java_gateway.lauch_gateway

java_gateway

def launch_gateway():
    if "PYSPARK_GATEWAY_PORT" in os.environ:
        gateway_port = int(os.environ["PYSPARK_GATEWAY_PORT"])
    else:
        SPARK_HOME = os.environ["SPARK_HOME"]
        # Launch the Py4j gateway using Spark's run command so that we pick up the
        # proper classpath and settings from spark-env.sh
        on_windows = platform.system() == "Windows"
        script = "./bin/spark-submit.cmd" if on_windows else "./bin/spark-submit"
        submit_args = os.environ.get("PYSPARK_SUBMIT_ARGS", "pyspark-shell")
        command = [os.path.join(SPARK_HOME, script)] + shlex.split(submit_args)

        # Start a socket that will be used by PythonGatewayServer to communicate its port to us
        callback_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
        callback_socket.bind(('127.0.0.1', 0))
        callback_socket.listen(1)
        callback_host, callback_port = callback_socket.getsockname()
        env = dict(os.environ)
        env['_PYSPARK_DRIVER_CALLBACK_HOST'] = callback_host
        env['_PYSPARK_DRIVER_CALLBACK_PORT'] = str(callback_port)

        # Launch the Java gateway.
        # We open a pipe to stdin so that the Java gateway can die when the pipe is broken
        if not on_windows:
            # Don't send ctrl-c / SIGINT to the Java gateway:
            def preexec_func():
                signal.signal(signal.SIGINT, signal.SIG_IGN)
            proc = Popen(command, stdin=PIPE, preexec_fn=preexec_func, env=env)
        else:
            # preexec_fn not supported on Windows
            proc = Popen(command, stdin=PIPE, env=env)

        gateway_port = None
        # We use select() here in order to avoid blocking indefinitely if the subprocess dies
        # before connecting
        while gateway_port is None and proc.poll() is None:
            timeout = 1  # (seconds)
            readable, _, _ = select.select([callback_socket], [], [], timeout)
            if callback_socket in readable:
                gateway_connection = callback_socket.accept()[0]
                # Determine which ephemeral port the server started on:
                gateway_port = read_int(gateway_connection.makefile(mode="rb"))
                gateway_connection.close()
                callback_socket.close()
        if gateway_port is None:
            raise Exception("Java gateway process exited before sending the driver its port number")