Even the best use of logging can help only when the application is actually running. Dead processes log no tales. Neither do hung processes. For those, some entity outside the process itself must be watching—some black-box tool monitoring the health and well-being of the application and its host.
This is the domain of monitoring systems. Figure 39, Conceptual View of a Monitoring System depicts a vastly simplified view of a monitoring system. The essential components of this third-party inspector are agents that collect information, a reliable transport mechanism, and the display and processing of the information.