Delayed connection creation

Original description

The readwritesprit router have specification called "Routing to every session backend" in this page.

https://mariadb.com/kb/en/mariadb-enterprise/mariadb-maxscale-22-readwritesplit/

For example, SET NAMES 'utf8' is always executed on the master server even if there is no write in the following statements.

So, a slave server with a high load could make the master server in the error state of "Too many connections".

I want a function that does not execute the session commands until it needs it.

Implementation Notes

This ties in with the improved storage of session commands so that the execution of session commands on the master can be postponed until a master connection is needed.