[GitHub] [kafka] gharris1727 commented on pull request #13165: KAFKA-14654: Connector classes should statically initialize with plugin classloader

["gharris1727 (via GitHub)" <gi...@apache.org>]

gharris1727 commented on PR #13165:
URL: https://github.com/apache/kafka/pull/13165#issuecomment-1560240995

   > I'm wondering if we can get better coverage for DelegatingClassLoader::scanPluginPath. Right now we verify in PluginsTest::newConnectorShouldInstantiateWithPluginClassLoader that if we've initialized a Plugins instance, and we invoke Plugins::newConnector, the constructor for that connector is called with the correct context classloader. But it seems like this isn't very powerful since, if the constructor is invoked multiple times, the last invocation's classloader will be recorded--so in this case, we're really testing Plugins::newConnector and not the instantiations that are performed during plugin discovery.
   
   Yeah this is a blind-spot in the existing tests. The "sampling" paradigm requires an instance of the object in order to perform the assertions, and the scanPluginPath implementation throws away the objects that it creates. The test does not and cannot assert that the TCCL is correct for the first version() call, for example.
   
   In this specific case the regression test is still sensitive, because the static initialization happens when the plugin constructor is first called (not when the Class<?> object is created). This means that we can assert the TCCL used in the first constructor via the staticClassloader inspection.
   
   I think the alternative would involve mocking/spying part of the scanPluginPath (such as versionFor), or keeping track of instantiated objects in SamplingTestPlugins, both of which seem messy, and would make this harder to refactor in the near future. Do you think this should be addressed now, or can it wait until the plugin path scanning refactor is landed?


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