⚡️perform_update less blocking

[AntoLC]

The Problem

Every perform_update call (document save) makes a synchronous, blocking HTTP call to the collaboration server before it can proceed. The same applies to the can_edit endpoint. This means:

• Every save adds the round-trip latency of the collaboration server
• If the collaboration server is slow or unreachable, the entire request hangs for up to 10 seconds (the timeout=10)

docs/src/backend/core/api/viewsets.py

Lines 729 to 733 in cbe6a67

	count, exists = CollaborationService().get_document_connection_info(
	document_id,
	self.request.session.session_key,
	)
	except requests.HTTPError as e:

docs/src/backend/core/services/collaboration_services.py

Lines 58 to 62 in cbe6a67

	try:
	response = requests.get(
	endpoint_url, headers=headers, params=querystring, timeout=10
	)
	except requests.RequestException as e:

Possible solution

We could improve the pattern to be more optimistic, and less blocking.

2 endpoints call _can_user_edit_document:

• can-edit
• document perfom_update

We could use a cache that last about 15mn:

CAN_EDIT_CACHE_TTL = 60*15
can_edit = self._can_user_edit_document(document.id, set_cache=True)
    cache.set(
        self._can_edit_cache_key(document.id),
        can_edit,
        timeout=CAN_EDIT_CACHE_TTL,
    )

• If the cache is empty, the requests are blocking so mainly the first time the user try to connect
• If the cache is not empty, request is unblocking and leaded by the cache, ⚠️ in the same time, we re-trigger a cache update in background (_can_user_edit_document)

Tip

can-edit is usually called before perfom_update by the frontend, increasing the chances that perfom_update will be ever unblocking.

Other way

Note

We could as well imagine a totally different way to save content !

During a save:

• frontend does a http request on the collaboration server instead of the django server
• collaboration server check if the condition are respected:
  • user is connected to the collab-server
  • if not if he is alone

Only collaboration server will trigger the save to the django server.

[AntoLC]

Possibly solved when migrating to yhub #2303