Communication Paradigms - Connect
Communication Paradigms - Connect
Communication Paradigms - Connect
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Some Additional Notes<br />
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When a broker receives a publish request from a given node, it must pass<br />
this subscription to all connected nodes where there is a corresponding<br />
matching subscription and also decide where to propagate this event<br />
through the network of brokers.<br />
Lines 2 and 3 achieve the first goal by matching the event against the<br />
subscription list and then forwarding the event to all the nodes with<br />
matching subscriptions.<br />
Lines 4 and 5 then use the match function again, this time matching the<br />
event against the routing table and forwarding only to the paths that lead<br />
to a subscription.<br />
Brokers must also deal with incoming subscription events.<br />
If the subscription event is from an immediately connected subscriber then<br />
this subscription must be entered in the subscriptions table (lines 7 and 8).<br />
Otherwise, the broker is an intermediary node and now knows that a<br />
pathway exists towards this subscription and hence an appropriate entry is<br />
added to the routing table (line 9). In both cases, this subscription event is<br />
then passed to all neighbours apart from the originating node (line 10).<br />
Adv. Dist. Systems G. Blair/ F. Taiani 46
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