PHP Application Architecture on Heroku

Question

I have a PHP app on Heroku, the app does lots of communication with external APIs, which in turn trigger jobs on the database, the results are then displayed in a Facebook app...

Currently I have 2 worker processes and a web process. The web process triggers the workers and monitors database flags to know when each worker job is complete...I know...this setup isn't great, ideally I'd like to get notified in my web process when each worker process is finished, but this doesn't seem to be possible...

Is there a better way to approach this in Heroku using PHP?

Maybe a PHP app on Heroku isn't the best solution, but I've written lots of PHP that I'd rather not re-write....

Thanks in advance...

Answer 1

I can think of two relatively straightforward things you can do without ditching PHP (though I have to mention that PHP doesn't have much to recommend it, and you would likely be better off with Python/Django, Python/Flask or Ruby/Rails):

One is that you can switch to Redis for managing your workers instead of using your database. The advantage to this is that Redis has a pub/sub system where you can subscribe to signals while you hold a connection open. This means that if a connection is open, for instance from a web process, you will be notified of a change immediately without having to poll.

Two is that you can switch to using ajax so that you don't block the loading of your page while you're waiting. Load your page immediately and then use javascript to hit a separate PHP page to periodically check for updates on the status of your job, and then use javascript to render the results on the page in place when the results are available.

Even better, use ajax long polling. Render your page immediately and then use javascript to send a request back. Then when your php page receives the second request, register a subscription with Redis and then also manually check for updates (if you're not using Redis, just check for updates). If there are no updates, then just wait until the subscription receives a message, or wait for 30 seconds, whichever. (To be honest, I've never done Redis subscriptions in PHP so I'm not sure how implement that -- if you can't do it easily then just poll every couple of seconds instead.) If the 30 second timer expires, return json that says there are no results and have the javascript retry immediately. If you do receive results within that time, return the results and have the javascript render them.