Play & Akka and blocking threads for database access

Question

I want to make a call to a database which has lots of data and it might take a while to return.

I plan to do that work inside a call to Akka.future(f) and use an Async{} to render the response when the work is done.

Does it make sense to do that, or should I just do the long database call in the controller, without sending the work to Akka?

Or is there a way to do non blocking database access?

Answer 1

If you're forced to use a blocking driver for your database (if for some reason the async driver for MySQL doesn't work out) consider setting up an Actor pool (using routing) with a PinnedDispatcher.

The PinnedDispatcher provides a thread per actor and, by setting up the router, will give you the ability to adjust the number of threads strictly responsible for handling the database calls. Easy scaling. Also, by using Actors you can structure the messages between actors (e.g. a message having the results of the database call) a little easier.

Answer 2

You can use Akka.future(f) and provide your own Akka configuration file to get more threads to process your database accesses. Look at this config file for example.

But you pointed it out: the real problem is in using a database driver that blocks. I don't know which DB you are using, but it's worth to take a look to MongoDB with ReactiveMongo for example. With ReactiveMongo all MongoDB operations are perfectly non-blocking and asynchronous. There is a good introduction here. Moreover, it deals very well with Play Framework (check the ReactiveMongo Play Plugin).

EDIT: You can also check "Configuring Playframework's internal Akka system" to tune the worker threads number.