» Submitting Applications

The spark-submit script located in Spark’s bin directory is used to launch applications on a cluster. Spark applications can be submitted to Nomad in either client mode or cluster mode.

» Client Mode

In client mode, the application driver runs on a machine that is not necessarily in the Nomad cluster. The driver’s SparkContext creates a Nomad job to run Spark executors. The executors connect to the driver and run Spark tasks on behalf of the application. When the driver’s SparkContext is stopped, the executors are shut down. Note that the machine running the driver or spark-submit needs to be reachable from the Nomad clients so that the executors can connect to it.

In client mode, application resources need to start out present on the submitting machine, so JAR files (both the primary JAR and those added with the --jars option) can not be specified using http: or https: URLs. You can either use files on the submitting machine (either as raw paths or file: URLs) , or use local: URLs to indicate that the files are independently available on both the submitting machine and all of the Nomad clients where the executors might run.

In this mode, the spark-submit invocation doesn’t return until the application has finished running, and killing the spark-submit process kills the application.

In this example, the spark-submit command is used to run the SparkPi sample application:

$ spark-submit --class org.apache.spark.examples.SparkPi \
    --master nomad \
    --conf spark.nomad.sparkDistribution=https://s3.amazonaws.com/nomad-spark/spark-2.1.0-bin-nomad.tgz \
    lib/spark-examples*.jar \
    10

» Cluster Mode

In cluster mode, the spark-submit process creates a Nomad job to run the Spark application driver itself. The driver’s SparkContext then adds Spark executors to the Nomad job. The executors connect to the driver and run Spark tasks on behalf of the application. When the driver’s SparkContext is stopped, the executors are shut down.

In cluster mode, application resources need to be hosted somewhere accessible to the Nomad cluster, so JARs (both the primary JAR and those added with the --jars option) can’t be specified using raw paths or file: URLs. You can either use http: or https: URLs, or use local: URLs to indicate that the files are independently available on all of the Nomad clients where the driver and executors might run.

Note that in cluster mode, the Nomad master URL needs to be routable from both the submitting machine and the Nomad client node that runs the driver. If the Nomad cluster is integrated with Consul, you may want to use a DNS name for the Nomad service served by Consul.

For example, to submit an application in cluster mode:

$ spark-submit --class org.apache.spark.examples.SparkPi \
    --master nomad \
    --deploy-mode cluster \
    --conf spark.nomad.sparkDistribution=http://example.com/spark.tgz \
    http://example.com/spark-examples.jar \
    10

» Next Steps

Learn how to customize applications.