Switch to github.com/golang/dep for vendoring

Signed-off-by: Mrunal Patel <mrunalp@gmail.com>

vendor/github.com/containers/storage/pkg/plugins/plugins.go

@@ -0,0 +1,270 @@
+// Package plugins provides structures and helper functions to manage Docker
+// plugins.
+//
+// Storage discovers plugins by looking for them in the plugin directory whenever
+// a user or container tries to use one by name. UNIX domain socket files must
+// be located under /run/oci-storage/plugins, whereas spec files can be located
+// either under /etc/oci-storage/plugins or /usr/lib/oci-storage/plugins. This
+// is handled by the Registry interface, which lets you list all plugins or get
+// a plugin by its name if it exists.
+//
+// The plugins need to implement an HTTP server and bind this to the UNIX socket
+// or the address specified in the spec files.
+// A handshake is send at /Plugin.Activate, and plugins are expected to return
+// a Manifest with a list of subsystems which this plugin implements.  As of
+// this writing, the known subsystem is "GraphDriver".
+//
+// In order to use a plugins, you can use the ``Get`` with the name of the
+// plugin and the subsystem it implements.
+//
+//	plugin, err := plugins.Get("example", "VolumeDriver")
+//	if err != nil {
+//		return fmt.Errorf("Error looking up volume plugin example: %v", err)
+//	}
+package plugins
+
+import (
+	"errors"
+	"sync"
+	"time"
+
+	"github.com/Sirupsen/logrus"
+	"github.com/docker/go-connections/tlsconfig"
+)
+
+var (
+	// ErrNotImplements is returned if the plugin does not implement the requested driver.
+	ErrNotImplements = errors.New("Plugin does not implement the requested driver")
+)
+
+type plugins struct {
+	sync.Mutex
+	plugins map[string]*Plugin
+}
+
+var (
+	storage          = plugins{plugins: make(map[string]*Plugin)}
+	extpointHandlers = make(map[string]func(string, *Client))
+)
+
+// Manifest lists what a plugin implements.
+type Manifest struct {
+	// List of subsystem the plugin implements.
+	Implements []string
+}
+
+// Plugin is the definition of a storage plugin.
+type Plugin struct {
+	// Name of the plugin
+	name string
+	// Address of the plugin
+	Addr string
+	// TLS configuration of the plugin
+	TLSConfig *tlsconfig.Options
+	// Client attached to the plugin
+	client *Client
+	// Manifest of the plugin (see above)
+	Manifest *Manifest `json:"-"`
+
+	// error produced by activation
+	activateErr error
+	// specifies if the activation sequence is completed (not if it is successful or not)
+	activated bool
+	// wait for activation to finish
+	activateWait *sync.Cond
+}
+
+// Name returns the name of the plugin.
+func (p *Plugin) Name() string {
+	return p.name
+}
+
+// Client returns a ready-to-use plugin client that can be used to communicate with the plugin.
+func (p *Plugin) Client() *Client {
+	return p.client
+}
+
+// NewLocalPlugin creates a new local plugin.
+func NewLocalPlugin(name, addr string) *Plugin {
+	return &Plugin{
+		name: name,
+		Addr: addr,
+		// TODO: change to nil
+		TLSConfig:    &tlsconfig.Options{InsecureSkipVerify: true},
+		activateWait: sync.NewCond(&sync.Mutex{}),
+	}
+}
+
+func (p *Plugin) activate() error {
+	p.activateWait.L.Lock()
+	if p.activated {
+		p.activateWait.L.Unlock()
+		return p.activateErr
+	}
+
+	p.activateErr = p.activateWithLock()
+	p.activated = true
+
+	p.activateWait.L.Unlock()
+	p.activateWait.Broadcast()
+	return p.activateErr
+}
+
+func (p *Plugin) activateWithLock() error {
+	c, err := NewClient(p.Addr, p.TLSConfig)
+	if err != nil {
+		return err
+	}
+	p.client = c
+
+	m := new(Manifest)
+	if err = p.client.Call("Plugin.Activate", nil, m); err != nil {
+		return err
+	}
+
+	p.Manifest = m
+
+	for _, iface := range m.Implements {
+		handler, handled := extpointHandlers[iface]
+		if !handled {
+			continue
+		}
+		handler(p.name, p.client)
+	}
+	return nil
+}
+
+func (p *Plugin) waitActive() error {
+	p.activateWait.L.Lock()
+	for !p.activated {
+		p.activateWait.Wait()
+	}
+	p.activateWait.L.Unlock()
+	return p.activateErr
+}
+
+func (p *Plugin) implements(kind string) bool {
+	if err := p.waitActive(); err != nil {
+		return false
+	}
+	for _, driver := range p.Manifest.Implements {
+		if driver == kind {
+			return true
+		}
+	}
+	return false
+}
+
+func load(name string) (*Plugin, error) {
+	return loadWithRetry(name, true)
+}
+
+func loadWithRetry(name string, retry bool) (*Plugin, error) {
+	registry := newLocalRegistry()
+	start := time.Now()
+
+	var retries int
+	for {
+		pl, err := registry.Plugin(name)
+		if err != nil {
+			if !retry {
+				return nil, err
+			}
+
+			timeOff := backoff(retries)
+			if abort(start, timeOff) {
+				return nil, err
+			}
+			retries++
+			logrus.Warnf("Unable to locate plugin: %s, retrying in %v", name, timeOff)
+			time.Sleep(timeOff)
+			continue
+		}
+
+		storage.Lock()
+		storage.plugins[name] = pl
+		storage.Unlock()
+
+		err = pl.activate()
+
+		if err != nil {
+			storage.Lock()
+			delete(storage.plugins, name)
+			storage.Unlock()
+		}
+
+		return pl, err
+	}
+}
+
+func get(name string) (*Plugin, error) {
+	storage.Lock()
+	pl, ok := storage.plugins[name]
+	storage.Unlock()
+	if ok {
+		return pl, pl.activate()
+	}
+	return load(name)
+}
+
+// Get returns the plugin given the specified name and requested implementation.
+func Get(name, imp string) (*Plugin, error) {
+	pl, err := get(name)
+	if err != nil {
+		return nil, err
+	}
+	if pl.implements(imp) {
+		logrus.Debugf("%s implements: %s", name, imp)
+		return pl, nil
+	}
+	return nil, ErrNotImplements
+}
+
+// Handle adds the specified function to the extpointHandlers.
+func Handle(iface string, fn func(string, *Client)) {
+	extpointHandlers[iface] = fn
+}
+
+// GetAll returns all the plugins for the specified implementation
+func GetAll(imp string) ([]*Plugin, error) {
+	pluginNames, err := Scan()
+	if err != nil {
+		return nil, err
+	}
+
+	type plLoad struct {
+		pl  *Plugin
+		err error
+	}
+
+	chPl := make(chan *plLoad, len(pluginNames))
+	var wg sync.WaitGroup
+	for _, name := range pluginNames {
+		if pl, ok := storage.plugins[name]; ok {
+			chPl <- &plLoad{pl, nil}
+			continue
+		}
+
+		wg.Add(1)
+		go func(name string) {
+			defer wg.Done()
+			pl, err := loadWithRetry(name, false)
+			chPl <- &plLoad{pl, err}
+		}(name)
+	}
+
+	wg.Wait()
+	close(chPl)
+
+	var out []*Plugin
+	for pl := range chPl {
+		if pl.err != nil {
+			logrus.Error(pl.err)
+			continue
+		}
+		if pl.pl.implements(imp) {
+			out = append(out, pl.pl)
+		}
+	}
+	return out, nil
+}