1# Retry 2 3This example shows how to enable and configure retry on gRPC clients. 4 5## Documentation 6 7[gRFC for client-side retry support](https://github.com/grpc/proposal/blob/master/A6-client-retries.md) 8 9## Try it 10 11This example includes a service implementation that fails requests three times with status 12code `Unavailable`, then passes the fourth. The client is configured to make four retry attempts 13when receiving an `Unavailable` status code. 14 15First start the server: 16 17```bash 18go run server/main.go 19``` 20 21Then run the client. Note that when running the client, `GRPC_GO_RETRY=on` must be set in 22your environment: 23 24```bash 25GRPC_GO_RETRY=on go run client/main.go 26``` 27 28## Usage 29 30### Define your retry policy 31 32Retry is enabled via the service config, which can be provided by the name resolver or 33a DialOption (described below). In the below config, we set retry policy for the 34"grpc.example.echo.Echo" method. 35 36MaxAttempts: how many times to attempt the RPC before failing. 37InitialBackoff, MaxBackoff, BackoffMultiplier: configures delay between attempts. 38RetryableStatusCodes: Retry only when receiving these status codes. 39 40```go 41 var retryPolicy = `{ 42 "methodConfig": [{ 43 // config per method or all methods under service 44 "name": [{"service": "grpc.examples.echo.Echo"}], 45 "waitForReady": true, 46 47 "retryPolicy": { 48 "MaxAttempts": 4, 49 "InitialBackoff": ".01s", 50 "MaxBackoff": ".01s", 51 "BackoffMultiplier": 1.0, 52 // this value is grpc code 53 "RetryableStatusCodes": [ "UNAVAILABLE" ] 54 } 55 }] 56 }` 57``` 58 59### Providing the retry policy as a DialOption 60 61To use the above service config, pass it with `grpc.WithDefaultServiceConfig` to 62`grpc.Dial`. 63 64```go 65conn, err := grpc.Dial(ctx,grpc.WithInsecure(), grpc.WithDefaultServiceConfig(retryPolicy)) 66``` 67