Make capture ID accessible through context (pingcap#150)

cdc/server.go

@@ -1,10 +1,25 @@
+// Copyright 2019 PingCAP, Inc.
+//
+// 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,
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
 package cdc
 
 import (
 	"context"
 	"net/http"
 	"strings"
 
+	"github.com/pingcap/ticdc/pkg/util"
+
 	"github.com/pingcap/log"
 	"go.uber.org/zap"
 )
@@ -78,6 +93,7 @@ func NewServer(opt ...ServerOption) (*Server, error) {
 // Run runs the server.
 func (s *Server) Run(ctx context.Context) error {
 	s.startStatusHTTP()
+	ctx = util.PutCaptureIDInCtx(ctx, s.capture.info.ID)
 	return s.capture.Start(ctx)
 }
 

pkg/util/ctx.go

@@ -0,0 +1,37 @@
+// Copyright 2019 PingCAP, Inc.
+//
+// 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,
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package util
+
+import "context"
+
+type ctxKey string
+
+const (
+	ctxKeyCaptureID = ctxKey("captureID")
+)
+
+// CaptureIDFromCtx returns a capture ID stored in the specified context.
+// It returns an empty string if there's no valid capture ID found.
+func CaptureIDFromCtx(ctx context.Context) string {
+	captureID, ok := ctx.Value(ctxKeyCaptureID).(string)
+	if !ok {
+		return ""
+	}
+	return captureID
+}
+
+// PutCaptureIDInCtx returns a new child context with the specified capture ID stored.
+func PutCaptureIDInCtx(ctx context.Context, captureID string) context.Context {
+	return context.WithValue(ctx, ctxKeyCaptureID, captureID)
+}

pkg/util/ctx_test.go

@@ -0,0 +1,35 @@
+// Copyright 2019 PingCAP, Inc.
+//
+// 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,
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package util
+
+import (
+	"context"
+
+	"github.com/pingcap/check"
+)
+
+type captureIDSuite struct{}
+
+var _ = check.Suite(&captureIDSuite{})
+
+func (s *captureIDSuite) TestShouldReturnCaptureID(c *check.C) {
+	ctx := PutCaptureIDInCtx(context.Background(), "ello")
+	c.Assert(CaptureIDFromCtx(ctx), check.Equals, "ello")
+}
+
+func (s *captureIDSuite) TestShouldReturnEmptyStr(c *check.C) {
+	c.Assert(CaptureIDFromCtx(context.Background()), check.Equals, "")
+	ctx := context.WithValue(context.Background(), ctxKeyCaptureID, 1321)
+	c.Assert(CaptureIDFromCtx(ctx), check.Equals, "")
+}