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From Brian Mearns <>
Subject Re: [users@httpd] Custom ETags
Date Thu, 15 Apr 2010 11:01:40 GMT
On Tue, Apr 13, 2010 at 4:50 PM, Florian S. <> wrote:
> Am Dienstag, den 13.04.2010, 10:34 -0400 schrieb Brian Mearns:
>> I'd like to use stronger and correlated ETag, namely the hash of the
>> content being served. Obviously it's a drag to do this in-line, so I'm
>> planning an automated task to generate the ETag values and store them
>> on the server. Is there any way I can get httpd to grab these stored
>> values for use in the Etag header? I'm flexible on how I store them:
>> in a database, in one large file, each in its own file named according
>> to the resource, etc.
>> Any ideas?
>> Thanks,
>> -Brian
> Hi,
> Here a short presentation of how I would face this problem:
> I found a nice & powerful way of including external scripts depending on
> URL/I: RewriteMap. I think its performance is sufficient, since the
> process gets spawned only once and the stdio-stuff happens only.
> Text-Databases are supported, too. The output (the ETag?) could be
> stored in a Envar with a corresponding RewriteRule (E-flag). Then you
> can do a few checks and/or use 'Header set ETag new_tag env=new_tag' or
> something similiar.
> Not tested at all & sounds strange, but may be a starting point.
> Regards:
>        Florian

Thanks, Florian. That's a pretty clever idea, definitely something
I'll add to my bag of tricks. I don't think it will help me in this
case, though, as it occurs to me that just setting the ETag header
isn't enough, I have to get Apache to act on it (honor conditional
requests). It sounds like the only real Apache solution is to create a
module to do what I want, but that's probably not going to happen
anytime soon.

In the mean time, I probably will just throw together a PHP script
through which all the appropriate resources are accessed. It can read
the Etags from the file/database and decide what to do with
conditional responses.

Thanks for the great idea!

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