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How to Monitor AWS ECS with Vigilmon

#aws #ecs #docker #monitoring

How to Monitor AWS ECS with Vigilmon

AWS Elastic Container Service (ECS) is a fully managed container orchestration service that runs Docker containers at scale. Whether you're using ECS with Fargate (serverless) or EC2 launch type, monitoring your containers and services requires more than just CloudWatch metrics.

This guide covers how to set up external monitoring for your ECS services using Vigilmon.

Why External Monitoring for ECS?

CloudWatch gives you internal metrics (CPU, memory, network), but it can't tell you:

  • Is your service actually responding to user requests?
  • Is the load balancer routing correctly?
  • Is your health check returning the right response?
  • Is your app slow even when container health checks pass?

Vigilmon monitors from outside AWS, giving you the user's perspective.

ECS Architecture and What to Monitor 

Users → Route 53 → ALB → ECS Service → Tasks (containers)
                         ↑
                  Target Group health checks
                         ↑
               Vigilmon external monitoring
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Primary monitoring target: Your Application Load Balancer (ALB) endpoint, because:

  • It represents what users actually hit
  • It validates the full stack (ALB → ECS → container → app → DB)
  • ALB DNS is stable even when tasks restart

Step 1: Add a Health Check to Your Container

For a Node.js service in ECS:

// src/health.js
const express = require('express');
const router = express.Router();

router.get('/health', async (req, res) => {
  const checks = {};
  let healthy = true;

  // Check database (if applicable)
  try {
    await db.query('SELECT 1');
    checks.db = 'ok';
  } catch (e) {
    checks.db = 'error';
    healthy = false;
  }

  res.status(healthy ? 200 : 503).json({
    status: healthy ? 'ok' : 'degraded',
    checks,
    taskId: process.env.ECS_CONTAINER_METADATA_URI, // ECS metadata
  });
});

module.exports = router;
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Step 2: Configure ECS Health Check in Task Definition 

{
  "containerDefinitions": [
    {
      "name": "myapp",
      "image": "123456789.dkr.ecr.us-east-1.amazonaws.com/myapp:latest",
      "healthCheck": {
        "command": ["CMD-SHELL", "curl -f http://localhost:8080/health || exit 1"],
        "interval": 30,
        "timeout": 10,
        "retries": 3,
        "startPeriod": 60
      },
      "portMappings": [
        {
          "containerPort": 8080,
          "protocol": "tcp"
        }
      ]
    }
  ]
}
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Step 3: Configure ALB Target Group Health Check

In your CloudFormation or Terraform:

# Terraform
resource "aws_lb_target_group" "myapp" {
  name     = "myapp-tg"
  port     = 8080
  protocol = "HTTP"
  vpc_id   = var.vpc_id

  health_check {
    enabled             = true
    path                = "/health"
    healthy_threshold   = 2
    unhealthy_threshold = 3
    timeout             = 10
    interval            = 30
    matcher             = "200"
  }

  target_type = "ip"  # For Fargate
}
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Step 4: Add External Monitoring in Vigilmon

  1. Sign up at vigilmon.online
  2. Click Add Monitor → HTTP/HTTPS Monitor
  3. URL: https://your-alb-dns.us-east-1.elb.amazonaws.com/health (or your custom domain if Route 53 is configured)
  4. Expected status: 200
  5. Expected keyword: "status":"ok"
  6. Check interval: 1 minute
  7. Alert via Slack, email, or PagerDuty webhook

Step 5: Monitor ECS Scheduled Tasks with Heartbeat

For ECS Scheduled Tasks (batch jobs, cron-based tasks), use a Vigilmon heartbeat monitor:

# ecs_task.py — scheduled task
import urllib.request
import os

def run_task():
    # ... your task logic ...

    # Ping Vigilmon heartbeat on success
    try:
        urllib.request.urlopen(
            f"https://hb.vigilmon.online/{os.environ['VIGILMON_HB_ID']}"
        )
    except Exception:
        pass  # Don't fail the task if heartbeat fails

if __name__ == "__main__":
    run_task()
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Set the heartbeat expected interval in Vigilmon to match your ECS scheduled task frequency.

Multi-Region ECS Monitoring

If you run ECS in multiple AWS regions:

Monitor URL Purpose
US East https://us-east-api.example.com/health Primary region up
US West https://us-west-api.example.com/health DR region up
EU West https://eu-api.example.com/health EU region up

Conclusion

AWS ECS is a powerful container platform, but CloudWatch alone won't tell you when your users can't reach your service. Vigilmon's external monitoring validates the full request path from the internet to your container — and alerts you within 60 seconds of failure.

Start monitoring your ECS services for free at vigilmon.online

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