package factory import ( "fmt" storagedriver "github.com/docker/distribution/registry/storage/driver" ) // driverFactories stores an internal mapping between storage driver names and their respective // factories var driverFactories = make(map[string]StorageDriverFactory) // StorageDriverFactory is a factory interface for creating storagedriver.StorageDriver interfaces // Storage drivers should call Register() with a factory to make the driver available by name. // Individual StorageDriver implementations generally register with the factory via the Register // func (below) in their init() funcs, and as such they should be imported anonymously before use. // See below for an example of how to register and get a StorageDriver for S3 // // import _ "github.com/docker/distribution/registry/storage/driver/s3-aws" // s3Driver, err = factory.Create("s3", storageParams) // // assuming no error, s3Driver is the StorageDriver that communicates with S3 according to storageParams type StorageDriverFactory interface { // Create returns a new storagedriver.StorageDriver with the given parameters // Parameters will vary by driver and may be ignored // Each parameter key must only consist of lowercase letters and numbers Create(parameters map[string]interface{}) (storagedriver.StorageDriver, error) } // Register makes a storage driver available by the provided name. // If Register is called twice with the same name or if driver factory is nil, it panics. // Additionally, it is not concurrency safe. Most Storage Drivers call this function // in their init() functions. See the documentation for StorageDriverFactory for more. func Register(name string, factory StorageDriverFactory) { if factory == nil { panic("Must not provide nil StorageDriverFactory") } _, registered := driverFactories[name] if registered { panic(fmt.Sprintf("StorageDriverFactory named %s already registered", name)) } driverFactories[name] = factory } // Create a new storagedriver.StorageDriver with the given name and // parameters. To use a driver, the StorageDriverFactory must first be // registered with the given name. If no drivers are found, an // InvalidStorageDriverError is returned func Create(name string, parameters map[string]interface{}) (storagedriver.StorageDriver, error) { driverFactory, ok := driverFactories[name] if !ok { return nil, InvalidStorageDriverError{name} } return driverFactory.Create(parameters) } // InvalidStorageDriverError records an attempt to construct an unregistered storage driver type InvalidStorageDriverError struct { Name string } func (err InvalidStorageDriverError) Error() string { return fmt.Sprintf("StorageDriver not registered: %s", err.Name) }