volume/drivers/extpoint.go

//go:generate pluginrpc-gen -i $GOFILE -o proxy.go -type volumeDriver -name VolumeDriver

package volumedrivers

import (
	"fmt"
	"sync"

	"github.com/docker/docker/pkg/plugins"
	"github.com/docker/docker/volume"
)

// currently created by hand. generation tool would generate this like:
// $ extpoint-gen Driver > volume/extpoint.go

var drivers = &driverExtpoint{extensions: make(map[string]volume.Driver)}

// NewVolumeDriver returns a driver has the given name mapped on the given client.
func NewVolumeDriver(name string, c client) volume.Driver {
	proxy := &volumeDriverProxy{c}
	return &volumeDriverAdapter{name, proxy}
}

type opts map[string]string

// volumeDriver defines the available functions that volume plugins must implement.
// This interface is only defined to generate the proxy objects.
// It's not intended to be public or reused.
type volumeDriver interface {
	// Create a volume with the given name
	Create(name string, opts opts) (err error)
	// Remove the volume with the given name
	Remove(name string) (err error)
	// Get the mountpoint of the given volume
	Path(name string) (mountpoint string, err error)
	// Mount the given volume and return the mountpoint
	Mount(name string) (mountpoint string, err error)
	// Unmount the given volume
	Unmount(name string) (err error)
}

type driverExtpoint struct {
	extensions map[string]volume.Driver
	sync.Mutex
}

// Register associates the given driver to the given name, checking if
// the name is already associated
func Register(extension volume.Driver, name string) bool {
	drivers.Lock()
	defer drivers.Unlock()
	if name == "" {
		return false
	}
	_, exists := drivers.extensions[name]
	if exists {
		return false
	}
	drivers.extensions[name] = extension
	return true
}

// Unregister dissociates the name from it's driver, if the association exists.
func Unregister(name string) bool {
	drivers.Lock()
	defer drivers.Unlock()
	_, exists := drivers.extensions[name]
	if !exists {
		return false
	}
	delete(drivers.extensions, name)
	return true
}

// Lookup returns the driver associated with the given name. If a
// driver with the given name has not been registered it checks if
// there is a VolumeDriver plugin available with the given name.
func Lookup(name string) (volume.Driver, error) {
	drivers.Lock()
	ext, ok := drivers.extensions[name]
	drivers.Unlock()
	if ok {
		return ext, nil
	}
	pl, err := plugins.Get(name, "VolumeDriver")
	if err != nil {
		return nil, fmt.Errorf("Error looking up volume plugin %s: %v", name, err)
	}

	drivers.Lock()
	defer drivers.Unlock()
	if ext, ok := drivers.extensions[name]; ok {
		return ext, nil
	}

	d := NewVolumeDriver(name, pl.Client)
	drivers.extensions[name] = d
	return d, nil
}

// GetDriver returns a volume driver by it's name.
// If the driver is empty, it looks for the local driver.
func GetDriver(name string) (volume.Driver, error) {
	if name == "" {
		name = volume.DefaultDriverName
	}
	return Lookup(name)
}