smlw.worker

Baseline functions for smlw workers.

RabbitMqService

The RabbitMqService class manages operations for connecting to and interacting with a RabbitMQ server. Its main responsibilities include:

• Connecting to the RabbitMQ server: Establishes an initial connection with RabbitMQ using a configurable connection string. It creates a communication channel and manages connection errors, including scheduling automatic reconnections in case of connection loss.

• Managing reconnections: If the connection to RabbitMQ is lost, the class handles automatic reconnection using scheduling. It attempts reconnections every 30 seconds until the connection is restored.

• Consuming messages: Once the connection is established, the class begins consuming messages from the specified queue. Received messages are processed through a configured worker service (workerService), which handles the message processing logic.

• Sending messages: Allows sending messages to a target queue. Messages are sent as JSON data and are marked as persistent to ensure they are not lost even in case of errors.

Key Features

1. Establish a connection:

   • Connects to the RabbitMQ server using the provided credentials and settings.
   • Handles connection losses with automatic reconnection attempts.

2. Automatic reconnection:

   • Schedules periodic reconnection attempts in case of connection interruption.
   • Uses node-schedule to manage scheduling.

3. Consuming messages from the queue:

   • Consumes messages from the specified queue and passes them to a worker service for processing.

4. Sending messages to the queue:

   • Sends messages to the target queue with persistence guarantees.

Dependencies

• amqplib: For interacting with RabbitMQ.
• node-schedule: For scheduling reconnection attempts.

USe Examples

const RabbitMqService = require('./RabbitMqService');
const workerService = {
    consumeTask: (task) => {
        // Logica per elaborare il compito
    }
};
const logger = {
    info: (message, meta) => console.log(message, meta),
    error: (message, meta) => console.error(message, meta)
};
const env = {
    RABBIT_MQ_CONNECTIONSTRING: 'amqp://localhost',
    RABBIT_MQ_LISTEN_QUEUE: 'my_queue',
    RABBIT_MQ_WRITE_QUEUE: 'my_write_queue'
};

const rabbitMqService = new RabbitMqService(env, workerService, logger);

(async () => {
    await rabbitMqService.connect();
})();

Logger

The Logger module provides a utility for logging workflows using the winston library. The default configuration saves logs to dedicated MongoDB collections and to rotating JSON files, and supports console logging.

Setup Function

The setup function configures the logger with the following options:

const setup = function(mongoConnectionString, dbName, enableDebugLog, hostname, logsPath, serviceName, enableConsoleLog)

WorkerService

Description

WorkerService is a class designed to handle the execution of tasks within a workflow using RabbitMQ as the messaging system. This class interacts with RabbitMqService to send and receive messages from RabbitMQ queues. It manages task execution and error handling during processing.