This tutorial uses ExampleService to illustrate how to write and on-board a service in CORD. ExampleService is a multi-tenant service that instantiates a VM instance on behalf of each tenant, and runs an Apache web server in that VM. This web server is then configured to serve a tenant-specified message (a string), where the tenant is able to set this message using CORD's control interface. From a service modeling perspective, ExampleService extends the base Service model with two fields:
service_message: A string that contains a message to display for the service as a whole (i.e., to all tenants of the service).tenant_message: A string that is displayed for a specific Tenant.These two fields are a simple illustration of a common pattern. A service model typically includes fields used to configure the service as a whole (service_message in this example) and fields used to control individual instances of the the service (tenant_message in this example). It would be common for the operator to set configuration-related fields when the service first starts up, and then set/adjust control-related fields on behalf of individual tenants as the service runs.
Tenant and ServiceInstance are two closely related terms. "Tenant" refers to the user or the consumer of a service. Often we partition a service into logical partitions, each for use by a tenant, thus making it a multi-tenant service. Each one of these tenant-specific partitions is referred to as a ServiceInstance.
The result of preparing ExampleService for on-boarding is the following set of files, all located in the xos directory of the exampleservice repository. When checked out, these files live in the CORD_ROOT/orchestration/xos_services/exampleservice directory on your local development machine.
| Component | Source Code (https://github.com/opencord/exampleservice/) |
|---|---|
| Data Model | xos/exampleservice.xproto |
| Synchronizer | xos/synchronizer/steps/sync_exampletenant.py xos/synchronizer/steps/exampletenant_playbook.yaml xos/synchronizer/Dockerfile.synchronizer |
| On-Boarding Spec | xos/exampleservice-onboard.yaml |
Earlier releases (3.0 and before) required additional files (mostly Python code) to on-board a service, including a REST API, a TOSCA API, and an Admin GUI. These components are now auto-generated from the models rather than coded by hand, although it is still possible to extend the GUI.
In addition to implementing these service-specific files, the final step to on-boarding a service requires you to modify an existing (or write a new) service profile. This tutorial uses the existing R-CORD profile for illustrative purposes. These profile definitions currently live in the profile_manifest directory of (https://github.com/opencord/platform-install/), which corresponds to the CORD_ROOT/build/platform-install/profile_manifests directory in your downloaded copy of the CORD source tree.
For this tutorial we recommend using a Virtual Pod (CiaB) as your development environment. By default CiaB brings up OpenStack, ONOS, and XOS running the R-CORD collection of services. This tutorial demonstrates how to add a new customer-facing service to R-CORD.
A Virtual Pod includes a build machine, a head node, switches, and a compute node all running as VMs on a single host. Before proceeding you should familiarize yourself with the CiaB environment and the POD Development Loop.
The first step is to create a set of models for the service. Before you do this, make a new root directory for your service, and within that directory, create an xos subdirectory. The xos subdirectory will hold files that XOS needs to on-board your service.
Your models live in a file named exampleservice.xproto in your service's xos directory. This file encodes the models in the service in a format called xproto which is a combination of Google Protocol Buffers and some XOS-specific annotations to facilitate the generation of service components, such as the GRPC and REST APIs, security policies, and database models among other things. It consists of two parts:
The Service model, which manages the service as a whole.
The ServiceInstance model, which manages tenant-specific (per-service-instance) state.
A Service model extends (inherits from) the XOS base Service model. At its head is a set of option declarations: the name of the service as a configuration string, and as a human readable one. Then follows a set of field definitions.
message ExampleService (Service){
option name = "exampleservice";
option verbose_name = "Example Service";
required string service_message = 1 [help_text = "Service Message to Display", max_length = 254, null = False, db_index = False, blank = False];
}
Your ServiceInstance model will extend the core TenantWithContainer class, which is a Tenant that creates a VM instance:
message ExampleServiceInstance (TenantWithContainer){
option name = "exampleserviceinstance";
option verbose_name = "Example Service Instance";
required string tenant_message = 1 [help_text = "Tenant Message to Display", max_length = 254, null = False, db_index = False, blank = False];
}
The following field specifies the message that will be displayed on a per-Tenant basis:
tenant_message = models.CharField(max_length=254, help_text="Tenant Message to Display")
Think of this as a tenant-specific (per service instance) parameter.
