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qrx.js
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qrx.js
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var uuid = require('node-uuid'),
redis = require('redis'),
Rx = require('rx').Rx
_ = require('underscore'),
os = require('os');
var WorkItem = require('./workitem'),
WorkQueue = require('./workqueue').WorkQueue,
WorkSet = require('./workset').WorkSet,
newRedisClient = require('./redisutils').newRedisClient,
ns = require('./messaging').ns,
Channel = require('./channels');
/**
* Wraps a node style callback in a timeout timer
* @param {function} callback
* @param {Integer} delay
*/
function callbackWithTimeout(callback, delay) {
// light the fuse
var timeoutId = setTimeout(function() {
timedCallback('timeout', null);
}, delay);
var timedCallback = function(err, result) {
// cut the red wire
clearTimeout(timeoutId);
callback(err, result);
};
return timedCallback;
}
/**
* Creates a 'complete' callback function for completed work
* @param {WorkQueueRx} queue
* @param {WorkItem) workItem
* @param {function} scheduleNextWorkFn
* @return {function} completed work callback
*/
function completeCallbackFn(queue, workItemJSON, scheduleNextWorkFn){
return function(error, completedWork) {
if (workItemJSON.status == 'pending') {
WorkItem.markCompleted(workItemJSON, error, completedWork);
queue.markWorkCompleted(workItemJSON, scheduleNextWorkFn);
}
}
}
var Qrx = module.exports = function() {
this.initialize.apply(this, arguments);
}
Qrx.prototype.initialize = function (options) {
options = options || {};
_.defaults(options, {qname: uuid.v1(), // default unique q name
redisOptions: null, // local host default
workTimeout: Number.MAX_VALUE,
workThrottle: 1,
completedThrottle: 1});
_.extend(this, options);
this.completedInFlight = 0;
// two clients are required to avoid blocking conditions
this.client = newRedisClient(options.redisOptions);
// every q get's a unique id
this.clientId = uuid.v1();
this.pending = new WorkQueue(ns(this.qname, 'pending'), this.redisOptions);
this.workingSet = new WorkSet(ns(this.qname, 'working'), this.redisOptions);
// all work enqueued by the client, is return to this client
this.completedQueueName = ns(this.qname, 'completed') + this.clientId;
// global redis count of workers on this queue
this.workerCount = ns(this.qname, 'worker-count');
this.STOP_MESSAGE = "QRX_STOP_QUEUE"
this.queueStopped = false;
this.statsChannel = new Channel({name:this.qname, redisOptions:options.redisOptions});
// setup stat counters
this.stats = {
pendingWorkCount:0,
completedWorkCount:0,
avgWorkTime:0,
completedWorkBytes:0,
errorCount:0,
lastError:null,
workerId:this.clientId,
workerHost:os.hostname()
};
// start the stats heartbeat
var self = this;
this.statsHeartbeat = Rx.Observable.Interval(1000).Subscribe(function(tick) {
self.statsChannel.send(self.stats);
});
}
/**
* Adds work to queue for workers
* @param {Object} work
* @param {function} callback
*/
Qrx.prototype.enqueue = function(work, callback) {
// push onto the queue
// work contains by name, where completed work should
var defaultCallback = function(err, workItem){
if (err){
throw err;
}
};
callback = callback || defaultCallback;
this.stats.pendingWorkCount++;
this.pending.enqueue(new WorkItem({work: work,
completedWorkQueue: this.completedQueueName}),
callback);
};
/**
* Halts all subscribed queue workers and sends completed to subscribers
* of completed work
*/
Qrx.prototype.stop = function() {
var self = this;
// stop the client side
// heart beat will stop due to completed flag
this.queueStopped = true;
this.client.get(this.workerCount, function(err, count){
for (var i = 0; i < count; i++){
// put as many stop messages as needed to term workers
self.pending.enqueue({work:this.STOP_MESSAGE}, function(err, workItem){});
}
});
}
/*
* Returns the observable of completed work items
* from the clients completed queue, signaled on the completed channel
* @return {Rx.Observable}
*/
Qrx.prototype.completedObservable = function() {
var self = this;
var rc = newRedisClient(this.redisOptions);
var pending = new WorkQueue(this.completedQueueName, this.redisOptions);
return Rx.Observable.Create(function(obs) {
function getNextCompleted() {
while(self.completedInFlight < self.completedThrottle){
self.completedInFlight++
pending.blockingDequeue(rc, 0, function(err, completedWorkItem){
if (!err){
obs.OnNext(completedWorkItem);
self.completedInFlight--;
if (!self.queueStopped){
Rx.Observable.Start(getNextCompleted);
