Troubleshooting a Web Application (Angular, Spring Boot, AWS MySQL RDS, ECS Fargate)

DHARMEDRA SAHU

Introduction

Running a web application built with Angular for the frontend, Spring Boot for the backend, AWS MySQL RDS for the database, and deployed on AWS ECS Fargate can be complex. Issues can arise in the client-side code, server-side logic, database queries, or infrastructure configuration. This guide provides a systematic, step-by-step approach to troubleshoot and resolve issues efficiently, ensuring minimal downtime and optimal performance.

Step-by-Step Troubleshooting Guide

1. Understand the Problem

Before diving into technical details, gather context to narrow down the issue.

  • Reproduce the Issue:

    • Attempt to replicate the problem in a controlled environment (e.g., staging or local setup).

    • Document the exact steps, inputs, and conditions that trigger the issue.

  • Collect Information:

    • Symptoms: Note error messages, UI behavior (e.g., blank page, slow loading), or HTTP status codes (e.g., 500, 404).

    • Environment: Identify the environment (production, staging, dev), browser, OS, and network conditions.

    • Logs: Retrieve logs from the frontend (browser console), backend (CloudWatch), and AWS services (ECS, RDS).

    • Recent Changes: Check for recent code deployments, configuration updates, or infrastructure changes.

  • User Feedback: If reported by a user, ask clarifying questions like, “What action triggered the error?” or “When did it start?”

2. Investigate the Frontend (Angular)

The Angular frontend is the user’s entry point, so start by checking for client-side issues.

  • Browser Developer Tools:

    • Open the browser’s developer tools (F12 or right-click → Inspect).

    • Console Tab: Look for JavaScript errors, uncaught exceptions, or warnings.

    • Network Tab: Inspect failed API calls (e.g., 400, 500, 504 errors), response payloads, headers, and response times.

    • Sources Tab: Debug TypeScript/JavaScript code by setting breakpoints if needed.

  • Angular-Specific Checks:

    • Verify Angular version and dependency compatibility in package.json.

    • Check for unhandled promises or observables causing runtime errors.

    • Ensure environment files (environment.ts or environment.prod.ts) point to the correct backend API endpoints.

    • Run ng serve or ng build locally to test the frontend independently.

  • Common Issues:

    • CORS Errors: Confirm the backend allows requests from the frontend’s domain.

    • Routing Issues: Verify Angular routes are correctly configured to avoid 404 errors.

    • UI Rendering: Check for broken templates or components due to missing data or incorrect bindings.

3. Examine the Backend (Spring Boot)

The Spring Boot backend handles API requests and business logic, so issues here often cause API failures or server errors.

  • Access Application Logs:

    • In AWS ECS Fargate, logs are sent to AWS CloudWatch. Navigate to the CloudWatch Logs group for your ECS task.

    • Look for stack traces, exceptions (e.g., NullPointerException), or custom log messages.

    • Enable detailed logging in Spring Boot by setting logging.level.org.springframework=DEBUG in application.properties.

  • API Testing:

    • Use Postman or curl to test API endpoints directly, bypassing the frontend.

    • Verify request parameters, headers (e.g., authentication tokens), and response codes.

    • Ensure the API is accessible from the ECS task’s endpoint (public or private).

  • Spring Boot Configuration:

    • Validate application.properties or application.yml for correct settings (e.g., database URL, AWS credentials).

    • Confirm the application connects to the correct AWS MySQL RDS instance.

    • Check Spring Security configurations to ensure requests aren’t blocked.

  • Common Issues:

    • Dependency Injection: Missing beans or misconfigured @Component/@Service annotations.

    • API Timeouts: Slow database queries or external service calls.

    • Authentication: Invalid JWT tokens or OAuth misconfigurations.

4. Verify the Database (AWS MySQL RDS)

Database issues can lead to slow performance, data inconsistencies, or application errors.

  • Connectivity:

    • Ensure Spring Boot can connect to the RDS instance.

    • Verify the RDS endpoint, port, username, password, and security group rules in the ECS task’s VPC.

    • Test connectivity using a MySQL client (e.g., MySQL Workbench) from an EC2 instance or local machine.

  • Query Performance:

    • Enable slow_query_log in the RDS parameter group to identify slow queries.

    • Run EXPLAIN on suspected queries to detect inefficient indexes or table scans.

    • Optimize queries or add indexes, testing changes in a non-production environment.

  • Data Integrity:

    • Check for missing or corrupted data due to recent migrations or updates.

    • Ensure data matches expected formats and constraints (e.g., no nulls in required fields).

  • RDS Monitoring:

    • Use AWS CloudWatch to monitor RDS metrics like CPU usage, free storage, or connection count.

    • Look for high latency, low storage, or connection limit issues.

  • Common Issues:

    • Connection Pool Exhaustion: Misconfigured connection pools (e.g., HikariCP) in Spring Boot.

    • Deadlocks: Concurrent transactions causing deadlocks (use SHOW ENGINE INNODB STATUS).

    • Schema Mismatches: Ensure the database schema aligns with Spring Boot entity models.

5. Inspect AWS Infrastructure (ECS Fargate)

Infrastructure issues in AWS ECS Fargate can cause application failures or connectivity problems.

  • ECS Task Health:

    • Check the ECS console to confirm tasks are in the RUNNING state.

