Bug: Avoid creating multiple Monitor threads for reused python workers for the same TaskContext
Status: Resolved | Priority: Major | Resolution: Fixed
Created: 09/Apr/21 15:50
Affects Version/s: 3.0.3

Currently this code will stop because of the high number of created threads:

{noformat}
    import pyspark

    conf=pyspark.SparkConf().setMaster("local[64]").setAppName("Test1")
    sc=pyspark.SparkContext.getOrCreate(conf)
    rows=70000
    data=list(range(rows))
    rdd=sc.parallelize(data,rows)
    assert rdd.getNumPartitions()==rows
    rdd0=rdd.filter(lambda x:False)
    assert rdd0.getNumPartitions()==rows
    rdd00=rdd0.coalesce(1)
    data=rdd00.collect()
    assert data==[]
{noformat}


The error is:


{noformat}
1/04/08 12:12:26 WARN NativeCodeLoader: Unable to load native-hadoop library for your platform... using builtin-java classes where applicable
21/04/08 12:12:29 WARN TaskSetManager: Stage 0 contains a task of very large size (4732 KiB). The maximum recommended task size is 1000 KiB.
[Stage 0:>                                                          (0 + 1) / 1][423.190s][warning][os,thread] Attempt to protect stack guard pages failed (0x00007f43d23ff000-0x00007f43d2403000).
[423.190s][warning][os,thread] Attempt to deallocate stack guard pages failed.
OpenJDK 64-Bit Server VM warning: INFO: os::commit_memory(0x00007f43d300b000, 16384, 0) failed; error='Not enough space' (errno=12)
[423.231s][warning][os,thread] Failed to start thread - pthread_create failed (EAGAIN) for attributes: stacksize: 1024k, guardsize: 0k, detached.
#
# There is insufficient memory for the Java Runtime Environment to continue.
# Native memory allocation (mmap) failed to map 16384 bytes for committing reserved memory.
# An error report file with more information is saved as:
# /home/ubuntu/PycharmProjects/<projekt-dir>/tests/hs_err_pid17755.log
[thread 17966 also had an error]
OpenJDK 64-Bit Server VM warning: INFO: os::commit_memory(0x00007f4b7bd81000, 262144, 0) failed; error='Not enough space' (errno=12)
ERROR:root:Exception while sending command.
Traceback (most recent call last):
  File "/opt/spark/python/lib/py4j-0.10.9-src.zip/py4j/java_gateway.py", line 1207, in send_command
    raise Py4JNetworkError("Answer from Java side is empty")
py4j.protocol.Py4JNetworkError: Answer from Java side is empty
During handling of the above exception, another exception occurred:
Traceback (most recent call last):
  File "/opt/spark/python/lib/py4j-0.10.9-src.zip/py4j/java_gateway.py", line 1033, in send_command
    response = connection.send_command(command)
  File "/opt/spark/python/lib/py4j-0.10.9-src.zip/py4j/java_gateway.py", line 1211, in send_command
    raise Py4JNetworkError(
py4j.protocol.Py4JNetworkError: Error while receiving
ERROR:py4j.java_gateway:An error occurred while trying to connect to the Java server (127.0.0.1:42439)
Traceback (most recent call last):
  File "/opt/spark/python/pyspark/rdd.py", line 889, in collect
    sock_info = self.ctx._jvm.PythonRDD.collectAndServe(self._jrdd.rdd())
  File "/opt/spark/python/lib/py4j-0.10.9-src.zip/py4j/java_gateway.py", line 1304, in __call__
    return_value = get_return_value(
  File "/opt/spark/python/lib/py4j-0.10.9-src.zip/py4j/protocol.py", line 334, in get_return_value
    raise Py4JError(
py4j.protocol.Py4JError: An error occurred while calling z:org.apache.spark.api.python.PythonRDD.collectAndServe
During handling of the above exception, another exception occurred:
