distribution/registry/storage/driver/factory/factory.go

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package factory
import (
"context"
"fmt"
storagedriver "github.com/distribution/distribution/v3/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/distribution/distribution/v3/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(ctx context.Context, 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(ctx context.Context, name string, parameters map[string]interface{}) (storagedriver.StorageDriver, error) {
driverFactory, ok := driverFactories[name]
if !ok {
return nil, InvalidStorageDriverError{name}
}
return driverFactory.Create(ctx, 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)
}