Application Delivery (ADX)

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Contributor
Posts: 35
Registered: ‎05-04-2009

Need help with SI health checks - real servers depend on other real servers

I am  working on a SI implementation that is a competitive takeover of a 5 year old F5  environment.  The existing F5 implementation has a perl script that is doing  something with some healthchecks that I have not been able to duplicate so far.  In  this scenario I need to configure the ServerIron to do normal HTTP healthchecks  on the web servers and then do all the normal load balancing stuff – no problem  (6 different web sites).  The problem I am having is a special server called "APS" (Application STatus) - it is some kind of managment server.

What  they do with this server is when the web site is in normal production, there is  a directory with a file called up.txt but when the web sites are in a  maintenance window the file up.txt gets deleted and a file called down.txt is  created and placed in the same directory.  When the down.txt file appears I need  to stop sending users to the web servers and redirect them to the webbappsdn  server.  On the webappsdn server is a simple web page that states the service is  down.

When  the web server maintenance is being performed the web servers are still up and  healthchecks are good.  I have not been able to find a good combination of  content match, Boolean and standard healthchecks that lets me be able to replace  this functionality of the F5s.  If anybody has any ideas or has done something  similar please let me know.  Any help is greatly  appreciated.

Super Contributor
Posts: 316
Registered: ‎05-01-2009

Re: Need help with SI health checks - real servers depend on other real servers

I would  suggest to have a look at nested health checks. You might want to do the  following:

1. Webserver1  is UP in case Webserver1 is UP AND up.txt is available at the app-status  server

2. Webserver2  is UP in case Webserver2 is UP AND up.txt is available at the app-status  server

3. APS is  UP in case APS is UP AND down.txt is available at the app-status  server

You would  have to bind ALL the three servers (webserver1, webserver2 and webappsdn) to the  virtual server. This should  work. The situation will be the following:

case 1: up.txt is there: there is no way that APS is up because this requires down.txt - but the webservers might be up

case 2: down.txt is there: there is no way that the webservers are up because this requires up.txt - but the APS server might be up

Contributor
Posts: 35
Registered: ‎05-04-2009

Re: Need help with SI health checks - real servers depend on other real servers

This is indeed working from what it looks like. Thanks for your help.

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