Zaqar

Zaqar is the OpenStack message service that provides multi-tenant, cloud-native messaging APIs for building distributed and loosely coupled applications.

• Multi-tenant, cloud messaging and notification service (messaging middleware)
• Support for both queue-based and topic-based message patterns (asynchronous messaging)
• HTTP- and WebSocket-based APIs for producers and consumers (application integration)
• Message persistence, TTL-based expiration, and claim-based consumption (message queueing)
• Integration with other OpenStack services for event distribution and application decoupling (cloud infrastructure)

More About Zaqar

Zaqar is the messaging service in the OpenStack ecosystem, designed to provide a cloud-based, multi-tenant messaging Application Programming Interface (API) that enables asynchronous communication between distributed components. It targets use cases where applications, microservices, and infrastructure services require decoupled communication channels without sharing implementation details or deployment topology. By exposing a web-friendly API over Hypertext Transfer Protocol (HTTP) and WebSocket (application integration), Zaqar supports messaging for public, private, and hybrid OpenStack deployments.

At its core, Zaqar implements message queueing and publish-subscribe patterns (messaging middleware). Applications interact with logical queues and topics rather than with brokers directly, which allows operators to choose and manage backend storage technologies independently from client applications. The service supports message persistence, time-to-live policies for messages, and claim-based consumption, where consumers claim messages for processing to avoid concurrent handling of the same message. These capabilities help coordinate work distribution, background processing, and event fan-out across services.

Zaqar exposes an HTTP-based Representational State Transfer (REST) API and a WebSocket API (application integration) that are compatible with typical web and service-oriented architectures. The API design allows language-agnostic clients, and multiple SDKs and client libraries exist within the OpenStack ecosystem to access the service. Authentication and authorization are integrated with the broader OpenStack identity model (identity and access), allowing operators to control which projects and users can create queues, post messages, and subscribe to notifications in a multi-tenant environment.

In enterprise and institutional environments, Zaqar is used to decouple application tiers, coordinate workflows, and propagate events between OpenStack services and tenant applications (cloud infrastructure). Workloads running on compute, container, or serverless platforms can use Zaqar queues to communicate status updates, schedule asynchronous tasks, or trigger downstream processing without direct dependencies. The multi-tenant design allows multiple projects to share a single messaging infrastructure while keeping data isolated by project scopes and access policies.

Zaqar’s architecture separates the API layer from the storage backend (service architecture). Deployments can select different storage drivers and scale the service horizontally in line with other OpenStack components. Operators can deploy Zaqar alongside other OpenStack services and manage it using the same deployment and lifecycle tooling. Within a technical directory or taxonomy, Zaqar fits primarily under cloud messaging services, message queueing and publish-subscribe infrastructure, and application integration middleware for OpenStack-based clouds.