Retry

This example shows how to enable and configure retry on gRPC clients.

Documentation

gRFC for client-side retry support

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:

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:

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.

        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.

conn, err := grpc.Dial(ctx,grpc.WithInsecure(), grpc.WithDefaultServiceConfig(retryPolicy))