Timur Mehrvarz wrote:
This is why it is a bit hard for me to understand, how notify() can be
so unreliable. I'd say, I am having one dropped notify() call for every
50 objects written to space. Roughly.
From some perspectives, one should be comfortable that on a single machine,
there shouldn't be any problems. However, software is "everywhere", and
software can have "bugs". The issues are whether you can have faith in the
software, or time to find every "real" bug. After working for AT&T and seeing
the amount of code that existed to just deal with auditing and validating the
software runtime environment, I changed my whole view of software[1].
I still need to implement your third suggestion (below). I can do so
next week. And I will report back, if this fully fixes the issue for me.
With Javaspaces, you should typically request notification, and then do a read
to see if there is an entry that matches the same template, and then take that
entry to process it if so.
Missing 1 in 50 or so sounds like a potential concurrency related bug. If you
increase the flow of data does that proportionally increase the missing
notifies? If you greatly reduce the flow does that make the notifies more reliable?
Gregg Wonderly
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[1]
I don't know how many people really know how extreme the measures are which make
sure that the telephone switching "keeps on switching". Audits of audits are
not uncommon. In the end, if you want your software to work reliably, you have
to test/validate every assumption/function you rely on.
I try to design audits and validations so that they provide real value, beyond
recovering from bugs silently. I always start out with warning level logging in
legs of code that I don't thing I should enter. If I see those legs being
entered, I start adding the collection of stack traces for the places where I
think those constraints are controlled. I go through all the effort to try and
find out more about what is causing the behavior. Test suites can find a lot of
these kinds of things early, but in general, there's always going to be more to
find once you are in the field.
