Problem
Cloud SQL reports error message when the client tries to connect to the PostgreSQL version 11 or below.
FATAL: Unsupported frontend protocol 1234.5680: server supports X.0 to Y.0
Environment
- Cloud SQL for PostgreSQL version 11 or below
Solution
- Upgrade the Cloud SQL instances to PostgreSQL 12.
- Disable the GSSAPI encrypted connection in the environment file by setting the gssencmode value to disable.
- Default value is prefer, which tries GSSAPI encrypted connection first, and fallback otherwise.
Cause
The root cause of the error is the fact that GSSAPI encrypted connections are only possible starting from PostgreSQL version 12.
The error message FATAL: Unsupported frontend protocol 1234.5680: server supports X.0 to Y.0 in the logs means that the client is trying to connect with the GSSAPI encrypted connection, but finds out that the server does not support the GSSAPI encrypted connection. The code 1234.5680 in the message is the GSSAPI Encryption request code. After getting the GSSAPI encrypted connection failure the client will try to establish a SSL connection. If it fails the console will log the same error message with 1234.5679 code, and will try to use other methods.