OpenStack Ceilometer is a telemetry and metering service that is part of the OpenStack ecosystem. It provides a framework for collecting, processing, and querying various metrics and measurements from different OpenStack services and resources. Ceilometer helps operators and administrators to gain insights into the usage and performance of their OpenStack cloud infrastructure.
The Ceilometer service is composed of several components, including the Ceilometer API, which serves as the primary interface for interacting with the service. Here are the key details about the Ceilometer API:
- Purpose: The Ceilometer API provides a RESTful interface that allows users to retrieve and manage metering data and statistics collected by Ceilometer. It serves as a central point for accessing and querying metric data across different OpenStack services.
- Data Collection: Ceilometer collects various types of data from OpenStack resources, such as virtual machines, storage volumes, networks, and more. It gathers metrics related to resource utilization, performance, and behavior. The API is responsible for receiving and processing these metrics.
- Authentication and Authorization: The Ceilometer API supports OpenStack’s identity service (Keystone) for authentication and authorization. Users must provide valid credentials to access the API endpoints. The API verifies the credentials against Keystone to ensure that the requester has the necessary permissions to perform the requested operations.
- API Endpoints: The Ceilometer API exposes a set of endpoints that allow users to interact with the service. These endpoints provide operations for retrieving metering data, querying metrics, managing alarms, and configuring Ceilometer settings.
- Data Queries: The API offers various query capabilities to retrieve specific metering data based on filters and parameters. Users can query metrics for a particular resource, time range, or other criteria. The API supports different query formats, including simple queries, complex queries using the Query Language (Ceilometer Query Language or CQL), and aggregate queries.
- Notifications: Ceilometer can also send event notifications to inform users about specific metric thresholds or changes. The API provides mechanisms for subscribing to these notifications and receiving them through message queues or webhooks.
- Integration with Other OpenStack Services: The Ceilometer API integrates with other OpenStack services, such as Nova (Compute), Cinder (Block Storage), Neutron (Networking), and more, to collect metrics from these services. It leverages the capabilities of these services to obtain information about resource usage and performance.
- Extension and Plugin System: Ceilometer supports an extension and plugin system that allows additional functionality and data collection. Users can develop and deploy their own plugins to extend the capabilities of Ceilometer and collect custom metrics.
Overall, the Ceilometer API acts as the main entry point for interacting with the Ceilometer service. It enables users to retrieve, query, and manage metering data and provides a flexible and scalable solution for monitoring and measuring OpenStack resources.