RFR: 8354024: [JMH] Create ephemeral UnixDomainSocketAddress provider with thread-safe close semantics [v2]

[Michael McMahon]

On Tue, 22 Apr 2025 09:44:04 GMT, Volkan Yazici <vyazici at openjdk.org> wrote:

>> `ServerUdsChannelHolder` is introduced to manage the life cycle of a `ServerSocketChannel` created using Unix domain sockets (UDS) in a thread-safe manner.
>> 
>> ### Testing
>> 
>> Changes can be tested as follows:
>> 
>> 
>> make build-microbenchmark
>> build/linux-x64/jdk/bin/java \
>>   -jar build/linux-x64/images/test/micro/benchmarks.jar \
>>   -f 1 -wi 1 -i 1 -t 2 \
>>   "(SocketChannelConnectionSetup|UnixSocketChannelReadWrite)"
>> 
>> 
>> ### Background
>> 
>> A UDS need to be pointed to a _non-existent_ file, which is to be created by `bind()`. The created file needs to be deleted as a part of the clean-up at exit. When tests employing UDS run in parallel, failures can happen at multiple places:
>> 
>> - `bind()` can fail, if the file is already created by another thread
>> - the clean-up of the socket file can fail, if the file is already deleted
>>   - reported for `SocketChannelConnectionSetup` in [8350915](https://bugs.openjdk.org/browse/JDK-8350915)
>>   - reported for `UnixSocketChannelReadWrite` in [8351601](https://bugs.openjdk.org/browse/JDK-8351601)
>> - the clean-up of the socket file parent directory can fail, if not all threads deleted their socket files, and hence, the folder is not empty
>>   - reported for in `SocketChannelConnectionSetup` in [8354024](https://bugs.openjdk.org/browse/JDK-8354024)
>> 
>> This PR introduces `ServerUdsChannelHolder` utility to manage the life cycle of a UDS and avoids above shared issues by:
>> - using a dedicated (temporary and unique) parent folder for the socket
>> - encapsulating the termination logic (i.e., closing the socket, deleting the socket file and its (dedicated) parent folder) in `AutoCloseable::close`
>
> Volkan Yazici has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Fix copyright year

test/micro/org/openjdk/bench/java/net/ServerUdsChannelHolder.java line 39:

> 37: 
> 38:     private final Path socketFilePath;
> 39: 

It's not clear to me why each `ServerSocketChannel` needs a separate temporary directory for its socket file. Also, is it possible to combine the functionality of the `ServerSocketChannelHolder` defined in one of the tests, with this clase?

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PR Review Comment: https://git.openjdk.org/jdk/pull/24568#discussion_r2079768594