[jboss-jira] [JBoss JIRA] (JGRP-1637) Counters overflow

[Bela Ban (JIRA)]

Bela Ban created JGRP-1637:
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             Summary: Counters overflow
                 Key: JGRP-1637
                 URL: https://issues.jboss.org/browse/JGRP-1637
             Project: JGroups
          Issue Type: Task
            Reporter: Bela Ban
            Assignee: Bela Ban
            Priority: Minor
             Fix For: 3.4


We have some counters which might see a lot of increments. Investigate which counters are affected (and how) by a potential wraparound, e.g. longs wrap around at 2^63 and go negative.

For example, storing delivery times in nanoseconds and totalling that number could end up with an overflow as e.g. 2ms = 2000000ns, for 1 million msgs/sec would overflow in roughly 7 weeks ! That's the reason org.jgroups.util.Average was created: instead of totalling delivery time and the number of deliveries to compute avg delivery time, we only maintain a fixed array of delivery times, and its elements are randomly overwritten with new values, so we only keep the (more or less) most recent N values to compute the average.

Using a long for a message sequence number should not be an issue: even if we send 1 million messages / sec, we could send for roughly 290'000 years !


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