-db_charset doesn't behave the same way as deprecated -db-config-*-charset settings

[tomkrouper]

Overview of the Issue

We use emoji in our application and because of that we need to use utf8mb4. We still have the old-style -db-config-<user>-charset settings which we changed to utf8mb4 and everything worked as expected. While working with this, I saw the deprecation notice, so I attempted to just use -db_charset utf8mb4. This did not work. @deepthi was able to point me to func Init(defaultSocketFile string) (*DBConfigs, error) which shows that -db_charset requires -db_host. Unfortunately, when I set -db_host, my.cnf gets ignored which causes other issues.

Expected behavior would be to have setting -db_charset be the same behavior as setting the charset on a user level.

Reproduction Steps

1. Spin up docker vitess/base.

2. Start vttablet with -db-config-dba-charset utf8mb4 -db-config-app-charset utf8mb4 -db-config-appdebug-charset utf8mb4 -db-config-allprivs-charset utf8mb4 -db-config-repl-charset utf8mb4 -db-config-filtered-charset utf8mb4 options

3. Insert data with emoji.

4. SELECT data, see emoji in output.

5. Spin up docker vitess/base.

6. Start vttablet with -db_charset utf8mb4`

7. Insert data with emoji.

8. SELECT data, see ? where emoji output should be.

Binary version

Example:

vitess@4792fbfd1caa:/vt/src/vitess.io/vitess$ vttablet --version
ERROR: logging before flag.Parse: E0221 22:23:34.724761    2113 syslogger.go:122] can't connect to syslog
Version: 613bb78e4 (Git branch 'master') built on Tue Feb 12 04:35:14 UTC 2019 by root@40b3289860a2 using go1.11.2 linux/amd64

Operating system and Environment details

docker vitess/base

[deepthi]

Fixed by #4814