# ECS Service Connect: DNS resolution failed for service endpoint within the same namespace

- **ID:** `cloud/aws-ecs-service-connect-dns-resolution-failure`
- **Domain:** cloud
- **Category:** network_error
- **Error Code:** `ECS.ServiceConnect.DNSResolution`
- **Verification:** ai_generated
- **Fix Rate:** 78%

## Root Cause

When using ECS Service Connect, tasks fail to resolve the DNS name of a service in the same namespace because the service discovery namespace is not properly associated with the VPC, or the service's DNS records are not propagated due to a misconfigured service connect configuration.

## Version Compatibility

| Version | Status | Introduced | Deprecated |
|---------|--------|------------|------------|
| AWS ECS: latest | active | — | — |
| AWS Cloud Map: latest | active | — | — |
| Amazon VPC: any | active | — | — |

## Workarounds

1. **Verify that the Cloud Map namespace is associated with the correct VPC. Run 'aws servicediscovery list-namespaces' and check the VPC configuration. If missing, create a new namespace with 'aws servicediscovery create-http-namespace --name my-namespace --vpc vpc-12345'.** (85% success)
   ```
   Verify that the Cloud Map namespace is associated with the correct VPC. Run 'aws servicediscovery list-namespaces' and check the VPC configuration. If missing, create a new namespace with 'aws servicediscovery create-http-namespace --name my-namespace --vpc vpc-12345'.
   ```
2. **Ensure the ECS task definition includes the 'awslogs' log driver and check the Service Connect logs for DNS queries using 'aws logs describe-log-groups' and filtering for 'DNS_RESOLUTION_FAILED'. Then update the service connect configuration with the correct 'clientAlias' and 'discoveryName'.** (80% success)
   ```
   Ensure the ECS task definition includes the 'awslogs' log driver and check the Service Connect logs for DNS queries using 'aws logs describe-log-groups' and filtering for 'DNS_RESOLUTION_FAILED'. Then update the service connect configuration with the correct 'clientAlias' and 'discoveryName'.
   ```

## Dead Ends

- **** — Overrides the default AWS DNS resolver, breaking Service Connect's built-in DNS resolution for the namespace. (80% fail)
- **** — IPs can change when tasks are redeployed or scaled; defeats the purpose of service discovery. (70% fail)
- **** — Restarting doesn't fix the underlying DNS configuration issue; the new tasks will face the same resolution failure. (50% fail)