Initial commit

vendor/github.com/hyperhq/hypercli/pkg/plugins/plugins.go

@@ -0,0 +1,222 @@
+// Package plugins provides structures and helper functions to manage Docker
+// plugins.
+//
+// Docker 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/docker/plugins, whereas spec files can be located
+// either under /etc/docker/plugins or /usr/lib/docker/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 of Docker subsystems which this plugin implements.
+//
+// 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 docker plugin.
+type Plugin struct {
+	// Name of the plugin
+	Name string `json:"-"`
+	// Address of the plugin
+	Addr string
+	// TLS configuration of the plugin
+	TLSConfig tlsconfig.Options
+	// Client attached to the plugin
+	Client *Client `json:"-"`
+	// Manifest of the plugin (see above)
+	Manifest *Manifest `json:"-"`
+
+	activatErr   error
+	activateOnce sync.Once
+}
+
+func newLocalPlugin(name, addr string) *Plugin {
+	return &Plugin{
+		Name:      name,
+		Addr:      addr,
+		TLSConfig: tlsconfig.Options{InsecureSkipVerify: true},
+	}
+}
+
+func (p *Plugin) activate() error {
+	p.activateOnce.Do(func() {
+		p.activatErr = p.activateWithLock()
+	})
+	return p.activatErr
+}
+
+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) implements(kind string) bool {
+	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))
+	for _, name := range pluginNames {
+		go func(name string) {
+			pl, err := loadWithRetry(name, false)
+			chPl <- plLoad{pl, err}
+		}(name)
+	}
+
+	var out []*Plugin
+	for i := 0; i < len(pluginNames); i++ {
+		pl := <-chPl
+		if pl.err != nil {
+			logrus.Error(err)
+			continue
+		}
+		if pl.pl.implements(imp) {
+			out = append(out, pl.pl)
+		}
+	}
+	return out, nil
+}