Yoopl is capable of monitoring hosts and services in two ways: actively and passively. Passive checks are described elsewhere, so we'll focus on active checks here. Active checks are the most common method for monitoring hosts and services. The main features of actives checks as as follows:
- Active checks are initiated by the Yoopl process
- Active checks are run on a regularly scheduled basis
How Are Active Checks Performed?
Active checks are initiated by the check logic in the Yoopl cron. When Yoopl needs to check the status of a host or service it will execute a script and pass it information about what needs to be checked. The checkcommand will then check the operational state of the host or service and report the results back to the Yoopl. Yoopl will process the results of the host or service check and take appropriate action as necessary (e.g. send notifications, run event handlers, etc).
More information on how checkcommand work can be found here.
When Are Active Checks Executed?
Active check are executed:
- At regular intervals, as defined by the check_interval and retry_interval options in your host and service definitions
- On-demand as needed
Regularly scheduled checks occur at intervals equaling either the
check_interval or the
retry_interval in your host or service definitions, depending on what type of state the host or service is in. If a host or service is in a HARD state, it will be actively checked at intervals equal to the
check_interval option. If it is in a SOFT state, it will be checked at intervals equal to the
On-demand checks are performed whenever Yoopl sees a need to obtain the latest status information about a particular host or service. For example, when Yoopl is determining the reachability of a host, it will often perform on-demand checks of parent and child hosts to accurately determine the status of a particular network segment. On-demand checks also occur in the predictive dependency check logic in order to ensure Yoopl has the most accurate status information.