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From "Steve Loughran (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HADOOP-13716) Add LambdaTestUtils class for tests; fix eventual consistency problem in contract test setup
Date Fri, 14 Oct 2016 08:49:20 GMT

     [ https://issues.apache.org/jira/browse/HADOOP-13716?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Steve Loughran updated HADOOP-13716:
------------------------------------
    Attachment: HADOOP-13716-branch-2-004.patch

patch 004 for branch-2; stripped out the lambdas and ran the tests. Interesting that I had
to make a local variable final...clearly java 8 is subtly different here
{code}
hadoop-common/src/test/java/org/apache/hadoop/fs/contract/AbstractContractRootDirectoryTest.java:[99,55]
local variable root is accessed from within inner class; needs to be declared final
{code}

Anu, thanks for +1-ing the patch. I want to do the checkstyle warnings on this before I apply
it. This patch here doesn't do that: it's just patch 003 with everything compiling/running
on branch-2

> 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-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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