The demote action is optional. It must only be supported by stateful resource agents, which means agents that discern between two distict roles: Master and Slave. Slave is functionally identical to the Started state in a stateless resource agent. Thus, while a regular (stateless) resource agent only needs to implement start and stop, a stateful resource agent must also support the demote action to be able to make a transition between the Master and Started (Slave) roles.

foobar_demote() {
    local rc

    # exit immediately if configuration is not valid
    foobar_validate_all || exit $?

    # test the resource's current state
    foobar_monitor
    rc=$?
    case "$rc" in
        "$OCF_RUNNING_MASTER")
            # Running as master. Normal, expected behavior.
            ocf_log debug "Resource is currently running as Master"
            ;;
        "$OCF_SUCCESS")
            # Alread running as slave. Nothing to do.
            ocf_log debug "Resource is currently running as Slave"
            return $OCF_SUCCESS
            ;;
        "$OCF_NOT_RUNNING")
            # Currently not running. Getting a demote action
            # in this state is unexpected. Exit with an error
            # and let the cluster manager recover.
            ocf_log err "Resource is currently not running"
            exit $OCF_ERR_GENERIC
            ;;
        *)
            # Failed resource. Let the cluster manager recover.
            ocf_log err "Unexpected error, cannot demote"
            exit $rc
            ;;
    esac

    # actually demote the resource here (make sure to immediately
    # exit with an $OCF_ERR_ error code if anything goes seriously
    # wrong)
    ocf_run frobnicate --unset-master-mode || exit $OCF_ERR_GENERIC

    # After the resource has been demoted, check whether the
    # demotion worked. If the resource demotion is asynchronous, the
    # agent may spin on the monitor function here -- if the resource
    # does not assume the Slave role within the defined timeout, the
    # cluster manager will consider the demote action failed.
    while true; do
        foobar_monitor
        if [ $? -eq $OCF_RUNNING_MASTER ]; then
            ocf_log debug "Resource still awaiting promotion"
            sleep 1
        else
            ocf_log debug "Resource demoted"
            break
        fi
    done

    # only return $OCF_SUCCESS if _everything_ succeeded as expected
    return $OCF_SUCCESS
}