Java 21 breaks access to netty-buffer class

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#1,106 opened on Apr 6, 2026 1 comment 0 reactions 0 assignees View on GitHub

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Assessment

Difficulty: 4/5
Estimated time: 3-5 days
Newbie friendliness: 42/100

Issue type: Bug
Clarity: Mostly clear
Activity status: Quiet
Tech stack: java
Domain: backend, data-engineering

Research direction

Start by reproducing the failure while starting an Arrow Flight server on Java 21, then inspect PooledByteBufAllocatorL and NettyAllocationManager as identified in the stack trace. Compare the relevant access behavior with Java 17; done means the IllegalAccessError no longer occurs and the server starts successfully.

Written by the indexing model from the issue text.

Description

Type: bug

Describe the bug, including details regarding any error messages, version, and platform.

When trying to start an Arrow Flight server use is made of class io.netty.buffer.PoolArena in netty-buffer that is no longer accessible in java 21 from class io.netty.buffer.PooledByteBufAllocatorL in arrow-memory-netty-buffer-patch-19.0.0.jar.
I think this might be caused by Java 21 being more restrictive than 17.

Stack trace

```java Exception in thread "main" java.lang.IllegalAccessError: failed to access class io.netty.buffer.PoolArena from class io.netty.buffer.PooledByteBufAllocatorL$InnerAllocator (io.netty.buffer.PoolArena is in unnamed module of loader 'app'; io.netty.buffer.PooledByteBufAllocatorL$InnerAllocator is in unnamed module of loader org.apache.hop.core.plugins.HopURLClassLoader @26612078) at io.netty.buffer.PooledByteBufAllocatorL$InnerAllocator.(PooledByteBufAllocatorL.java:141) at io.netty.buffer.PooledByteBufAllocatorL.(PooledByteBufAllocatorL.java:46) at org.apache.arrow.memory.netty.NettyAllocationManager.(NettyAllocationManager.java:54) at org.apache.arrow.memory.netty.DefaultAllocationManagerFactory.(DefaultAllocationManagerFactory.java:26) at java.base/java.lang.Class.forName0(Native Method) at java.base/java.lang.Class.forName(Class.java:423) at java.base/java.lang.Class.forName(Class.java:414) at org.apache.arrow.memory.DefaultAllocationManagerOption.getFactory(DefaultAllocationManagerOption.java:105) at org.apache.arrow.memory.DefaultAllocationManagerOption.getDefaultAllocationManagerFactory(DefaultAllocationManagerOption.java:92) at org.apache.arrow.memory.BaseAllocator$Config.getAllocationManagerFactory(BaseAllocator.java:826) at org.apache.arrow.memory.ImmutableConfig.access$001(ImmutableConfig.java:20) at org.apache.arrow.memory.ImmutableConfig$InitShim.getAllocationManagerFactory(ImmutableConfig.java:80) at org.apache.arrow.memory.ImmutableConfig.(ImmutableConfig.java:43) at org.apache.arrow.memory.ImmutableConfig$Builder.build(ImmutableConfig.java:492) at org.apache.arrow.memory.BaseAllocator.(BaseAllocator.java:72) at org.apache.hop.arrow.flight.ArrowFlightServer.(ArrowFlightServer.java:59) at org.apache.hop.arrow.command.ArrowCommand.run(ArrowCommand.java:108) at picocli.CommandLine.executeUserObject(CommandLine.java:2045) at picocli.CommandLine.access$1500(CommandLine.java:148) at picocli.CommandLine$RunLast.executeUserObjectOfLastSubcommandWithSameParent(CommandLine.java:2469) at picocli.CommandLine$RunLast.handle(CommandLine.java:2461) at picocli.CommandLine$RunLast.handle(CommandLine.java:2423) at picocli.CommandLine$AbstractParseResultHandler.execute(CommandLine.java:2277) at picocli.CommandLine$RunLast.execute(CommandLine.java:2425) at picocli.CommandLine.execute(CommandLine.java:2174) at org.apache.hop.hop.Hop.main(Hop.java:131)

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