The second step is to define a synchronizer for the service. Synchronizers are processes that run continuously, checking for changes to service's model(s). When a synchronizer detects a change, it applies that change to the underlying system. For ExampleService, the ServiceInstance model is the model we will want to synchronize, and the underlying system is a compute instance. In this case, we’re using TenantWithContainer to create this instance for us.
XOS Synchronizers are typically located in the xos/synchronizer directory of your service.
Note: Earlier versions included a tool to track model dependencies, but today it is sufficient to create a file named
model-depswith the contents:{}.
The Synchronizer has two parts: A container that runs the synchronizer process, and a playbook (typically Ansible) that configures the underlying system. The following describes how to construct both.
First, create a file named exampleservice-synchronizer.py:
#!/usr/bin/env python
# Runs the standard XOS synchronizer
import importlib
import os
import sys
from xosconfig import Config
config_file = os.path.abspath(os.path.dirname(os.path.realpath(__file__)) + '/exampleservice_config.yaml')
Config.init(config_file, 'synchronizer-config-schema.yaml')
synchronizer_path = os.path.join(os.path.dirname(
os.path.realpath(__file__)), "../../synchronizers/new_base")
sys.path.append(synchronizer_path)
mod = importlib.import_module("xos-synchronizer")
mod.main()
The above is boilerplate. It loads and runs the default xos-synchronizer module in it’s own Docker container. To configure this module, create a file named exampleservice_config.yaml, which specifies various configuration and logging options:
name: exampleservice-synchronizer accessor: username: xosadmin@opencord.org password: "@/opt/xos/services/exampleservice/credentials/xosadmin@opencord.org" required_models: - ExampleService - ExampleServiceInstance - ServiceDependency - ServiceMonitoringAgentInfo dependency_graph: "/opt/xos/synchronizers/exampleservice/model-deps" steps_dir: "/opt/xos/synchronizers/exampleservice/steps" sys_dir: "/opt/xos/synchronizers/exampleservice/sys" model_policies_dir: "/opt/xos/synchronizers/exampleservice/model_policies"
NOTE: Historically, synchronizers were named “observers”, so
s/observer/synchronizer/when you come upon this term in the XOS code and documentation.
Second, create a directory within your synchronizer directory named steps. In steps, create a file named sync_exampleserviceinstance.py:
import os import sys from synchronizers.new_base.SyncInstanceUsingAnsible import SyncInstanceUsingAnsible from synchronizers.new_base.modelaccessor import * from xos.logger import Logger, logging parentdir = os.path.join(os.path.dirname(__file__), "..") sys.path.insert(0, parentdir) logger = Logger(level=logging.INFO)
Bring in some basic prerequities. Also include the models created earlier, and SyncInstanceUsingAnsible which will run the Ansible playbook in the Instance VM.
class SyncExampleServiceInstance(SyncInstanceUsingAnsible):
provides = [ExampleServiceInstance]
observes = ExampleServiceInstance
requested_interval = 0
template_name = "exampleserviceinstance_playbook.yaml"
service_key_name = "/opt/xos/synchronizers/exampleservice/exampleservice_private_key"
def __init__(self, *args, **kwargs):
super(SyncExampleServiceInstance, self).__init__(*args, **kwargs)
def get_exampleservice(self, o):
if not o.owner:
return None
exampleservice = ExampleService.objects.filter(id=o.owner.id)
if not exampleservice:
return None
return exampleservice[0]
# Gets the attributes that are used by the Ansible template but are not
# part of the set of default attributes.
def get_extra_attributes(self, o):
fields = {}
fields['tenant_message'] = o.tenant_message
exampleservice = self.get_exampleservice(o)
fields['service_message'] = exampleservice.service_message
return fields
def delete_record(self, port):
# Nothing needs to be done to delete an exampleservice; it goes away
# when the instance holding the exampleservice is deleted.
pass
Third, create a run-from-api.sh file for your synchronizer.
