# etcd/clientv3

[![Godoc](https://img.shields.io/badge/go-documentation-blue.svg?style=flat-square)](https://godoc.org/github.com/coreos/etcd/clientv3)

`etcd/clientv3` is the official Go etcd client for v3.

## Install

```bash
go get github.com/coreos/etcd/clientv3
```

## 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`](http://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
```

etcd uses `cmd/vendor` directory to store external dependencies, which are
to be compiled into etcd release binaries. `client` can be imported without
vendoring. For full compatibility, it is recommended to vendor builds using
etcd's vendored packages, using tools like godep, as in
[vendor directories](https://golang.org/cmd/go/#hdr-Vendor_Directories).
For more detail, please read [Go vendor design](https://golang.org/s/go15vendor).

## 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/github.com/coreos/etcd/etcdserver/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/coreos/etcd/blob/master/clientv3/example_metrics_test.go).

## Namespacing

The [namespace](https://godoc.org/github.com/coreos/etcd/clientv3/namespace) package provides `clientv3` interface wrappers to transparently isolate client requests to a user-defined prefix.

## Examples

More code examples can be found at [GoDoc](https://godoc.org/github.com/coreos/etcd/clientv3).
