grpcproxy: add 'register' address

For https://github.com/coreos/etcd/issues/6902.

proxy/grpcproxy/logger.go

@@ -0,0 +1,19 @@
+// Copyright 2017 The etcd Authors
+//
+// 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 grpcproxy
+
+import "github.com/coreos/pkg/capnslog"
+
+var plog = capnslog.NewPackageLogger("github.com/coreos/etcd", "grpcproxy")

proxy/grpcproxy/register.go

@@ -0,0 +1,74 @@
+// Copyright 2017 The etcd Authors
+//
+// 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 grpcproxy
+
+import (
+	"github.com/coreos/etcd/clientv3"
+	"github.com/coreos/etcd/clientv3/concurrency"
+	"github.com/coreos/etcd/clientv3/naming"
+
+	"golang.org/x/time/rate"
+	gnaming "google.golang.org/grpc/naming"
+)
+
+// allow maximum 1 retry per second
+const registerRetryRate = 1
+
+// register registers itself as a grpc-proxy server by writing prefixed-key
+// with session of specified TTL (in seconds). The returned channel is closed
+// when the client's context is canceled.
+func register(c *clientv3.Client, prefix string, addr string, ttl int) <-chan struct{} {
+	rm := rate.NewLimiter(rate.Limit(registerRetryRate), registerRetryRate)
+
+	donec := make(chan struct{})
+	go func() {
+		defer close(donec)
+
+		for rm.Wait(c.Ctx()) == nil {
+			ss, err := registerSession(c, prefix, addr, ttl)
+			if err != nil {
+				plog.Warningf("failed to create a session %v", err)
+				continue
+			}
+			select {
+			case <-c.Ctx().Done():
+				ss.Close()
+				return
+
+			case <-ss.Done():
+				plog.Warning("session expired; possible network partition or server restart")
+				plog.Warning("creating a new session to rejoin")
+				continue
+			}
+		}
+	}()
+
+	return donec
+}
+
+func registerSession(c *clientv3.Client, prefix string, addr string, ttl int) (*concurrency.Session, error) {
+	ss, err := concurrency.NewSession(c, concurrency.WithTTL(ttl))
+	if err != nil {
+		return nil, err
+	}
+
+	gr := &naming.GRPCResolver{Client: c}
+	if err = gr.Update(c.Ctx(), prefix, gnaming.Update{Op: gnaming.Add, Addr: addr}, clientv3.WithLease(ss.Lease())); err != nil {
+		return nil, err
+	}
+
+	plog.Infof("registered %q with %d-second lease", addr, ttl)
+	return ss, nil
+}

proxy/grpcproxy/register_test.go

@@ -0,0 +1,76 @@
+// Copyright 2017 The etcd Authors
+//
+// 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 grpcproxy
+
+import (
+	"testing"
+	"time"
+
+	"github.com/coreos/etcd/clientv3"
+	"github.com/coreos/etcd/clientv3/naming"
+	"github.com/coreos/etcd/integration"
+	"github.com/coreos/etcd/pkg/testutil"
+
+	gnaming "google.golang.org/grpc/naming"
+)
+
+func Test_register(t *testing.T) {
+	defer testutil.AfterTest(t)
+
+	clus := integration.NewClusterV3(t, &integration.ClusterConfig{Size: 1})
+	defer clus.Terminate(t)
+	cli := clus.Client(0)
+	paddr := clus.Members[0].GRPCAddr()
+
+	testPrefix := "test-name"
+	wa := createWatcher(t, cli, testPrefix)
+	ups, err := wa.Next()
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(ups) != 0 {
+		t.Fatalf("len(ups) expected 0, got %d (%v)", len(ups), ups)
+	}
+
+	donec := register(cli, testPrefix, paddr, 5)
+
+	ups, err = wa.Next()
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(ups) != 1 {
+		t.Fatalf("len(ups) expected 1, got %d (%v)", len(ups), ups)
+	}
+	if ups[0].Addr != paddr {
+		t.Fatalf("ups[0].Addr expected %q, got %q", paddr, ups[0].Addr)
+	}
+
+	cli.Close()
+	clus.TakeClient(0)
+	select {
+	case <-donec:
+	case <-time.After(5 * time.Second):
+		t.Fatal("donec 'register' did not return in time")
+	}
+}
+
+func createWatcher(t *testing.T, c *clientv3.Client, prefix string) gnaming.Watcher {
+	gr := &naming.GRPCResolver{Client: c}
+	watcher, err := gr.Resolve(prefix)
+	if err != nil {
+		t.Fatalf("failed to resolve %q (%v)", prefix, err)
+	}
+	return watcher
+}