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Re: 5.8.2 and 5.8.n binary compatibility

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Alan Burlison
November 4, 2003 00:35
Re: 5.8.2 and 5.8.n binary compatibility
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Stas Bekman wrote:

> Alan, your worries have been accounted for. This is precisely the reason 
> I wanted to have a test that mounts an attack on stashes. So we now test 
> that mod_perl 2.0 works just fine if and when such attack happens. 
> Notice that I talk only about stashes, since that's where the black 
> magic overlaps with mod_perl functionality. All other hashes in the 
> "user" space should have no effect on mod_perl.
> It just proves again how important is to write tests before you start 
> solving a problem. We saw mod_perl 2.0 goes broken immediately after 
> plan C was implemented. Though once Nick changed the threshold for 
> rehashing from 4 to 14 the breakage has disappeared, because the normal 
> tests didn't happen to trigger it (that's where your worry kicks in). 
> Now that we have a specific test that mounts the attack and it verifies 
> that the attack was successful (to prevent cases of future changes in 
> the rehashing algorithm) we are covered 100%. If we didn't have this 
> test you indeed would have seen random failures reported by users some 
> time later.

Thanks Stas, now I feel all warm and cozy ;-)

> I doubt that plan C affects any other projects, that don't mess with 
> hashing internals like mod_perl does, any different that they get 
> affected by changes in 5.8.1. So if Tk and DBI did fine with 5.8.1 they 
> will do just as fine with 5.8.2 (assuming of course that they don't 
> mimic mod_perl ;)

Nice job BTW, you and Nick deserve a lot of thanks for all the effort you 
have put in to nail this.

Alan Burlison

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