Event service

Event service allows consumers to send domain events. These events can be used to support additional capabilities aside from the application itself; out of the box, the event service logs domain events to the event log which can be used for traceability of domain operations.

Client roles

client urn:ads:platform:event-service

name	description
event-sender	Sender role for event service. This role is used to allow a service account to send domain events via the event service. Note that the account with the role will be able to send any domain event including platform defined events.

Concepts

Event definition

Event definition is an optional metadata description of a domain event (identified by a specific namespace and name). They are used for downstream capabilities. For example, the payload schema description allows the notification service to validate variables within notification message templates. Event definitions are configured in the configuration service under the platform:event-service namespace and name.

Event

Domain events represent key changes at a domain model level. For example, an intake application process could include events like: application draft created, application submitted, application processing started, application processing completed.

Event log

Event log records all events emitted via the event service and keeps basic metrics including a count of different events. These metrics can represent key domain metrics; in the intake application example, the count of application submitted events represents the volume of applications.

Code examples

Configure an event definition

Event definitions are configured using the configuration service. Note that new configuration may take up to 15 mins to apply.

  const configurationServiceUrl = 'https://configuration-service.adsp.alberta.ca';
  const request = {
    operation: 'UPDATE',
    update: {
      'domain-service': {
        name: 'domain-service',
        definitions: {
          'domain-event': {
            name: 'domain-event',
            description: 'Signalled on significant domain state change.',
            payloadSchema: {
              type: 'object',
              properties: {
                value: { type: 'string' }
              }
            }
          }
        }
      }
    }
  }

  await fetch(
    `${configurationServiceUrl}/configuration/v2/configuration/platform/event-service`,
    {
      method: 'PATCH',
      headers: {
        'Authorization': `Bearer ${accessToken}`,
        'Content-Type': 'application/json'
      },
      body: JSON.stringify(request),
    }
  );

Send an event

  const event = {
    namespace: 'support-program',
    name: 'application-submitted',
    timestamp: '2021-10-12T15:03:50Z',
    correlationId: 'f669be59-bd38-4ca4-8749-19248060fc63',
    context: {
    },
    payload: {
      application: {
        id: 'f669be59-bd38-4ca4-8749-19248060fc63',
        /* ... */
      }
      applicant: {
        id: 'a8e5ec09-d60a-4c60-94bd-71dc97d8c80e',
        username: 'testy.mctester@acme.com',
      }
    }
  }

  await fetch(
    'https://event-service.adsp.alberta.ca/event/v1/events',
    {
      method: 'POST',
      headers: {
        'Authorization': `Bearer ${accessToken}`,
        'Content-Type': 'application/json',
      },
      body: JSON.stringify(event),
    }
  );

Search the event log

The event log is stored as a value (event-service:event) in the value service and can be queried using the value API.

  const valueServiceUrl = 'https://value-service.adsp.alberta.ca';
  const top = 50;
  const timestampMin = `2021-10-10T12:00:00Z`;

  const response = await fetch(
    `${valueServiceUrl}/value/v1/event-service/values/event?top=${top}&timestampMin=${timestampMin}`,
    {
      method: 'GET',
      headers: { Authorization: `Bearer ${accessToken}` }
    }
  );

  const {
    results,
    page,
  } = await response.json();