gRPC Retrying Example

The Retrying example provides a HelloWorld gRPC client & server which demos the effect of client retry policy configured on the ManagedChannel via gRPC ServiceConfig. Retry policy implementation & configuration details are outlined in the proposal.

This retrying example is very similar to the hedging example in its setup. The RetryingHelloWorldServer responds with a status UNAVAILABLE error response to a specified percentage of requests to simulate server resource exhaustion and general flakiness. The RetryingHelloWorldClient makes a number of sequential requests to the server, several of which will be retried depending on the configured policy in retrying_service_config.json. Although the requests are blocking unary calls for simplicity, these could easily be changed to future unary calls in order to test the result of request concurrency with retry policy enabled.

One can experiment with the RetryingHelloWorldServer failure conditions to simulate server throttling, as well as alter policy values in the retrying_service_config.json to see their effects. To disable retrying entirely, set environment variable DISABLE_RETRYING_IN_RETRYING_EXAMPLE=true before running the client. Disabling the retry policy should produce many more failed gRPC calls as seen in the output log.

See the section for how to build and run the example. The executables for the server and the client are retrying-hello-world-server and retrying-hello-world-client.