Senlin

Senlin is an OpenStack service for clustering and managing homogeneous compute, storage, or network resources through a unified, policy-driven abstraction layer (infrastructure orchestration).

• Cluster management of homogeneous resources with lifecycle operations such as create, update, scale, and delete (infrastructure orchestration).
• Policy-based control for placement, load balancing, health management, and scaling behaviors (policy and governance).
• Profile-based abstraction of underlying resources, mapping cluster nodes to Nova servers, Heat stacks, or other resource types (resource modeling).
• Integration with OpenStack authentication, networking, and compute services through standard APIs (cloud platform integration).
• RESTful Application Programming Interface (API) and driver-based architecture for extensible back ends and custom policy or profile plugins (extensibility framework).

More About Senlin

Senlin is an OpenStack clustering service (infrastructure orchestration) that focuses on managing groups of homogeneous resources such as Virtual Machine (VM) instances, load balancer members, or other cloud objects as logical clusters. It provides a common abstraction to define clusters, their desired state, and the rules that govern their lifecycle, rather than treating each resource as an isolated entity. The service exposes this functionality through a RESTful API that other OpenStack services or external systems can call.

At the core of Senlin is the concept of a profile (resource modeling), which defines how an individual node in a cluster is created, updated, and deleted. Profiles can represent different underlying technologies, for example mapping a node to a Nova server or to a Heat stack when such drivers are enabled. By attaching a profile to a cluster, operators standardize the configuration of all nodes in that cluster and simplify lifecycle management operations.

Senlin implements cluster-level operations (infrastructure orchestration) such as create, delete, resize, and update, and it coordinates the corresponding actions on each node according to the selected profile and configured policies. Policies (policy and governance) are separate objects that can be attached to clusters to control behaviors such as placement, scaling rules, health checking, and load distribution, depending on which policy types are enabled in a deployment. The policy engine evaluates these rules and translates them into actions on the underlying OpenStack services.

In enterprise environments, Senlin is used to manage groups of OpenStack resources that must behave as a unit, for example application server pools or worker node groups. Operators can define desired capacities for clusters and apply scale-out or scale-in policies that adjust the number of nodes. Health management policies can monitor nodes and trigger recovery actions such as recreating failed instances, helping maintain service continuity at the cluster level instead of handling failures per node.

Senlin integrates with core OpenStack components (cloud platform integration), including Keystone for authentication and authorization, and other services such as Nova or Heat through their APIs when corresponding drivers are configured. The service uses an engine, API, and conductor architecture, relying on the common OpenStack messaging and persistence patterns. Its plugin-based design (extensibility framework) allows operators and vendors to implement custom profile types, policy types, and drivers for additional resource back ends.

From a directory and taxonomy perspective, Senlin fits into cloud infrastructure automation and orchestration, specifically as a clustering and policy engine for OpenStack-managed resources. It is relevant where administrators want to enforce uniform configuration, centralized policies, and automated lifecycle management for groups of cloud resources inside OpenStack deployments.