0cfda8461f
This patch changes PySpark so that the GatewayServer's port is communicated back to the Python process that launches it over a local socket instead of a pipe. The old pipe-based approach was brittle and could fail if `spark-submit` printed unexpected to stdout. To accomplish this, I wrote a custom `PythonGatewayServer.main()` function to use in place of Py4J's `GatewayServer.main()`. Closes #3424. Author: Josh Rosen <joshrosen@databricks.com> Closes #4603 from JoshRosen/SPARK-2313 and squashes the following commits: 6a7740b [Josh Rosen] Remove EchoOutputThread since it's no longer needed 0db501f [Josh Rosen] Use select() so that we don't block if GatewayServer dies. 9bdb4b6 [Josh Rosen] Handle case where getListeningPort returns -1 3fb7ed1 [Josh Rosen] Remove stdout=PIPE 2458934 [Josh Rosen] Use underscore to mark env var. as private d12c95d [Josh Rosen] Use Logging and Utils.tryOrExit() e5f9730 [Josh Rosen] Wrap everything in a giant try-block 2f70689 [Josh Rosen] Use stdin PIPE to share fate with driver 8bf956e [Josh Rosen] Initial cut at passing Py4J gateway port back to driver via socket
112 lines
5.3 KiB
Python
112 lines
5.3 KiB
Python
#
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# Licensed to the Apache Software Foundation (ASF) under one or more
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# contributor license agreements. See the NOTICE file distributed with
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# this work for additional information regarding copyright ownership.
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# The ASF licenses this file to You under the Apache License, Version 2.0
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# (the "License"); you may not use this file except in compliance with
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# the License. You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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#
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import atexit
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import os
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import select
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import signal
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import shlex
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import socket
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import platform
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from subprocess import Popen, PIPE
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from py4j.java_gateway import java_import, JavaGateway, GatewayClient
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from pyspark.serializers import read_int
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def launch_gateway():
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SPARK_HOME = os.environ["SPARK_HOME"]
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if "PYSPARK_GATEWAY_PORT" in os.environ:
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gateway_port = int(os.environ["PYSPARK_GATEWAY_PORT"])
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else:
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# Launch the Py4j gateway using Spark's run command so that we pick up the
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# proper classpath and settings from spark-env.sh
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on_windows = platform.system() == "Windows"
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script = "./bin/spark-submit.cmd" if on_windows else "./bin/spark-submit"
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submit_args = os.environ.get("PYSPARK_SUBMIT_ARGS")
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submit_args = submit_args if submit_args is not None else ""
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submit_args = shlex.split(submit_args)
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command = [os.path.join(SPARK_HOME, script)] + submit_args + ["pyspark-shell"]
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# Start a socket that will be used by PythonGatewayServer to communicate its port to us
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callback_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
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callback_socket.bind(('127.0.0.1', 0))
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callback_socket.listen(1)
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callback_host, callback_port = callback_socket.getsockname()
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env = dict(os.environ)
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env['_PYSPARK_DRIVER_CALLBACK_HOST'] = callback_host
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env['_PYSPARK_DRIVER_CALLBACK_PORT'] = str(callback_port)
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# Launch the Java gateway.
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# We open a pipe to stdin so that the Java gateway can die when the pipe is broken
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if not on_windows:
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# Don't send ctrl-c / SIGINT to the Java gateway:
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def preexec_func():
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signal.signal(signal.SIGINT, signal.SIG_IGN)
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env["IS_SUBPROCESS"] = "1" # tell JVM to exit after python exits
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proc = Popen(command, stdin=PIPE, preexec_fn=preexec_func, env=env)
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else:
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# preexec_fn not supported on Windows
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proc = Popen(command, stdin=PIPE, env=env)
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gateway_port = None
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# We use select() here in order to avoid blocking indefinitely if the subprocess dies
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# before connecting
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while gateway_port is None and proc.poll() is None:
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timeout = 1 # (seconds)
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readable, _, _ = select.select([callback_socket], [], [], timeout)
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if callback_socket in readable:
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gateway_connection = callback_socket.accept()[0]
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# Determine which ephemeral port the server started on:
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gateway_port = read_int(gateway_connection.makefile())
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gateway_connection.close()
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callback_socket.close()
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if gateway_port is None:
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raise Exception("Java gateway process exited before sending the driver its port number")
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# In Windows, ensure the Java child processes do not linger after Python has exited.
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# In UNIX-based systems, the child process can kill itself on broken pipe (i.e. when
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# the parent process' stdin sends an EOF). In Windows, however, this is not possible
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# because java.lang.Process reads directly from the parent process' stdin, contending
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# with any opportunity to read an EOF from the parent. Note that this is only best
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# effort and will not take effect if the python process is violently terminated.
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if on_windows:
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# In Windows, the child process here is "spark-submit.cmd", not the JVM itself
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# (because the UNIX "exec" command is not available). This means we cannot simply
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# call proc.kill(), which kills only the "spark-submit.cmd" process but not the
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# JVMs. Instead, we use "taskkill" with the tree-kill option "/t" to terminate all
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# child processes in the tree (http://technet.microsoft.com/en-us/library/bb491009.aspx)
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def killChild():
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Popen(["cmd", "/c", "taskkill", "/f", "/t", "/pid", str(proc.pid)])
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atexit.register(killChild)
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# Connect to the gateway
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gateway = JavaGateway(GatewayClient(port=gateway_port), auto_convert=False)
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# Import the classes used by PySpark
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java_import(gateway.jvm, "org.apache.spark.SparkConf")
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java_import(gateway.jvm, "org.apache.spark.api.java.*")
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java_import(gateway.jvm, "org.apache.spark.api.python.*")
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java_import(gateway.jvm, "org.apache.spark.mllib.api.python.*")
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# TODO(davies): move into sql
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java_import(gateway.jvm, "org.apache.spark.sql.*")
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java_import(gateway.jvm, "org.apache.spark.sql.hive.*")
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java_import(gateway.jvm, "scala.Tuple2")
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return gateway
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