Usage limit alerts

[Xkonti]

As Val Town account comes with limits (executions, CPU time, storage) it would be helpful to preview it ( #8 ) and set up alerts for when specific thresholds are met. Those alerts could:

• send a notification, just like Vals send execution errors
• trigger specific val, this way user's sytems can quickly react to the problem and possibly mitigate downtime
• allow to query current / average usage status from Vals

Example 1

Val Town user uses the platform as a backend that resizes images and caches them for a short time. To do that it implements some kind of cache through Blob Storage to store multiple versions of the image. The user could set up an alert for 80% if storage limit usage. When that threshold is crossed it triggers a Val that will perform cleanup of oldest cached images to make sure there is always room for new images. Additionally the system could check storage usage in real-time to decide if the image upload request should be denied to not interrupt resizing that's in progress.

Example 2

User created a large number of APIs that do a lot of processing. The user would like to be able to implement a dynamic rate-limit on all of those APIs in case of approaching CPU time. This way the user can delay/enqueue/reject some of the CPU-heavy operations reducing the risk other systems failing.