} else {
obs.OnCompleted();
}
} else {
obs.OnError(err);
}
});
}
}
Rx.Observable.Start(getNextCompleted);
return function(){rc.quit();};
});
};
/////////////////
// Worker Side //
/////////////////
/**
* Returns an observable stream of co-operative work
* with every Rx subscription creating a new reactive work scream
* @return {Rx.Observable} stream of work to do
*/
Qrx.prototype.workObservable = function() {
// immediately 'complete' any workers who subscribe
// to a stopped queue
if (this.queueStopped) {
return Rx.Observable.Empty();
}
var self = this;
var rc = newRedisClient(this.redisOptions);
rc.incr(this.workerCount);
// each work subscription keeps track of how much work
// is in flight
var workInFlight = 0;
return Rx.Observable.Create(function(obs) {
function getNextWork(){
// this will set n callbacks where n == throttle
while (workInFlight < self.workThrottle){
workInFlight++;
self.pending.blockingDequeue(rc, 0, function(err, workItem) {
if (workItem.work != this.STOP_MESSAGE) {
// add it to the working set
self.workingSet.addToSet(workItem, function(err, result) {
if (!err){
// dispatch to the worker
// workers get only the information they need
workItem.startTime = Date.now();
var workObj = {work: workItem.work,
callback:callbackWithTimeout(completeCallbackFn(self,
workItem,
function() {
workInFlight--;
Rx.Observable.Start(getNextWork);}
), self.workTimeout)};
// catch any work exception
try {
obs.OnNext(workObj);
} catch (exn){
// set the exception and mark the work complete
workObj.callback(exn, null);
// Rx next tick self schedule
Rx.Observable.Start(getNextWork);
}
} else {
// fail the worker
obs.OnError(err);
}
});
} else {
// signal worker complete
obs.OnCompleted();
}
});
}
}
// initial kick-off
Rx.Observable.Start(getNextWork);
return function(){rc.quit();};
});
}
Qrx.prototype.updateCounters = function(completedWork, byteCount) {
// update worker stats
this.stats.pendingWorkCount--;
this.stats.completedWorkCount++
this.stats.avgWorkTime =
(completedWork.endTime - completedWork.startTime) / this.stats.completedWorkCount;
if (completedWork.error) {
this.stats.errorCount++;
this.stats.lastError = completedWork.error;
} else {
this.stats.completedWorkBytes += byteCount
}
}
Qrx.prototype.markWorkCompleted = function(completedWorkItem,
scheduleNextWorkFn) {
// TODO: Set a redis transaction
var self = this;
this.workingSet.removeFromSet(completedWorkItem.id, function(err, removedCount) {
// ingnore subsequent repeated completion calls
if (!err && (removedCount > 0)){
// abstraction breach
// deliever the complted work item
var completedWorkJSON = JSON.stringify(completedWorkItem);
self.updateCounters(completedWorkItem, completedWorkJSON.length);
self.client.lpush(completedWorkItem.completedWorkQueue,
completedWorkJSON,
function(err, length) {
if (!err) {
scheduleNextWorkFn();
}
});
} else {
// redis err throw
if (!err){
//console.warn('warn: Multiple calls to mark completed');
}
}
});
};
Qrx.prototype.setWorkThrottle = function(t) {
this.workThrottle = t;
}
/**
* Resets the stats of the work queue
*/
Qrx.prototype.clear = function(){
this.pending.empty();
}
Qrx.prototype.statsObservable = function(period) {
// returns the rolled-up stats for the Qrx cluster
period = period || 3000;
// dictionary of cluster stats updates by workingId
var qrxStats = {};
var updateCount = 0;
// subscribe to the stats channel for every worker
var statsSubs = this.statsChannel.subscribe(function(statsUpdate){
function updateSummary(running, nextUpdate) {
updateCount++;
running.totalPendingWorkCount += nextUpdate.pendingWorkCount;
running.totalCompletedWorkCount += nextUpdate.completedWorkCount;
running.totalErrorCount += nextUpdate.errorCount;
running.totalErrorRate = running.totalErrorCount/running.totalCompletedWorkCount;
running.totalCompletedWorkBytes += nextUpdate.completedWorkBytes;
running.totalAvgWorkTime = running.totalAvgWorkTime + nextUpdate.avgWorkTime/updateCount;
}
qrxStats[statsUpdate.workerId] = statsUpdate;
qrxStats['summary'] = {totalPendingWorkCount: 0,
totalCompletedWorkCount: 0,
totalErrorCount: 0,
totalErrorRate: 0,
totalAvgWorkTime: 0,
totalCompletedWorkBytes: 0} || qrxStats['summary'];
updateSummary(qrxStats['summary'], statsUpdate);
});
// summarize all values for cluster
return Rx.Observable.Create(function(obs){
var statsHeartbeat = Rx.Observable.Interval(period).Subscribe(function(beat) {
obs.OnNext(qrxStats);
return function() {statsSubs.Dispose(); statsHeartbeat.Dispose();}
});
});
}