README.md
# etcd/clientv3
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`etcd/clientv3` is the official Go etcd client for v3.
## Install
```bash
go get go.etcd.io/etcd/client/v3
```
Warning: As etcd 3.5.0 was not yet released, the command above does not work.
After first pre-release of 3.5.0 [#12498](https://github.com/etcd-io/etcd/issues/12498),
etcd can be referenced using:
```
go get go.etcd.io/etcd/client/v3@v3.5.0-pre
```
## Get started
Create client using `clientv3.New`:
```go
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`](https://www.grpc.io) for remote procedure calls. And `clientv3` uses
[`grpc-go`](https://github.com/grpc/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:
```go
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:
1. context error: canceled or deadline exceeded.
2. gRPC error: see [api/v3rpc/rpctypes](https://godoc.org/go.etcd.io/etcd/api/v3rpc/rpctypes).
Here is the example code to handle client errors:
```go
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](https://github.com/grpc-ecosystem/go-grpc-prometheus). See the [examples](https://github.com/etcd-io/etcd/blob/main/tests/integration/clientv3/examples/example_metrics_test.go).
## Namespacing
The [namespace](https://godoc.org/go.etcd.io/etcd/client/v3/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`.
## Examples
More code [examples](https://github.com/etcd-io/etcd/tree/main/tests/integration/clientv3/examples) can be found at [GoDoc](https://pkg.go.dev/go.etcd.io/etcd/client/v3).