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https://issues.apache.org/jira/browse/HADOOP-13716?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15592732#comment-15592732
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Anu Engineer commented on HADOOP-13716:
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+1, I will commit this shortly to trunk, branch-2 and branch-2.8.
A small nit :
In {{LambdaTestUtils.java:84}} a comment seems to be wrong.
{noformat}
* Example: Wait 30s for a condition to be met, with a sleep of 30s
{noformat}
I will fix this while committing to "sleep of 500ms" between each probe
> Add LambdaTestUtils class for tests; fix eventual consistency problem in
> contract test setup
> --------------------------------------------------------------------------------------------
>
> 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
> Assignee: Steve Loughran
> Attachments: HADOOP-13716-001.patch, HADOOP-13716-002.patch,
> HADOOP-13716-003.patch, HADOOP-13716-005.patch, HADOOP-13716-006.patch,
> HADOOP-13716-branch-2-004.patch
>
>
> 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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