“manila-scheduler” service

The Manila scheduler is a component of OpenStack Manila that handles the task of selecting the best available storage backend to satisfy a user’s request for a file share. The Manila scheduler is responsible for determining the optimal storage backend based on various factors such as capacity, performance, availability, and user-specified requirements. It ensures that the requested file share is provisioned on an appropriate storage backend that meets the user’s needs.

Here’s a detailed explanation of the OpenStack Manila scheduler:

1. Request Processing: When a user submits a request to create or manage a file share, it is received by the Manila API service. The API service validates the request and passes it to the Manila scheduler.
2. Scheduler Filters: The Manila scheduler uses a set of filters to eliminate unsuitable storage backends based on specific criteria. Each filter is responsible for evaluating the available backends against a specific attribute or requirement. For example, there can be filters for capacity, driver capabilities, network connectivity, or availability zones.
3. Weighting and Scoring: Once the filters have narrowed down the list of eligible storage backends, the scheduler applies a weighting and scoring mechanism to rank them. The weights and scores are configured based on priorities and policies defined by the cloud administrator. This helps prioritize certain backends over others according to specific requirements or constraints.
4. Backend Selection: Using the weighted scores, the scheduler selects the best storage backend that satisfies the user’s request. The selection process takes into account factors like performance, capacity, availability, and any other custom requirements defined by the user or the cloud administrator.
5. Backend Affinity: The scheduler can be configured to respect backend affinity, which means it tries to provision file shares on the same backend as previously created shares for the same project or user. This helps maintain consistency or take advantage of specific features provided by the chosen backend.
6. Scheduling Policies: OpenStack Manila provides the flexibility to define custom scheduling policies. These policies can be used to implement complex rules for backend selection based on different attributes or criteria. For example, a policy can ensure that file shares from a specific project are always provisioned on a specific backend.
7. Error Handling: In case a selected storage backend fails or becomes unavailable during the provisioning process, the scheduler retries the selection process with the remaining available backends until a successful allocation is made. If all backends fail, the user receives an appropriate error message indicating the unavailability of suitable resources.

The Manila scheduler plays a crucial role in efficiently allocating file shares to the appropriate storage backends within an OpenStack Manila deployment. It considers various factors, applies policies, and leverages filtering mechanisms to make informed decisions and provide a seamless file sharing experience to cloud users.