EZ4: Queue

It uses the power of reflection to provide a contract that determines how to build and connect queue components.

Getting started

Install

npm install @ez4/queue @ez4/local-queue @ez4/aws-queue -D

Create queue

// file: queue.ts
import type { Environment, Service } from '@ez4/common';
import type { Queue } from '@ez4/queue';

// MyQueue message
type MyQueueMessage = {
  foo: string;
  bar: number;
};

// MyQueue declaration
export declare class MyQueue extends Queue.Unordered<MyQueueMessage> {
  retention: 600;

  subscriptions: [
    Queue.UseSubscription<{
      handler: typeof eventHandler;
    }>
  ];

  variables: {
    myVariable: Environment.Variable<'MY_VARIABLE'>;
  };

  services: {
    otherService: Environment.Service<OtherService>;
    variables: Environment.ServiceVariables;
  };
}

// MyQueue message handler
export function eventHandler(request: Queue.Incoming<MyQueueMessage>, context: Service.Context<MyQueue>): void {
  const { otherService, variables } = context;
  const { message } = request;

  // Access message contents
  message.foo;

  // Access injected services
  otherService.call();

  // Access injected variables
  variables.myVariable;
}

Use queue

// file: handler.ts
import type { Service } from '@ez4/common';
import type { MyQueue } from './queue';

// Any other handler that has injected MyQueue service
export async function anyHandler(_request: any, context: Service.Context<DummyService>) {
  const { myQueue } = context;

  await myQueue.sendMessage({
    foo: 'foo',
    bar: 123
  });
}

Queue properties

Service

| Name | Type | Description | | ------------- | ----------------------- | ------------------------------------------------------------------ | | fifoMode | Queue.UseFifoMode<> | Enable and configure the FIFO mode options. | | deadLetter | Queue.UseDeadLetter<> | Enable and configure the dead-letter queue options. | | subscriptions | Queue.UseSubscription<> | All subscriptions associated to the queue. | | delay | integer | Maximum delay (in seconds) to make messages available. | | polling | integer | Maximum wait time (in seconds) for receiving messages. | | retention | integer | Maximum retention time (in minutes) for all messages in the queue. | | timeout | integer | Maximum acknowledge time (in seconds) for the handler. | | variables | object | Environment variables associated to all subscription. | | services | object | Injected services associated to all subscription. |

Use type helpers for fifoMode, deadLetter and subscriptions properties.

Subscriptions

| Name | Type | Description | | ------------ | -------- | ----------------------------------------------------- | | listener | function | Life-cycle listener function for the subscription. | | handler | function | Entry-point handler function for the subscription. | | variables | object | Environment variables associated to the subscription. | | logRetention | integer | Log retention (in days) for the handler. | | memory | integer | Memory available (in megabytes) for the handler. | | concurrency | integer | Maximum number of concurrent executions handlers. | | batch | integer | Maximum number of messages per handler invocation. |

Examples

• Get started with queue
• Importing queue

Providers

• Local provider
• AWS provider

License

MIT License