Hi Lars, Do you have any examples for the methods that you described for Spark batch and Streaming?
Thanks! On Wed, Mar 30, 2016 at 2:41 AM, Lars Albertsson <la...@mapflat.com> wrote: > Thanks! > > It is on my backlog to write a couple of blog posts on the topic, and > eventually some example code, but I am currently busy with clients. > > Thanks for the pointer to Eventually - I was unaware. Fast exit on > exception would be a useful addition, indeed. > > Lars Albertsson > Data engineering consultant > www.mapflat.com > +46 70 7687109 > > On Mon, Mar 28, 2016 at 2:00 PM, Steve Loughran <ste...@hortonworks.com> > wrote: > > this is a good summary -Have you thought of publishing it at the end of > a URL for others to refer to > > > >> On 18 Mar 2016, at 07:05, Lars Albertsson <la...@mapflat.com> wrote: > >> > >> I would recommend against writing unit tests for Spark programs, and > >> instead focus on integration tests of jobs or pipelines of several > >> jobs. You can still use a unit test framework to execute them. Perhaps > >> this is what you meant. > >> > >> You can use any of the popular unit test frameworks to drive your > >> tests, e.g. JUnit, Scalatest, Specs2. I prefer Scalatest, since it > >> gives you choice of TDD vs BDD, and it is also well integrated with > >> IntelliJ. > >> > >> I would also recommend against using testing frameworks tied to a > >> processing technology, such as Spark Testing Base. Although it does > >> seem well crafted, and makes it easy to get started with testing, > >> there are drawbacks: > >> > >> 1. I/O routines are not tested. Bundled test frameworks typically do > >> not materialise datasets on storage, but pass them directly in memory. > >> (I have not verified this for Spark Testing Base, but it looks so.) > >> I/O routines are therefore not exercised, and they often hide bugs, > >> e.g. related to serialisation. > >> > >> 2. You create a strong coupling between processing technology and your > >> tests. If you decide to change processing technology (which can happen > >> soon in this fast paced world...), you need to rewrite your tests. > >> Therefore, during a migration process, the tests cannot detect bugs > >> introduced in migration, and help you migrate fast. > >> > >> I recommend that you instead materialise input datasets on local disk, > >> run your Spark job, which writes output datasets to local disk, read > >> output from disk, and verify the results. You can still use Spark > >> routines to read and write input and output datasets. A Spark context > >> is expensive to create, so for speed, I would recommend reusing the > >> Spark context between input generation, running the job, and reading > >> output. > >> > >> This is easy to set up, so you don't need a dedicated framework for > >> it. Just put your common boilerplate in a shared test trait or base > >> class. > >> > >> In the future, when you want to replace your Spark job with something > >> shinier, you can still use the old tests, and only replace the part > >> that runs your job, giving you some protection from regression bugs. > >> > >> > >> Testing Spark Streaming applications is a different beast, and you can > >> probably not reuse much from your batch testing. > >> > >> For testing streaming applications, I recommend that you run your > >> application inside a unit test framework, e.g, Scalatest, and have the > >> test setup create a fixture that includes your input and output > >> components. For example, if your streaming application consumes from > >> Kafka and updates tables in Cassandra, spin up single node instances > >> of Kafka and Cassandra on your local machine, and connect your > >> application to them. Then feed input to a Kafka topic, and wait for > >> the result to appear in Cassandra. > >> > >> With this setup, your application still runs in Scalatest, the tests > >> run without custom setup in maven/sbt/gradle, and you can easily run > >> and debug inside IntelliJ. > >> > >> Docker is suitable for spinning up external components. If you use > >> Kafka, the Docker image spotify/kafka is useful, since it bundles > >> Zookeeper. > >> > >> When waiting for output to appear, don't sleep for a long time and > >> then check, since it will slow down your tests. Instead enter a loop > >> where you poll for the results and sleep for a few milliseconds in > >> between, with a long timeout (~30s) before the test fails with a > >> timeout. > > > > org.scalatest.concurrent.Eventually is your friend there > > > > eventually(stdTimeout, stdInterval) { > > listRestAPIApplications(connector, webUI, true) should > contain(expectedAppId) > > } > > > > It has good exponential backoff, for fast initial success without using > too much CPU later, and is simple to use > > > > If it has weaknesses in my tests, they are > > > > 1. it will retry on all exceptions, rather than assertions. If there's a > bug in the test code then it manifests as a timeout. ( I think I could play > with Suite.anExceptionThatShouldCauseAnAbort()) here. > > 2. it's timeout action is simply to rethrow the fault; I like to exec a > closure to grab more diagnostics > > 3. It doesn't support some fail-fast exception which your code can raise > to indicate that the desired state is never going to be reached, and so the > test should fail fast. Here a new exception and another entry in > anExceptionThatShouldCauseAnAbort() may be the answer. I should sit down > and play with that some more. > > > > > >> > >> This poll and sleep strategy both makes tests quick in successful > >> cases, but still robust to occasional delays. The strategy does not > >> work if you want to test for absence, e.g. ensure that a particular > >> message if filtered. You can work around it by adding another message > >> afterwards and polling for its effect before testing for absence of > >> the first. Be aware that messages can be processed out of order in > >> Spark Streaming depending on partitioning, however. > >> > >> > >> I have tested Spark applications with both strategies described above, > >> and it is straightforward to set up. Let me know if you want > >> clarifications or assistance. > >> > >> Regards, > >> > >> > >> > >> Lars Albertsson > >> Data engineering consultant > >> www.mapflat.com > >> +46 70 7687109 > >> > >> > >> On Wed, Mar 2, 2016 at 6:54 PM, SRK <swethakasire...@gmail.com> wrote: > >>> Hi, > >>> > >>> What is a good unit testing framework for Spark batch/streaming jobs? > I have > >>> core spark, spark sql with dataframes and streaming api getting used. > Any > >>> good framework to cover unit tests for these APIs? > >>> > >>> Thanks! > >>> > >>> > >>> > >>> -- > >>> View this message in context: > http://apache-spark-user-list.1001560.n3.nabble.com/Unit-testing-framework-for-Spark-Jobs-tp26380.html > >>> Sent from the Apache Spark User List mailing list archive at > Nabble.com. > >>> > >>> --------------------------------------------------------------------- > >>> To unsubscribe, e-mail: user-unsubscr...@spark.apache.org > >>> For additional commands, e-mail: user-h...@spark.apache.org > >>> > >> > >> --------------------------------------------------------------------- > >> To unsubscribe, e-mail: user-unsubscr...@spark.apache.org > >> For additional commands, e-mail: user-h...@spark.apache.org > >> > >> > > >