mirror of https://github.com/k3s-io/k3s
86 lines
2.7 KiB
Markdown
86 lines
2.7 KiB
Markdown
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# etcd/clientv3
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[](https://godoc.org/github.com/coreos/etcd/clientv3)
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`etcd/clientv3` is the official Go etcd client for v3.
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## Install
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```bash
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go get github.com/coreos/etcd/clientv3
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```
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## Get started
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Create client using `clientv3.New`:
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```go
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cli, err := clientv3.New(clientv3.Config{
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Endpoints: []string{"localhost:2379", "localhost:22379", "localhost:32379"},
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DialTimeout: 5 * time.Second,
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})
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if err != nil {
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// handle error!
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}
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defer cli.Close()
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```
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etcd v3 uses [`gRPC`](http://www.grpc.io) for remote procedure calls. And `clientv3` uses
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[`grpc-go`](https://github.com/grpc/grpc-go) to connect to etcd. Make sure to close the client after using it.
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If the client is not closed, the connection will have leaky goroutines. To specify client request timeout,
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pass `context.WithTimeout` to APIs:
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```go
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ctx, cancel := context.WithTimeout(context.Background(), timeout)
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resp, err := cli.Put(ctx, "sample_key", "sample_value")
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cancel()
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if err != nil {
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// handle error!
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}
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// use the response
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```
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etcd uses `cmd/vendor` directory to store external dependencies, which are
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to be compiled into etcd release binaries. `client` can be imported without
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vendoring. For full compatibility, it is recommended to vendor builds using
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etcd's vendored packages, using tools like godep, as in
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[vendor directories](https://golang.org/cmd/go/#hdr-Vendor_Directories).
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For more detail, please read [Go vendor design](https://golang.org/s/go15vendor).
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## Error Handling
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etcd client returns 2 types of errors:
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1. context error: canceled or deadline exceeded.
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2. gRPC error: see [api/v3rpc/rpctypes](https://godoc.org/github.com/coreos/etcd/etcdserver/api/v3rpc/rpctypes).
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Here is the example code to handle client errors:
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```go
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resp, err := cli.Put(ctx, "", "")
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if err != nil {
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switch err {
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case context.Canceled:
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log.Fatalf("ctx is canceled by another routine: %v", err)
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case context.DeadlineExceeded:
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log.Fatalf("ctx is attached with a deadline is exceeded: %v", err)
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case rpctypes.ErrEmptyKey:
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log.Fatalf("client-side error: %v", err)
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default:
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log.Fatalf("bad cluster endpoints, which are not etcd servers: %v", err)
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}
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}
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```
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## Metrics
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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).
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## Namespacing
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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.
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## Examples
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More code examples can be found at [GoDoc](https://godoc.org/github.com/coreos/etcd/clientv3).
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