[jboss-jira] [JBoss JIRA] (JGRP-1763) TimeService

[Bela Ban (JIRA)]

Bela Ban created JGRP-1763:
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             Summary: TimeService
                 Key: JGRP-1763
                 URL: https://issues.jboss.org/browse/JGRP-1763
             Project: JGroups
          Issue Type: Feature Request
            Reporter: Bela Ban
            Assignee: Bela Ban
             Fix For: 3.5


New service which provides wall clock time at a coarse (configurable) granularity. 

Motivation: {{System.currentTimeMillis()}} or {{System.nanoTime()}} is sometimes called frequently, e.g. by {{TCPConnectionMap$TCPConnection.updateLastAccessed()}} or in FD/FD_ALL. This has a cost, especially when a lock is held (system calls while a lock is held cause preemption and the thread losing its time slice).
However, the 2 examples above don't need the exact time, but an approximation of it is OK.

GOALS:
* Provide a time service which returns  the last cached value of {{System.timeCurrentMillis()}}
* This is a quick and efficient call
* {{TimeService}} registers a timer task which updates its internal cached value every N milliseconds (configurable), e.g. every 500 ms

BENEFIT:
For example, in TCPConnection, the timestamp is updated whenever we send or receive a message from the peer. The timestamp is used to expire and close a connection (if configured), and can be updated 100'000 times a second. If the time service provided the current time in ms every 500ms, then {{System.currentTimeMillis()}} would only be called 2 times during a second instead of 100'000 times !

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