@Setup
    public void start() {
        server = Server.builder()
                       .http(0)
                       .service("/empty", (ctx, req) -> HttpResponse.of("\"\""))
                       .build();
        server.start().join();
        client = newClient();
    }
The base for {@link WithDuplicator} and {@link WithoutDuplicator} microbenchmarks.
benchmarks/jmh/src/jmh/java/com/linecorp/armeria/core/client/retry/RetryingClientBase.java