Ambiguity of consecutive remove and create events

[marcvef]

Ambiguity of consecutive remove and create events

[fvennetier]

Hello.
I did some investigation. Here is a recap.

Operation	Event type	Contains user metadata	Contains chunks	Used by
Object create	storage.content.new	yes	no	Replicator
Object delete	storage.content.deleted	no	yes	Content cleaner, Replicator
Object create (overwrite) (1)	storage.content.deleted	no	yes	Content cleaner, Replicator
Object create (overwrite) (2)	storage.content.new	yes	no	Replicator
Object append	storage.content.append	no (can't be changed)	no	Replicator
Object update (chunk mod) (1)	storage.content.deleted	no (missing version)	yes (partial)	Content cleaner, Replicator
Object update (chunk mod) (2)	storage.content.new	yes (partial)	no	Replicator
Object change property	storage.content.update	yes	no	Replicator
Object truncate (1)	storage.content.deleted	no (missing header)	yes (partial)	Content cleaner, Replicator
Object truncate (2)	storage.content.new	yes (partial)	no	Replicator

As you pointed out, it is not possible (or hard) to know which operation triggered the event. For OpenIO SDS internal operations, we did not need to distinguish them.

I see two possible evolutions:

1. Create new types of events for object overwrite, update and truncation, which could include both contents of storage.content.new and storage.content.deleted events.
2. Keep the existing events, but add a new field telling which kind of operation triggered the event emission. This solution is easier to implement, and does not break compatibility.

[marcvef]

Hi Florent, thanks for the detailed reply and considering the change!

I don't think it is necessary to create new types of events. Keeping the existing events and adding some additional information, as you suggested in Option 2, is sufficient and would help significantly.