Application Delivery (ADX)

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Contributor
Posts: 39
Registered: ‎05-04-2009

Health Check Q: How do I link the health of a real server on the health check status of another device or service using ServerIrons?

Health Check Q: How do I link the health of a real server on the health check status of another device or service using ServerIrons?

I do have a web server and I would like to ensure the web server is going down in case another backend web server is going down. Is this possible?

Thx for your help.

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

Re: Health Check Q: How do I link the health of a real server on the health check status of another device or service using ServerIrons?

I guess you would like to do the following:

both real server do have a web server installed and you would like to ensure that the front end web server is going down in two cases:

1st: the frontend web server itself is going down

2nd: the backend web server is going down

Is this correct?

If so my suggestion would be the following:

Create to healtck's - one for the frontend and one for the backend server. This would look like:

healthck frontend tcp

  dest-ip  192.168.101.101

  port  80

  protocol  http

  protocol http  url "GET /"

  l7-check


healthck backend tcp

dest-ip 192.168.101.102

port  80

protocol http

protocol http url "GET /"

l7-check

Create a combined healthck (it is called boolean health check policy):

healthck both boolean

  and frontend backend

The frontend healthck is only TRUE/successful in case the real server 192.168.101.101 is getting health checked successfully. Same for the backend one. The "both" healthck is only TRUE/sucessful in case the frontend one AND the backend one is TRUE/successful.

Bind the combined one to the frontend server and the backend one to the backend server:

server real frontend 192.168.101.101

  port 80 healthck both


server real backend 192.168.101.102

  port 80 healthck backend

and you do have what you want.

At least I hope so.

Contributor
Posts: 39
Registered: ‎05-04-2009

Re: Health Check Q: How do I link the health of a real server on the health check status of another device or service using ServerIrons?

I am going to try this but I do not get how to check the reply from the real servers - I would like to look into the actual HTTP reply. The real servers need to respond with a special string otherwise they are not really up and running. Ideas?

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

Re: Health Check Q: How do I link the health of a real server on the health check status of another device or service using ServerIrons?

My example does not fit 100% to this requirement - you do need to configure so called match-lists on top of the stuff above.

Let me use an example again: the backend web server needs to respond with "IamFEELINGgood" to be up and running.

Add the following to the example above:

http  match-list web-ok

default down

up  simple "IamFEELINGgood”

healthck backend tcp

dest-ip 192.168.101.102

port  80

protocol http

protocol http url "GET /"

protocol http content-match web-ok

l7-check

Feel free to change the query to something else than "GET /" in case you would like to request a special page. Happy now?

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