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Greywolf_99040's avatar
Greywolf_99040
Icon for Nimbostratus rankNimbostratus
Oct 31, 2011

properly return 304?

Hi, folks, I know this looks "f5-irrelevant" but bear with me a moment.

 

 

 

Problem: Database getting pounded on app cache rebuild

 

Symptom: Too many connections to database

 

Desired solution: To have the F5 return a properly crafted 304 response so that the caller understands that his request has not changed, based on a URI, which is taken from an external data file, presumably type "String"

 

 

 

in v9 and v10, I need help on:

 

 

 

* writing a properly crafted 304 response

 

 

 

* constructing an external data file and an iRule that makes use of this data file; if the DB is overloaded, I want the data file to contain a universal match, while if the DB is not overloaded, I want the data file to contain a string that is not likely to match, because in the iRule, if the incoming URI matches the class lookup in the file, it is to send out the properly crafted 304, while if there is no match, the request is simply passed through.

 

 

 

[This was previously listed as "need to test for the existence of a file". Ostensibly it would be cool just to have it send back the content of a file if it exists but not to error out if it DOESN'T exist.]

 

 

 

Signed,

 

 

 

One Very Confused iRule Student.

 

application delivery
dev
devops
iRules

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  • Kurt_Knochner_5's avatar
    Kurt_Knochner_5
    Icon for Cirrus rankCirrus
    Nov 01, 2011
    I need a directive that will let me test for a file

     

     

    where is that file located? On the LB or some where else? Furthermore an example for the several cases would help to understand better what you want to do. BTW: you are trying to match ///nomatch/// and /*, but against WHAT are you comparing those strings? The content of a file? I think I'm a bit confused ;-)

     

     

    Regards

     

    Kurt Knochner
  • Greywolf_99040's avatar
    Greywolf_99040
    Icon for Nimbostratus rankNimbostratus
    Nov 01, 2011
    Good Day, Kurt, thanks for your reply. It occurred to me that I was not succinct in what I needed, even in my own mind. I have tried to restate the problem as it lies, in hopes it will make more sense.

     

     

  • Patrick_Chang_7's avatar
    Patrick_Chang_7
    Historic F5 Account
    Nov 01, 2011
    iRules do not have access to the file system. However, they do have access to external data groups. You just have to have another process that can write to that file on the F5 system. Please keep in mind that the format of this external data group must be correct and that it has changed between version 9 and version 10 of F5's code. As for constructing a proper 304 message:

     

    Use HTTP::respond
  • Greywolf_99040's avatar
    Greywolf_99040
    Icon for Nimbostratus rankNimbostratus
    Nov 01, 2011
    Patrick, thanks, yes, I get all that; however, just placing the following iRule [for testing a 304 response] does not work -- I get "Web page not available"

     

     

    when HTTP_REQUEST {

     

    HTTP::respond 304

     

    }

     

     

    What am I doing wrong, including what am I expecting to happen that is not happening?

     

     

    Yes, I am a WebAdmin/f5 NOOOOOOOOOB!

     

  • Michael_Yates's avatar
    Michael_Yates
    Icon for Nimbostratus rankNimbostratus
    Nov 01, 2011
    Hi Grewolf,

     

     

    I would guess that your iRule is working correctly and that the 304's that the iRule is returning are causing your browser to pull the content from Cache.

     

     

    I would suggest using a tool like HTTPWatch or Fiddler2 to view the HTTP::status codes that are being returned (they also proved a lot of nice additional information). HTTPWatch has a free version and Fiddler2 is free.

     

     

    If you want a shortcut you can just change the status code to a 403 or 500 and verify that the iRule is indeed working.

     

     
when HTTP_REQUEST {
HTTP::respond 403
}

     

    Hope this helps.