Hi Qui.

I assume you are referring to this line of code: https://github.com/daos-stack/daos/blob/master/src/control/server/server_utils.go#L518

In this case, the false value indicates that the group update request does not need to be synchronous. You can see the request handler here: https://github.com/daos-stack/daos/blob/master/src/control/server/mgmt_system.go#L187

The reason for this is to allow for efficient batching of group updates during large-scale membership changes (e.g. system bringup or when many nodes are marked dead by SWIM). In this mode, the group update will happen within 500ms (maybe less, depending on when the ticker last fired).

Hope that helps.

mjmac