FAQ

How can I achieve data locality?

For any MongoDB deployment, the Mongo Spark Connector sets the preferred location for a DataFrame or Dataset to be where the data is:

• For a non sharded system, it sets the preferred location to be the hostname(s) of the standalone or the replica set.

• For a sharded system, it sets the preferred location to be the hostname(s) of the shards.

To promote data locality,

• Ensure there is a Spark Worker on one of the hosts for non-sharded system or one per shard for sharded systems.

• Use a nearest read preference to read from the local mongod.

• For a sharded cluster, you should have a mongos on the same nodes and use localThreshold configuration to connect to the nearest mongos. To partition the data by shard use the ShardedPartitioner Configuration.

How do I resolve Unrecognized pipeline stage name Error?

In MongoDB deployments with mixed versions of mongod, it is possible to get an Unrecognized pipeline stage name: '$sample' error. To mitigate this situation, explicitly configure the partitioner to use and define the Schema when using DataFrames.

How can I use mTLS for authentication?

To use mTLS, include the following options when you run spark-submit:

--driver-java-options -Djavax.net.ssl.trustStore=<path to your truststore.jks file> \
--driver-java-options -Djavax.net.ssl.trustStorePassword=<your truststore password> \
--driver-java-options -Djavax.net.ssl.keyStore=<path to your keystore.jks file> \
--driver-java-options -Djavax.net.ssl.keyStorePassword=<your keystore password> \
-conf spark.executor.extraJavaOptions=-Djavax.net.ssl.trustStore=<path to your truststore.jks file> \
-conf spark.executor.extraJavaOptions=-Djavax.net.ssl.trustStorePassword=<your truststore password> \
-conf spark.executor.extraJavaOptions=-Djavax.net.ssl.keyStore=<path to your keystore.jks file> \
-conf spark.executor.extraJavaOptions=-Djavax.net.ssl.keyStorePassword=<your keystore password> \