JMC-6466: Visualize the new Dictionary Events

[Ken Dobson]

Hi all,

  I spoke to the implementer of the dictionary size events and got some
ideas for rules/visualizations that I thought I'd share here to get some
feedback. The full event attributes can be viewed here
https://bugs.openjdk.java.net/browse/JDK-8185525 .

  For these possible rules most of them seem pretty straightforward it's
just a matter of deciding what the appropriate heuristics are.

Possible Rules

1. Check for frequent table resizing

2.Check for large difference between maximumBucketSize and
AverageBucketSize as it can indicate a security issue

3. Check BucketCountVariance and bucketCountStandardDev for large values
that indicate irregular distribution

4. Large insertion and removal rates (post start-up phase)

  These events default to being emitted every 10s. I think most of these
rules could be achieved using a sliding window much like a number of other
rules are implemented.

Visualization

1. A visualization for when a table resizes

  Something like a line chart could easily added to show this. However not
sure what page it would best fit on.

  Please respond if you think any or all of these possible rules are worth
implementing as well if you have ideas as to what appropriate heuristics
might be to trigger these rules. As well any other visualization ideas
would be great as well.

Thanks,

Ken Dobson