perhap

perhap is an event store described within a domain driven design and functional programming context.

How it works

perhap is strictly an immutable event store. It accepts new events, and responds to queries about existing events.

Events are immutable, organized hierarchically using the following structure:

• Realm
  • Domain
    • Aggregate root / Entity
      • Event type
        • Event

New events

Any event can be added using arbitrary data at all levels, i.e. a user of the event store may record an event of a new type, for a new entity, even for a new domain, without first creating the domain, entity, or event type.

The API for adding an event over HTTP is to post event data to a URL specifying the domain, event type, and entity.

curl -X POST https://perhap-server/[realm]/[domain]/[entity]/[event_type] -d '{"event": [event data]}'

Example:

curl -X POST https://perhap-server/performance/communications/59535c06-79c4-4499-bfcc-c695aaebf491/click -d '{"event": {"URI": "http://..."}}'

status codes...

Querying

Querying events follows the same hierarchy as creating new events, but uses a GET instead of a POST. The portion of the hierarchy that is included in the request indicates the scope of the data returned. Some query strings are provided to limit the results within a given scope.

Retrieving events:

• Retrieve all events for a given entity: curl -X GET https://perhap-server/[realm]/[domain]/[entity]
• Retrieve a specific event: curl -X GET https://perhap-server/[realm]/[domain]/[event-id]
• Retrieve all events within a given domain: curl -X GET https://perhap-server/[realm]/[domain]

Retrieving lists of keys:

• List all domains: curl -X GET https://perhap-server/[realm]/keys
• List all entities within a domain: curl -X GET https://perhap-server/[realm]/[domain]/keys

Filtering results:

• Retrieve all events occuring after a known event: curl -X GET https://perhap-server/[realm]/[domain]/[entity]?following=[event-id]

status codes...

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