Raghu Angadi created PIG-2815:
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Summary: class loader management in PigContext
Key: PIG-2815
URL: https://issues.apache.org/jira/browse/PIG-2815
Project: Pig
Issue Type: Bug
Components: impl
Affects Versions: 0.9.0
Reporter: Raghu Angadi
Fix For: 0.11
The way {{PigContext.classloader}} and resolveClassName() are managed can lead
to strange class loading issues, especially when not all {{register}}
statements are at the top (example in the first comment).
Two factors contribute to this: sometimes only one of them and sometimes
together:
# a new classloader (CL) is created after registering each jar.
** but the new jar's parent is the root CL rather than previous CL,
effectively throwing previous CL away.
# resolveClassName() caches classes based on just the name
** A class is not defined by name alone. Classes loaded by two different
unrelated CLs are different objects even if both extract the class from same
physical jar file.
** because of (1), the cached class is not necessarily same as the class
that would be loaded based on 'current' CL
having different class objects for same class have many subtle side effects.
e.g. there would be two instances of static variables.
I think both should be fixed.. thought fixing one of them might be good enough
in many cases. I will add a patch.
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