Hi, Most of the readers of this mailing list probably know that James has been using project reactor [1], an implementation of Reactive Streams, to improve its usage of resources and lower the latency of operations for some time.
For a long time, the Mailbox part of James has a Pub/Sub system to allow for modular extension of James default behavior like learning for Spam, indexing in ElasticSearch, etc. Recenlty, we reworked that Pub/Sub to be able to implement a distributed version of it by integrating RabbitMQ. During this work we wrote an extensive test suite to define the right contracts a Mailbox Pub/Sub system should support and we reworked the single-node version (called InVmEventBus) to rely on reactor. However, listeners are still not able to make use of reactive streams because we didn't changed the way listeners work. You can either have a synchronous listener: it means that for a given event, the delivery method call with return only when all listeners got called (or an error occured) or an asynchronous listener, which basically means we won't wait for the listener return to go ahead. When a listener does some IO, like for example ElasticSearch indexer, we don't leverage the fact that IO are asynchronous and thus we block threads waiting for the IO. Given everything is reactor based, it would be a much better use of resources to let the listeners work with `Publisher` type and use non- block APIs. We could probably provide an adapter API to allow non-reactive listeners to use the traditional API and wrapping listener calls into some reactive types. What would you think about this change? Feedback is more than welcome. Cheers, [1] https://projectreactor.io -- Matthieu Baechler --------------------------------------------------------------------- To unsubscribe, e-mail: server-dev-unsubscr...@james.apache.org For additional commands, e-mail: server-dev-h...@james.apache.org
