It appears that the Mysql wait_timeout value under Windows is different to that of Linux. Currently using Sequel 3.16.0 and ruby 1.8.7 under Windows to connect to a local Mysql using the mysql or mysql2 adapter always fails and yields:

Mysql2::Error: Variable 'wait_timeout' can't be set to the value of '2592000'

Setting it to 10 times less than this (259200 or 3 days) instead of the current 30 days works OK.

Looking at the Mysql docs tells me that under Windows this value is limited to: 1-2147483 :(

This is definitely a bug. I'm not sure I understand the issue completely, but at present I don't think we can just check on the client OS, since the valid range depends on the database server OS. Because of this, I think that setting the value used to 2147483 seems the most reasonable course of action.

Fixed: https://github.com/jeremyevans/sequel/commit/1b07852beca048ac1ed144b09b4703bc115a6456

If you needed to you can:

select @@version_compile_os;

after connecting and then set the wait_timeout variable accordingly, but that's probably too messy and I don't know how far back in mysql versions that variable is valid. Maybe best stick to setting it to lowest common denominator.