RFR: 8316649: JMX connection timeout cannot be changed and uses the default of 0 (infinite)

[Kevin Walls]

On Tue, 21 Nov 2023 17:57:32 GMT, Kevin Walls <kevinw at openjdk.org> wrote:

> RMI Connections (in general) should use a timeout on the Socket connect call by default.
> 
> JMX connections use RMI and some connection failures never terminate.  The hang described in 8316649 is hard to reproduce manually: the description says it can be caused by a firewall that never returns a response.
> 
> src/java.rmi/share/classes/sun/rmi/transport/tcp/TCPChannel.java
> has other timeouts but nothing to control the initial Socket connect.
> 
> Defaulting to a 1 minute timeout on connect has no effect on existing tests for RMI and JMX, and should go unnoticed in applications unless there really is a significant connection delay.  Specifying zero for the new System Property sun.rmi.transport.tcp.initialConnectTimeout uses the old code path of a connect with no timeout.
> 
> I have a test, but it is not realistically usable: although specifying a 1 millisecond timeout will often fail (as expected/desired for the test), it will often pass as the connection happens immediately.

Thanks for the feedback.
Additionally, there can be a concern that affecting all RMI activity with the timeout property could produce unintended side-effects.

At the moment the demand for the timeout is not strong, and the behaviour is what it has been for many years, so I am going to close this without progressing it.

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PR Comment: https://git.openjdk.org/jdk/pull/16771#issuecomment-1835814563