[jira] [Created] (BEAM-308) PipelineOptions throws when using package-private PipelineOptions interfaces from multiple packages

["Scott Wegner (JIRA)" <ji...@apache.org>]

Scott Wegner created BEAM-308:
---------------------------------

             Summary: PipelineOptions throws when using package-private PipelineOptions interfaces from multiple packages
                 Key: BEAM-308
                 URL: https://issues.apache.org/jira/browse/BEAM-308
             Project: Beam
          Issue Type: Bug
          Components: sdk-java-core
            Reporter: Scott Wegner
            Assignee: Scott Wegner
            Priority: Minor


If a PipelineOptions instance is used as multiple PipelineOptions package-private interfaces from different packages, {{PipelineOptions.as}} will throw an exception:

{quote}
java.lang.IllegalArgumentException: non-public interfaces from different packages

	at java.lang.reflect.Proxy$ProxyClassFactory.apply(Proxy.java:652)
	at java.lang.reflect.Proxy$ProxyClassFactory.apply(Proxy.java:592)
	at java.lang.reflect.WeakCache$Factory.get(WeakCache.java:244)
	at java.lang.reflect.WeakCache.get(WeakCache.java:141)
	at java.lang.reflect.Proxy.getProxyClass0(Proxy.java:455)
	at java.lang.reflect.Proxy.getProxyClass(Proxy.java:405)
	at org.apache.beam.sdk.options.PipelineOptionsFactory.validateWellFormed(PipelineOptionsFactory.java:620)
	at org.apache.beam.sdk.options.ProxyInvocationHandler.as(ProxyInvocationHandler.java:209)
	at org.apache.beam.sdk.options.ProxyInvocationHandler.invoke(ProxyInvocationHandler.java:135)
	at com.sun.proxy.$Proxy6.as(Unknown Source)
{quote}

This fails because ProxyInvocationHandler attempts to create a Java Proxy object implementing the full set of interfaces, which has the [restriction|https://docs.oracle.com/javase/7/docs/api/java/lang/reflect/Proxy.html#getProxyClass(java.lang.ClassLoader,%20java.lang.Class...)]: 

bq. All non-public interfaces must be in the same package; otherwise, it would not be possible for the proxy class to implement all of the interfaces, regardless of what package it is defined in.

This can be triggered in a couple edge-case scenarios:

# {{PipelineOptions.as}} is called on the same PipelineOptions instance with multiple package-private interfaces.
# {{PipelineOptionsFactory.register}} is called with a package-private interface, and then {{PipelineOptions.as}} is called with a different package-private instance.

We hit the second scenario in [DataflowSDK unit tests|https://github.com/GoogleCloudPlatform/DataflowJavaSDK/pull/286#issuecomment-221438063]. It's hard to trigger, but possible.

----

I propose we make the behavior for package-private options explicit:

# Give a better exception message if we hit this issue in {{PipelineOptions.as}} listing the non-public interfaces and what packages they're in.
# Explicitly reject non-public interfaces from {{PipelineOptionsFactory.register}}, since this state is global and is easier to cause issues.



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