1e599e5005
### What changes were proposed in this pull request? Add support of `TaskContext.get()` in a barrier task from Python side, this makes it easier to migrate legacy user code to barrier execution mode. ### Why are the changes needed? In Spark Core, there is a `TaskContext` object which is a singleton. We set a task context instance which can be TaskContext or BarrierTaskContext before the task function startup, and unset it to none after the function end. So we can both get TaskContext and BarrierTaskContext with the object. However we can only get the BarrierTaskContext with `BarrierTaskContext`, we will get `None` if we get it by `TaskContext.get` in a barrier stage. This is useful when people switch from normal code to barrier code, and only need a little update. ### Does this PR introduce any user-facing change? Yes. Previously: ```python def func(iterator): task_context = TaskContext.get() . # this could be None. barrier_task_context = BarrierTaskContext.get() # get the BarrierTaskContext instance ... rdd.barrier().mapPartitions(func) ``` Proposed: ```python def func(iterator): task_context = TaskContext.get() . # this could also get the BarrierTaskContext instance which is same as barrier_task_context barrier_task_context = BarrierTaskContext.get() # get the BarrierTaskContext instance ... rdd.barrier().mapPartitions(func) ``` ### How was this patch tested? New UT tests. Closes #26239 from ConeyLiu/barrier_task_context. Authored-by: Xianyang Liu <xianyang.liu@intel.com> Signed-off-by: HyukjinKwon <gurwls223@apache.org>
234 lines
7.4 KiB
Python
234 lines
7.4 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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from __future__ import print_function
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from pyspark.java_gateway import local_connect_and_auth
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from pyspark.serializers import write_int, UTF8Deserializer
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class TaskContext(object):
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"""
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Contextual information about a task which can be read or mutated during
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execution. To access the TaskContext for a running task, use:
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:meth:`TaskContext.get`.
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"""
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_taskContext = None
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_attemptNumber = None
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_partitionId = None
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_stageId = None
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_taskAttemptId = None
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_localProperties = None
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_resources = None
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def __new__(cls):
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"""Even if users construct TaskContext instead of using get, give them the singleton."""
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taskContext = cls._taskContext
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if taskContext is not None:
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return taskContext
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cls._taskContext = taskContext = object.__new__(cls)
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return taskContext
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@classmethod
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def _getOrCreate(cls):
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"""Internal function to get or create global TaskContext."""
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if cls._taskContext is None:
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cls._taskContext = TaskContext()
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return cls._taskContext
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@classmethod
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def _setTaskContext(cls, taskContext):
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cls._taskContext = taskContext
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@classmethod
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def get(cls):
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"""
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Return the currently active TaskContext. This can be called inside of
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user functions to access contextual information about running tasks.
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.. note:: Must be called on the worker, not the driver. Returns None if not initialized.
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"""
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return cls._taskContext
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def stageId(self):
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"""The ID of the stage that this task belong to."""
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return self._stageId
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def partitionId(self):
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"""
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The ID of the RDD partition that is computed by this task.
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"""
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return self._partitionId
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def attemptNumber(self):
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""""
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How many times this task has been attempted. The first task attempt will be assigned
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attemptNumber = 0, and subsequent attempts will have increasing attempt numbers.
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"""
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return self._attemptNumber
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def taskAttemptId(self):
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"""
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An ID that is unique to this task attempt (within the same SparkContext, no two task
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attempts will share the same attempt ID). This is roughly equivalent to Hadoop's
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TaskAttemptID.
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"""
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return self._taskAttemptId
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def getLocalProperty(self, key):
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"""
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Get a local property set upstream in the driver, or None if it is missing.
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"""
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return self._localProperties.get(key, None)
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def resources(self):
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"""
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Resources allocated to the task. The key is the resource name and the value is information
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about the resource.
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"""
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return self._resources
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BARRIER_FUNCTION = 1
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def _load_from_socket(port, auth_secret):
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"""
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Load data from a given socket, this is a blocking method thus only return when the socket
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connection has been closed.
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"""
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(sockfile, sock) = local_connect_and_auth(port, auth_secret)
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# The barrier() call may block forever, so no timeout
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sock.settimeout(None)
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# Make a barrier() function call.
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write_int(BARRIER_FUNCTION, sockfile)
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sockfile.flush()
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# Collect result.
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res = UTF8Deserializer().loads(sockfile)
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# Release resources.
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sockfile.close()
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sock.close()
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return res
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class BarrierTaskContext(TaskContext):
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"""
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.. note:: Experimental
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A :class:`TaskContext` with extra contextual info and tooling for tasks in a barrier stage.
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Use :func:`BarrierTaskContext.get` to obtain the barrier context for a running barrier task.
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.. versionadded:: 2.4.0
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"""
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_port = None
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_secret = None
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@classmethod
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def _getOrCreate(cls):
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"""
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Internal function to get or create global BarrierTaskContext. We need to make sure
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BarrierTaskContext is returned from here because it is needed in python worker reuse
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scenario, see SPARK-25921 for more details.
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"""
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if not isinstance(cls._taskContext, BarrierTaskContext):
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cls._taskContext = object.__new__(cls)
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return cls._taskContext
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@classmethod
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def get(cls):
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"""
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.. note:: Experimental
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Return the currently active :class:`BarrierTaskContext`.
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This can be called inside of user functions to access contextual information about
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running tasks.
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.. note:: Must be called on the worker, not the driver. Returns None if not initialized.
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An Exception will raise if it is not in a barrier stage.
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"""
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if not isinstance(cls._taskContext, BarrierTaskContext):
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raise Exception('It is not in a barrier stage')
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return cls._taskContext
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@classmethod
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def _initialize(cls, port, secret):
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"""
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Initialize BarrierTaskContext, other methods within BarrierTaskContext can only be called
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after BarrierTaskContext is initialized.
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"""
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cls._port = port
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cls._secret = secret
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def barrier(self):
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"""
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.. note:: Experimental
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Sets a global barrier and waits until all tasks in this stage hit this barrier.
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Similar to `MPI_Barrier` function in MPI, this function blocks until all tasks
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in the same stage have reached this routine.
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.. warning:: In a barrier stage, each task much have the same number of `barrier()`
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calls, in all possible code branches.
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Otherwise, you may get the job hanging or a SparkException after timeout.
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.. versionadded:: 2.4.0
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"""
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if self._port is None or self._secret is None:
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raise Exception("Not supported to call barrier() before initialize " +
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"BarrierTaskContext.")
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else:
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_load_from_socket(self._port, self._secret)
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def getTaskInfos(self):
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"""
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.. note:: Experimental
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Returns :class:`BarrierTaskInfo` for all tasks in this barrier stage,
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ordered by partition ID.
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.. versionadded:: 2.4.0
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"""
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if self._port is None or self._secret is None:
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raise Exception("Not supported to call getTaskInfos() before initialize " +
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"BarrierTaskContext.")
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else:
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addresses = self._localProperties.get("addresses", "")
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return [BarrierTaskInfo(h.strip()) for h in addresses.split(",")]
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class BarrierTaskInfo(object):
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"""
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.. note:: Experimental
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Carries all task infos of a barrier task.
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:var address: The IPv4 address (host:port) of the executor that the barrier task is running on
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.. versionadded:: 2.4.0
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"""
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def __init__(self, address):
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self.address = address
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