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Al_s_296685's avatar
Al_s_296685
Icon for Nimbostratus rankNimbostratus
Oct 08, 2017

F5 BIG-IP Irule - redirect to individual node for external monitoring

Hi all

I'm looking at implementing an external monitoring solution whereby we do something like the following

  1. read the URI and see if it contains formatting like this "/monitoring/servername" (filter on the "monitoring/" part and set that as a variable)

  2. use that variable as the pool name and send traffic to it (ideally create the pool dynamically based on DNS)

  3. rewrite the uri to remove the "/monitoring/servername" (where servername can be anything) to "*" (whatever is behind /monitoring/servername)

e.g if the f5 receives the following traffic:

HTTP GET: http://testing.com/login/login.aspx/monitoring/server21

It should interpret the string, send the traffic to server21, and remove the /monitoring/server21 from the URI.

i have looked at both policies and irules for this and I am pretty sure I need an irule. However I am not 100% on what to do. I would like the irule to be as flexible as possible ideally.

I know the below does not work but I am just trying to piece it together now... help?

   when HTTP_REQUEST { 
 Check if path contains /monitoring 
    if {[HTTP::path] contains "/monitoring "}{ 
 use getfield to split the uri based on monitoring/ and then return the server name after that
    set server_id [getfield [HTTP::uri] "monitoring/" 1 ]

 Replace /monitoring  with / in the path 
    HTTP::redirect [string map {/monitoring /} [HTTP::path]] 
    pool ${server_id}
    } 
}
application delivery
iRules

3 Replies

  • Al_s_296685's avatar
    Al_s_296685
    Icon for Nimbostratus rankNimbostratus
    Oct 09, 2017

    ok, im getting there towards answering my own question.

    any refinements on this would be appreciated:

    when HTTP_REQUEST { 
 Check if path contains /monitoring 
    if {[HTTP::path] contains "/monitoring/"}{ 

 use getfield to split the uri based on monitoring/ and then return the server name after that
    set server_id [getfield [HTTP::uri] "monitoring/" 2 ]
   log local0. "Server id: $server_id"

 Replace /monitoring and servername in the path 
    set toremove [string range [HTTP::uri] [expr {[string first "/monitoring/" [HTTP::uri]]}] end] 
    log local0. "part of uri to remove: $toremove"
    set replace "/"
    set uri [string map [list $toremove $replace] [HTTP::uri]]
    log local0. "New URI = $uri"
    HTTP::uri $uri

redirect or rewrite uri?
  HTTP::redirect "http://[HTTP::host]$uri"

    pool "/Common/${server_id}"
    } 
}
  • Faruk_AYDIN's avatar
    Faruk_AYDIN
    Icon for Altostratus rankAltostratus
    Oct 09, 2017

    Change the second part(replace) of your irule like this :

    when HTTP_REQUEST { 
 Check if path contains /monitoring 
    if {[HTTP::path] contains "/monitoring/"}{ 

 use getfield to split the uri based on monitoring/ and then return the server name after that
    set server_id [getfield [HTTP::uri] "monitoring/" 2 ]
   log local0. "Server id: $server_id"

 Replace /monitoring and servername in the path 
    set uri [string range [HTTP::uri] 0 [expr {[string first "/monitoring/" [HTTP::uri]] - 1}]] 
    log local0. "orginal part of uri: $uri"
    HTTP::uri $uri

redirect or rewrite uri?
  HTTP::redirect "http://[HTTP::host]$uri"
    pool "/Common/${server_id}"
    } 
}

    If I were you, I would use node ip (and w/o node port) instead of Server name, like this:

    when HTTP_REQUEST { 
 Check if path contains /monitoring 
    if {[HTTP::path] contains "/monitoring/"}{ 

 use getfield to split the uri based on monitoring/ and then return the node ip after that
    set server_id [getfield [HTTP::uri] "monitoring/" 2 ]
   log local0. "Node IP: $node_ip"

 Omit /monitoring and nodeip in the path 
    set uri [string range [HTTP::uri] 0 [expr {[string first "/monitoring/" [HTTP::uri]] - 1}]] 
    log local0. "orginal part of uri: $uri"
    HTTP::uri $uri

 Send the request to the specified node
    node $node_ip 80
    
    } 
}
  • jomedusa's avatar
    jomedusa
    Icon for Altocumulus rankAltocumulus
    Aug 19, 2021

    I have been looking for something similar to this for a bit...do you have any updates or current config that is in production? I am going to test with the above snippet and see the results.

     

    Any additional information would be appreciated.

     

    Joe