Production Monitoring

To monitor the Docker application in a production environment, it is essential to implement logging, metrics collection, and health checks. This can be achieved using various tools and techniques tailored to JavaScript applications running in Docker containers.

1. Logging

Implement structured logging to capture detailed application activity. This can be done using a logging library such as winston in your JavaScript code.

Example code snippet:

const winston = require('winston');

const logger = winston.createLogger({
  level: 'info',
  format: winston.format.json(),
  transports: [
    new winston.transports.Console(),
    new winston.transports.File({ filename: 'combined.log' })
  ],
});

// Use the logger throughout your application
logger.info('Application started');
logger.error('An error occurred', { error: error });

In a production setup, logs can be centralized using services like ELK Stack (Elasticsearch, Logstash, Kibana) or Fluentd.

2. Metrics Collection

To collect performance metrics for the application, implement a monitoring library such as prom-client for Node.js.

Example setup in your main application file:

const client = require('prom-client');

// Create a Registry to register the metrics
const register = new client.Registry();

// Create and register a Gauge metric
const gauge = new client.Gauge({
  name: 'app_memory_usage_bytes',
  help: 'Memory usage of the application in bytes',
  registers: [register],
});

// Function to record memory usage periodically
setInterval(() => {
  const memoryUsage = process.memoryUsage().heapUsed;
  gauge.set(memoryUsage);
}, 5000);

// Expose metrics endpoint
app.get('/metrics', (req, res) => {
  res.setHeader('Content-Type', register.contentType);
  res.end(register.metrics());
});

Ensure the application exposes the /metrics endpoint and consider using a service such as Prometheus to scrape these metrics at regular intervals.

3. Health Checks

Configure health checks in the docker-compose.yml file to ensure the application remains responsive.

Example addition to docker-compose.yml:

version: "3.7"

services:
  docs:
    build:
      context: .
      dockerfile: Dockerfile
      target: dev
    ports:
      - 8000:8000
    volumes:
      - ./:/app
    healthcheck:
      test: ["CMD", "curl", "-f", "http://localhost:8000/health"]
      interval: 30s
      timeout: 10s
      retries: 3

Here, a health check is defined to periodically send a request to the /health endpoint, which should return a status indicating the application is running well.

4. Monitoring Tools

Consider using a complete monitoring stack that integrates with your Docker containers, such as Grafana and Prometheus, for visualizing metrics and alerts.

• Prometheus: Set up Prometheus to scrape the /metrics endpoint.

• Grafana: Use Grafana to create dashboards that visualize application performance and system metrics.

Conclusion

By implementing logging, metrics collection, and health checks within your Dockerized JavaScript application, you can ensure robust monitoring in a production environment. This setup allows for proactive identification of issues and performance optimization.

Source: docker/getting-started