Scala Spark Cassandra安装

Question

1. How many ways are there to run Spark? If I just declare dependencies in build.sbt, Spark is supposed to be downloaded and works? But if I want to run Spark locally (download the Spark tar file, winutils...), how can I specify in scala code that I want to run my code against the local Spark and not against the dependencies downloaded in the IntelliJ?

2. In order to connect Spark to Cassandra, do I need a local installation of Spark? I read somewhere it's not possible to connect from a "programmatically" Spark to a local Cassandra database

Answer 1

1) Spark runs in a slightly strange way, there is your application (the Spark Driver and Executors) and there is the Resource Manager (Spark Master/Workers, Yarn, Mesos or Local).

In your code you can run against the in process manager (local) by specifying the master as local or local[n] . The Local mode requires no installation of Spark as it will be automatically setup in the process you are running. This would be using the dependencies you downloaded.

To run against a Spark Master which is running locally, you use a spark:// url that points at your particular local Spark Master instance. Note that this will cause executor JVMS to start separate from your application necessitating the distribution of application code and dependencies. (Other resource managers have there own identifying urls)

2) You do not need a "Resource Manager" to connect to C* from Spark but this ability is basically for debugging and testing. To do this you would use the local master url. Normal Spark usage should have an external Resource Manager because without an external resource manager the system cannot be distributed.

For some more Spark Cassandra examples see

https://github.com/datastax/SparkBuildExamples