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amazon-web-servicesapache-sparkemr

Number of executors and cores

I am new to spark and would like to know how many cores and executors have to be used in a spark job and AWS if we have 2 slave c4.8xlarge nodes and 1 c4.8x large master node. I have tried different combinations but not able to understand the concept.

Thank you.

Solution

  • Cloudera guys gave good explanation on that

    https://www.youtube.com/watch?v=vfiJQ7wg81Y

    If, let's say you have 16 cores on your node(I think this is exactly your case), then you give 1 for yarn to manage this node, then you devide 15 to 3, so each executor has 5 cores. Also, you have java overhead which is Max(384M, 0.07*spark.executor.memory). So, if you have 3 executors per node, then you have 3*Max(384M, 0.07*spark.executor.memory) overhead for JVMs, the rest can be used for memory containers. enter image description here

    However, on a cluster with many users working simultaneously, yarn can push your spark session out of some containers, making spark go all the way back through the DAG and bringing all the RDD to the present state, which is bad. That is why you need to make --num-executors, --executor-memory and --executor-cores slightly less to give some space to other users in advance. But this doesn't apply to AWS where you are the only one user.

    --executor-memory 18Gb should work for you btw

    More details on turning your cluster parameters http://blog.cloudera.com/blog/2015/03/how-to-tune-your-apache-spark-jobs-part-2/