python exampleservice-synchronizer.py
Finally, create a Dockerfile for your synchronizer, name it Dockerfile.synchronizer and place it in the synchronizer directory with the other synchronizer files:
FROM xosproject/xos-synchronizer-base:candidate
COPY . /opt/xos/synchronizers/exampleservice
ENTRYPOINT []
WORKDIR "/opt/xos/synchronizers/exampleservice"
# Label image
ARG org_label_schema_schema_version=1.0
ARG org_label_schema_name=exampleservice-synchronizer
ARG org_label_schema_version=unknown
ARG org_label_schema_vcs_url=unknown
ARG org_label_schema_vcs_ref=unknown
ARG org_label_schema_build_date=unknown
ARG org_opencord_vcs_commit_date=unknown
ARG org_opencord_component_chameleon_version=unknown
ARG org_opencord_component_chameleon_vcs_url=unknown
ARG org_opencord_component_chameleon_vcs_ref=unknown
ARG org_opencord_component_xos_version=unknown
ARG org_opencord_component_xos_vcs_url=unknown
ARG org_opencord_component_xos_vcs_ref=unknown
LABEL org.label-schema.schema-version=$org_label_schema_schema_version \
org.label-schema.name=$org_label_schema_name \
org.label-schema.version=$org_label_schema_version \
org.label-schema.vcs-url=$org_label_schema_vcs_url \
org.label-schema.vcs-ref=$org_label_schema_vcs_ref \
org.label-schema.build-date=$org_label_schema_build_date \
org.opencord.vcs-commit-date=$org_opencord_vcs_commit_date \
org.opencord.component.chameleon.version=$org_opencord_component_chameleon_version \
org.opencord.component.chameleon.vcs-url=$org_opencord_component_chameleon_vcs_url \
org.opencord.component.chameleon.vcs-ref=$org_opencord_component_chameleon_vcs_ref \
org.opencord.component.xos.version=$org_opencord_component_xos_version \
org.opencord.component.xos.vcs-url=$org_opencord_component_xos_vcs_url \
org.opencord.component.xos.vcs-ref=$org_opencord_component_xos_vcs_ref
CMD bash -c "cd /opt/xos/synchronizers/exampleservice; ./run-from-api.sh"
In the same steps directory, create an Ansible playbook named exampleserviceinstance_playbook.yml which is the “master playbook” for this set of plays:
# exampletenant_playbook
- hosts: "{{ instance_name }}"
connection: ssh
user: ubuntu
sudo: yes
gather_facts: no
vars:
- tenant_message: "{{ tenant_message }}"
- service_message: "{{ service_message }}"
This sets some basic configuration, specifies the host this Instance will run on, and the two variables that we’re passing to the playbook.
roles: - install_apache - create_index
This example uses Ansible’s Playbook Roles to organize steps, provide default variables, organize files and templates, and allow for code reuse. Roles are created by using a set directory structure.
In this case, there are two roles, one that installs Apache, and one that creates the index.html file from a Jinja2 template.
Create a directory named roles inside steps, then create two directories named for your roles: install_apache and create_index.
Within install_apache, create a directory named tasks, then within that directory, a file named main.yml. This will contain the set of plays for the install_apache role. To that file add the following:
- name: Install apache using apt
apt:
name=apache2
update_cache=yes
This will use the Ansible apt module to install Apache.
Next, within create_index, create two directories, tasks and templates. In templates, create a file named index.html.j2, with the contents:
ExampleService
Service Message: "{{ service_message }}"
Tenant Message: "{{ tenant_message }}"
These Jinja2 Expressions will be replaced with the values of the variables set in the master playbook.
In the tasks directory, create a file named main.yml, with the contents:
- name: Write index.html file to apache document root
template:
src=index.html.j2
dest=/var/www/html/index.html
This uses the Ansible template module to load and process the Jinja2 template then put it in the dest location. Note that there is no path given for the src parameter: Ansible knows to look in the templates directory for templates used within a role.
As a final step, you can check your playbooks for best practices with ansible-lint if you have it available.
