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

[Kevin Walls]

JMX RMI Connections 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.

Changing the base RMI implementation may not be desirable at this time.

JMX can use a new ClientSocketFactory for RMI which implements the connect timeout, which can recognise a new JMX-specific property `com.sun.management.jmxremote.rmi.tcpConnectTimeout`
(named like the existing com.sun.management.jmxremote... properties)

Defaulting to a 1 minute timeout on connect has no effect on existing tests, and should go unnoticed unless there really is a significant connection delay. Specifying zero for the new System Property will use the old technique of a connect with no timeout.

This can be tested, but it is not realistically usable: although specifying a 1 millisecond timeout will often fail (as expected/desired for the test), it will very often pass as the connection happens immediately.

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

Commit messages:
 - whitespace
 - remove commented out code
 - complete class rename
 - 8316649: JMX connection timeout cannot be changed and uses the default of 0 (infinite)

Changes: https://git.openjdk.org/jdk/pull/16856/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=16856&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8316649
  Stats: 72 lines in 2 files changed: 68 ins; 0 del; 4 mod
  Patch: https://git.openjdk.org/jdk/pull/16856.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/16856/head:pull/16856

PR: https://git.openjdk.org/jdk/pull/16856