OpenStack Compute Service
OpenStack Compute Service, also known as Nova, is a cloud computing service that provides virtual machines (VMs) and other resources to users. It is one of the core components of the OpenStack platform and is responsible for managing and orchestrating the lifecycle of VMs.
Introduction to OpenStack Compute Service
OpenStack Compute Service allows users to create and manage VM instances, which are virtualized computing resources that behave like physical servers. Users can launch instances with predefined or custom configurations, such as the number of CPUs, amount of memory, and storage capacity.
The Compute Service provides an API that allows users to interact with it programmatically. This API is based on the OpenStack Compute API, which is a RESTful web service. Users can use various programming languages like Python, Java, and Ruby to interact with the Compute Service API.
Getting Started with the Compute Service API
To get started with the Compute Service API, you need to have access to an OpenStack deployment that includes the Compute Service. You also need to have the necessary credentials, including an authentication token and the URL of the API endpoint.
Authentication and Authorization
Before making API requests, you need to authenticate with the Compute Service. This is done by sending a POST request to the /v3/auth/tokens endpoint with the necessary credentials. The response will include an authentication token that needs to be included in subsequent API requests.
Creating an Instance
To create an instance, you need to send a POST request to the /v2.1/servers endpoint with the required parameters, such as the name, flavor, and image of the instance. The flavor defines the compute resources that will be allocated to the instance, such as the number of CPUs, amount of memory, and storage capacity. The image specifies the operating system and software that will be installed on the instance.
import requests
auth_url = 'http://auth_url'
username = 'your_username'
password = 'your_password'
project_id = 'your_project_id'
# Authenticate with the Compute Service
auth_response = requests.post(f'{auth_url}/v3/auth/tokens',
json={
'auth': {
'identity': {
'methods': ['password'],
'password': {
'user': {
'name': username,
'domain': {'name': 'default'},
'password': password
}
}
},
'scope': {
'project': {
'id': project_id
}
}
}
})
auth_token = auth_response.headers['X-Subject-Token']
# Create an instance
instance_name = 'test-instance'
flavor_id = '1'
image_id = '2'
network_id = '3'
keypair_name = 'test-keypair'
create_instance_response = requests.post('http://compute_url/v2.1/servers',
headers={'X-Auth-Token': auth_token},
json={
'server': {
'name': instance_name,
'flavorRef': flavor_id,
'imageRef': image_id,
'networks': [{'uuid': network_id}],
'key_name': keypair_name
}
})
Managing Instances
Once an instance is created, you can perform various operations on it, such as starting, stopping, and deleting it. These operations can be done by sending HTTP requests to the appropriate endpoints of the Compute Service API.
To start an instance, you need to send a POST request to the /v2.1/servers/{server_id}/action endpoint with the os-start action.
# Start an instance
instance_id = '4'
start_instance_response = requests.post(f'http://compute_url/v2.1/servers/{instance_id}/action',
headers={'X-Auth-Token': auth_token},
json={'os-start': {}})
To stop an instance, you need to send a POST request to the /v2.1/servers/{server_id}/action endpoint with the os-stop action.
# Stop an instance
stop_instance_response = requests.post(f'http://compute_url/v2.1/servers/{instance_id}/action',
headers={'X-Auth-Token': auth_token},
json={'os-stop': {}})
To delete an instance, you need to send a DELETE request to the /v2.1/servers/{server_id} endpoint.
# Delete an instance
delete_instance_response = requests.delete(f'http://compute_url/v2.1/servers/{instance_id}',
headers={'X-Auth-Token': auth_token})
State Diagram
The following state diagram illustrates the lifecycle of an instance in the OpenStack Compute Service.
stateDiagram
[*] --> Building
Building --> Active : create instance
Active --> Stopping : stop instance
Stopping --> Active : start instance
Active --> Deleting : delete instance
Deleting --> [*] : instance deleted
Conclusion
In this article, we have explored the OpenStack Compute Service and its API. We have learned how to authenticate with the service, create instances, and manage their lifecycle. The Compute Service provides a powerful and flexible way to provision and manage virtual machines in an OpenStack cloud environment. By using the Compute
