MySQL Bugs: #72543: remove the spam warnings: Client failed to provide its character set

Bug #72543	remove the spam warnings: Client failed to provide its character set
Submitted:	6 May 2014 5:15	Modified:	3 Nov 2014 18:04
Reporter:	Shane Bester (Platinum Quality Contributor)	Email Updates:
Status:	Closed	Impact on me:	None
Category:	MySQL Server: Security: Privileges	Severity:	S3 (Non-critical)
Version:	5.6.20	OS:	Any
Assigned to:		CPU Architecture:	Any

Description:
Error log gets filled with spam like this:

[Warning] Client failed to provide its character set. 'latin1' will be used as client character set.
[Warning] Client failed to provide its character set. 'latin1' will be used as client character set.

How to repeat:
Simplest example, login to server with an 4.0.forever client.

Suggested fix:
I suggest to disable the useless warning totally.  Or, keep it and consider:

o)  include the client IP address/port and client_capabilities
o)  ability to suppress the warning if log_warnings < 2

HAProxy's mysql-check option causes this warning as well. A solution for suppressing this warning would be helpful to keep error logs clean.

A way to suppress this warning would be appreciated.  We upgraded to 5.6.20 and the error logs are now filled with the following message:

2014-09-30 07:36:55 11072 [Warning] Client failed to provide its character set. 'utf8' will be used as client character set.

This is making it hard to see any actual issues in the log.

Noted in 5.6.23, 5.7.6 changelogs.

The server no longer logs the following warnings because they are
uninformative: Client failed to provide its character set. 'charset'
will be used as client character set.

$ git show -s b3373e4
commit b3373e414abe051cb3db5e7eb2125584e173ed72
Author: Venkata Sidagam <venkata.sidagam@oracle.com>
Date:   Mon Nov 3 22:35:41 2014 +0530

    Bug #18708334 REMOVE THE SPAM WARNINGS: CLIENT FAILED TO PROVIDE ITS CHARACTER SET
    
    Description:
    When we try to connect mysql-5.6 server with mysql-4.0 client the error log gets filled with below warning message
    "[Warning] Client failed to provide its character set. 'latin1' will be used as client character set"
    
    Analysis: Since the the client protocol is older than 4.1 and the 4.0 client is not providing the character set while trying to connect to the server. so, the warning message is sent to error log file
    
    Fix: Since the warning message is not necessary, we are removing the warning message.