RFR: 8030616: sun/management/jmxremote/bootstrap/RmiBootstrapTest fails intermittently with cannot find a free port [v2]

[Mark Sheppard]

On Thu, 20 Oct 2022 10:01:19 GMT, Jaikiran Pai <jpai at openjdk.org> wrote:

>> Can I please get a review of this test only change which proposes to fix the recent intermittent failures in `RmiBootstrapTest` reported in https://bugs.openjdk.org/browse/JDK-8030616?
>> 
>> The test has been intermittently failing with `cannot find a free port after 10 tries`.  The tests uses the `jdk.test.lib.Utils.getFreePort()` utility method to get a free port to use in the tests. That port is then used to create and bind a JMX connector server. The issue resides in the fact that the `getFreePort` utility uses loopback address to identify a free port, whereas the JMX connector server uses that identified port to bind to a non-loopback address - there's logic in `sun.rmi.transport.tcp.TCPEndpoint` line 117 which calls `InetAddress.getLocalHost()` which can and does return a non-loopback address. This effectively means that the port that was identified as free (on loopback) may not really be free on (some other address) and a subsequent attempt to bind against it by the connector server will end up with a `BindException`.
>> 
>> Data collected in failures on the CI system has shown that this is indeed the case and the port that was chosen (for loopback) as free was already used by another process on a different address. The test additionally has logic to attempt retries upto a maximum of 10 times to find a new free port on such `BindException`. Turns out the next free port (on loopback) returned by `jdk.test.lib.Utils.getFreePort()` is incremental and it so happens that the systems where this failed had a process listening on a range of 10 to 12 ports, so these too ended up with `BindException` when the JMX connector server used that port for a different address.
>> 
>> The commit here makes sure that the JMX connector server in the test is now configured to loopback address as the address to bind to. That way the test uses the correct address (loopback) on which the port was free.
>> 
>> The commit also has a change to the javadoc of the test utility `jdk.test.lib.Utils.getFreePort()` to clarify that it returns a free port on loopback address. This now matches what the implementation of that method does.
>> 
>> Multiple test runs after this change hasn't yet run into the failure.
>
> Jaikiran Pai has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains three additional commits since the last revision:
> 
>  - Merge latest from master branch
>  - remove unintentionally committed file
>  - 8030616: sun/management/jmxremote/bootstrap/RmiBootstrapTest fails intermittently with cannot find a free port

yes, I think we found the change will be benefial

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Marked as reviewed by msheppar (Reviewer).

PR: https://git.openjdk.org/jdk/pull/10322