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- Active checks are initiated by the Shinken Enterprise poller process
- Active checks run on a regular scheduled basis
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Active checks are initiated by the check logic in the Shinken Enterprise daemon. When Shinken Enterprise needs to check the status of a host or a check, it will execute a plugin and show the information about what needs to be checked. The plugin will then check the operational state of the host or check and report the results back to the Shinken Enterprise daemon. The scheduler daemon will process the results of the host or check and take the appropriate action if necessary (e.g. send notifications, ask for event handlers, etc).
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In most cases you'll use Shinken Enterprise to monitor your hosts and checks using regularly scheduled :ref:`active checks <thebasics/activechecks>`. Active checks can be used to "poll" a device or check for status information every so often. Shinken Enterprise also supports a way to monitor hosts and checks passively instead of actively. They key features of passive checks are the following:
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The major difference between active and passive checks is that active checks are initiated and performed by Shinken Enterprise, while passive checks are performed by external applications.
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- The external application writes the results of the check to the external command named pipe (a named pipe is a "memory pipe", so there is no disk IO involved).
- Shinken Enterprise reads the external command file and places the results of all passive checks into a queue for processing by the appropriate process in the Shinken Enterprise cloud.
- Shinken Enterprise will get results each second and scan the check result queue. Each check result that is found in the queue is processed in the same way - regardless whether the check was active or passive. Shinken Enterprise may send out notifications, log alerts, etc. depending on the check result information.
The processing of active and passive check results is essentially the same. This allows for seamless integration of status information from external applications with Shinken Enterprise.
Enabling Passive Checks
In order to enable passive checks in Shinken Enterprise, you'll need to do the following:
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External applications can submit passive check check results to Shinken Enterprise by writing a PROCESS_check_CHECK_RESULT external command to the external command pipe, which is essentially a file handle that you write to as you would do with a file.
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A check must be defined in Shinken Enterprise before Shinken it will accept passive check results for it! Shinken Enterprise will ignore all check results for checks that have not been configured before it was last (re)started.
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A host must be defined in Shinken Enterprise before you can submit passive check results for it! Shinken Enterprise will ignore all check results for hosts that had not been configured before it was last (re)started.
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Unlike with active host checks, Shinken Enterprise does not (by default) attempt to determine whether or host is DOWN or UNREACHABLE with passive checks. Rather, Shinken Enterprise takes the passive check result to be the actual state the host is in and doesn't try to determine the hosts' actual state using the reachability logic . This can cause problems if you are submitting passive checks from a remote host.
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