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I want to run my first flink code, so I created a virtual environement and I run it with: python tab.py I find : What's wrong with my Pyflink setup that Python UDFs throw py4j exceptions? but it doesn't work.

f_puras
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Zak_Stack
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1 Answers1

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Temporary solution: use openjdk < 17

The (temporary) solution I have found was to enforce install of openjdk < 17:

# Installation with mamba (conda):
mamba create -n flink "python<3.10" "openjdk<17" cython -c conda-forge
conda activate flink
pip install apache-flink --no-cache

This should allow you to run the script mentioned in your link.

Undelying problem for OpenJDK >= 17

Otherwise (for OpenJDK >= 17), there is an open issue https://github.com/py4j/py4j/issues/515 regarding the following error:


# --- Error triggered with OpenJDK >= 17 ---

java.lang.reflect.InaccessibleObjectException: Unable to make field private final byte[] java.lang.String.value accessible: module java.base does not "opens java.lang" to unnamed module


# --- Full traceback (trying to run PyFlink) ---
  File "/Users/test_flink.py", line 28, in <module>
    tutorial()
  File "/Users/test_flink.py", line 20, in tutorial
    ds.print()
  File "/opt/homebrew/Caskroom/miniconda/base/envs/flink/lib/python3.9/site-packages/pyflink/datastream/data_stream.py", line 883, in print
    j_data_stream_sink = self._align_output_type()._j_data_stream.print()
  File "/opt/homebrew/Caskroom/miniconda/base/envs/flink/lib/python3.9/site-packages/py4j/java_gateway.py", line 1321, in __call__
    return_value = get_return_value(
  File "/opt/homebrew/Caskroom/miniconda/base/envs/flink/lib/python3.9/site-packages/pyflink/util/exceptions.py", line 146, in deco
    return f(*a, **kw)
  File "/opt/homebrew/Caskroom/miniconda/base/envs/flink/lib/python3.9/site-packages/py4j/protocol.py", line 326, in get_return_value
    raise Py4JJavaError(
py4j.protocol.Py4JJavaError: An error occurred while calling o82.print.
: java.lang.reflect.InaccessibleObjectException: Unable to make field private final byte[] java.lang.String.value accessible: module java.base does not "opens java.lang" to unnamed module @a803f94
    at java.base/java.lang.reflect.AccessibleObject.checkCanSetAccessible(AccessibleObject.java:354)
    at java.base/java.lang.reflect.AccessibleObject.checkCanSetAccessible(AccessibleObject.java:297)
    at java.base/java.lang.reflect.Field.checkCanSetAccessible(Field.java:178)
    at java.base/java.lang.reflect.Field.setAccessible(Field.java:172)
    at org.apache.flink.api.java.ClosureCleaner.clean(ClosureCleaner.java:106)
    at org.apache.flink.api.java.ClosureCleaner.clean(ClosureCleaner.java:132)
    at org.apache.flink.api.java.ClosureCleaner.clean(ClosureCleaner.java:132)
    at org.apache.flink.api.java.ClosureCleaner.clean(ClosureCleaner.java:69)
    at org.apache.flink.streaming.api.environment.StreamExecutionEnvironment.clean(StreamExecutionEnvironment.java:2308)
    at org.apache.flink.streaming.api.datastream.DataStream.clean(DataStream.java:202)
    at org.apache.flink.streaming.api.datastream.DataStream.addSink(DataStream.java:1242)
    at org.apache.flink.streaming.api.datastream.DataStream.print(DataStream.java:936)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77)
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.base/java.lang.reflect.Method.invoke(Method.java:568)
    at org.apache.flink.api.python.shaded.py4j.reflection.MethodInvoker.invoke(MethodInvoker.java:244)
    at org.apache.flink.api.python.shaded.py4j.reflection.ReflectionEngine.invoke(ReflectionEngine.java:357)
    at org.apache.flink.api.python.shaded.py4j.Gateway.invoke(Gateway.java:282)
    at org.apache.flink.api.python.shaded.py4j.commands.AbstractCommand.invokeMethod(AbstractCommand.java:132)
    at org.apache.flink.api.python.shaded.py4j.commands.CallCommand.execute(CallCommand.java:79)
    at org.apache.flink.api.python.shaded.py4j.GatewayConnection.run(GatewayConnection.java:238)
    at java.base/java.lang.Thread.run(Thread.java:833)

The error comes form a change in Java's API that forbids access to private attributes.

Note the warning when running above-mentioned script under openjdk==11:

WARNING: An illegal reflective access operation has occurred
WARNING: Illegal reflective access by org.apache.flink.api.java.ClosureCleaner (file:/opt/homebrew/Caskroom/miniconda/base/envs/flink/lib/python3.9/site-packages/pyflink/lib/flink-dist-1.16.1.jar) to field java.lang.String.value
WARNING: Please consider reporting this to the maintainers of org.apache.flink.api.java.ClosureCleaner
WARNING: Use --illegal-access=warn to enable warnings of further illegal reflective access operations
WARNING: All illegal access operations will be denied in a future release
Jean Monet
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