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From "Gerhard Froehlich" <g-froehl...@gmx.de>
Subject RE: Caching and key collision?
Date Tue, 15 Jan 2002 18:13:10 GMT
Hi,

>From: Berin Loritsch [mailto:bloritsch@apache.org]
>
>
>Kuhnle@heinrich-partner.de wrote:
>
>> 
>> Hi,
>> 
>> I noticed caching is done by generating a key with generateKey. This 
>> returns a long, which is commonly generated through hashing. The 
>> documentation says "This key must be unique inside the space of this 
>> component", which hashing does not guarantee. Won't this lead the cache 
>> to confusing two different cacheable objects (files/server pages/etc.) 
>> which accidently have the same cache value? This sure is an unlikely 
>> event, but ist still can happen. Also, on pipelines with many program 
>> steps, the cache generates very long file names some operatings systems 
>> can't cope with.
>
>
>Regarding the last issue, I have been a victim of that.  Windows 9x
>cannot handle the long filenames generated by the cache.

I recommend to switch off the filesystem swaping in the current version (2.0).
It's buggy. In the next release (2.0.1) there will be a much better swapping
system and this problem will be solved. I'm sorry.

There is a switch called "filesystem" in the <store/> configuration where 
you can switch off the filesystem swapping!

>However, Windows NT and just about every Unix can, so to me this is a
>minor issue--who in their right mind would want to serve anything from
>Windows?
>
>
>A more fundamental issue however is in regards to how quickly an OS
>
>is on seeks.  Windows favors shallow directories and large numbers of files
>in a directory.  UNIX favors deep directories and small numbers of files
>in a directory.
>
>When you go to the extreme that each does not like, you *really* notice
>the slowness.  I have had my Windows machine block for 15 seconds at a
>time while navigating very deep hierarchies (this is especially true on
>Win 9x).  Again, while working on a Perl webapp that cached info on the
>drive, Linux would pause for a few seconds (5-6) when there were about
>1000 entries in a directory before displaying the contents of the directory.
>
>If we could tune our cache to favor what the OS favors, it would add
>just that extra something to make the cache even faster.

As I said in next version 2.0.1 there will be much better solution, which
fix this "long filename" issues. Please stand by!

Sorry, but I'm still learning!

Greets
  Gerhard
 
"God put me on this Earth to accomplish a certain number of things. 
Right now, I am so far behind I shall never die."


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