Scheduler Hint Extension#
A Scheduler Hint allows a cloud server to be built near to, or far from, an
existing server within a specific zone. If a build request with a hint can not
be satisfied then the build will not succeed, and the server, which will have a
ERROR and a task state of
scheduling, must be manually
A zone is a logical container for servers. The Public IP Zone is the zone in which a Public IP can be shared between two or more servers.
Why use scheduler hints?#
The following use cases identify some reasons you might use scheduler hints:
- Reduce server density - You may have two or more VM's on the same
physical host. By specifying the
farparameter, you may mitigate risk.
- Mitigate impact of maintenances - If Rackspace needs to reboot all
servers for maintenance, specifying the
farparameter, helps to ensure that all servers aren't affected at once.
- Build servers in the same 'Public IP zone' (cell) - In order to share an
IP between two servers they need to be in the same Cell, by specifying the
- Build servers to achieve lowest latency: If you have certain applications
that are sensitive to latency and want to build components of those as close
to one another as possible, specify the
nearparameter. This might lower availability.
- Build servers to achieve higher availability: If you need to ensure parts
of your application are as far away from each other as possible, specify the
farparameter. This might increase latency.