Handle Presence Cleanup in Housekeeping Process

[chacha912]

Description:

When a document is explicitly detached, the presence is removed from the presences through PresenceChange{type: 'clear'}. This helps keep snapshot presence lightweight. However, when the client does not explicitly invoke detach, there is an issue that the presence not to be cleared.

Currently, during housekeeping, the document state is updated using clientInfo.DetachDocument(). It is also necessary to clear the presence at this point.

yorkie/server/backend/housekeeping/housekeeping.go

Lines 171 to 177 in 65c8164

	for _, clientInfo := range candidates {
	if _, err := clients.Deactivate(
	ctx,
	h.database,
	clientInfo.ProjectID,
	clientInfo.ID,
	); err != nil {

yorkie/server/clients/clients.go

Lines 72 to 80 in 65c8164

	if err := clientInfo.DetachDocument(id); err != nil {
	return nil, err
	}
	// TODO(hackerwins): We need to remove the presence of the client from the document.
	// Be careful that housekeeping is executed by the leader. And documents are sharded
	// by the servers in the cluster. So, we need to consider the case where the leader is
	// not the same as the server that handles the document.

Why:
To prevent continuous growth of the presence snapshot.