#3742
  • Created on
    2013-11-22 07:28
  • Reported by
    drewhk
  • Status
    New
  • Priority
    Normal (3)
  • Assigned to
    -
  • Milestone
    Rollins
  • Plan Level
    Subtask
  • Due Date
    -

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Replace the PhiAccrualDetector with a simple timeout detector

The phi accrual detector does not bring anything on the table.
- according to measurements, heartbeats delays cannot be assumed to be normal in general
- most of our advice boils down to tweaking the acceptable-heartbeat-pause parameter
- the original promise of the paper -- probabilities being easier to use compared to plain timeouts -- is not true. Most people are not interested whether it is 99.66% probable that the system is up, they are interested how much time it takes for that system to respond to requests

I recommend using a simple timeout based detector, which reduces the tunable parameters to one, reducing configuration confusion as a result. Since FDs are pluggable, people can drop in whatever they want for custom behavior.
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  on 2013-11-22 07:36 *
By Patrik Nordwall
I don't really disagree, but a possible usage for **some** users of cluster FD with the new back from unreachable would be to have a low (or zero) acceptable-heartbeat-pause to be able to detect failures quickly with acceptable false positives.
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  on 2013-11-22 07:43 *
By drewhk
I think it is exactly the scenario where a simple timeout based one is preferred. Unreachability in most of the cases is better defined in terms of delay than probability of being down.
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  on 2013-11-22 07:44 *
By drewhk
That said, the Phi can remain so people can use it, I just recommend to make a simpler one to be the default.
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  on 2013-12-03 10:43 *
By viktorklang
I think Accrual FD will be more interesting once we mix trust into the picture.
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  on 2014-02-26 08:33 *
By viktorklang
Status changed from New to Invalid
since FDs are pluggable, the user can choose whatever FD he/she wants.
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  on 2014-02-27 04:13 *
By drewhk
Yes, the question here is the recommended default. Since most of the actual use of the Phi accrual failure detector boils down to tuning the acceptable-heartbeat-pause we can make the default configuration easier by having a simple threshold detector as default. I don't see this ticket as invalid.
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  on 2014-02-28 06:46 *
By viktorklang
It's outside the scope of what we are going to deliver out of the box right now.
Feel free to open it and move it to community contributions.
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  on 2014-02-28 07:06 *
By drewhk
We should deliver it out of the box for 2.4. I don't see how this is community contribution, but I can put it there.
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  on 2014-02-28 07:25 *
By drewhk
Status changed from Invalid to New
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  on 2014-02-28 07:26 *
By drewhk
For some reason assembla does not allow me to change the milestone of this ticket.
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  on 2014-03-31 07:58 *
By bjorn.antonsson@typesafe.com
Milestone changed from Current to Rollins