Generate Internal Events to Trigger Event Policies
Understanding Internal Events
Internal events are events that you create to trigger an event policy. Internal events are not generated by Junos OS processes, and they do not have any associated system log messages. You can configure up to 10 internal events, and you can generate an internal event based on a time interval or the time of day. Event policies can match on internal events in the same way that they match on other events.
If you attempt to commit a configuration with more than 10 internal events, Junos OS generates an error, and the commit fails.
To configure an internal event, include the following
statements at the [edit event-options] hierarchy level:
[edit event-options] generate-event { event-name (time-interval seconds <start-time start-time> | time-of-day time) <no-drift>; }
You can configure the time-interval option to generate events at a specific frequency, or you can configure
the time-of-day option to generate events
at a specific time of day. Starting in Junos OS Release 14.1, you
can configure the no-drift option for internal events.
When you configure no-drift, Junos OS does not propagate
the delay caused in triggering an event to the triggering of the next
event.
The start-time option enables you
to specify the start date and time for interval-based events. Thus,
the start-time option must be configured
with the time-interval option. If you
configure the start-time option by itself
or with the time-of-day option and commit
the configuration, the device generates an error, and the commit fails.
For example:
[edit event-options generate-event event-midnight start-time]
'start-time "2020-9-1.16:50:00 -0700"'
'time-interval' is mandatory for 'start-time' configuration
error: commit failed: (statements constraint check failed)
How to Generate Events at a Specific Time of Day
To generate an event at a specific time of day, configure the time-of-day statement, and specify the time at which the event
will occur. A time-of-day event is relative to the local
device time and is configured using 24-hour time format hh:mm:ss. You can optionally include a UTC offset
to specify a time relative to UTC (Coordinated Universal Time). The
syntax is hh:mm:ss(+|-)hhmm, where the sign is plus (+) for east of UTC and minus (-)
for west of UTC.
Coordinated Universal Time is the time on the 0° longitude meridian, also known as the Greenwich meridian. The standard time in most time zones is an integral number of hours offset from UTC.
If you omit the UTC offset, Junos OS automatically generates
the offset for the time-of-day statement
in the configuration based on the local time zone setting for the
device. For example, consider a device that uses Eastern Standard
Time (UTC−05:00) for its local time. The following command configures
an internal event called event-midnight, which is generated
at 12:00 AM (00:00:00) every night.
[edit] user@host# set event-options generate-event event-midnight time-of-day 00:00:00
The resulting configuration automatically includes the device’s offset from UTC.
user@host# show event-options
generate-event {
event-midnight time-of-day "00:00:00 -0500";
}
If you configure the time relative to UTC, and the offset is
different from that of the device, Junos OS automatically converts
the time to reflect the device’s local time and offset from
UTC in the configuration. The following example configures an additional
internal event called event-midnight-cst that is generated
every night at 12:00 AM (00:00:00) with an offset that is six hours
behind UTC.
[edit] user@host# set event-options generate-event event-midnight-cst time-of-day 00:00:00-0600
The resulting configuration displays the event using the device's local time and UTC offset.
user@host# show event-options
generate-event {
event-midnight time-of-day "00:00:00 -0500";
event-midnight-cst time-of-day "01:00:00 -0500";
}
If the same device is shipped to a different location, and it is configured to use a new time zone, any configured internal events reflect the new local time and time-zone offset. For example:
[edit] user@host# set system time-zone America/Los_Angeles user@host# commit
user@host# show event-options
generate-event {
event-midnight time-of-day "21:00:00 -0800";
event-midnight-cst time-of-day "22:00:00 -0800";
}
If you modify the system time by issuing the set
date operational mode command, we recommend that you also issue
the commit full or the restart event-process command. Otherwise, an internal event based on the time of day might
not be generated at the configured time.
For example, if you configure the device to generate an internal
event at 15:55:00, and then you modify the system time from 15:47:17
to 15:53:00, the event is generated when the system time is approximately
16:00 instead of at the configured time, 15:55:00. You can correct
this problem by issuing the commit full or the restart
event-process command.
Event policies can match on internal events in the same way
that they match on other events. The following example generates an
internal event called it-is-midnight at 12:00 AM (00:00:00)
every night. When the eventd process receives the it-is-midnight event, it triggers the midnight-chores event policy,
which takes certain actions.