The next step is to define an on-boarding recipe for the service. By convention, we use <servicename>-onboard.yaml, and place it in the xos directory of the service.
The on-boarding recipe is a TOSCA specification that lists all of the resources for your synchronizer. It's basically a collection of everything that has been created above. For example, here is the on-boarding recipe for ExampleService:
tosca_definitions_version: tosca_simple_yaml_1_0
description: Onboard the exampleservice
imports:
- custom_types/xos.yaml
topology_template:
node_templates:
exampleservice:
type: tosca.nodes.ServiceController
properties:
base_url: file:///opt/xos_services/exampleservice/xos/
# The following will concatenate with base_url automatically, if
# base_url is non-null.
xproto: ./
private_key: file:///opt/xos/key_import/exampleservice_rsa
public_key: file:///opt/xos/key_import/exampleservice_rsa.pub
Note that this recipe (when executed) on-boards ExampleService in the sense that it registers the service with the system (i.e., loads its model into XOS), but it does not provision the service or create instances of the service. These latter steps can be done through CORD's GUI or REST API, or by submitting yet other TOSCA workflows to a running CORD POD (all based on end-points that are auto-generated from these on-boarded models). Additional information on how to provision and use the service is given in the last section of this tutorial.
The final step to on-boarding a service is to include it in one or more service profiles that are to be built and installed. Service profiles are currently defined as part of the CORD build system, so this involves editing some build-related configuration files. These files can be found in the CORD_ROOT/build/platform-install directory of the checkout out source code.
Inserting ExampleService in a service profile requires creating or modifying one of the .yml files in build/platform-install/profile_manifests of your local repo. In the following, we use rcord.yml as an illustrative example. There are potentially three sections of this file that need attention.
First, modify the xos_services section to identify exampleservice as a service to include in the profile. Doing this effectively points the build system at the model and synchronizer specifications you've just defined.
xos_services:
... (lines omitted)...
- name: exampleservice
path: orchestration/xos_services/exampleservice
keypair: exampleservice_rsa
synchronizer: true
Second, optionally tell the build system to download and install an image into CORD. In our particular case, ExampleService uses the trusty-server-multi-nic that is included in R-CORD for other purposes.
xos_images:
- name: "trusty-server-multi-nic".
url: "http://www.vicci.org/opencloud/trusty-server-cloudimg-amd64-disk1.img.20170201"
checksum:
"sha256:ebf007ba3ec1043b7cd011fc6668e2a1d1d4c69c41071e8513ab355df7a057cb"
... (lines omitted)...
Third, optionally specify any GUI extensions associated with the service. This is done in the enabled_gui_extensions section of the profile manifest. ExampleService does not include a GUI extension.
Today, a few other build-related configuration files require editing to produce a deployment that includes ExampleService. (These details will be hidden in future releases.)
Add the service's synchronizer image to build/docker_images.yml
Add the service's synchronizer image to docker_image_whitelist for the scenarios you want your service to run in. For example, ExampleService is included in these two files:
build/scenarios/cord/config.ymlbuild/scenarios/single/config.ymlBecause the build system is integrated with the git and repo tools, if your service is not already checked into gerrit.opencord.org, you will also need to add the service to the manifest file CORD_ROOT/.repo/manifest.xml. Then run git init in the service’s source tree.
Once ExampleService is on-boarded into a running POD, it is available to be provisioned, controlled and used. This can be done via the CORD GUI or REST API, but the most common way is to input a TOSCA workflow into the running POD. Typically, each service contributes a TOSCA recipe to run as soon as the POD comes up (i.e., as the last stage of the build system), so as to verify that the installation was successful.
This recipe is generated from a Jinja2 template, which is customized at build-time with specific details for the target POD (e.g., the site that hosts the POD). This results in a .yaml TOSCA file that is passed to the deployed POD and executed.
The ExampleService template is defined by the following file:
build/platform-install/roles/exampleservice-config/templates/test-exampleservice.yaml.j2
It is an historical artifact that this template is in the build/platform-install/roles/exampleservice-config/templates directory. Templates for new services are instead located in build/platform-install/roles/cord-profile/templates. For example, see template-service.yaml.j2 in that directory for a template similar to the one used for ExampleService.
