private synchronized void clearTaskStore() {
        for (final Entry<ProcessorFilter, ProcessorTaskQueue> entry : queueMap.entrySet()) {
            final ProcessorFilter filter = entry.getKey();
            if (filter != null) {
                final ProcessorTaskQueue queue = queueMap.remove(filter);
                if (queue != null) {
                    ProcessorTask streamTask = queue.poll();
                    while (streamTask != null) {
                        streamTask = queue.poll();
                    }
                }
            }
        }
    }
Return the next task to perform. Called by worker threads. Also assigns
the task to the node asking for the job
stroom-processor/stroom-processor-impl/src/main/java/stroom/processor/impl/ProcessorTaskQueueManagerImpl.java