7f46da223d
The existing client may connect to different endpoint from the specific endpoint to be maintained. Maintenance operations do not go through raft at all, so it might run into issue if the server hasn't finished applying the authentication request. Let's work with an example. Assuming the existing client connects to ep1, while the user wants to maintain ep2. If we getToken again, it sends an authentication request, which goes through raft. When the specific endpoint receives the maintenance request, it might haven't finished previous authentication request, but the new token is already carried in the context, so it will reject the maintenance request due to invalid token. We already have retry logic in `unaryClientInterceptor` and `streamClientInterceptor`. When the token expires, it can automatically refresh the token, so it should be safe to remove the `getToken` logic in `maintenance.dial` Signed-off-by: Benjamin Wang <wachao@vmware.com>
etcd/client/v3
etcd/clientv3 is the official Go etcd client for v3.
Install
go get go.etcd.io/etcd/client/v3
Get started
Create client using clientv3.New:
import clientv3 "go.etcd.io/etcd/client/v3"
func main() {
cli, err := clientv3.New(clientv3.Config{
Endpoints: []string{"localhost:2379", "localhost:22379", "localhost:32379"},
DialTimeout: 5 * time.Second,
})
if err != nil {
// handle error!
}
defer cli.Close()
}
etcd v3 uses gRPC for remote procedure calls. And clientv3 uses
grpc-go to connect to etcd. Make sure to close the client after using it.
If the client is not closed, the connection will have leaky goroutines. To specify client request timeout,
pass context.WithTimeout to APIs:
ctx, cancel := context.WithTimeout(context.Background(), timeout)
resp, err := cli.Put(ctx, "sample_key", "sample_value")
cancel()
if err != nil {
// handle error!
}
// use the response
For full compatibility, it is recommended to install released versions of clients using go modules.
Error Handling
etcd client returns 2 types of errors:
- context error: canceled or deadline exceeded.
- gRPC error: see api/v3rpc/rpctypes.
Here is the example code to handle client errors:
resp, err := cli.Put(ctx, "", "")
if err != nil {
switch err {
case context.Canceled:
log.Fatalf("ctx is canceled by another routine: %v", err)
case context.DeadlineExceeded:
log.Fatalf("ctx is attached with a deadline is exceeded: %v", err)
case rpctypes.ErrEmptyKey:
log.Fatalf("client-side error: %v", err)
default:
log.Fatalf("bad cluster endpoints, which are not etcd servers: %v", err)
}
}
Metrics
The etcd client optionally exposes RPC metrics through go-grpc-prometheus. See the examples.
Namespacing
The namespace package provides clientv3 interface wrappers to transparently isolate client requests to a user-defined prefix.
Request size limit
Client request size limit is configurable via clientv3.Config.MaxCallSendMsgSize and MaxCallRecvMsgSize in bytes. If none given, client request send limit defaults to 2 MiB including gRPC overhead bytes. And receive limit defaults to math.MaxInt32.