Monitoring 500 Errors Across ECS Services Behind a Load Balancer

To effectively monitor 500 errors across all your ECS services on Fargate, including those not directly connected to the Application Load Balancer (ALB), you'll need to implement a more comprehensive monitoring strategy. Here are some approaches you can consider:

1. Service Connect: If you're not already using it, consider implementing AWS ECS Service Connect for your internal service-to-service communication. This will allow you to monitor traffic between services and provide metrics for all services, not just the one connected to the ALB.

2. Custom Metrics: Implement custom CloudWatch metrics within each of your ECS services. You can have your applications report their own 500 error counts directly to CloudWatch, regardless of how the traffic reaches them.

3. Distributed Tracing: Implement a distributed tracing solution like AWS X-Ray or a third-party APM (Application Performance Monitoring) tool. This will allow you to trace requests as they flow through your entire system, making it easier to identify which service is generating 500 errors.

4. Standardize Logging: While you mentioned not to suggest log filtering due to different formats, standardizing your logging across services would greatly simplify error monitoring. Consider implementing a consistent logging format across all services.

5. Load Balancer Request Tracing: Enable request tracing on your ALB. This adds a unique ID to each request via the X-Amzn-Trace-Id header. You can then correlate this ID with your application logs to track requests across services.

6. Service Mesh: Consider implementing a service mesh solution like AWS App Mesh. This can provide consistent observability across all your services, including detailed metrics on errors and latency.

By combining these approaches, you should be able to gain visibility into 500 errors across all your ECS services, regardless of whether they're directly connected to the ALB or not. This will allow you to quickly identify which specific service is experiencing issues when you receive an alert.

Remember, the key is to implement a solution that provides end-to-end visibility across your entire application stack, rather than relying solely on the metrics provided by the ALB.

Sources
Should incoming traffic to an ECS service go through service connect for monitoring purposes? | AWS re:Post
Is there a way to track which ECS task a request is forwarded to by a NLB? | AWS re:Post

Hello Tatev,

You can have HTTP 5xx error metrics with Service Connect if your services don't use ELB.

From AWS Docs:

HTTPCode_Target_5XX_Count
The number of HTTP response codes with numbers 500 to 599 generated by the applications in these tasks. These tasks are the targets. This metric only counts the responses sent to the Service Connect proxies by the applications in these tasks, not responses sent directly.

This metric is only available if you have configured Amazon ECS Service Connect and the appProtocol is HTTP or HTTP2 in the port mapping in the task definition.

Useful statistics: Average, Minimum, Maximum, Sum.

Unit: Count.