https://github.com/openark/orchestrator/blob/master/docs/deployment.md#adding-promotion-rules

Adding promotion rules
Some servers are better candidate for promotion in the event of failovers. Some servers aren't good picks. Examples:

A server has weaker hardware configuration. You prefer to not promote it.
A server is in a remote data center and you don't want to promote it.
A server is used as your backup source and has LVM snapshots open at all times. You don't want to promote it.
A server has a good setup and is ideal as candidate. You prefer to promote it.
A server is OK, and you don't have any particular opinion.
You will announce your preference for a given server to orchestrator in the following way:

orchestrator -c register-candidate -i ${::fqdn} --promotion-rule ${promotion_rule}
Supported promotion rules are:

• prefer
• neutral
• prefer_not
• must_not

Promotion rules expire after an hour. That's the dynamic nature of orchestrator. You will want to setup a cron job that will announce the promotion rule for a server:

*/2 * * * * root "/usr/bin/perl -le 'sleep rand 10' && /usr/bin/orchestrator-client -c register-candidate -i this.hostname.com --promotion-rule prefer"
This setup comes from production environments. The cron entries get updated by puppet to reflect the appropriate promotion_rule. A server may have prefer at this time, and prefer_not in 5 minutes from now. Integrate your own service discovery method, your own scripting, to provide with your up-to-date promotion-rule.