private long releaseAll() {
        long total = 0;
        for (final Entry<ProcessorFilter, ProcessorTaskQueue> entry : queueMap.entrySet()) {
            final ProcessorFilter filter = entry.getKey();
            total += releaseQueuedFilterTasks(filter);
        }
        return total;
    }
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