Added Logging for SubscriberNotififierMiddleware

[ruudk]

Currently, there is no way to know which Subscribers have been called.

This pull request adds support for logging inside a copy of NotifiesMessageSubscribersMiddleware.

To enable this you'll need to add the following to event_bus_logging.yml:

    simple_bus.event_bus.notifies_message_subscribers_middleware:
        class: SimpleBus\Message\Logging\LoggingNotifiesMessageSubscribersMiddleware
        public: false
        arguments:
            - @simple_bus.event_bus.event_subscribers_resolver
            - @logger
            - %simple_bus.event_bus.logging.level%
        tags:
            - { name: event_bus_middleware, priority: -1000 }

[ruudk]

@matthiasnoback Is this the right way to do this?

[matthiasnoback]

@ruudk Thanks for suggesting this addition - it's a really useful one. Instead of solving this with an extra class, I would have liked to be able to solve it with decoration. However, that's impossible, since you need to add log messages before and after call_user_func().

Since psr/log is a required dependency of this package already, I'd suggest simply adding the logging functionality to the existing NotifiesMessageSubscribersMiddleware. Just allow null for the extra $logger argument and when null is provided, replace it with an instance of NullLogger.

In the SymfonyBridge we can make the extra argument configurable.

[ruudk]

I'll create a PR soon :)

[ruudk]

I'm wondering. Why is there no subscriber_bus? That would allow me to easily log it using a Middleware. It could also use the WrapsMessageHandlingInTransaction so the handling of a Subscriber works the same as that of a Command.

[matthiasnoback]

If an event subscriber requires a database transaction, then it's intending to make a persistent change, which is exactly what commands are used for ;) So in that case, just create a new command, and let the command bus handle it.

[ruudk]

@matthiasnoback I changed it a bit so that call_user_func gets called via a proteted method. I think this is cleaner and better. What do you think?

[ruudk]

It looks like this now:

[matthiasnoback]

Ah, well, maybe I wasn't clear: my idea was not to extend the existing class, but just to add logging to the existing NotifiesMessageSubscribersMiddleware class. You should make the last two constructor arguments optional (level should be LogLevel::DEBUG by default), and when no logger was provided, just create an instance of NullLogger inside the constructor.

[ruudk]

@matthiasnoback Voila! Ready? :)

[matthiasnoback]

Nice work!

[matthiasnoback]

I merged the code, but I know realize that there should be something in the docs about this as well - could you please add a note about it? Would you also like to work on a PR for the bundle?

[ruudk]

I'll take care of it!