Application Performance Rule of Three – Active, Passive and User Experience

One of the more interesting developments in IT Management is end user experience monitoring. An end user experience monitor performs a complete transaction, going through several services if required, to validate the entire working state of the service. An example is our MAPI User Experience Monitor. With this one monitor, we validate the subsystem everyone in the office uses for email -works. We send an email and pick it up from the appropriate mailbox. This tests connectivity, Exchange protocol, authentication, message routing, message store, and potentially clustering services. 

For example, if you expected it to take 20 seconds to send a message and get a response from someone@exchange.com and in reality it took 40 seconds, you would receive an alert. Notice that you are simulating user experience through a synthetic transaction. Correlating this to server performance will provide you greater insight into your application performance from the end user perspective. 

So why is this important? Most server monitoring is passive monitoring of performance counter values and the like. Active monitoring tests a component using the appropriate protocol and measures the response. Passive monitoring won't tell you when a firewall is preventing inbound connections, active monitoring will.  However, connecting with an SMTP service and authenticating does not mean the email will reach the mailbox!  Spam filters, message routing, or bogus MX records can trick an "active monitor". However, the best implementation is to use a mix of active, passive & user experience monitors.