org.apache.spark.api.python.PythonGatewayServer.scala Maven / Gradle / Ivy

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/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.spark.api.python

import java.io.{DataOutputStream, File, FileOutputStream}
import java.net.InetAddress
import java.nio.charset.StandardCharsets.UTF_8
import java.nio.file.Files

import py4j.GatewayServer

import org.apache.spark.SparkConf
import org.apache.spark.internal.Logging
import org.apache.spark.util.Utils

/**
 * Process that starts a Py4J GatewayServer on an ephemeral port.
 *
 * This process is launched (via SparkSubmit) by the PySpark driver (see java_gateway.py).
 */
private[spark] object PythonGatewayServer extends Logging {
  initializeLogIfNecessary(true)

  def main(args: Array[String]): Unit = {
    val secret = Utils.createSecret(new SparkConf())

    // Start a GatewayServer on an ephemeral port. Make sure the callback client is configured
    // with the same secret, in case the app needs callbacks from the JVM to the underlying
    // python processes.
    val localhost = InetAddress.getLoopbackAddress()
    val builder = new GatewayServer.GatewayServerBuilder()
      .javaPort(0)
      .javaAddress(localhost)
      .callbackClient(GatewayServer.DEFAULT_PYTHON_PORT, localhost, secret)
    if (sys.env.getOrElse("_PYSPARK_CREATE_INSECURE_GATEWAY", "0") != "1") {
      builder.authToken(secret)
    } else {
      assert(sys.env.getOrElse("SPARK_TESTING", "0") == "1",
        "Creating insecure Java gateways only allowed for testing")
    }
    val gatewayServer: GatewayServer = builder.build()

    gatewayServer.start()
    val boundPort: Int = gatewayServer.getListeningPort
    if (boundPort == -1) {
      logError("GatewayServer failed to bind; exiting")
      System.exit(1)
    } else {
      logDebug(s"Started PythonGatewayServer on port $boundPort")
    }

    // Communicate the connection information back to the python process by writing the
    // information in the requested file. This needs to match the read side in java_gateway.py.
    val connectionInfoPath = new File(sys.env("_PYSPARK_DRIVER_CONN_INFO_PATH"))
    val tmpPath = Files.createTempFile(connectionInfoPath.getParentFile().toPath(),
      "connection", ".info").toFile()

    val dos = new DataOutputStream(new FileOutputStream(tmpPath))
    dos.writeInt(boundPort)

    val secretBytes = secret.getBytes(UTF_8)
    dos.writeInt(secretBytes.length)
    dos.write(secretBytes, 0, secretBytes.length)
    dos.close()

    if (!tmpPath.renameTo(connectionInfoPath)) {
      logError(s"Unable to write connection information to $connectionInfoPath.")
      System.exit(1)
    }

    // Exit on EOF or broken pipe to ensure that this process dies when the Python driver dies:
    while (System.in.read() != -1) {
      // Do nothing
    }
    logDebug("Exiting due to broken pipe from Python driver")
    System.exit(0)
  }
}