Cloud monitoring sometimes means monitoring tools running in the cloud. It sometimes means tools that monitor applications running in the cloud. And it sometimes means both. Are cloud monitoring tools different than the monitoring tools we're used to running in our data centers? Not necessarily. But certainly today's Web applications -- regardless of where they're running -- present a new set of challenges, and the makers of monitoring tools are racing to meet them.
We still have the sophisticated agents that watch the entire application stack and report on everything happening within. And we still have the external monitors that pretend to be visitors, requesting URLs and timing the responses. But the tool makers are extending these traditional architectures with adaptive mechanisms that react to the statistics or the responses and probe the system with further tests. The tests are growing more sophisticated and doing a better job of detecting hidden failures.
Today's monitoring tools are also casting a wider net, supplementing their site testing with additional data. Some tools integrate data gathered from the Web server, application server, and the network. Others search out data from third-party partners that can reveal how the website is performing. If the external data reveals problems, the monitoring tool can deploy more tests that probe the website to explain why the numbers aren't adding up.
Whether cloud-based or cloud-oriented, cloud monitoring tools generally work like the monitoring tools we already know. They watch the network, ping the servers, download Web pages, and track the performance of URLs. But if your website is knit together from a bunch of machines that may be anywhere, there's no longer a reason to insist on doing all of the monitoring locally. Or if your Web application lives in the cloud, reacting to the traffic and load by growing and shrinking dynamically, then it makes sense to use cloud-based monitoring services that can also grow and shrink with demand.