Switching databases in Symfony upon application events

We’re big fans of the PHP Symfony2 framework and Doctrine2 ORM but a recent project involved a REST API for a multi-client system where each client wanted their database fully separated from each other, but we only knew which client database to connect to once a user had logged in (so no easy config.yml and parameters.yml configuration).

The login gets handled via Java Web Tokens using the excellent Lexik JWT Authentication bundle. So the first call to /auth/login_check with a username and password retrieves a token along with a id of the client (added using the onAuthenticationSuccessResponse listener documented here. Subsequent requests supply a HTTP Authorization header with the token and a custom “client” header specifying the id of the client (also documented in the above link).

This gave us stateless authentication for our API, but we still had to actually switch the Doctrine dbal connection to point to the right database. The solution (inspired by this Stack Overflow question) involved an onKernelRequest() event listener to switch the database from a base database (holds login / authentication data and is referenced in the default connection settings – or whichever connection you’re overriding – of your config.yml file) to the desired database and update the tokenStorage object accordingly. As a tip though, it’s best to keep the base and individual databases schematically identical as possible for reasons explained later.

First create the Event Listener:

Then add this to the services.yml file:

Then add the client databases to the end of the parameters-dist.yml file:

The security.yml file looks something like:

Conclusion:
This solution works fairly well in providing multi-database connectivity based on a site event (in this case user login) with the occasional bit of peering underneath’s Symfony’s hood. As mentioned above, keeping the base database schematically identical (i.e. same table structure, differing data) to your individual databases is very highly advisable. Some Symfony logic occurs before the onKernalRequest event gets fired (looking at your forms) so functionality limitations can otherwise occur there. Also parsers like the Nelmio Api Documentation bundle typically build pre-authentication (so whilst the base database is still selected).

Doctrine Migrations can also be enabled with a little tinkering (I may write a new post on how to do this if there is demand) but again, it helps if the schemas are identical (although isn’t vital).

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