[GitHub] [pulsar] jerrypeng edited a comment on pull request #10878: Remove the unwanted dependencies in the pulsar function's instance jar and make SchemaInfo an interface

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jerrypeng edited a comment on pull request #10878:
URL: https://github.com/apache/pulsar/pull/10878#issuecomment-859661172


   @eolivelli there are three classloaders used:
   
   1. rootClassLoader - contains only the API interfaces for Pulsar Client API, Functions, and IO
   
   2. instanceClassLoader - is a child of rootClassLoader. Contains API interfaces + all the implementations and framework code e.g. pulsar-client-original, pulsar-function-instance, etc
   
   3. functionClassLoader - is a child of the rootClassLoader.  Contains API interfaces + user submitted classes, i.e. classes in the JAR or NAR the use submittied.
   
   The rootClassLoader can be viewed as loading the classes that contain the interfaces in which the function instance / framework code interacts with the user submitted submitted classes that implement the Pulsar Function / IO interfaces.
   
   When the JavaInstanceRunnable thread is running code that is framework code, i.e. Pulsar Function Instance code, the thread context loader needs to be set to instanceClassLoader.  When the JavaInstanceRunnable thread is running code that is user submitted, e.g. when source.open(), sink.open, function.process(), etc, is called, the thread context loader needs to be set to functionClassLoader.


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