Revisions and saving

Two people can edit the same dashboard at the same time. Revisions make sure neither silently overwrites the other.

How revisions work

Every dashboard has a revision number that goes up by one on each save.

Loading a dashboard returns its revision in the ETag header, such as "3".
Saving sends that value back in If-Match: "3".
If the dashboard is still at revision 3, the save succeeds and returns ETag: "4".
If someone saved in between, the server answers 409 Conflict and stores nothing.

Creating without clobbering

A dashboard that does not exist loads as data: null with ETag: "0". Saving with If-Match: "0" creates it only if nobody else created it first.

After a conflict

Keep the person’s edits and let them compare with the latest version. Do not resend the old document with the new revision: that would erase the other person’s changes.

In the web app, a conflict shows Unsaved changes and a Reload button. Your edits stay on screen until you reload.

Autosave

The web app saves on its own about 1.5 seconds after you stop editing. It does not save while a save is running, and it stops after a failed save until you act. React applications get the same behavior from useDashboardAutosave.

Deleting and reusing an address

Deleting a dashboard keeps its revision counter. If someone creates a new dashboard at the same address, it starts above the old revision. An editor who still has the old dashboard open gets a conflict instead of overwriting the new one.

Saves without a revision

A PUT without If-Match replaces the dashboard unconditionally. It exists for older clients. Always send If-Match in new code.