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java_gateway is a Python module that allows launching a gateway process to establish communication channel to Py4JServer.



launch_gateway reads PYSPARK_GATEWAY_PORT and PYSPARK_GATEWAY_SECRET environment variables if defined and assumes that the child Java gateway process has already been started (e.g. PythonGatewayServer).

Otherwise, launch_gateway builds the command to start spark-submit:

  1. Finds SPARK_HOME with ./bin/spark-submit
  2. Appends all the configuration properties (from the input conf) using --conf
  3. Appends PYSPARK_SUBMIT_ARGS environment variable if defined or assumes pyspark-shell

launch_gateway sets up _PYSPARK_DRIVER_CONN_INFO_PATH environment variable to point at an unique temporary file.

launch_gateway configures a pipe to stdin for the corresponding Java gateway process to use to monitor the Python process.

launch_gateway starts bin/spark-submit command and waits for a connection info file to be created at _PYSPARK_DRIVER_CONN_INFO_PATH. launch_gateway reads the port and the secret from the file once available.

launch_gateway connects to the gateway using py4j's ClientServer or JavaGateway based on PYSPARK_PIN_THREAD environment variable.

launch_gateway imports Spark packages and classes (using py4j):

  • org.apache.spark.SparkConf
  • org.apache.spark.api.python.*
  • org.apache.spark.mllib.api.python.*
  • org.apache.spark.resource.*
  • org.apache.spark.sql.*
  • org.apache.spark.sql.api.python.*
  • org.apache.spark.sql.hive.*
  • scala.Tuple2

launch_gateway is used when:

Last update: 2021-03-05