60 lines
3.4 KiB
Markdown
60 lines
3.4 KiB
Markdown
<!--[metadata]>
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+++
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title = "Docker Registry Storage Driver"
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description = "Explains how to use the storage drivers"
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keywords = ["registry, service, driver, images, storage"]
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[menu.main]
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parent="smn_registry_ref"
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identifier="smn_registry_drivers"
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+++
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<![end-metadata]-->
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# Docker Registry Storage Driver
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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](storage-drivers/inmemory.md): A temporary storage driver using a local inmemory map. This exists solely for reference and testing.
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- [filesystem](storage-drivers/filesystem.md): A local storage driver configured to use a directory tree in the local filesystem.
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- [s3](storage-drivers/s3.md): A driver storing objects in an Amazon Simple Storage Solution (S3) bucket.
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- [azure](storage-drivers/azure.md): A driver storing objects in [Microsoft Azure Blob Storage](http://azure.microsoft.com/en-us/services/storage/).
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- [rados](storage-drivers/rados.md): A driver storing objects in a [Ceph Object Storage](http://ceph.com/docs/master/rados/) pool.
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- [swift](storage-drivers/swift.md): A driver storing objects in [Openstack Swift](http://docs.openstack.org/developer/swift/).
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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 off of the [Register](http://golang.org/pkg/database/sql/#Register) and [Open](http://golang.org/pkg/database/sql/#Open) methods in the builtin [database/sql](http://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` will return an `InvalidStorageDriverError`.
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## Driver Contribution
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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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