Why does n8n on ECS lose DB credentials, causing 'password authentication failed for user "dbadmin"' error?

Below is an explanation of the issue based on your description:

Problem Overview

When running n8n on ECS with PostgreSQL configured via environment variables, the deployment works fine at first but then—after about a week—n8n loses its connection to the database. The error message you see is:

password authentication failed for user "dbadmin"

Key Points

• Environment Variables:
  Your configuration is set using a shell script that exports the required environment variables (e.g., DB_TYPE, DB_POSTGRESDB_DATABASE, DB_POSTGRESDB_USER, etc.). These variables are used by n8n when connecting to PostgreSQL.
  Example:

  BASHCopied
  export DB_TYPE=postgresdb  
  export DB_POSTGRESDB_DATABASE=n8n  
  export DB_POSTGRESDB_HOST=$RDS_ENDPOINT  
  export DB_POSTGRESDB_PORT=$RDS_PORT  
  export DB_POSTGRESDB_USER=$RDS_USERNAME  
  export DB_POSTGRESDB_PASSWORD=$RDS_PASSWORD  
  export DB_POSTGRESDB_SCHEMA=n8n

• Error Details:
  Despite the initial success, after about a week, the container starts failing to connect to the database because PostgreSQL rejects the authentication for the user "dbadmin". This indicates that somewhere in the process the value for DB_POSTGRESDB_USER is being interpreted (or defaulted) as dbadmin rather than the expected value (for example, "n8n" if that’s what you set).

Possible Causes

1. Credential Mismatch or Rotation:

   • The user stored in $RDS_USERNAME appears to be "dbadmin" (since the error says so). If your actual credentials in the database have been rotated, changed, or are out of sync with what’s provided in the environment, PostgreSQL will reject the connection.

2. Environment Variable Persistence:

   • If the shell script is used only during initial container start or deployment in ECS, the values might not persist after a container restart or update. This could lead to the container falling back to defaults or older values that are no longer valid.
   • Ensure that the environment variables are being correctly passed into the Docker container every time it starts.

3. Configuration Drift Over Time:

   • In some ECS setups, if the container gets redeployed or restarted without the new environment variables re-applied correctly, it might end up with a cached configuration that doesn’t match your current/password-protected database credentials.

Recommendations

• Double-Check Credentials:
  Verify that the values assigned to $RDS_USERNAME and $RDS_PASSWORD match the credentials on your PostgreSQL instance. If there’s a rotation policy or if credentials are updated, ensure that these changes are simultaneously updated in your ECS environment configuration.

• Ensure Proper Environment Variable Injection:
  Instead of exporting variables in a shell script at runtime, consider configuring them directly within your ECS task definition or using a secrets management system. This way, every container start uses the correct and current credentials.

• Review Container Restart Behavior:
  Look into how ECS handles environment changes upon container restarts. Ensuring that the container is not reverting to stale configuration can help eliminate the intermittent failure.

• Logging & Debugging:
  Implement logging at container startup to print (safely, without exposing secrets) the current environment variables or a marker indicating that the correct configuration was loaded. This can help diagnose if the correct values are being used consistently.

Conclusion

The error "password authentication failed for user 'dbadmin'" suggests that PostgreSQL is rejecting the connection due to credential issues. Since the deployment works initially, the likely problem is that after some time the container loses or loads incorrect environment variable values—possibly due to a restart or misconfiguration. Verifying that the credential values are current and consistently passed into your Docker container should help resolve this issue.

If further help is needed regarding setting up PostgreSQL with n8n in an ECS and Docker environment, feel free to ask!