Role-Specific Parameters¶
A service can be associated with multiple roles, like nova-compute
service can be associated with ComputeRole1 and ComputeRole2. The
nova-compute service takes multiple parameters like NovaVcpuPinSet,
NovaReservedHostMemory, etc. It is possible to provide separate values
specific to a role with the following changes in the user environment file:
parameter_defaults:
NovaReservedHostMemory: 512
ComputeRole1Parameters:
NovaReservedHostMemory: 2048
ComputeRole2Parameter:
NovaReservedHostMemory: 1024
The format to provide role-specific parameters is <RoleName>Parameters,
where the RoleName is the name of the role as defined in the
roles_data.yaml template.
In the above specified example, the value “512” will be applied all the roles
which has the nova-compute service, where as the value “2048” will be
applied only on the ComputeRole1 role and the value “1024” will be applied
only on the ComputeRole2 role.
With this approach, the service implementation has to merge the role-specific parameters with the global parameters in their definition template. The role- specific parameter takes higher precedence than the global parameters.
For any custom service which need to use role-specific parameter, the parameter merging should be done. Here is a sample parameter merging example which will be done by the service implementation:
RoleParametersValue:
type: OS::Heat::Value
properties:
type: json
value:
map_replace:
- map_replace:
- neutron::agents::ml2::ovs::datapath_type: NeutronDatapathType
neutron::agents::ml2::ovs::vhostuser_socket_dir: NeutronVhostuserSocketDir
vswitch::dpdk::driver_type: NeutronDpdkDriverType
vswitch::dpdk::host_core_list: HostCpusList
vswitch::dpdk::pmd_core_list: NeutronDpdkCoreList
vswitch::dpdk::memory_channels: NeutronDpdkMemoryChannels
vswitch::dpdk::socket_mem: NeutronDpdkSocketMemory
- values: {get_param: [RoleParameters]}
- values:
NeutronDatapathType: {get_param: NeutronDatapathType}
NeutronVhostuserSocketDir: {get_param: NeutronVhostuserSocketDir}
NeutronDpdkDriverType: {get_param: NeutronDpdkDriverType}
HostCpusList: {get_param: HostCpusList}
NeutronDpdkCoreList: {get_param: NeutronDpdkCoreList}
NeutronDpdkMemoryChannels: {get_param: NeutronDpdkMemoryChannels}
NeutronDpdkSocketMemory: {get_param: NeutronDpdkSocketMemory}
Note
As of now, not all parameters can be set per role, it is based on the service or template implementation. Each service should have the implementation to merge the global parameters and role-specific parameters, as explained in the above example. And today, not all services have this merging logic, check the parameter usage before using it as role-specific.
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