8. Glossary

Message

A message consists of a broker::topic and a broker::data. Broker stores messages as copy-on-write tuples (broker::data_message). This allows Broker to pass messages to many receivers without having to copy the content for each subscriber.

Filter

Each endpoint (see Section 2.1.1) controls the amount of data it receives from others by providing a list of topic prefixes. Whenever an endpoint publishes data, this list (the filter) is used to determine which peering endpoint should receive the data. For example, if the endpoints A and B have a peering relationship and B has announced the filter [/zeek/events/123/, /zeek/events/234/] then A would forward messages for the topic /zeek/events/123/foo to B, while not forwarding messages for the topic /zeek/events/456/foo.