Migration service unable to connect to the authorized network

[tobyjames51]

Hi,

I'm new to GCP and I am migrating the data from one old CloudSQL MySQL to a new instance using the CDC approach of migration service (since the old one is still used by the application and cannot go for a major downtime). The migration service is failing to connect to the source database giving the error I/O timeout. I have already added the public IP address of the instance in the authorized networks list. What could be the possible reasons for this failure?

Thanks in advance

[ms4446]

The I/O timeout error you're encountering during the CDC migration from your source CloudSQL MySQL instance, even after adding the IP to the authorized networks, could be from several factors.

Network connectivity is a common issue. While you've authorized the IP, other firewall rules at the VPC or project level could still block traffic. If the source database uses a private IP, ensure the migration service has proper VPC peering or VPN setup to access it. Additionally, if your network employs a proxy or NAT, verify that the migration service is correctly configured to handle or bypass these.

On the database configuration side, ensure the MySQL user has the required remote access privileges, such as REPLICATION CLIENT and REPLICATION SLAVE, rather than granting all privileges, which may be excessive. Check MySQL configuration settings like max_connections and wait_timeout, which can affect connectivity. If the source database is under heavy load, it may fail to accept new connections, leading to timeouts.

In terms of migration service configuration, ensure it uses the correct connectivity method (public or private IP) and that the service account has the necessary roles, such as Cloud SQL Client, to access the source database.

For troubleshooting, review the CloudSQL logs for connection-related errors. You can test network connectivity by using nc (netcat) or gcloud ssh from a VM in the same network to connect to the database’s IP and port (3306). If connectivity issues persist, use the cloudsql-connectivity-test tool, and consider contacting Google Cloud Support for further investigation.