := metadata.FromOutgoingContext(ctx)
+	if !ok {
+		md = metadata.Pairs(grpcMetadataKey, string(traceContext))
+	} else {
+		md = md.Copy() // metadata is immutable, copy.
+		md[grpcMetadataKey] = []string{string(traceContext)}
+	}
+	ctx = metadata.NewOutgoingContext(ctx, md)
+
+	err = invoker(ctx, method, req, reply, cc, opts...)
+	if err != nil {
+		// TODO: standardize gRPC label names?
+		span.SetLabel("error", err.Error())
+	}
+	return err
+}
+
+// GRPCServerInterceptor returns a grpc.UnaryServerInterceptor that enables the tracing of the incoming
+// gRPC calls. Incoming call's context can be used to extract the span on servers that enabled this option:
+//
+//	span := trace.FromContext(ctx)
+//
+// If the client is nil, then the interceptor just invokes the handler.
+//
+// The functionality in gRPC that this feature relies on is currently experimental.
+func (c *Client) GRPCServerInterceptor() grpc.UnaryServerInterceptor {
+	if c == nil {
+		return func(ctx context.Context, req interface{}, _ *grpc.UnaryServerInfo, handler grpc.UnaryHandler) (interface{}, error) {
+			return handler(ctx, req)
+		}
+	}
+	return func(ctx context.Context, req interface{}, info *grpc.UnaryServerInfo, handler grpc.UnaryHandler) (resp interface{}, err error) {
+		md, _ := metadata.FromIncomingContext(ctx)
+		var traceHeader string
+		if header, ok := md[grpcMetadataKey]; ok {
+			traceID, spanID, opts, ok := tracecontext.Decode([]byte(header[0]))
+			if ok {
+				// TODO(jbd): Generate a span directly from string(traceID), spanID and opts.
+				traceHeader = fmt.Sprintf("%x/%d;o=%d", traceID, spanID, opts)
+			}
+		}
+		span := c.SpanFromHeader(info.FullMethod, traceHeader)
+		defer span.Finish()
+		ctx = NewContext(ctx, span)
+		return handler(ctx, req)
+	}
+}