Forum Discussion

Igor_Morgado_38's avatar
Igor_Morgado_38
Icon for Nimbostratus rankNimbostratus
Feb 03, 2011

HTTP response data (html body) rewrite - questions

Hello

Im trying to apply a stream profile to change a string in html response from server the source is:


body  marginheight="0" marginwidth="0" rightmargin="0" leftmargin="0" topmargin="0"  onload="onLoadBody()"

I want to set as 


body  marginheight="0" marginwidth="0" rightmargin="0" leftmargin="0" topmargin="0"

Creating a stream profile seems not work, my actual configuration in stream profile is:


Source: onload="onLoadBody()"
Target:  (empty) tried put some placeholder  and also didnt worked.

My VS has the following configs:


virtual vs_mgp {
   snat automap
   pool mgp_http_pool
   destination 172.27.0.251:http
   ip protocol tcp
   persist mgp_pr_srcaddr
   profiles {
      mgp-http-lan-optimized-caching {}
      mgp-oneconnect {}
      mgp-tcp-lan-optimized {
         serverside
      }
      mgp_remove_onload {}
      tcp-wan-optimized {
         clientside
      }
   }
}
ltm profile http mgp-http-lan-optimized-caching {
    defaults-from http-lan-optimized-caching
    insert-xforwarded-for disabled
    ramcache disabled
    ramcache-uri-exclude none
    ramcache-uri-include none
    ramcache-uri-pinned none
    response-chunking rechunk
}
ltm profile one-connect mgp-oneconnect {
    defaults-from oneconnect
}
ltm profile stream mgp_remove_onload {
    defaults-from stream
    source "onload=\"onLoadBody()\""
    target TAGME
}

application delivery
dev
devops
iRules
  • hooleylist's avatar
    hooleylist
    Icon for Cirrostratus rankCirrostratus
    Feb 03, 2011
    Hi Igor,

     

     

    Can you wrap the code and configuration portions in [ code ] [/ code ] tags so the post is legible?

     

     

    Thanks, Aaron
  • hooleylist's avatar
    hooleylist
    Icon for Cirrostratus rankCirrostratus
    Feb 03, 2011
    Is the server sending compressed response payloads? If so, LTM won't decompress it before applying the stream profile. You could check the responses using a browser plugin like HttpFox for Firefox or Fiddler2. If you want to prevent server response payload compression, you can use a simple iRule: 

    
when HTTP_REQUEST {
   HTTP:header remove "Accept-Encoding"
}

    You could also use an iRule to configure the stream filter and only apply it to text responses. By default, when you use a stream profile and HTTP profile, both request and response payloads will have the stream filter applied. For examples of an iRule, you can check the STREAM::expression wiki page:

    http://devcentral.f5.com/wiki/default.aspx/iRules/stream__expression

    Aaron
  • Igor_Morgado_38's avatar
    Igor_Morgado_38
    Icon for Nimbostratus rankNimbostratus
    Feb 03, 2011
    Right,

    As you told, stream is applied *before* the decompression. But on iRules will I got the payload uncompressed?

    If so I can let the compress working as is, and do the irule.

    Something like: (shamelessly coppied from devcentral wiki üòâ 

    when HTTP_REQUEST {
    Disable the stream filter for all requests
   STREAM::disable
}
when HTTP_RESPONSE {

    Check if response type is text
   if {[HTTP::header value Content-Type] contains "text"}{

       Remove Body onload attribute
      STREAM::expression "@onload=\"onLoadBody()\"@@"

       Enable the stream filter for this response only
      STREAM::enable
   }
}

    That is it?

  • hooleylist's avatar
    hooleylist
    Icon for Cirrostratus rankCirrostratus
    Feb 04, 2011
    That looks good to me. You could avoid the backslash escapes by using curly braces to prevent interpretation:

     

     

    STREAM::expression {@onload="onLoadBody()"@@}

     

     

    Also, I'm referring to server response payload. LTM compression should be done to responses after the stream filter is applied (though I haven't explicitly tested this before).

     

     

    Aaron
  • Igor_Morgado_38's avatar
    Igor_Morgado_38
    Icon for Nimbostratus rankNimbostratus
    Feb 04, 2011
    Nice. It worked, but I have noticed that my problem was the Accept Encoding.

     

     

    I understood that stream happens BEFORE deflating. But removing the Accept-encoding header didnt I lose the compression client site? If so how can I get the best of two worlds?

     

     

    Being able to stream profile and keep compression on client side.

     

     

    Cheers,
  • hooleylist's avatar
    hooleylist
    Icon for Cirrostratus rankCirrostratus
    Feb 07, 2011
    If you have compression licensed on LTM, you could enable it in a custom HTTP profile. LTM would apply the stream profile/iRule first and then compress the response content.

     

     

    Aaron