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# Retry
This example shows how to enable and configure retry on gRPC clients.
## Documentation
[gRFC for client-side retry support](https://github.com/grpc/proposal/blob/master/A6-client-retries.md)
## Try it
This example includes a service implementation that fails requests three times with status
code `Unavailable`, then passes the fourth. The client is configured to make four retry attempts
when receiving an `Unavailable` status code.
First start the server:
```bash
go run server/main.go
```
Then run the client. Note that when running the client, `GRPC_GO_RETRY=on` must be set in
your environment:
```bash
GRPC_GO_RETRY=on go run client/main.go
```
## Usage
### Define your retry policy
Retry is enabled via the service config, which can be provided by the name resolver or
a DialOption (described below). In the below config, we set retry policy for the
"grpc.example.echo.Echo" method.
MaxAttempts: how many times to attempt the RPC before failing.
InitialBackoff, MaxBackoff, BackoffMultiplier: configures delay between attempts.
RetryableStatusCodes: Retry only when receiving these status codes.
```go
var retryPolicy = `{
"methodConfig": [{
// config per method or all methods under service
"name": [{"service": "grpc.examples.echo.Echo"}],
"waitForReady": true,
"retryPolicy": {
"MaxAttempts": 4,
"InitialBackoff": ".01s",
"MaxBackoff": ".01s",
"BackoffMultiplier": 1.0,
// this value is grpc code
"RetryableStatusCodes": [ "UNAVAILABLE" ]
}
}]
}`
```
### Providing the retry policy as a DialOption
To use the above service config, pass it with `grpc.WithDefaultServiceConfig` to
`grpc.Dial`.
```go
conn, err := grpc.Dial(ctx,grpc.WithInsecure(), grpc.WithDefaultServiceConfig(retryPolicy))
```
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