private void addWithQueueAndRetry(final Path sourceDir) {
        LOGGER.debug("'{}' - addWithQueueAndRetry(), dir: {}", destinationName, sourceDir);
        // Add to the forward queue to isolate the caller from failures in the delegate.
        // This will move sourceDir into the queue dir
        forwardQueue.add(sourceDir);
    }
Holds the state relating to retries. Held in binary form.
stroom-proxy/stroom-proxy-app/src/main/java/stroom/proxy/app/handler/RetryingForwardDestination.java