Activation Interval
When a member becomes disconnected, the group facility revises the ordinals of the remaining members, which respond by adjusting their operating roles. This process is not instantaneous: it takes time to detect, to revise, and to adjust.
You can supply the activation interval property as a guide for the group service during the detect and revise phases. The group service derives appropriate heartbeat and timeout intervals from this property, aiming to complete these two phases within the activation interval you supply. That is, when a member becomes disconnected, you can expect that all affected group members receive new ordinals in approximately this time.
In contrast, the length of the adjust phase depends on the application, and the time it requires to switch operating roles.
In the interim, the application processes as a group might miss some messages. You can implement strategies to compensate for this possibility, as appropriate to application requirements.
If you omit the activation interval property, its default value is 5 seconds.