[edit event-options]
generate-event {
it-is-midnight time-of-day "00:00:00 -0500";
}
policy midnight-chores {
events it-is-midnight;
then {
... actions ...
}
}
How to Generate Events at Repeated Time Intervals
You can generate an event at repeated intervals, for example,
every hour, by configuring the time-interval statement
and specifying the interval frequency in seconds. The time interval
can range from 60 through 2,592,000 seconds. Junos OS generates
the first event starting at approximately one time interval after
you commit the configuration.
For example, the following command configures an event called event-every-hour that gets generated every hour:
[edit] user@host# set event-options generate-event event-every-hour time-interval 3600
The following event policy takes certain actions every 3600 seconds when the
event-every-hour event is generated:
[edit event-options]
generate-event {
event-every-hour time-interval 3600;
}
policy hourly-checks {
events event-every-hour;
then {
... actions ...
}
}
On supported devices, you can optionally configure the date
and time at which Junos OS starts generating interval-based events.
Configuring a start time enables the device to generate events at
predictable times, for example, even after a device reboot. To specify
a start time for an event, configure the start-time option
in addition to the time-interval option. The start time
is relative to the local device time and is configured using 24-hour
time format. The syntax is: yyyy-mm-dd.hh:mm. For example:
[edit event-options generate-event] user@host# set every-fifteen-minutes time-interval 900 start-time 2020-09-01.16:50
If you do not configure the start-time option, Junos
OS generates the first event at approximately one time interval after
you commit the configuration, depending on the time required for the
commit operation to complete. If you configure a start time that occurs
after the commit time, Junos OS generates the first event at the configured
start time, and the next event at one time interval after the start
time, and so on. If you configure a start time that is chronologically
before the commit time, then Junos OS generates the first event at
the next time that is an integral number of time intervals after the
start time. Table 1 compares the different scenarios for the initial event times
based on the start time, if configured, and the time at which the
configuration is committed.
|
|
Commit time |
First event |
Second Event |
|---|---|---|---|---|
900 |
– |
2020-09-01.17:00:08 |
2020-09-01.17:15:30 |
2020-09-01.17:30:30 |
900 |
2020-09-01.17:10 |
2020-09-01.17:00:08 |
2020-09-01.17:10:00 |
2020-09-01.17:25:00 |
900 |
2020-09-01.16:50 |
2020-09-01.17:00:08 |
2020-09-01.17:05:00 |
2020-09-01.17:20:00 |
900 |
2020-09-01.16:50 |
2020-09-01.17:17:08 |
2020-09-01.17:20:00 |
2020-09-01.17:35:00 |
Similarly, if you configure a start time, Junos OS still generates the next event based on the configured start time even if you reboot the device or restart the event process. Table 2 compares the initial event times after the device is rebooted. As shown in the table, when you specify a start time, the device predictably generates the next event as an integral number of time intervals after the start time. When you do not specify a start time, the next event is one time interval after the device comes back online and starts the event process. In this case, it took several minutes for the device to reboot and start the Junos OS processes, so the event occurs well after the time for the next expected event.
|
|
First event |
Reboot time |
Next Event |
|---|---|---|---|---|
900 |
– |
2020-09-01.16:50:00 |
2020-09-01.16:55:00 |
2020-09-01.17:13:08 |
900 |
2020-09-01.16:50 |
2020-09-01.16:50:00 |
2020-09-01.16:55:00 |
2020-09-01.17:05:00 |
You can optionally include a UTC offset to specify a start time
relative to UTC by appending (+|-)hhmm to the time, where the sign is plus (+) for east of UTC and minus
(-) for west of UTC, for example, 2020-09-14.11:00‑0800. Even if
you specify a UTC offset, the start-time configuration always displays the time and UTC offset for the device’s
local time zone.
The following example configures the start time with a UTC offset:
[edit event-options generate-event] user#host# set every-twenty-minutes time-interval 1200 start-time 2020-09-16.20:30-0200
The resulting configuration displays the event time and UTC offset for the device’s local time zone.
[edit event-options generate-event] user@host# show every-twenty-minutes time-interval 1200 start-time "2020-9-16.17:30:00 -0500";