Antwort: RE: [Mod_gzip] Request Handling

Thu, 9 Oct 2003 22:43:28 EDT

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Hi Etienne...
This is Kevin Kiley...

Someone mentioned this a few messages back but since
you still haven't said which 'Application Server' you are 
using I thought I would also mention this...

...sometimes the only way to get the output of an 'Application
Server' compressed ( versus simple CGI backend ) is to make
sure you have an 'include handler' statement for this particular
back-end Server in your mod_gzip config file.

The way most 'Application Servers' work with Apache follows
the original 'Coldfusion' model.

The authors of the Application Server usually write a small
'mod_xxxxx' module of their own for Apache and you usually
have to install that into your Apache Server.

What this module usually does is 'intercept' requests that 
the Application Server is supposed to handle.

Almost all of these "Application Server" modules do this in
the same way the original 'ColdFusion' Apache module
did it. They register a 'handler' name into the request
structure at one of the low-level Apache 'hooks' and then
some 'higher-up' hook sees the 'handler' name and
knows that this request is meant for that particular
Application Server.

Example: At the lowest level hook possible... the
mod_coldfusion module registers a 'handler' name
of 'coldfusion' on any request that Coldfusion is
supposed to handle.

The problem here is that once a higher level hook
has 'seen' this handler name and sent the transaction
to the application server... it usually does a 'Return ZERO'
from the hook and in Apache code this means that no
other handlers get called for that transaction.

So... to make a long, boring story short... it usually isn't
enough to just enter some URI inclusion 'rules' in 
the mod_gzip config and expect them to get compressed
if the request gets passed off to a 'back end' Application
Server.

You must ALSO have something like this ( which is what
works for ColdFusion... )

mod_gzip_item_include handler coldfusion

Now what happens is that mod_gzip has a chance to
intercept the transactions that are going to be given
a 'handler' name of 'coldfusion' but ONLY if the URI
matches some other 'regular' rule that you have
established for compressing output.

I know this all sounds a little complicated but many 
people are not aware of this 'handler' scheme in Apache
unless they use something like ColdFusion.

It's a little obscure but it's the way Apache works.

Any module that wanted to intercept transactions for
back-end servers using this 'handler name' scheme would
have to have a similar parameter so the NAME of the
handler can be set at runtime.

If your 'Application Server' does NOT have it's own small
'mod_xxx' module that needs to be installed into Apache
and/or does not follow this standard 'ColdFusion' approach
I would be curious to know exactly how it DOES work?

Later...
Kevin

PS: The actual NAME of the handler that is going to be
registered inside Apache does NOT necessarily have
to match the name of the Application Server module that
gets installed into Apache.

In the case of ColdFusion... they just 'happen' to be the
same. The Application Server module you install is called
'mod_coldfusion' and the 'handler' name just happens to
be 'coldfusion' as well ( lowercase ).

In truth... the ONLY way to be SURE what the actual 'handler'
name might be is to look at the source code for the Application
Server module and see exactly what 'handler' name they are
registering at runtime.

The name of the module could be mod_super_back_end_server
but the 'handler' name being registered could be anything such
as 'super_back_end_server_whatchamacallit'.

It isn't a military secret so anyone familiar with the Application
Server should know what this 'handler' name is... but if things
don't seem to work then the first thing to verify is that you
have the right HANDLER NAME for this particular
Application Server. Don't make any 'assumptions' about it.

In a message dated 10/9/2003 5:20:29 AM Central Daylight Time, 
Michael.Schroepl@telekurs.de writes:

> 
> 
> Hi Etienne,
> 
> 
> > Is this functionality currently in the mod_gzip module or
> > is that something that we would have to request from you?
> 
> please tell us more about what you mean by "application
> server".
> Do you mean a separate HTTP server (which you might then
> embed via mod_proxy into some other "compressing Apache"
> as a front-end), or do you mean something inside the same
> Apache, which is more like an Apache Handler, servlet
> engine or CGI script?
> 
> In any case, mod_gzip is able to compress content that has
> been produced by URL requests, be it static or dynamic con-
> tent. So all you have to do is write the proper mod_gzip
> inclusion rules to cover your content in both detection
> phases (see
>      http://www.schroepl.net/projekte/mod_gzip/config.htm#filters
> for details), and it should work then.
> 
> Regards, Michael
> 
> 
> _______________________________________________
> mod_gzip mailing list
> mod_gzip@lists.over.net
> http://lists

