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

[Daniel Fuchs]

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.

src/java.rmi/share/classes/sun/rmi/transport/tcp/TCPDirectSocketFactory.java line 46:

> 44:     private static final int connectTimeout =    // default 1 minute
> 45:         AccessController.doPrivileged((PrivilegedAction<Integer>) () ->
> 46:             Integer.getInteger("sun.rmi.transport.tcp.initialConnectTimeout", 60 * 1000).intValue());

An exception here will prevent the class from being initialized, any subsequent attempts to use the class will then produce hard to diagnose error. If the class is not loaded by the main thread, such exception/error could be swallowed unless an uncaught exception handler was registered. I would suggest implementing the logic in a static block, catch any exception and revert to default behaviour (i.e. 0) if the value supplied for the property is not an integer, or not a valid integer, etc...

-------------

PR Review Comment: https://git.openjdk.org/jdk/pull/16771#discussion_r1403258620