Changing config at runtime

OpenStack Newton introduces the ability to reload (or ‘mutate’) certain configuration options at runtime without a service restart. The following projects support this:

  • Compute (nova)

Check individual options to discover if they are mutable.

In practice

A common use case is to enable debug logging after a failure. Use the mutable config option called ‘debug’ to do this (providing log_config_append has not been set). An admin user may perform the following steps:

  1. Log onto the compute node.

  2. Edit the config file (EG nova.conf) and change ‘debug’ to True.

  3. Send a SIGHUP signal to the nova process (For example, pkill -HUP nova).

A log message will be written out confirming that the option has been changed. If you use a CMS like Ansible, Chef, or Puppet, we recommend scripting these steps through your CMS.