MySQL Bugs: #51440: configuration file option proxy-backend-addresses cannot be set multiple times

Bug #51440	configuration file option proxy-backend-addresses cannot be set multiple times
Submitted:	24 Feb 2010 1:54	Modified:	26 Feb 2010 16:36
Reporter:	Dario Souza	Email Updates:
Status:	Closed	Impact on me:	None
Category:	MySQL Proxy: Install/Config	Severity:	S2 (Serious)
Version:	0.8.0	OS:	Any
Assigned to:	MC Brown	CPU Architecture:	Any
Tags:	configuration config file addresses

Description:
The configuration option proxy-read-only-backend-addresses or proxy-backend-addresses cannot be set multiple times and therefore cannot be used to set more than one backend server.

How to repeat:

1) create a file called /etc/mysql-proxy.cnf:

[mysql-proxy]
proxy-read-only-backend-addresses       = db-slave-1:3306
proxy-read-only-backend-addresses       = db-slave-2:3306
proxy-read-only-backend-addresses       = db-slave-4:3306
proxy-read-only-backend-addresses       = db-slave-3:3306
user                                    = mysql
proxy-address                           = :3306
proxy-pool-no-change-user               = true
log-file                                = /var/log/mysql-proxy.log
log-level                               = message  

2) start the proxy with:
mysql-proxy --defaults-file=/etc/mysql-proxy.cnf --daemon

3) try to connect to the proxy

4) check the log file:
2010-02-23 22:46:18: (message) mysql-proxy 0.8.0 started
2010-02-23 22:46:18: (message) proxy listening on port :3306
2010-02-23 22:46:18: (message) added read/write backend: 127.0.0.1:3306
2010-02-23 22:46:18: (message) added read-only backend: db-slave-3:3306

Note that it inserted the loopback address, creating another serious condition. The proxy loops itself when trying to connect to itself

Suggested fix:
allow configuration file to set multiple backend addresses
do not set loopback address (it was not specified in any way)
do not allow the listening interface:port to be set as a backend address

Thank you for your report.

The documentation does not mention how the ini file configuration works, which is slightly different to the command line options:
On the command line multiple proxy-backend-addresses can be set by repeating the option.
In the ini file, list the multiple addresses in one proxy(-read-only)-backend-addresses= separated by commas, like:

proxy-read-only-backend-addresses       = db-slave-1:3306, db-slave-2:3306, db-slave-3:3306, db-slave-4:3306

In general, if the option name is the plural, the above applies to it. If not, then that option is misnamed.
Should you find a case like that, we greatly appreciate a bug report.

I'm setting this to documenting because it is just an omission in the documentation.

I've added notes to the documentation on the format differences on the command line and config file, including explicit examples for this and read-only-backend-addresses.