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<HTML><FONT FACE=3Darial,helvetica><FONT  SIZE=3D2><BR>
Hi Etienne...<BR>
This is Kevin Kiley...<BR>
<BR>
Someone mentioned this a few messages back but since<BR>
you still haven't said which 'Application Server' you are <BR>
using I thought I would also mention this...<BR>
<BR>
...sometimes the only way to get the output of an 'Application<BR>
Server' compressed ( versus simple CGI backend ) is to make<BR>
sure you have an 'include handler' statement for this particular<BR>
back-end Server in your mod_gzip config file.<BR>
<BR>
The way most 'Application Servers' work with Apache follows<BR>
the original 'Coldfusion' model.<BR>
<BR>
The authors of the Application Server usually write a small<BR>
'mod_xxxxx' module of their own for Apache and you usually<BR>
have to install that into your Apache Server.<BR>
<BR>
What this module usually does is 'intercept' requests that <BR>
the Application Server is supposed to handle.<BR>
<BR>
Almost all of these "Application Server" modules do this in<BR>
the same way the original 'ColdFusion' Apache module<BR>
did it. They register a 'handler' name into the request<BR>
structure at one of the low-level Apache 'hooks' and then<BR>
some 'higher-up' hook sees the 'handler' name and<BR>
knows that this request is meant for that particular<BR>
Application Server.<BR>
<BR>
Example: At the lowest level hook possible... the<BR>
mod_coldfusion module registers a 'handler' name<BR>
of 'coldfusion' on any request that Coldfusion is<BR>
supposed to handle.<BR>
<BR>
The problem here is that once a higher level hook<BR>
has 'seen' this handler name and sent the transaction<BR>
to the application server... it usually does a 'Return ZERO'<BR>
from the hook and in Apache code this means that no<BR>
other handlers get called for that transaction.<BR>
<BR>
So... to make a long, boring story short... it usually isn't<BR>
enough to just enter some URI inclusion 'rules' in <BR>
the mod_gzip config and expect them to get compressed<BR>
if the request gets passed off to a 'back end' Application<BR>
Server.<BR>
<BR>
You must ALSO have something like this ( which is what<BR>
works for ColdFusion... )<BR>
<BR>
mod_gzip_item_include handler coldfusion<BR>
<BR>
Now what happens is that mod_gzip has a chance to<BR>
intercept the transactions that are going to be given<BR>
a 'handler' name of 'coldfusion' but ONLY if the URI<BR>
matches some other 'regular' rule that you have<BR>
established for compressing output.<BR>
<BR>
I know this all sounds a little complicated but many <BR>
people are not aware of this 'handler' scheme in Apache<BR>
unless they use something like ColdFusion.<BR>
<BR>
It's a little obscure but it's the way Apache works.<BR>
<BR>
Any module that wanted to intercept transactions for<BR>
back-end servers using this 'handler name' scheme would<BR>
have to have a similar parameter so the NAME of the<BR>
handler can be set at runtime.<BR>
<BR>
If your 'Application Server' does NOT have it's own small<BR>
'mod_xxx' module that needs to be installed into Apache<BR>
and/or does not follow this standard 'ColdFusion' approach<BR>
I would be curious to know exactly how it DOES work?<BR>
<BR>
Later...<BR>
Kevin<BR>
<BR>
PS: The actual NAME of the handler that is going to be<BR>
registered inside Apache does NOT necessarily have<BR>
to match the name of the Application Server module that<BR>
gets installed into Apache.<BR>
<BR>
In the case of ColdFusion... they just 'happen' to be the<BR>
same. The Application Server module you install is called<BR>
'mod_coldfusion' and the 'handler' name just happens to<BR>
be 'coldfusion' as well ( lowercase ).<BR>
<BR>
In truth... the ONLY way to be SURE what the actual 'handler'<BR>
name might be is to look at the source code for the Application<BR>
Server module and see exactly what 'handler' name they are<BR>
registering at runtime.<BR>
<BR>
The name of the module could be mod_super_back_end_server<BR>
but the 'handler' name being registered could be anything such<BR>
as 'super_back_end_server_whatchamacallit'.<BR>
<BR>
It isn't a military secret so anyone familiar with the Application<BR>
Server should know what this 'handler' name is... but if things<BR>
don't seem to work then the first thing to verify is that you<BR>
have the right HANDLER NAME for this particular<BR>
Application Server. Don't make any 'assumptions' about it.<BR>
<BR>
<BR>
<BR>
<BR>
In a message dated 10/9/2003 5:20:29 AM Central Daylight Time, Michael.Schro=
epl@telekurs.de writes:<BR>
<BR>
<BR>
<BLOCKQUOTE TYPE=3DCITE style=3D"BORDER-LEFT: #0000ff 2px solid; MARGIN-LEFT=
: 5px; MARGIN-RIGHT: 0px; PADDING-LEFT: 5px"><BR>
<BR>
Hi Etienne,<BR>
<BR>
<BR>
&gt; Is this functionality currently in the mod_gzip module or<BR>
&gt; is that something that we would have to request from you?<BR>
<BR>
please tell us more about what you mean by "application<BR>
server".<BR>
Do you mean a separate HTTP server (which you might then<BR>
embed via mod_proxy into some other "compressing Apache"<BR>
as a front-end), or do you mean something inside the same<BR>
Apache, which is more like an Apache Handler, servlet<BR>
engine or CGI script?<BR>
<BR>
In any case, mod_gzip is able to compress content that has<BR>
been produced by URL requests, be it static or dynamic con-<BR>
tent. So all you have to do is write the proper mod_gzip<BR>
inclusion rules to cover your content in both detection<BR>
phases (see<BR>
&nbsp;&nbsp;&nbsp;&nbsp; http://www.schroepl.net/projekte/mod_gzip/config.ht=
m#filters<BR>
for details), and it should work then.<BR>
<BR>
Regards, Michael<BR>
<BR>
<BR>
_______________________________________________<BR>
mod_gzip mailing list<BR>
mod_gzip@lists.over.net<BR>
http://lists</BLOCKQUOTE><BR>
<BR>
</FONT></HTML>
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