GitHub user original-brownbear opened a pull request:
https://github.com/apache/kafka/pull/2761
KAFKA-4692: Make testNo thread safe
https://issues.apache.org/jira/browse/KAFKA-4692 should be resolved by this.
The problem here (or at least one problem, causing trouble) appears to have
been that the `testNo` field is not thread-safe the way it is used here
(`volatile` doesn't help anything really) to generate a unique test number (for
creating non-conflicting topic names).
If two instances of this class are set up inside the same fork and
`testNo++;` is run in one just as the other runs e.g.
```java
private void createTopics() throws InterruptedException {
streamOneInput = "stream-one-" + testNo;
outputTopic = "output-" + testNo;
CLUSTER.createTopic(streamOneInput, 3, 1);
CLUSTER.createTopic(outputTopic);
}
```
then both will have the same value for the topic names while sharing the
same static `CLUSTER` field too.
I fixed this by simply making the actually used `testNo` an instance
variable that is derived from an increasing static counter for each test in an
atomic way. I think this should resolve any naming collisions here.
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/original-brownbear/kafka KAFKA-4692
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/kafka/pull/2761.patch
To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:
This closes #2761
----
commit 4d2468318897f37b00dab0ad63c36ae3004a9165
Author: Armin Braun <m...@obrown.io>
Date: 2017-03-29T19:27:59Z
KAFKA-4692: Make testNo thread safe
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