The first part of test-exampleservice.yaml.j2 includes some core object reference that ExampleService uses, for example, the trusty-server-multic-nic image, the small flavor, and both the management_network and the public_network.
topology_template:
node_templates:
# site, image, fully created in deployment.yaml
{{ site_name }}:
type: tosca.nodes.Site
properties:
must-exist: true
name: {{ site_humanname }}
m1.small:
type: tosca.nodes.Flavor
properties:
name: m1.small
must-exist: true
trusty-server-multi-nic:
type: tosca.nodes.Image
properties:
name: trusty-server-multi-nic
must-exist: true
# private network template, fully created somewhere else
private:
type: tosca.nodes.NetworkTemplate
properties:
must-exist: true
name: Private
# management networks, fully created in management-net.yaml
management_network:
type: tosca.nodes.Network
properties:
must-exist: true
name: management
# public network, fully created somewhere else
public_network:
type: tosca.nodes.Network
properties:
must-exist: true
name: public
This is followed by the specification of a private network used by ExampleService :
exampleservice_network:
type: tosca.nodes.Network
properties:
name: exampleservice_network
labels: exampleservice_private_network
requirements:
- template:
node: private
relationship: tosca.relationships.BelongsToOne
- owner:
node: {{ site_name }}_exampleservice
relationship: tosca.relationships.BelongsToOne
The next part of the workflow provisions the Slice (and related instances and networks) in which ExampleService runs. These definitions reference the dependencies established above.
# CORD Slices
{{ site_name }}_exampleservice:
description: Example Service Slice
type: tosca.nodes.Slice
properties:
name: {{ site_name }}_exampleservice
default_isolation: vm
network: noauto
requirements:
- site:
node: mysite
relationship: tosca.relationships.BelongsToOne
- service:
node: exampleservice
relationship: tosca.relationships.BelongsToOne
- default_image:
node: trusty-server-multi-nic
relationship: tosca.relationships.BelongsToOne
- default_flavor:
node: m1.small
relationship: tosca.relationships.BelongsToOne
# CORD NetworkSlices
exampleservice_slice_management_network:
type: tosca.nodes.NetworkSlice
requirements:
- network:
node: management_network
relationship: tosca.relationships.BelongsToOne
- slice:
node: {{ site_name }}_exampleservice
relationship: tosca.relationships.BelongsToOne
exampleservice_slice_public_network:
type: tosca.nodes.NetworkSlice
requirements:
- network:
node: public_network
relationship: tosca.relationships.BelongsToOne
- slice:
node: {{ site_name }}_exampleservice
relationship: tosca.relationships.BelongsToOne
exampleservice_slice_exampleservice_network:
type: tosca.nodes.NetworkSlice
requirements:
- network:
node: exampleservice_network
relationship: tosca.relationships.BelongsToOne
- slice:
node: {{ site_name }}_exampleservice
relationship: tosca.relationships.BelongsToOne
Finally, the recipe instantiates the service object that represents ExampleService (exampleservice) and spins up a Service Instance on behalf of the first tenant (exampletenant1).
exampleservice:
type: tosca.nodes.ExampleService
properties:
name: exampleservice
public_key: {{ lookup('file', config_cord_profile_dir + '/key_import/exampleservice_rsa.pub') }}
private_key_fn: /opt/xos/services/exampleservice/keys/exampleservice_rsa
service_message: hello
artifacts:
pubkey: /opt/cord_profile/key_import/exampleservice_rsa.pub
exampletenant1:
type: tosca.nodes.ExampleServiceInstance
properties:
name: exampletenant1
tenant_message: world
requirements:
- owner:
node: exampleservice
relationship: tosca.relationships.BelongsToOne
Note that these definitions initialize the service_message and tenant_message, respectively. As a consequence, sending an HTTP GET request to ExampleService will result in the response: hello world. Subsequently, the user can interact with ExampleService via CORD's GUI or REST API to change those values.