[ale] Tomcat Monitoring

[cfowler at outpostsentinel.com (Chris Fowler)]

> From: "Chuck Payne" <terrorpup at gmail.com>
> To: "Atlanta Linux Enthusiasts - Yes! We run Linux!" <ale at ale.org>
> Sent: Tuesday, October 4, 2016 9:20:39 AM
> Subject: [ale] Tomcat Monitoring

> Guys,

> I got a couple of Tomcat Apps that when Jenkins does a build the app
> stop responding.

> I can't use tcp port monitor with Nagios, because tomcat is up.

> So is there a way to monitor an app with Nagios, that is the pages
> stop responding. I can get an alert, if I have to write my own jsp
> page to monitor.

Bit behind here. My Xfinity Business is down and I had to link my router to the Xfinity AP on my neighbor's modem. 

1. Define "down". To some ICMP reply is up. To others it is not. Down/Up is an abstract idea that can be very different per application. 

2. You can write a nagios plugin that can go to the web page, grok for some text you'd expect and alarm if it gets a 500 or the code it not there. 

3. I had a user problem when my GUI devs did an update. Their update would take a minute, but some users would see that when the page refreshed. They'd contact us. I instructed my developers to give the user an "under maintenance page" with a 5 minute countdown to refresh. This ended those calls. 

4. Log all exceptions, etc to a file and look at those as needed. You're probably already doing this. 

Your concern is correct. Just because the app engine is up does not mean the app is working. 
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