private static void updateRequestTimeout(ServiceRequestContext ctx, long longPollingTimeoutMillis) {
        final long requestTimeoutMillis = ctx.requestTimeoutMillis();
        if (requestTimeoutMillis > 0) {
            ctx.setRequestTimeoutMillis(TimeoutMode.EXTEND, longPollingTimeoutMillis);
        }
    }
Extends the request timeout by the specified {@code longPollingTimeoutMillis}, because otherwise
the client will get {@code "503 Service Unavailable} due to a {@link RequestTimeoutException} before
long-polling finishes.
core/src/main/java/com/linecorp/armeria/server/healthcheck/HealthCheckService.java