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From Remy Maucherat <r...@apache.org>
Subject Re: svn commit: r1036595 - in /tomcat/trunk: java/org/apache/catalina/ java/org/apache/catalina/ha/session/ java/org/apache/catalina/session/ test/org/apache/catalina/session/
Date Fri, 26 Nov 2010 18:46:26 GMT
On Thu, 2010-11-25 at 16:33 +0000, Mark Thomas wrote:
> I wouldn't call it bad. It doesn't do any harm (apart from adding a very
> small amount of overhead), and it would help if the random source
> selected ended up not being that random.
> 
> I thought the trade-off of protection against bad choices of random
> sources was worth the minimal overhead added. I'm not against removing
> it entirely, if there is consensus to do so.

MD5 is now known as a bad hash (it was fine at the time the code was
written), so does it actually improve anything ?

Also, isn't SecureRandom always available now ? This is 10+ years old
code, probably.

> For SecureRandom, yes. I did test this locally and it achieves
> thread-safety by using an internal sync and it did create a significant
> bottleneck. That is why I went the parallel route. Reading from a stream
> has a similar sync so again that is why I went the parallel route.

Ok. The internal lock is a much smaller sync than the old sync block, so
it would be a bit better. It is possible it is noticeable, though. The
question is if this yields a good enough session creation rate.

> How about this as an approach to reduce the complexity:
> 1. Remove the MD5 code (optional)
> 2. Default to /dev/urandom then SecureRandom. Don't fall back to Random.
> 3. Provide a class that implements Random that reads data from a file
> 4. If randomFile is specified, use the the class from 3 as the Random source
> 
> That should reduce the current 3 Queues to one. I doubt it will improve
> performance much but it should make the code clearer.
> 
> Thoughts?

I don't know what the best solution is. /dev/urandom could also only be
used as seed only to a SecureRandom, this is more Javaish.
So about the MD5, I don't think it is useful anymore.

Rémy



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