iRule to force usage of Content Distribution [Modify HTML Out]

OK, just to clarify a few things before I respond in full;

 

 

1) Presently, you are redirecting based on request URI yes?

 

2) You'd rather rewrite responses to avoid the redirect yes?

 

3) Is there a direct correlation between the request URI and the CDN URI? So would www.site.com/images/test.jpg be located at cdn.site.com/images/test.jpg? If not, this is going to be a very long iRule =]

Hello! Thank you for the swift response...

 

 

1) Presently, you are redirecting based on request URI yes?

 

 

Yes - if the request URI ends with an image extension, it will redirect

 

 

2) You'd rather rewrite responses to avoid the redirect yes?

 

 

Yes - unless I can find some confirmation all browsers (including mobile browsers) will follow redirect requests for images.. I have not been able to confirm nor deny this

 

 

3) Is there a direct correlation between the request URI and the CDN URI? So would www.site.com/images/test.jpg be located at cdn.site.com/images/test.jpg? If not, this is going to be a very long iRule =]

 

 

Yes, it is literally www.site.com/blah.jpg == cdn.site.com/blah.jpg, so on and so forth.

 

 

The CDN provider uses a cname (cdn.site.com) and just correlates that to an origin source which has images in the exact same path.

Is it possible to modify the html output? or would that be too exaustive on the device itself?i think it is possible. i do not know whether it is too exhaustive on the device or not. anyway, the following code is just a simple example.

 

 

e.g.

 

 

[root@ve10:Active] config  b virtual bar list
virtual bar {
   snat automap
   pool foo
   destination 172.28.19.79:80
   ip protocol 6
   rules myrule
   profiles {
      myhttp {}
      stream {}
      tcp {}
   }
}
[root@ve10:Active] config  b pool foo list
pool foo {
   members 200.200.200.101:80 {}
}
[root@ve10:Active] config  b profile myhttp list
profile http myhttp {
   defaults from http
   header erase "Accept-Encoding"
}

 original content

[root@ve10:Active] config  curl -i http://200.200.200.101
HTTP/1.1 200 OK
Date: Tue, 27 Nov 2012 15:47:46 GMT
Server: Apache/2.2.3 (CentOS)
Last-Modified: Sat, 27 Oct 2012 03:22:35 GMT
ETag: "4183f3-59-f28f94c0"
Accept-Ranges: bytes
Content-Length: 89
Content-Type: text/html; charset=UTF-8

...snipped...
This is 101 host.

...snipped...

 modified content

[root@ve10:Active] config  curl -i http://172.28.19.79
HTTP/1.1 200 OK
Date: Tue, 27 Nov 2012 15:47:54 GMT
Server: Apache/2.2.3 (CentOS)
Last-Modified: Sat, 27 Oct 2012 03:22:35 GMT
ETag: "4183f3-59-f28f94c0"
Accept-Ranges: bytes
Content-Type: text/html; charset=UTF-8
Transfer-Encoding: chunked

...snipped...
This is 101 host.

...snipped...

I think you missed the iRule Nitass?

thanks Steve. 🙂

[root@ve10:Active] config  b rule myrule list
rule myrule {
   when HTTP_REQUEST {
  STREAM::disable
}
when HTTP_RESPONSE {
  if { [HTTP::header value Content-Type] contains "text" }{
    STREAM::expression {&".*?\.gif&&}
    STREAM::enable
  }
}
when STREAM_MATCHED {
  STREAM::replace [string map {\" \"http://cdn.site.com/} [STREAM::match]]
}
}

Just out of interest Nitass why do you delete the HTTP Accept-Encoding header? Doesn't the iRule event execute before compression takes place?

The forum code munged the stream expression. It should be:

 

 

STREAM::expression {@".*?\.gif@@}

 

 

Also make sure that the config loads after updating the iRule as the unbalanced double quote might throw off the parser.

 

 

Steve, you remove the Accept-Encoding header on requests to the pool to prevent the server from sending compressed response content. Compressed content isn't decompressed by TMM before applying the stream filter.

 

 

Aaron

Thanks as ever Aaron.