As explained in the article Getting started with custom alerts, custom alerts can be run at a specific interval starting at a given time of the day by defining the Interval type, Interval and Start time.
For example, to make a custom alert run once per week at 12 PM, you would set the interval type to "days", the interval to 7 and the start time to 12 PM. This alert begins its alert cycle whenever the proxy notices that the time is 12 PM.
If, however, you wanted to the query to run only on a specific day of the week, you would have to time the creation of the custom alert correctly. For example, to make an alert run every Friday at 12 PM, you would create the alert on Thursday evening or Friday morning and set the start time to 12 PM. This would work for as long as there were no restarts to the server or to the proxy. After a restart, the proxy would start the alert interval cycle the next time it's 12 PM again, which might not be a Friday.
To avoid this, we can move some of the interval logic to the SQL query itself. To make sure a custom alert query is run every Friday at 12 PM, do the following steps:
- Create an alert and set its Interval type to "hours".
- Set the Interval to 24.
- Set the Start time to 12 PM.
- In the SQL text, wrap the query inside a check for the day of the week:
This way the query is run every day at 12 PM, but it will only return values and thus possibly cause alerts on Fridays.