Asynchronous Processing or Message Queues in PHP (Cakephp)

Asynchronous processing or message queues in PHP (CakePHP)

I've had excellent results with BeanstalkD and a back-end written in PHP to retrieve jobs and then act on them. I wrapped the actual job-running in a bash-script to keep running if even if it exited (unless I do a 'exit(UNIQNUM);', when the script checks it and will actually exit). In that way, the restarted PHP script clears down any memory that may have been used, and can start afresh every 25/50/100 jobs it runs.

A couple of the advantages of using it is that you can set priorities and delays into a BeanstalkD job - "run this at a lower priority, but don't start for 10 seconds". I've also queued a number of jobs up at the some time (run this now, in 5 seconds and again after 30 secs).

With the appropriate network configuration (and running it on an accessible IP address to the rest of your network), you can also run a beanstalkd deamon on one server, and have it polled from a number of other machines, so if there are a large number of tasks being generated, the work can be split off between servers. If a particular set of tasks needs to be run on a particular machine, I've created a 'tube' which is that machine's hostname, which should be unique within our cluster, if not globally (useful for file uploads). I found it worked perfectly for image resizing, often returning the finished smaller images to the file system before the webpage itself that would refer to it would refer to the URL it would be arriving at.

I'm actually about to start writing a series of articles on this very subject for my blog (including some techniques for code that I've already pushed several million live requests through) - My URL is linked from my user profile here, on Stackoverflow.

(I've written a series of articles on the subject of Beanstalkd and queuing of jobs)

Asynchronous requestAction

Is there any reason why you wouldn't use a shell for this?
Please take a look at: CakePHP Shells

"Deferred Execution" is probably what you are after here, basically you want to send one command not have the user waiting around for it? If so then you can use a Message Queue to handle this pretty easily.

We use CakeResque and Redis to send 1000's of emails and perform other API calls

CakeResque - Deferred Processing for CakePHP

There are other message queues that are available but this is really simple to get working and probably wont need much of a change to your code.

Executing a long action

In the event of long-running server-side actions in a web application like this, a good approach is to separate the queueing of the actions (which should be handled by the web application) from the running of the actions (which should be handled by a different server-side application).

In this case it could be as simple as the web application inserting a record into a database table which indicates that User X has requested Action Y to be processed at Time Z. A back-end process (always-running daemon, scheduled script, whatever you prefer) would be constantly polling that database table to look for new entries. ("New" might be denoted by something like an "IsComplete" column in that table.) It could poll every minute, every few minutes, every hour... whatever is a comfortable balance between server performance and the responsiveness of an action beginning when it's requested.

Once the action is complete, the server-side application that ran the action would mark it as complete in the database and would store the results wherever you need them to be stored. (Another database table or set of tables? A file? etc.) The web application can check for these results whenever you need it to (such as on each page load, maybe there could be some sort of "current status" of queued actions on each page so the user can see when it's ready).

The reason for all of this is simply to keep the user-facing web application responsive. Even if you do things like increase timeouts, users' browsers may still give up. Or the users themselves may give up after staring at a blank page and a spinning cursor for too long. The user interface should always respond back to the user quickly.

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