# Flink YARN tests

`flink-yarn-test` collects test cases which are deployed to a local Apache Hadoop YARN cluster. 
There are several things to consider when running these tests locally:

* `YarnTestBase` spins up a `MiniYARNCluster`. This cluster spawns processes outside of the IDE's JVM 
  to run the workers on. `JAVA_HOME` needs to be set to make this work.
* The Flink cluster within each test is deployed using the `flink-dist` binaries. Any changes made 
  to the code will only take effect after rebuilding the `flink-dist` module.
* Each `YARN*ITCase` will have a local working directory for resources like logs to be stored. These 
  working directories are located in `flink-yarn-tests/target/` (see 
  `find flink-yarn-tests/target -name "*.err" -or -name "*.out"` for the test's output).
* There is a known problem causing test instabilities due to our usage of Hadoop 2.8.3 executing the 
  tests. This is caused by a bug [YARN-7007](https://issues.apache.org/jira/browse/YARN-7007) that 
  got fixed in [Hadoop 2.8.6](https://issues.apache.org/jira/projects/YARN/versions/12344056). See 
  [FLINK-15534](https://issues.apache.org/jira/browse/FLINK-15534) for further details on the 
  related discussion.