VMware Cloud Director fails to connect to RabbitMQ with ACCESS_REFUSED – Login was refused using authentication mechanism PLAIN

Products

• VMware Cloud Director

Issue/Introduction

• VMware Cloud Director logs show repeated AMQP authentication failures when connecting to RabbitMQ.
• cell-runtime.log contains entries similar to: org.springframework.amqp.AmqpAuthenticationException: com.rabbitmq.client.AuthenticationFailureException: ACCESS_REFUSED - Login was refused using authentication mechanism PLAIN
• AMQP connectivity tests via the UI may succeed.
• The RabbitMQ username appears as guest.

Environment

• 10.3
• 10.4
• 10.5
• 10.6

Cause

• This issue occurs when VCD is configured to use invalid or restricted RabbitMQ credentials.  
• By default RabbitMQ disables or limits access for the guest account unless explicitly configured.
• If VMware Cloud Director is still using this account or an incorrect password, authentication will fail.

Resolution

1. Log in to the RabbitMQ management UI.
2. Create a dedicated RabbitMQ user with a known password.
3. Assign the user to the required virtual host (default is '/')
4. Update the VCD AMQP settings to use the new credentials.
5. Check the cell-runtime.log to confirm AMQP connections are succeeding.

Additional Information

• Default RabbitMQ ports: 5672 (non-SSL) and 5671 (SSL/TLS).
• Default virtual host: '/'
• Always use a dedicated user rather than the default guest account for production systems.