Date

October 2012

Status

In progress

Proposers

Michelle Argus
Justin Clark-Casey (justincc)

Introduction

This may encompass many improvements to groups, but the first is to cache login information in groups to improve group IM, such that an IM isn't sent to every single user, even those offline.

Proposal

Please see mailing-list e-mails [1], [2] and [5]. The changes for OpenSimulator and XmlRpcGroups are in [3] and [4].

These changes send login status information and time to the groups service from the simulator. This allows an extra 'offline' parameter to be passed to GetGroupMembers to control whether all or only online members of a group are returned.

PROS: Only a single network call (which may be cached for a period) required on each group IM. Reasonably simple. May allow messaging across multiple OpenSimulator installations.

CONS: Extra calls to groups service on each login/logout. Groups service has to cache extra information. Cached information not reuseable by other services.

Alternatives

One alternative is for the simulator itself to call GridUserService.LoggedIn for each member of the group on each IM. However this has a very high overhead with large groups.

It may be possible to improve this by adding a new GridUserService call that accepts a list of UUIDs and only returns information for those which are logged in. However, this would need to be called for each group IM, unless this was cached for short periods of time.

PROS:

Groups service doesn't need to handle online status.
One source of online status truth that cannot become inconsistent with information cached in the groups service.
Other services can also use the same simulator-side group users online caching, though this may not be a big factor.
Groups service data can be backed up without any possible worries about inconsistent online status if it needs to be restored.

CONS:

Every group IM still requires an extra network call to GridUser services, though the results could be cached for a short period of time (e.g. 20 seconds).
Comparatively complex.
If code external to OpenSimulator wanted to know online users for a group, it would have to call Presence service (and possibly cache information) itself rather than just being able to query the groups service.
Inconsistency between presence service and groups service online information may not be important - possibly the worst that could happen is some users do not receive group members until they relog.