task-queue-worker

A powerful tool for background processing of tasks that are run by making standard http requests.

The task-queue-worker is a NodeJS worker that monitors one or more message queues for tasks to run via http. Just like Google App Engine Task queues

Concept

The task-queue-worker should be run as a process on one or more machines and monitors a set of predefined message queues. It expects JSON messages in a special format. At a minimum such message must contain an url key. The task-queue-worker then requests the URL and upon receiving a 2xx status code removes the message from the queue.

Please have a look at the message format for more details.

Client

Example

var TqwClient = require( "task-queue-worker" ).Client;
var client = new TqwClient( queue: "myqueuename" );
client.send( { "url": "http://some.domain.com/job/to/run" }, function( err ){
	// ...
});

TODO

Message format

Minimal working message:

{
	"url": "http://some.domain.com/job/to/run"
}

This will result in a GET request to the above URL.
If the status code of the reply is in the 2xx range the message will be removed from the queue.
If the status code is not in the 2xx range the message will not be deleted and should pop up again after its invisibility timer runs out.

The following parameters let you control message handling of the task-queue-worker:

• url (string) Required Must be a valid URL.
• method (string) (Default: GET) Possible values: GET, DELETE, PUT, POST
• body (string) The body to send when the value of method is POST. If the value of body can be parsed as JSON the request will be sent with application/json as content-type. Otherwise with appliction/x-www-form-urlencoded. If body is used and no method has been defined automatically POST would be used.
• delay (number) (Default: 3) Defines the initial delay. If set to 0 the message will be processed imediately. Otherwise ist will wail for n seconds until it will be processed.
• retrylimit (number) (Default: 3) Setting this to -1 disables the retrylimit, leaving the message in the queue forever if it does not process successfully.
• retrydelay (number or array) If a number is supplied the visibility timeout of that message will be set to retrydelay seconds after an unsuccessful request. If an array is supplied (e.g. [120,240,3600]) the retry delay will increase gradually. See also the changeMessageVisibility method of rsmq
• maxts (number) (Default: -1) A unix timestamp in seconds after which the message should not be processed anymore and will be deleted and handled as an error. A value of -1 disabled the maxts check.
• timeout (number) (Default: 10) Time in seconds to wait for a reply for this request. Must be between 1 and 3600.
• failqueue (string) The name of the queue where the message is moved after it did not process successfully. Either by reaching the retrylimit or the maxts value. If no failqueue is supplied the message will just be deleted.
• maxredirects (number) (Default: 10) The maximum number of redirects to follow. If 0 is set it will not follow HTTP 3xx responses and judge them as error.

Defaults: If the task-queue-worker is used as module you the defaults, expect url and body can be within the options

Running task-queue-worker as process

The task-queue-worker will be started from the command line.

node worker.js -k QueuesToMonitor

Parameters:

• -q, --queues: (string) Comma separated list of queues to monitor (e.g. -q alerts,jobs,uptimecheck)
• -k, -k???: (string) Name of Redis SET that contains all queues to monitor (e.g. -k tqm:QueuesToMonitor). By using the -k parameter you can make sure that multiple task-queue-workers are using the same setting.
• -t, --taskcount (number) The amount of concurrent tasks the task-queue-worker will handle. (Default: 5)

Note: If -q or -k contains no queues or are not supplied the tasks-queue-worker will exit.

eventually as taskqueuewoker -k QueuesToMonitor if installed globally.

Using task-queue-worker as module

TODO

Example

var TQW = require( "task-queue-worker" )
var worker = new TQW.Worker()
worker.on( "error", function( err ){} )
worker.on( "success", function( response ){} )

Events

• error

Workflow

TODO Diagram

1. Request a message until the number of tasks is reached.
2. If no message is received gradually increase the requests for the next message to 1,2,3,5 secconds and go to 1.
3. Process the message with the timeout. If the message returns a 2xx status code delete the message. And go to 1.
4. If the message cannot be requeued (see retrylimit and maxts parameters) delete it (and add it to the failqueue if supplied). Go to 1.
5. If retrydelay is supplied modify the Message visibility (changeMessageVisibility)
6. Go to 1.

Supported queues

Currently only rsmq is supported.

Want to implement another message queue? Please send me a pull request and include some docs and tests.

Release History

|Version|Date|Description| |:--:|:--:|:--| |v0.3.3|2014-10-13|Fixed configuration if used as internal module| |v0.3.1|2014-10-13|Dispose volatile object| |v0.3.0|2014-10-13|Added message option delay + bugfixes and validations| |v0.2.0|2014-09-22|Updated module to use the new basic class.|

The MIT License (MIT)

Copyright © 2013 Patrick Liess, http://www.tcs.de

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the “Software”), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

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