Bug Alert: Durable Subscriber Name Length / KAHA Explosions

[dlindquist <ju...@dlindquist.com>]

This is a bug heads-up for anyone who might be running into the same problem. 
(I'm building a simplified example for bug submission, but in the meantime,
to help anyone with similar problems.)

If you:
* Have 2 or more topics with a durable subscriber
* The combination of clientid + subscribername has a length > 99 characters
* The broker has 'persistent=true'
* You have a reasonable volume of requests coming through

Then the 'kaha' store (default, I guess?) will blow up on every single
message send with exceptions either like:

"could not locate file data-something--1"  (note double-dash -- index is
'-1')

OR:

"java.lang.IndexOutOfBoundsException"

(Note that the exact number of characters in the limit has not been
conclusively proven -- once I finish the bug submission example, I'll know
for sure. Additionally, the exact circumstances has not been completely
proven, but the list above seems to produce it.)

This is an exceptionally nasty one as it only applies to the file-store --
the in-memory handling of stuff seems just fine (no such limits) -- if you
say 'persistent=false', there will be no issues.  Additionally, there is
nothing to tell you WHY things are blowing up, or to reject names that are
too long -- it appears that it just makes an assumption on the file-store
side.

I have NOT yet tested whether this same 99-character limitation applies to
topic names, but I am suspicious that it may.

Hopefully this prevents someone else from spending unfruitful hours banging
their head against a wall ;-)
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