Architecture

When the API receives a new post, the first thing that happens is that the document get transformed (this is done so all documents for all defined applications have the same structure). This document is then forwarded to the loader which stores it in Elasticsearch. At the same time however, this document is forwarded to the percolator which determines if there are any users registered for near-time delivery of the alert. If so, then the subfetcher will fetch the associated email address(es) and forward the result to the mailer, which takes care of the email formatting and actually sending out the email.

Additionally there is a digest maker which runs at a regular interval and fetches documents from the last period from Elasticsearch, then runs the percolator queries, fetch the associated email addresses and forwards the result(s) to the mailer.