Timeperiod definitions allow you to control when various aspects of the monitoring and alerting logic can operate. For instance, you can restrict:
When regularly scheduled host and service checks can be performed
When notifications can be sent out
When notification escalations can be used
When dependencies are valid
Precedence in Time Periods
Timeperiod definitions may contain multiple types of directives, including weekdays, days of the month, and calendar dates. Different types of directives have different precendence levels and may override other directives in your timeperiod definitions. The order of precedence for different types of directives (in descending order) is as follows:
Calendar date (2008-01-01)
Specific month date (January 1st)
Generic month date (Day 15)
Offset weekday of specific month (2nd Tuesday in December)
Offset weekday (3rd Monday)
Normal weekday (Tuesday)
Examples of different timeperiod directives can be found here.
How Time Periods Work With Host and Service Checks
Host and service definitions have an optional check_period directive that allows you to specify a timeperiod that should be used to restrict when regularly scheduled, active checks of the host or service can be made.
If you do not use the check_period directive to specify a timeperiod, Icinga will be able to schedule active checks of the host or service anytime it needs to. This is essentially a 24x7 monitoring scenario.
Specifying a timeperiod in the check_period directive allows you to restrict the time that Icinga perform regularly scheduled, active checks of the host or service. When Icinga attempts to reschedule a host or service check, it will make sure that the next check falls within a valid time range within the defined timeperiod. If it doesn't, Icinga will adjust the next check time to coincide with the next "valid" time in the specified timeperiod. This means that the host or service may not get checked again for another hour, day, or week, etc.
On-demand checks and passive checks are not restricted by the timeperiod you specify in the check_period directive. Only regularly scheduled active checks are restricted.
Unless you have a good reason not to do so, I would recommend that you monitor all your hosts and services using timeperiods that cover a 24x7 time range. If you don't do this, you can run into some problems during "blackout" times (times that are not valid in the timeperiod definition):
The status of the host or service will appear unchanged during the blackout time.
Contacts will mostly likely not get re-notified of problems with a host or service during blackout times.
If a host or service recovers during a blackout time, contacts will not be immediately notified of the recovery.
How Time Periods Work With Contact Notifications
By specifying a timeperiod in the notification_period directive of a host or service definition, you can control when Icinga is allowed to send notifications out regarding problems or recoveries for that host or service. When a host notification is about to get sent out, Icinga will make sure that the current time is within a valid range in the notification_period timeperiod. If it is a valid time, then Icinga will attempt to notify each contact of the problem or recovery.
You can also use timeperiods to control when notifications can be sent out to individual contacts. By using the service_notification_period and host_notification_period directives in contact definitions, you're able to essentially define an "on call" period for each contact. Contacts will only receive host and service notifications during the times you specify in the notification period directives.
Examples of how to create timeperiod definitions for use for on-call rotations can be found here.
How Time Periods Work With Notification Escalations
Service and host notification escalations have an optional escalation_period directive that allows you to specify a timeperiod when the escalation is valid and can be used. If you do not use the escalation_period directive in an escalation definition, the escalation is considered valid at all times. If you specify a timeperiod in the escalation_period directive, Icinga will only use the escalation definition during times that are valid in the timeperiod definition.
How Time Periods Work With Dependencies
Service and host dependencies have an optional dependency_period directive that allows you to specify a timeperiod when the dependendies are valid and can be used. If you do not use the dependency_period directive in a dependency definition, the dependency can be used at any time. If you specify a timeperiod in the dependency_period directive, Icinga will only use the dependency definition during times that are valid in the timeperiod definition.
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