Been thinking this would be worth trying for a while now. Set a config option for syncprov to send Persist messages to a multicast group instead of the original TCP session. All the consumers would also join the group and listen for updates. This would also exercise the cldap:// support in libldap.

Implementation details: since datagrams are unreliable, we need to include sequence numbers on each message, which the consumer can check to make sure it hasn't missed an update. Moreover, it should be able to send a request to the provider to resend (over the TCP session) the message corresponding to a given sequence number.

(Currently I envision using a small circular array in the provider to remember the last N messages for potential retransmit.)

Config: both consumer and provider will need to be configured with a particular multicast group ID. It should be possible to participate in more than 1 group at a time (in which case, an update must be explicitly sent to each active group) but in general, I expect a cluster of cooperating MMR servers to all use a single multicast group, and so any update will only need to be forwarded to the network once.

Thoughts?