forked from TrueCloudLab/distribution
69 lines
3.7 KiB
Markdown
69 lines
3.7 KiB
Markdown
---
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description: Explains how to use storage drivers
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keywords: registry, on-prem, images, tags, repository, distribution, storage drivers, advanced
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title: Registry storage driver
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---
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This document describes the registry storage driver model, implementation, and explains how to contribute new storage drivers.
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## Provided drivers
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This storage driver package comes bundled with several drivers:
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- [inmemory](inmemory): A temporary storage driver using a local inmemory map. This exists solely for reference and testing.
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- [filesystem](filesystem): A local storage driver configured to use a directory tree in the local filesystem.
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- [s3](s3): A driver storing objects in an Amazon Simple Storage Service (S3) bucket.
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- [azure](azure): A driver storing objects in [Microsoft Azure Blob Storage](https://azure.microsoft.com/en-us/services/storage/).
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- [gcs](gcs): A driver storing objects in a [Google Cloud Storage](https://cloud.google.com/storage/) bucket.
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- oss: *NO LONGER SUPPORTED*
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- swift: *NO LONGER SUPPORTED*
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## Storage driver API
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The storage driver API is designed to model a filesystem-like key/value storage in a manner abstract enough to support a range of drivers from the local filesystem to Amazon S3 or other distributed object storage systems.
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Storage drivers are required to implement the `storagedriver.StorageDriver` interface provided in `storagedriver.go`, which includes methods for reading, writing, and deleting content, as well as listing child objects of a specified prefix key.
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Storage drivers are intended to be written in Go, providing compile-time
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validation of the `storagedriver.StorageDriver` interface.
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## Driver selection and configuration
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The preferred method of selecting a storage driver is using the `StorageDriverFactory` interface in the `storagedriver/factory` package. These factories provide a common interface for constructing storage drivers with a parameters map. The factory model is based on the [Register](https://golang.org/pkg/database/sql/#Register) and [Open](https://golang.org/pkg/database/sql/#Open) methods in the builtin [database/sql](https://golang.org/pkg/database/sql) package.
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Storage driver factories may be registered by name using the
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`factory.Register` method, and then later invoked by calling `factory.Create`
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with a driver name and parameters map. If no such storage driver can be found,
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`factory.Create` returns an `InvalidStorageDriverError`.
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## Driver contribution
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New storage drivers are not currently being accepted.
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See <https://github.com/distribution/distribution/issues/3988> for discussion.
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There are forks of this repo that implement custom storage drivers.
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These are not supported by the OCI distribution project.
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The known forks are:
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- Storj DCS: <https://github.com/storj/docker-registry>
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- HuaweiCloud OBS: <https://github.com/setoru/distribution/tree/obs>
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- us3: <https://github.com/lambertxiao/distribution/tree/main>
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- Baidu BOS: <https://github.com/dolfly/distribution/tree/bos>
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- HDFS: <https://github.com/haosdent/distribution/tree/master>
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### Writing new storage drivers
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To create a valid storage driver, one must implement the
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`storagedriver.StorageDriver` interface and make sure to expose this driver
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via the factory system.
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#### Registering
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Storage drivers should call `factory.Register` with their driver name in an `init` method, allowing callers of `factory.New` to construct instances of this driver without requiring modification of imports throughout the codebase.
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## Testing
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Storage driver test suites are provided in
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`storagedriver/testsuites/testsuites.go` and may be used for any storage
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driver written in Go. Tests can be registered using the `RegisterSuite`
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function, which run the same set of tests for any registered drivers.
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