Concurrent CEDICT DB upgrades

[kirlat]

When two tabs are loading a Lexis service simultaneously for the first time in a browser, the IndexedDB storage for CEDICT data does not exist yet and two tabs will try to create it and download CEDICT data into it at the same time. The current version of LexisCS monitors this concurrency and prevents concurrent IndexedDB upgrade operations from happening.

The process in a tab that started first will continue with its DB creation and data downloading and all other processes will stop their own upgrades to avoid blocking each other. All the processes in tabs that were blocked will print the following message into the console:
A database change has occurred. You should refresh this browser window or close it down.
Once pages within those tabs will be reloaded the LexisCS functionality within them will become available.

The situation described above will not happen often, only when DB data needs to be downloaded or DB needs to be upgraded and two tabs with Alpheios active are loaded at the same time. I think it can be considered an edge case.

Would that be acceptable to treat this situation like described above or can we do anything better?

[kirlat]

This is already implemented in the current version of LexisCS. If we're satisfied with how it is currently this issue can probably be closed.