    • For failed tasks, view the Stopped Tasks section for errors (e.g., out-of-memory, misconfigured environment variables).

  • CloudWatch Logs:

    • Inspect container logs for startup or runtime errors.

    • Look for ECS-specific issues, such as failed health checks or container crashes.

  • Networking:

    • Verify that ECS tasks are in the correct VPC, subnet, and security group.

    • Ensure security groups allow inbound traffic on the application port (e.g., 8080) and outbound traffic to RDS.

    • If using an Application Load Balancer (ALB), check health checks and target group status.

  • Scaling and Resources:

    • Confirm sufficient CPU and memory allocation in the ECS task definition (e.g., 0.5 vCPU, 1 GB RAM).

    • Check if auto-scaling policies are triggering correctly or if tasks are throttled.

  • Environment Variables:

    • Ensure environment variables (e.g., database credentials, API keys) are set in the ECS task definition.

  • Common Issues:

    • Task Failures: Incorrect Docker image or missing environment variables.

    • Load Balancer Issues: Misconfigured ALB listener rules or unhealthy targets.

    • VPC Misconfigurations: Security groups or network ACLs blocking traffic.

6. Trace Requests End-to-End

Tracing requests across the application stack helps pinpoint the failure.

  • Distributed Tracing:

    • Use AWS X-Ray to trace requests from frontend to backend to database.

    • Identify bottlenecks, such as slow API calls or database queries.

  • End-to-End Testing:

    • Simulate user actions with tools like Cypress (frontend) or Postman (backend).

    • Verify the entire request flow from browser to ECS to RDS.

  • Performance Metrics:

    • Monitor performance using CloudWatch, New Relic, or Datadog.

    • Look for high latency, memory leaks, or CPU spikes.

7. Narrow Down the Root Cause

  • Isolate Components: Test the frontend, backend, and database independently.

  • Hypothesize and Test: Form hypotheses (e.g., “Slow database query” or “ECS memory issue”) and test with controlled changes.

  • Rollback Changes: If the issue started after a deployment, roll back to a previous version to confirm the cause.

8. Resolve the Issue

  • Apply Fixes:

    • Frontend: Fix Angular code, templates, or API calls.

    • Backend: Patch Spring Boot code, optimize queries, or adjust configurations.

    • Database: Add indexes, clean up data, or scale RDS resources.

    • Infrastructure: Update ECS task definitions, security groups, or ALB settings.

  • Test Fixes:

    • Deploy fixes in a staging environment first.

    • Verify the issue is resolved without introducing new problems.

  • Document: Record the root cause, solution, and preventive measures.

9. Prevent Future Issues

  • Monitoring and Alerts:

    • Set up CloudWatch alarms for error rates, RDS storage, or ECS task failures.

    • Use automated monitoring tools to detect anomalies.

  • Automated Testing:

    • Implement unit tests for Spring Boot and Angular.

    • Use integration tests for API-to-database interactions.

    • Add end-to-end tests for user workflows.

  • CI/CD Pipeline:

    • Use a robust CI/CD pipeline with automated tests.

    • Implement blue-green deployments to reduce risk.

  • Maintenance:

    • Keep Angular, Spring Boot, and MySQL dependencies updated.

    • Monitor RDS storage and performance regularly.

    • Review ECS task resource usage periodically.

10. Escalate if Needed

  • If the issue persists:

    • Check AWS documentation or support forums.

    • Consult team members or AWS Support (if on an enterprise plan).

    • Search for similar issues on Stack Overflow or relevant platforms.

Example: Troubleshooting a 500 Internal Server Error

  1. Reproduce: User reports a 500 error when submitting a form.

  2. Frontend: Browser console shows /api/submit returning a 500 error.

  3. Backend Logs: CloudWatch logs reveal a NullPointerException in a Spring Boot controller.

  4. Code Review: Identify a missing null check in the controller’s input validation.

  5. Database: Confirm the database query is valid.

  6. Fix: Add null check, test locally, and deploy to staging.

  7. Verify: Confirm form submission works in staging, then deploy to production.

  8. Prevent: Add unit tests and set up CloudWatch alarms for 500 errors.

Best Practices for Efficient Troubleshooting

  • Use a Checklist: Follow a structured process to avoid missing steps.

  • Log Everything: Enable comprehensive logging in Spring Boot and Angular.

  • Reproduce Locally: Use Docker to mimic the ECS Fargate setup locally.

  • Automate Tasks: Use scripts for log retrieval or API testing.

  • Stay Methodical: Avoid hasty changes that could introduce new issues.

Tools to Aid Troubleshooting

  • Frontend: Browser Developer Tools, Angular CLI, Postman.

  • Backend: Spring Boot Actuator, Logback.

  • Database: MySQL Workbench, AWS RDS Console, CloudWatch Logs Insights.

  • Infrastructure: AWS Management Console, AWS CLI, AWS X-Ray.

  • Monitoring: CloudWatch, New Relic, Datadog.

Conclusion

Troubleshooting a web application on Angular, Spring Boot, AWS MySQL RDS, and ECS Fargate requires a methodical approach, covering frontend, backend, database, and infrastructure. By following this guide, you can efficiently identify and resolve issues, improve application reliability, and prevent future problems. For specific issues, share error details or logs for tailored assistance.
 

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