Spark - Error "A master URL must be set in your configuration" when submitting an app

The TLDR:

.config("spark.master", "local")

a list of the options for spark.master in spark 2.2.1

I ended up on this page after trying to run a simple Spark SQL java program in local mode. To do this, I found that I could set spark.master using:

SparkSession spark = SparkSession
.builder()
.appName("Java Spark SQL basic example")
.config("spark.master", "local")
.getOrCreate();

An update to my answer:

To be clear, this is not what you should do in a production environment. In a production environment, spark.master should be specified in one of a couple other places: either in $SPARK_HOME/conf/spark-defaults.conf (this is where cloudera manager will put it), or on the command line when you submit the app. (ex spark-submit --master yarn).

If you specify spark.master to be 'local' in this way, spark will try to run in a single jvm, as indicated by the comments below. If you then try to specify --deploy-mode cluster, you will get an error 'Cluster deploy mode is not compatible with master "local"'. This is because setting spark.master=local means that you are NOT running in cluster mode.

Instead, for a production app, within your main function (or in functions called by your main function), you should simply use:

SparkSession
.builder()
.appName("Java Spark SQL basic example")
.getOrCreate();

This will use the configurations specified on the command line/in config files.

Also, to be clear on this too: --master and "spark.master" are the exact same parameter, just specified in different ways. Setting spark.master in code, like in my answer above, will override attempts to set --master, and will override values in spark-defaults.conf, so don't do it in production. Its great for tests though.

also, see this answer. which links to a list of the options for spark.master and what each one actually does.

a list of the options for spark.master in spark 2.2.1

Worked for me after replacing

SparkConf sparkConf = new SparkConf().setAppName("SOME APP NAME");

with

SparkConf sparkConf = new SparkConf().setAppName("SOME APP NAME").setMaster("local[2]").set("spark.executor.memory","1g");

Found this solution on some other thread on stackoverflow.

Where is the sparkContext object defined, is it inside the main function?

I too faced the same problem, the mistake which i did was i initiated the sparkContext outside the main function and inside the class.

When I initiated it inside the main function, it worked fine.