TripleO Role-Specific Parameters

OpenStack installer TripleO provides a flexibility to the operators to define their own custom roles. A custom role can be defined by associating a list of predefined (or custom-defined) services. A TripleO service can be associated with multiple roles, which brings in the requirement to keep the parameter to be role-specific. This has been achevied in Pike release by introducing a new parameter RoleParameters to the TripleO service template.

By default, not all parameters are role-specific. Additional implementation has to be provided on a TripleO service template to enable role-specific parameters support. With role-specific parameters supported, a parameter can be provided as role-specific or global (as like existing). The preference is given to the role-specific parameter if provided, else the global parameter values are applied.

All the parameters which should be applied to a particular role should be provided with <RoleName>Parameters as like below example. Here, <RoleName> is the name of the role as defined in the roles_data.yaml.

Lets us consider we have multiple compute roles in a cluster like

• Compute
• ComputeOvsDpdk
• ComputeSriov

Below example demonstrates how to target a parameter specific to a role. Here the parameter NovaReserveHostMemory will have the value as 1024 in Compute and ComputeSriov roles, where as the role ComputeOvsDpdk will have the value as 4096.

parameter_defaults:
  NovaReservedHostMemory: 1024
  ComputeOvsDpdkParameters:
    NovaReservedHostMemory: 4096

Facts about using role-specific:

• It is possible provide only the role-specific parameter without global definition, in which case the default value of the service is applied for the other roles
• It is possible to define a parameter for all the roles as role-specific with/without global definition

Role-specific parameters in Pike (OSP12)

Service: nova_compute

• NovaVcpuPinSet
• NovaReservedHostMemory

Service: neutron_ovs_dpdk_agent

• OvsDpdkCoreList
• OvsDpdkMemoryChannels
• OvsDpdkSocketMemory
• OvsPmdCoreList
• NeutronDatapathType
• NeutronVhostuserSocketDir

Service: neutron_sriov_agent

• NeutronPhysicalDevMappings
• NeutronExcludeDevices
• NeutronSriovNumVFs

Service: opendaylight_ovs

• HostAllowedNetworkTypes
• OvsEnableDpdk
• VhostuserSocketDir
• OvsVhostuserMode
• OpenDaylightProviderMappings

Other Versions

The role-specific feature is available in Pike release (OSP12), where as the custom roles is available from Newton release (OSP10). If it is required to support role-specific parameter prior to Pike releases, it is possible with a workaround for certain template parameters.

Parameters used by Puppet

Instead of using the template parameter, the corresponding parameter’s hiera variable could be overriden for a particular role with <RoleName>ExtraConfig parameter.

For the same example as explained above, it is possible to provide it via hiera value. First we need to find the hiera value of the parameter NovaReservedHostMemory form the tripleo-heat-templates repository, which is nova::compute::reserved_host_memory. Then following sample overrides the hiera value for the ComputeOvsDpdk role:

parameter_defaults:
  NovaReservedHostMemory: 1024
  ComputeOvsDpdkExtraConfig:
    nova::compute::reserved_host_memory: 4096

Note: Overriding via hiera varibles for complex datatypes like map or list should be analyzed well in order to understand how the parameter is accepted in the puppet.

Parameters in first-boot scripts (cloud-init)

In OSP10, there has been few configurations which are done as part of the first-boot scripts, like ComputeKernelArgs, HostIsolatedCoreList. If we need to support role-specific parameters for these parameters, the implementation of the first-boot script has to enhanced to handle multiple parameters. Note that it is entierly in the deployer’s purview to modify the script as per their defined roles. The below sample code provides an overview of how this could be acheived considering the above examples.

heat_template_version: 2014-10-16
parameters:
  ComputeSriovKernelArgs:
    type: string
  ComputeSriovHostnameFormat:
    type: string
    default: computesriov
  ComputeOvsDpdkKernelArgs:
    type: string
  ComputeOvsDpdkHostnameFormat:
    type: string
    default: computeovsdpdk

resources:
  userdata:
    type: OS::Heat::MultipartMime
    properties:
      parts:
      - config: {get_resource: compute_kernel_args}

  compute_kernel_args:
    type: OS::Heat::SoftwareConfig
    properties:
      config:
        str_replace:
          template: |
            #!/bin/bash
            set -x
            SRIOV=$COMPUTE_SRIOV_HOSTNAME_FORMAT
            SRIOV=$(echo $SRIOV | sed  's/\%index\%//g' | sed 's/\%stackname\%//g') ;

            DPDK=$COMPUTE_DPDK_HOSTNAME_FORMAT
            DPDK=$(echo $DPDK | sed  's/\%index\%//g' | sed 's/\%stackname\%//g') ;

            if [[ $(hostname) == *$SRIOV* ]] ; then
              # Scripts for SR-IOV role
            fi

            if [[ $(hostname) == *$DPDK* ]] ; then
              # Scripts for OvS DPDK role
            fi            
          params:
            $KERNEL_ARGS_SRIOV: {get_param: ComputeSriovKernelArgs}
            $COMPUTE_SRIOV_HOSTNAME_FORMAT: {get_param: ComputeSriovHostnameFormat}
            $KERNEL_ARGS_DPDK: {get_param: ComputeOvsDpdkKernelArgs}
            $COMPUTE_DPDK_HOSTNAME_FORMAT: {get_param: ComputeOvsDpdkHostnameFormat}