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Last updated: 7 Sep 2020

publishing-api: RabbitMQ

For information about how we use RabbitMQ, see here.

Post-publishing notifications

After an edition is changed, a message is published to RabbitMQ. It will be published to the published_documents topic exchange with the routing_key "#{edition.schema_name}.#{event_type}". Interested parties can subscribe to this exchange to perform post-publishing actions. For example, a search indexing service would be able to add/update the search index based on these messages. Or an email notification service would be able to send email updates (see https://github.com/alphagov/email-alert-service).

event_type

  • major: Used when an edition is published with an update_type of major.
  • minor: Used when an edition is published with an update_type of minor.
  • republish: Used when an edition is published with an update_type of republish.
  • links: Used whenever links related to an edition have changed.
  • unpublish: Used when an edition is unpublished.

Previewing a message for a document_type

After content is updated, a message is generated and published to the RabbitMQ exchange. Each message has a shared format, however the contents of the message is affected by the publishing app and what data it sends over.

As messages for different formats can vary, we have created a rake task to allow us to easily generate example messages. The example message is generated from the most recently published message (based off of last public_updated_at) for the entered document type:

$ bundle exec rake queue:preview_recent_message[<document_type>]