distribution/storagedriver/factory/factory.go

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package factory
import (
"fmt"
"github.com/docker/docker-registry/storagedriver"
"github.com/docker/docker-registry/storagedriver/ipc"
)
// 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
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]string) (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.
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 run in-process, the StorageDriverFactory must first be registered with the given name
// If no in-process drivers are found with the given name, this attempts to create an IPC driver
// If no in-process or external drivers are found, an InvalidStorageDriverError is returned
func Create(name string, parameters map[string]string) (storagedriver.StorageDriver, error) {
driverFactory, ok := driverFactories[name]
if !ok {
// No registered StorageDriverFactory found, try ipc
driverClient, err := ipc.NewDriverClient(name, parameters)
if err != nil {
return nil, InvalidStorageDriverError{name}
}
err = driverClient.Start()
if err != nil {
return nil, err
}
return driverClient, nil
}
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)
}