Running Spark on AWS EMR, how to run driver on master node? - amazon-web-services

Question

It seems that by default EMR deploys the Spark driver to one of the CORE nodes, resulting in the MASTER node being virtually un-utilized. Is it possible to run the driver program on the MASTER node instead? I have experimented with the --deploy-mode arguments to no avail.
Here is my instance groups JSON definition:
[
{
"InstanceGroupType": "MASTER",
"InstanceCount": 1,
"InstanceType": "m3.xlarge",
"Name": "Spark Master"
},
{
"InstanceGroupType": "CORE",
"InstanceCount": 3,
"InstanceType": "m3.xlarge",
"Name": "Spark Executors"
}
]
Here is my configurations JSON definition:
[
{
"Classification": "spark",
"Properties": {
"maximizeResourceAllocation": "true"
},
"Configurations": []
},
{
"Classification": "spark-env",
"Properties": {
},
"Configurations": [
{
"Classification": "export",
"Properties": {
},
"Configurations": [
]
}
]
}
]
Here is my steps JSON definition:
[
{
"Name": "example",
"Type": "SPARK",
"Args": [
"--class", "com.name.of.Class",
"/home/hadoop/myjar-assembly-1.0.jar"
],
"ActionOnFailure": "TERMINATE_CLUSTER"
}
]
I am using aws emr create-cluster with --release-label emr-4.3.0.

Answer 1

Setting the location of the driver
With spark-submit, the flag --deploy-mode can be used to select the location of the driver.
Submitting applications in client mode is advantageous when you are debugging and wish to quickly see the output of your application. For applications in production, the best practice is to run the application in cluster mode. This mode offers you a guarantee that the driver is always available during application execution. However, if you do use client mode and you submit applications from outside your EMR cluster (such as locally, on a laptop), keep in mind that the driver is running outside your EMR cluster and there will be higher latency for driver-executor communication.
https://blogs.aws.amazon.com/bigdata/post/Tx578UTQUV7LRP/Submitting-User-Applications-with-spark-submit

Answer 2

I don't think it is a waste. When running Spark on EMR, the master node will run Yarn RM, Livy Server, and maybe other applications you selected. And if you run in client mode, the majority of the driver program will run on the master node as well.
Note that the driver program could be heavier than the tasks on executors, e.g. collecting all results from all executors, in which case you need to allocate enough resources to your master node if it is where the driver program is running.