Christopher Tubbs created ACCUMULO-4642:
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Summary: Remove SystemConfiguration.getInstance()
Key: ACCUMULO-4642
URL: https://issues.apache.org/jira/browse/ACCUMULO-4642
Project: Accumulo
Issue Type: Improvement
Reporter: Christopher Tubbs
Assignee: Christopher Tubbs
Priority: Minor
In working with ACCUMULO-4050, I've realized that we need to do some internal
refactoring to get better control over HdfsZooInstance. This would enable
better testing (because we could inject a mock Instance more easily, and in
more places). It would also allow us to reuse objects without storing them
statically in the JVM.
Fully realizing this would involve a lot of work, moving the static state to a
single "context" object constructed on server startup, and shared (in part or
in whole) as needed throughout the runtime server code.
However, I think we can get there incrementally, by starting with eliminating
the SystemConfiguration.getInstance() method. This causes
SystemConfigurationFactory to also have a getInstance() method, and that means
that SystemConfigurationFactory is being used like the context object I
describe, but redundantly instead of AccumuloServerContext, or a
server-specific subclass.
Eliminating SystemConfiguration.getInstance() might involve an intermediate
step of adding Instance parameters to many methods which currently take only a
SystemConfigurationFactory, because components will not be able to get the
Instance from that configuration factory any longer. However, even this
intermediate step will be progress towards moving to a single shared context
object, which provides access to both the Instance and the configuration
factory.
If we can move directly to the context object, that would probably be better,
but it would involve a lot more changes, in particular to the way the server
code is initialized. Then again, those changes might be good to prioritize
anyway, because all our server components seem to initialize differently, and
it would be nice to rewrite their bootstrap code to follow the same pattern.
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