Worker walkthrough

In addition to common features available to all services, a worker has access to:

• the PostgreSQL database;

• the OpenSearch instance;

• a Temporal worker for running Temporal workflows and activities, within a specific namespace and for a given task queue.

Unlike a consumer, a worker is in charge of long running, unpredictable, and deterministic tasks.

Environment variables

Required environment variables for a worker, in addition to the ones mentioned in Service framework:

• CROWD_TEMPORAL_SERVER_URL: Temporal server URL to connect to.

• CROWD_TEMPORAL_NAMESPACE: Temporal namespace for which the worker will execute workflows and activities.

• CROWD_TEMPORAL_TASKQUEUE: Temporal task queue for which the worker will execute workflows and activities.

• CROWD_TEMPORAL_ENCRYPTION_KEY_ID: Unique identifier (name) of the encryption key to use.

• CROWD_TEMPORAL_ENCRYPTION_KEY: 32 length encryption key use to encode/decode data between Temporal server, workers, and clients.

Required environment variables if PostgreSQL is enabled:

• CROWD_DB_READ_HOST: PostgreSQL reader instance URL to connect to.

• CROWD_DB_WRITE_HOST: PostgreSQL writer instance URL to connect to.

• CROWD_DB_PORT: PostgreSQL port of the host to connect to.

• CROWD_DB_USERNAME: PostgreSQL user to use to connect.

• CROWD_DB_PASSWORD: PostgreSQL password to use to connect.

• CROWD_DB_DATABASE: PostgreSQL database to connect to.

Required environment variables if OpenSearch is enabled:

• CROWD_OPENSEARCH_NODE: URL of the OpenSearch node to connect to.

• CROWD_OPENSEARCH_AWS_REGION: AWS Region of the OpenSearch instance.

• CROWD_OPENSEARCH_AWS_ACCESS_KEY_ID: AWS Access Key ID to use to connect to OpenSearch.

• CROWD_OPENSEARCH_AWS_SECRET_ACCESS_KEY: AWS Secret Access Key to use to connect to OpenSearch.

Example

In ./services/apps/<service>/src/main.ts:

import { Config } from '@crowd/standard'
import { ServiceWorker, Options } from '@crowd/worker'

const config: Config = {
  producer: {
    enabled: false,
  },
  temporal: {
    enabled: false,
  },
  redis: {
    enabled: false,
  },
}

const options: Options = {
  postgres: {
    enabled: true,
  },
  opensearch: {
    enabled: false,
  },
}

const svc = new ServiceWorker(config, options)

setImmediate(async () => {
  await svc.init()
  await svc.start()
})

The worker archetype automatically imports and bundles all workflows exported in workflow.ts and all activities exported in activities.ts.

All Temporal workflows must be exported in ./services/apps/<service>/src/workflows.ts, like this:

import { example } from './workflows/greet'

export { example }

All Temporal activities must be exported in ./services/apps/<service>/src/activities.ts, like this:

import { greet } from './activities/greet'

export { greet }