gRPC naming and discovery

You are viewing documentation for etcd version: v3.1

etcd v3.1 documentation is no longer actively maintained. The version you are currently viewing is a static snapshot. For up-to-date documentation, see the latest release, v3.4, or the current documentation.

etcd provides a gRPC resolver to support an alternative name system that fetches endpoints from etcd for discovering gRPC services. The underlying mechanism is based on watching updates to keys prefixed with the service name.

Using etcd discovery with go-grpc

The etcd client provides a gRPC resolver for resolving gRPC endpoints with an etcd backend. The resolver is initialized with an etcd client and given a target for resolution:

import (
	etcdnaming ""



cli, cerr := clientv3.NewFromURL("http://localhost:2379")
r := &etcdnaming.GRPCResolver{Client: cli}
b := grpc.RoundRobin(r)
conn, gerr := grpc.Dial("my-service", grpc.WithBalancer(b))

Managing service endpoints

The etcd resolver treats all keys under the prefix of the resolution target following a “/” (e.g., “my-service/") with JSON-encoded go-grpc naming.Update values as potential service endpoints. Endpoints are added to the service by creating new keys and removed from the service by deleting keys.

Adding an endpoint

New endpoints can be added to the service through etcdctl:

ETCDCTL_API=3 etcdctl put my-service/ '{"Addr":"","Metadata":"..."}'

The etcd client’s GRPCResolver.Update method can also register new endpoints with a key matching the Addr:

r.Update(context.TODO(), "my-service", naming.Update{Op: naming.Add, Addr: "", Metadata: "..."})

Deleting an endpoint

Hosts can be deleted from the service through etcdctl:

ETCDCTL_API=3 etcdctl del my-service/

The etcd client’s GRPCResolver.Update method also supports deleting endpoints:

r.Update(context.TODO(), "my-service", naming.Update{Op: naming.Delete, Addr: ""})

Registering an endpoint with a lease

Registering an endpoint with a lease ensures that if the host can’t maintain a keepalive heartbeat (e.g., its machine fails), it will be removed from the service:

lease=`ETCDCTL_API=3 etcdctl lease grant 5 | cut -f2 -d' '`
ETCDCTL_API=3 etcdctl put --lease=$lease my-service/ '{"Addr":"","Metadata":"..."}'
ETCDCTL_API=3 etcdctl lease keep-alive $lease

© etcd Authors 2021 | Documentation Distributed under CC-BY-4.0

© 2021 The Linux Foundation. All rights reserved. The Linux Foundation has registered trademarks and uses trademarks.
For a list of trademarks of The Linux Foundation, please see our Trademark Usage page.

gRPC naming and discovery