Arvados

• controller runs an outgoing mailer goroutine
• config file has configuration information to connect to an SMTP server

Things users are interested in (should be able to check a box that says "notify me"):

• A thing has been shared with you
• A workflow has completed/failed
• Something in a project changed
• A collection changed

Should we use the existing websocket code for event management?

Currently don't care about queuing -- for email, it's already asynchronous. In the future we might want to keep track of undelivered messages for the Workbench 2.

Do Prometheus alerts make sense as a event delivery mechanism?