Service template sections description¶
As mentioned in the previous sections of the developer guide, there are several sections of the template’s output that need to be filled out for creating a service in TripleO.
In this document we will attempt to enumerate all of them and explain the reasoning behind them.
Note that you can also find useful information in the tht deployment readme.
What’s the bare-minimum?¶
Before, digging into details, it’s always good to know what the bare-minimum is. So lets look at a very minimal service template:
heat_template_version: rocky
description: Configure Red Hat Subscription Management.
parameters:
RoleNetIpMap:
default: {}
type: json
ServiceData:
default: {}
description: Dictionary packing service data
type: json
ServiceNetMap:
default: {}
description: Mapping of service_name -> network name. Typically set
via parameter_defaults in the resource registry. This
mapping overrides those in ServiceNetMapDefaults.
type: json
RoleName:
default: ''
description: Role name on which the service is applied
type: string
RoleParameters:
default: {}
description: Parameters specific to the role
type: json
EndpointMap:
default: {}
description: Mapping of service endpoint -> protocol. Typically set
via parameter_defaults in the resource registry.
type: json
RhsmVars:
default: {}
description: Hash of ansible-role-redhat-subscription variables
used to configure RHSM.
# The parameters contains sensible data like activation key or password.
hidden: true
tags:
- role_specific
type: json
resources:
# Merging role-specific parameters (RoleParameters) with the default parameters.
# RoleParameters will have the precedence over the default parameters.
RoleParametersValue:
type: OS::Heat::Value
properties:
type: json
value:
map_replace:
- map_replace:
- vars: RhsmVars
- values: {get_param: [RoleParameters]}
- values:
RhsmVars: {get_param: RhsmVars}
outputs:
role_data:
description: Role data for the RHSM service.
value:
service_name: rhsm
config_settings:
tripleo::rhsm::firewall_rules: {}
upgrade_tasks: []
step_config: ''
host_prep_tasks:
- name: Red Hat Subscription Management configuration
vars: {get_attr: [RoleParametersValue, value, vars]}
block:
- include_role:
name: redhat-subscription
Lets go piece by piece and explain what’s going on.
Version and description¶
As with any other heat template, you do need to specify the
heat_template_version
, and preferably give a description of what the
stack/template does.
Parameters¶
You’ll notice that there are a bunch of heat parameters defined in this template that are not necessarily used. This is because service templates are created in the form of a heat resource chain object. This type of objects can create a “chain” or a set of objects with the same parameters, and gather the outputs of them. So, eventually we pass the same mandatory parameters to the chain. This happens in the common/services.yaml file. Lets take a look and see how this is called:
ServiceChain:
type: OS::Heat::ResourceChain
properties:
resources: {get_param: Services}
concurrent: true
resource_properties:
ServiceData: {get_param: ServiceData}
ServiceNetMap: {get_param: ServiceNetMap}
EndpointMap: {get_param: EndpointMap}
RoleName: {get_param: RoleName}
RoleParameters: {get_param: RoleParameters}
Here we can see that the mandatory parameters for the services are the following:
ServiceData: Contains an entry called
net_cidr_map
, which is a map that has the CIDRs for each network in your deployment.ServiceNetMap: Contains a mapping that tells you what network is each service configured at. Typical entries will look like:
BarbicanApiNetwork: internal_api
.EndpointMap: Contains the keystone endpoints for each service. With this you’ll be able to get what port, what protocol, and even different entries for the public, internal and admin endpoints.
RoleName: This is the name of the role on which the service is applied. It could be one of the default roles (e.g. “Controller” or “Compute”), or a custom role, depending on how you’re deploying.
RoleParameters: A Map containing parameters to be applied to the specific role.
So, if you’re writing a service template yourself, these are the parameters you have to copy into your template.
Aside from these parameters, you can define any other parameter yourself for
the service, and in order for your service to consume the parameter, you need
to pass them via parameter_defaults
.
The role_data
output¶
This is the sole output that will be read and parsed in order to get the relevant information needed from your service. It’s value must be a map, and from the aforementioned example, it minimally contains the following:
service_name
: This is the name of the service you’re configuring. The format is lower case letters and underscores. Setting this is quite important, since this is how TripleO reports what services are enabled, and generates appropriate hieradata, such as a list of all services enabled, and flags that say that your service is enabled on a certain node.config_settings
: This will contain a map of key value pairs; the map will be written to the hosts in the form of hieradata, which puppet can then run and use to configure your service. Note that the hieradata will only be written on hosts that are tagged with a role that enables your service.upgrade_tasks
: These are ansible tasks that run when TripleO is running an upgrade with your service enabled. If you don’t have any upgrade tasks to do, you still have to specify this output, but it’s enough to set it as an empty list.step_config
: This defines what puppet manifest should be run to configure your service. It typically is a string with the specificinclude
statement that puppet will run. If you’re not configuring your service with puppet, then you need to set this value as an empty string. There is an exception, however: When you’re configuring a containerized service. We’ll dig into that later.
These are the bare-minimum sections of role_data
you need to set up.
However, you might have noticed that the example we linked above has another
section called host_prep_data
. This section is not mandatory, but it is one
of the several ways you can execute Ansible tasks on the host in order to
configure your service.