tripleo-docs/doc/source/advanced_deployment/role_specific_parameters.rst
Saravanan KR daf1e3b7ad Add documentation for role-specific parameters support
With recent update, parameters can be provided to per role basis, this
patch adds the documentation to explain the usage and limitations.

Change-Id: Idf2642be660880b1fdd9cd962c7f84c69d1cf41a
2017-06-12 17:37:49 +05:30

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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.