The /whisk.system/alarms
package can be used to fire a trigger at a specified frequency. Alarms are useful for setting up recurring jobs or tasks, such as invoking a system backup action every hour.
The package includes the following feeds.
Entity | Type | Parameters | Description |
---|---|---|---|
/whisk.system/alarms | package | - | Alarms and periodic utility. |
/whisk.system/alarms/interval | feed | minutes, trigger_payload, startDate, stopDate | Fire Trigger event on an interval based schedule. |
/whisk.system/alarms/once | feed | date, trigger_payload, deleteAfterFire | Fire Trigger event once on a specific date. |
/whisk.system/alarms/alarm | feed | cron, trigger_payload, startDate, stopDate | Fire Trigger event on a time-based schedule using cron. |
The /whisk.system/alarms/interval
feed configures the Alarm service to fire a Trigger event on an interval based schedule. The parameters are as follows:
minutes
(required): An integer representing the length of the interval (in minutes) between trigger fires.
trigger_payload
(optional): The value of this parameter becomes the content of the Trigger every time the Trigger is fired.
startDate
(optional): The date when the first trigger will be fired. Subsequent fires will occur based on the interval length specified by the minutes
parameter.
stopDate
(optional): The date when the Trigger will stop running. Triggers will no longer be fired once this date has been reached.
Note: The startDate
and stopDate
parameters support an integer or string value. The integer value represents the number of milliseconds since 1 January 1970 00:00:00 UTC and the string value should be in the ISO 8601 format (http://www.ecma-international.org/ecma-262/5.1/#sec-15.9.1.15).
The following example creates a trigger that is fired once every 2 minutes. The Trigger fires as soon as possible, and will stop firing January 31, 2019, 23:59:00 UTC.
wsk trigger create interval \ --feed /whisk.system/alarms/interval \ --param minutes 2 \ --param trigger_payload "{\"name\":\"Odin\",\"place\":\"Asgard\"}" \ --param stopDate "2019-01-31T23:59:00.000Z"
Each generated event includes parameters, which are the properties that are specified by the trigger_payload
value. In this case, each Trigger event has the parameters name=Odin
and place=Asgard
.
The /whisk.system/alarms/once
feed configures the Alarm service to fire a trigger event on a specified date. The parameters are as follows:
date
(required): The date when the Trigger will be fired. The Trigger will be fired just once at the given time.
Note: The date
parameter supports an integer or string value. The integer value represents the number of milliseconds since 1 January 1970 00:00:00 UTC and the string value should be in the ISO 8601 format (http://www.ecma-international.org/ecma-262/5.1/#sec-15.9.1.15).
trigger_payload
(optional): The value of this parameter becomes the content of the Trigger when the Trigger is fired.
deleteAfterFire
(optional, default: false): The value of this parameter determines whether the Trigger and potentially all of its associated rules will be deleted after the Trigger is fired.
false
: No action will be taken after the Trigger fires.true
: The Trigger will be deleted after it fires.rules
: The Trigger and all of its associated rules will be deleted after it fires.The following is an example of creating a trigger that will be fired once on December 25, 2019, 12:30:00 UTC. After the Trigger fires it will be deleted as well as all of its associated rules.
wsk trigger create fireOnce \ --feed /whisk.system/alarms/once \ --param trigger_payload "{\"name\":\"Odin\",\"place\":\"Asgard\"}" \ --param date "2019-12-25T12:30:00.000Z" \ --param deleteAfterFire "rules"
The /whisk.system/alarms/alarm
feed configures the Alarm service to fire a Trigger event at a specified frequency. The parameters are as follows:
cron
(required): A string, based on the UNIX crontab syntax that indicates when to fire the Trigger in Coordinated Universal Time (UTC). The string is a sequence of five fields that are separated by spaces: X X X X X
. For more information, see: http://crontab.org. The following strings are examples that use varying duration's of frequency.
* * * * *
: The Trigger fires at the top of every minute.0 * * * *
: The Trigger fires at the top of every hour.0 */2 * * *
: The Trigger fires every 2 hours (that is, 02:00:00, 04:00:00, ...).0 9 8 * *
: The Trigger fires at 9:00:00AM (UTC) on the eighth day of every month.Note: The parameter cron
supports five or six fields. Not all OpenWhisk vendors may support 6 fields so please check their documentation for support. For more details about using this custom cron syntax, see: https://github.com/ncb000gt/node-cron. Here is an example using six fields notation:
*/30 * * * * *
: every thirty seconds.trigger_payload
(optional): The value of this parameter becomes the content of the Trigger every time the Trigger is fired.
startDate
(optional): The date when the Trigger will start running. The Trigger fires based on the schedule specified by the cron parameter.
stopDate
(optional): The date when the Trigger will stop running. Triggers are no longer fired once this date is reached.
Note: The startDate
and stopDate
parameters support an integer or string value. The integer value represents the number of milliseconds since 1 January 1970 00:00:00 UTC, and the string value should be in the ISO 8601 format (http://www.ecma-international.org/ecma-262/5.1/#sec-15.9.1.15).
The following is an example of creating a trigger that fires once every 2 minutes with name
and place
values in the trigger event. The Trigger will not start firing until January 1, 2019, 00:00:00 UTC and will stop firing January 31, 2019, 23:59:00 UTC.
wsk trigger create periodic \ --feed /whisk.system/alarms/alarm \ --param cron "*/2 * * * *" \ --param trigger_payload "{\"name\":\"Odin\",\"place\":\"Asgard\"}" \ --param startDate "2019-01-01T00:00:00.000Z" \ --param stopDate "2019-01-31T23:59:00.000Z"
Note: The parameter maxTriggers
is deprecated and will be removed soon. To stop the Trigger, use the stopDate
parameter.