post-upgrade health-check throws false warning: The database collation 'en_US.utf8' is not supported by Confluence. You need to use 'utf-8'.

Bug Summary:

post-upgrade health-check throws false warning: The database collation 'en_US.utf8' is not supported by Confluence. You need to use 'utf-8'.

Environment:

Confluence 6.4 -> upgraded to 6.14.2, postgresql 9.6

Steps to replicate

1. Create postgres database with en_US.utf8 collation/cset:

   CREATE DATABASE test_db with ENCODING 'UTF-8' LC_COLLATE 'en_US.utf8' LC_CTYPE 'en_US.utf8' TEMPLATE template0 OWNER postgres;
   

1. Create new Confluence environment (using the oldest supported version of the installer), use database created in previous step
2. Download latest Confluence installer file, proceed with upgrading existing environment
3. Start Confluence after the upgrade

Expected results

Confluence starts without any issues

Actual results

Following warning is displayed during the startup:

We discovered a problem while preparing to start Confluence. If you're a Confluence admin, you can either fix this problem now or ignore it, and start Confluence anyway.
Database: The database collation 'en_US.utf8' is not supported by Confluence. You need to use 'utf-8'.

Notes

This occurs because the health check verifies against all utf-8 collations, and does not include utf8. utf8 is a supported collation, we are incorrectly reporting this as a failure.

Workaround

If using Docker, the initdb args can be overridden by setting POSTGRES_INITDB_ARGS to the below as per the example (this is using Kitematic).

--encoding=UTF8 --lc-collate='en_US.UTF-8' --lc-ctype='en_US.UTF-8'

It is safe to ignore the health check failure now and continue - it will only appear on upgrade.