Steve Loughran created HADOOP-13716:
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Summary: Add an Eventually class to await eventual completion of
lambda expressions
Key: HADOOP-13716
URL: https://issues.apache.org/jira/browse/HADOOP-13716
Project: Hadoop Common
Issue Type: New Feature
Components: test
Affects Versions: 2.8.0
Reporter: Steve Loughran
To make our tests robust against timing problems and eventual consistent
stores, we need to do more spin & wait for state.
We have some code in {{GenericTestUtils.waitFor}} to await a condition being
met, but the predicate it calls doesn't throw exceptions, there's no way for a
probe to throw an exception, and all you get is the eventual "timed out"
message.
We can do better, and in closure-ready languages (scala & scalatest, groovy and
some slider code) we've examples to follow. Some of that work has been
reimplemented slightly in {{S3ATestUtils.eventually}}
I propose adding a class in the test tree, {{Eventually}} to be a
successor/replacement for these.
# has an eventually/waitfor operation taking a predicate that throws an
exception
# has an "evaluate" exception which tries to evaluate an answer until the
operation stops raising an exception. (again, from scalatest)
# plugin backoff strategies (from Scalatest; lets you do exponential as well as
linear)
# option of adding a special handler to generate the failure exception (e.g.
run more detailed diagnostics for the exception text, etc).
# be Java 8 lambda expression friendly
# be testable and tested itself.
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