how have others conquered external monitor resource alloc problems?

Hey I thought I'd chime in here because I did some work with external monitors over the past couple of days. It seems that the LTM will not execute any commands after receiving anything in STDOUT (i.e. after the "echo" command). So when the check is successful, the "rm -f $pidfile" command in your script does not get executed. I was troubleshooting the fact that my PID file was not getting cleaned up when I expected it to (my script was similar to yours - echo, then rm). But then I noticed the last comment in this Tech Tip:

 

https://devcentral.f5.com/Tutorials/TechTips/tabid/63/articleType/ArticleView/articleId/151/LTM-External-Monitors-The-Basics.aspx

 

 

 

FYI: When the external monitor script outputs "UP" than the deletion of the PIDFILE never occurs, neither does any further commands after the output of "UP"

 

 

It does however delete the PID if the monitor fails. I can only assume the F5 kills the script immediately once any output is detected...

 

 

 

After I read that I did some more testing, and sure enough, that's what I found too despite not being able to find any documentation on it. Not sure that's directly related to your scalability issue, but thought you might want to be aware of it as you develop your automation.