Reverse health monitor not working

Thanks for pointing me to the prospect of an external health monitor. With some learning and testing, I was able to accomplish my goal. I used the sample code in this article.

Note that with LTM 11.x and higher, you create an external monitor differently than before. This article details the methods pre and post v11.

I only had to make changes in 2 areas:

Send the request request and check the response nc $IP $PORT | grep "my receive string" 2>&1 > /dev/null

I changed the "my receive string" to the text the server returns. (The above line, for the folks who may be new to scripting and/or shell scripting, is the real heart of this script. It uses netcat (nc) to make a connection to the server's IP and port and look for a response. Note that you dont' change the $IP and $PORT text because those are variables which the script gets from the monitor configuration object. You can run NC from the LTM command line to see what it does.)

Apparently with an External monitor, there is no "reverse" option. To compensate for this, I changed this line:

if [ $? -eq 0 ]

to this:

if [ $? -ne 0 ]

This changes "equals" to "not equals", so that if the script does find the expected string, then the health check fails. This gives the same effect as the reverse option. (This above line is the core element that determines if the health check fails or not. It's checking if the nc command returns a success (an error code "0", or yes/affirmative).

So, thanks again for the assistance with this.