Firebase Work Queue

queue.js

// ref.transaction() can be used in place of ref.set()
queueChildRef.transaction(function(theItem) {
	    dataToProcess = theItem;
	    if(theItem) {
	    	return null; // if there is still a value, delete it and claim job
	    } else {
	    	return; // if there is not a value, abort transaction. job already claimed
	    }
	}, function(error, committed, snapshot, dummy) {
            if (error) throw error;
            if(committed) {
                console.log("Claimed a job.");
            } else {
                console.log("Another worker beat me to the job.");
            }
        }
);