Module observability listener performance issue on publishEvent

[Groax256]

In org.springframework.modulith.observability.ModuleEventListener#onApplicationEvent search for module by type uses simpleName which means it cannot short-circuit condition in org.springframework.modulith.core.ApplicationModule#contains(java.lang.String) with package name. The search is implemented on streams so it does not scale well with increasing number of classes. As a result it has to scan hundreds of classes with ArchUnit on each publishEvent call.

There are 21 modules and 1180 classes in my project and on publishEvent there is significant perfomance hit from ModuleEventListener.

I use Modulith 1.3.1 but based on code source the issue will be the same in 1.4.0

[odrotbohm]

I don't recall why we are looking up the module by the String type name. The only thing I can imagine is that at the time, the methods taking JavaClass and Class instances were introduced.

Unfortunately, the lower layers all immediately flip to the by-name code path, most likely to end up at a canonical place. We can certainly fix that, but ultimately, an initial lookup will have to traverse all modules and all types contained in them. I am also hesitant to build up caches on the ApplicationModules level as that might grow unboundedly.

That said, a local cache in ModuleEntityListener might be a good compromise, as usually the number of event types is much smaller than all application types combined. Plus, aside from the application startup and shutdown, they're very likely to be application (module) types in the first place.

WDYT?

[odrotbohm]

Feel free to give the 1.4 snapshots a try. If this improves the situation, I can backport this into 1.3.