Custom Query (2152 matches)

Reported by dread, 4 years ago.

Use cases

• Register for package changes
• Register for all revisions
• Notified of a package change
• Notified of a revision
• Deregistration
• Configuration of port in pylons config

Design

• Default port: 5672 (standard for AMQP)
• Exchange name: 'ckan'
• Exchange type: topic exchange (most flexible)
• Routing keys: (see below)

Routing detail

Routing key format: "OBJ_TYPE" (NB tags should be identified by their name, not ID)

Example routing keys

• 'package' - Package edited/created
• 'resource' - Resource edited/created
• 'revision' - Any change
• 'db.clean'
• 'db.rebuild'

Example queue bindings that clients may use:

• * - no filtering - client receives all notifications
• package - only changes to packages
• revision - all revisions
• db - all database operations

Versioning

Since message payloads will be tied into the REST Entities, it makes sense to join up with the REST versioning. This could be achieved by providing new exchanges called 'ckan-1.1' perhaps?

Documentation

• How to use
• simple example of an external client?

Reported by dread, 4 years ago.

Which events to notify on

Listed by domain object, these are the notification message 'change types' that will be sent:

• Package
• PackageResource

Also it is clear that it could be useful to know when db-wide maintenance is carried out:

• db - 'clean', 'rebuild' (db is wiped and replaced with new data), 'upgrade' (migration)

Ignored domain objects

These parts of the domain model will not carry notifications as no use case has been identified for them:

• Revision
• Group
• Tag
• Rating
• User - list of users is sensitive info
• Relationships - complicated
• Authz - complicated and sensitive info
• License - change of a license's metadata is a question for the 'license service'

Message format

A notification message's header contains the routing key, identifying the object type. The client is probably interested in the object (all use cases so far), so it makes sense to send the object in the payload. This should be the JSON-encoded dictionary exactly as provided for the object's REST Entity.

For the 'db' notifications there shall be no payload.

Reported by dread, 4 years ago.

Currently search indexing is triggered directly using a Postgresql db callback. Now take advantage of the Notification system to register interest in all package changes and db changes to trigger this instead.

The indexing shall run in a separate shell/process, managed by supervisord.