Service and Topology Tracking

Service Tracking

  • Users can subscribe for contents of and changes to the global address binding table.
  • They receive an event at each change matching the range indicated in the subscription.
  • There is a match when an bound/unbound instance or range overlaps with range subscribed for.
  • Received events contain the bound/unbound socket’s service address and socket address.

Cluster Topology Tracking

  • Cluster topology tracking is a special case of service tracking, also based on the binding table contents
  • Peer node availability, as seen from the own node, is represented by the built-in service type 0.
  • Cluster connectivity tracking is also possible by subscribing for availability of individual links, using the built-in service type 2.
  • Using these mechanisms, and by connecting to other cluster nodes's topology servers, it is possible for a user to build and track the overall connectivity matrix of the whole cluster.

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Group Membership Tracking

  • Communication group members can optionally subscribe for join/leave/close/ /crash/lost-contact events for other group members.
  • Membership events are received in a member socket in the form of out-of-band empty messages.
  • Event order is guaranteed, - a join event always arrives before the first message from the new member, - a leave event always arrive after the last message from the leaving member.
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