How to Submit Spark Application through Livy REST API
Apache Livy supports using REST APIs to submit Spark applications, it is quite similar to use “spark-submit” in vanilla Spark. In this article we will briefly introduce how to use Livy REST APIs to submit Spark applications, and how to transfer existing “spark-submit” command to REST APIs.
In vanilla Spark, normally we should use “spark-submit” command to submit Spark application to a cluster, a “spark-submit” command is like:
--class: The entry point for your application (e.g. org.apache.spark.examples.SparkPi).
--master: The master URL for the cluster (e.g. spark://220.127.116.11:7077).
--deploy-mode: Whether to deploy your driver on the worker nodes (cluster) or locally as an external client (client) (default: client).
application-jar: Path to a bundled jar including your application and all dependencies. The URL must be globally visible inside of your cluster, for instance, an hdfs:// path or a file:// path that is present on all nodes.
application-arguments: Arguments passed to the main method of your main class, if any.
To make Spark application running on cluster manager, we should specify “--master” and “--deploy-mode” to choose which cluster manager to run Spark application in which mode. Beside, we should let “spark-submit” to know the application’s entry point as well as application jar, arguments, these are specified through “--class”, “<application-jar>” and “[application-argument]”.
It is quite easy to use “spark-submit” command to specify different arguments, user can use “spark-submit --help” to show all the supported arguments.
Then how to use Livy REST APIs to submit Spark applications?
Using Livy REST APIs
Livy REST APIs offers the equal ability to submit application through REST APIs, let’s see how to convert the above “spark-submit” command to a REST protocol.
This is a JSON protocol to submit Spark application, to submit Spark application to cluster manager, we should use HTTP POST request to send above JSON protocol to Livy Server:
curl -H "Content-Type: application/json" -X POST -d ‘<JSON Protocol>’ <livy-host>:<port>/batches
As you can see most of the arguments are the same, but there still has some differences:
“master” and “deployMode” cannot be directly specified in REST API, instead you have two ways to specify these:
Via Livy configurations “livy.spark.master” and “livy.spark.deploy-mode”. Livy will honor this two configurations and set in session creation.
Via Spark configurations, setting “spark.master” and “spark.submit.deployMode” in “conf” field of REST protocol.
The “application-jar” should be reachable by remote cluster manager, which means this “application-jar” should be put onto a distributed file system like HDFS. This is different from “spark-submit” because “spark-submit” also handles uploading jars from local disk, but Livy REST APIs doesn’t do jar uploading.
For all the other settings including environment variables, they should be configured in spark-defaults.conf and spark-env.sh file under <SPARK_HOME>/conf.
Here is the example to transfer “spark-submit” command to Livy REST APIs.