Traceback (most recent call last):
  File "/opt/spark/python/lib/py4j-0.10.9-src.zip/py4j/java_gateway.py", line 977, in _get_connection
    connection = self.deque.pop()
IndexError: pop from an empty deque
During handling of the above exception, another exception occurred:
Traceback (most recent call last):
  File "/opt/spark/python/lib/py4j-0.10.9-src.zip/py4j/java_gateway.py", line 1115, in start
    self.socket.connect((self.address, self.port))
ConnectionRefusedError: [Errno 111] Connection refused
Traceback (most recent call last):
  File "/opt/spark/python/pyspark/rdd.py", line 889, in collect
    sock_info = self.ctx._jvm.PythonRDD.collectAndServe(self._jrdd.rdd())
  File "/opt/spark/python/lib/py4j-0.10.9-src.zip/py4j/java_gateway.py", line 1304, in __call__
    return_value = get_return_value(
  File "/opt/spark/python/lib/py4j-0.10.9-src.zip/py4j/protocol.py", line 334, in get_return_value
    raise Py4JError(
py4j.protocol.Py4JError: An error occurred while calling z:org.apache.spark.api.python.PythonRDD.collectAndServe
During handling of the above exception, another exception occurred:
Traceback (most recent call last):
  File "/opt/spark/python/lib/py4j-0.10.9-src.zip/py4j/java_gateway.py", line 977, in _get_connection
    connection = self.deque.pop()
IndexError: pop from an empty deque
During handling of the above exception, another exception occurred:
Traceback (most recent call last):
  File "/opt/spark/python/lib/py4j-0.10.9-src.zip/py4j/java_gateway.py", line 1115, in start
    self.socket.connect((self.address, self.port))
ConnectionRefusedError: [Errno 111] Connection refused
During handling of the above exception, another exception occurred:
Traceback (most recent call last):
  File "<input>", line 3, in <module>
  File "/opt/pycharm-2020.2.3/plugins/python/helpers/pydev/_pydev_bundle/pydev_umd.py", line 197, in runfile
    pydev_imports.execfile(filename, global_vars, local_vars)  # execute the script
  File "/opt/pycharm-2020.2.3/plugins/python/helpers/pydev/_pydev_imps/_pydev_execfile.py", line 18, in execfile
    exec(compile(contents+"\n", file, 'exec'), glob, loc)
  File "/home/ubuntu/PycharmProjects/SPO_as_a_Service/tests/test_modeling_paf.py", line 992, in <module>
    test_70000()
  File "/home/ubuntu/PycharmProjects/SPO_as_a_Service/tests/test_modeling_paf.py", line 974, in test_70000
    data=rdd00.collect()
  File "/opt/spark/python/pyspark/rdd.py", line 889, in collect
    sock_info = self.ctx._jvm.PythonRDD.collectAndServe(self._jrdd.rdd())
  File "/opt/spark/python/pyspark/traceback_utils.py", line 78, in __exit__
    self._context._jsc.setCallSite(None)
  File "/opt/spark/python/lib/py4j-0.10.9-src.zip/py4j/java_gateway.py", line 1303, in __call__
    answer = self.gateway_client.send_command(command)
  File "/opt/spark/python/lib/py4j-0.10.9-src.zip/py4j/java_gateway.py", line 1031, in send_command
    connection = self._get_connection()
  File "/opt/spark/python/lib/py4j-0.10.9-src.zip/py4j/java_gateway.py", line 979, in _get_connection
    connection = self._create_connection()
  File "/opt/spark/python/lib/py4j-0.10.9-src.zip/py4j/java_gateway.py", line 985, in _create_connection
    connection.start()
  File "/opt/spark/python/lib/py4j-0.10.9-src.zip/py4j/java_gateway.py", line 1127, in start
    raise Py4JNetworkError(msg, e)
py4j.protocol.Py4JNetworkError: An error occurred while trying to connect to the Java server (127.0.0.1:42439)
{noformat}