mirror of
https://github.com/genuinetools/reg.git
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338 lines
7.6 KiB
Go
338 lines
7.6 KiB
Go
// Package plugins provides structures and helper functions to manage Docker
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// plugins.
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//
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// Docker discovers plugins by looking for them in the plugin directory whenever
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// a user or container tries to use one by name. UNIX domain socket files must
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// be located under /run/docker/plugins, whereas spec files can be located
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// either under /etc/docker/plugins or /usr/lib/docker/plugins. This is handled
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// by the Registry interface, which lets you list all plugins or get a plugin by
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// its name if it exists.
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//
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// The plugins need to implement an HTTP server and bind this to the UNIX socket
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// or the address specified in the spec files.
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// A handshake is send at /Plugin.Activate, and plugins are expected to return
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// a Manifest with a list of of Docker subsystems which this plugin implements.
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//
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// In order to use a plugins, you can use the ``Get`` with the name of the
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// plugin and the subsystem it implements.
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//
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// plugin, err := plugins.Get("example", "VolumeDriver")
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// if err != nil {
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// return fmt.Errorf("Error looking up volume plugin example: %v", err)
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// }
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package plugins // import "github.com/docker/docker/pkg/plugins"
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import (
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"errors"
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"sync"
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"time"
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"github.com/docker/go-connections/tlsconfig"
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"github.com/sirupsen/logrus"
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)
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// ProtocolSchemeHTTPV1 is the name of the protocol used for interacting with plugins using this package.
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const ProtocolSchemeHTTPV1 = "moby.plugins.http/v1"
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var (
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// ErrNotImplements is returned if the plugin does not implement the requested driver.
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ErrNotImplements = errors.New("Plugin does not implement the requested driver")
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)
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type plugins struct {
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sync.Mutex
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plugins map[string]*Plugin
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}
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type extpointHandlers struct {
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sync.RWMutex
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extpointHandlers map[string][]func(string, *Client)
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}
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var (
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storage = plugins{plugins: make(map[string]*Plugin)}
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handlers = extpointHandlers{extpointHandlers: make(map[string][]func(string, *Client))}
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)
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// Manifest lists what a plugin implements.
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type Manifest struct {
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// List of subsystem the plugin implements.
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Implements []string
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}
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// Plugin is the definition of a docker plugin.
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type Plugin struct {
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// Name of the plugin
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name string
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// Address of the plugin
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Addr string
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// TLS configuration of the plugin
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TLSConfig *tlsconfig.Options
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// Client attached to the plugin
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client *Client
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// Manifest of the plugin (see above)
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Manifest *Manifest `json:"-"`
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// wait for activation to finish
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activateWait *sync.Cond
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// error produced by activation
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activateErr error
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// keeps track of callback handlers run against this plugin
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handlersRun bool
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}
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// Name returns the name of the plugin.
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func (p *Plugin) Name() string {
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return p.name
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}
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// Client returns a ready-to-use plugin client that can be used to communicate with the plugin.
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func (p *Plugin) Client() *Client {
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return p.client
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}
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// Protocol returns the protocol name/version used for plugins in this package.
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func (p *Plugin) Protocol() string {
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return ProtocolSchemeHTTPV1
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}
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// IsV1 returns true for V1 plugins and false otherwise.
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func (p *Plugin) IsV1() bool {
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return true
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}
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// NewLocalPlugin creates a new local plugin.
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func NewLocalPlugin(name, addr string) *Plugin {
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return &Plugin{
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name: name,
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Addr: addr,
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// TODO: change to nil
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TLSConfig: &tlsconfig.Options{InsecureSkipVerify: true},
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activateWait: sync.NewCond(&sync.Mutex{}),
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}
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}
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func (p *Plugin) activate() error {
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p.activateWait.L.Lock()
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if p.activated() {
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p.runHandlers()
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p.activateWait.L.Unlock()
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return p.activateErr
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}
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p.activateErr = p.activateWithLock()
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p.runHandlers()
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p.activateWait.L.Unlock()
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p.activateWait.Broadcast()
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return p.activateErr
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}
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// runHandlers runs the registered handlers for the implemented plugin types
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// This should only be run after activation, and while the activation lock is held.
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func (p *Plugin) runHandlers() {
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if !p.activated() {
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return
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}
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handlers.RLock()
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if !p.handlersRun {
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for _, iface := range p.Manifest.Implements {
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hdlrs, handled := handlers.extpointHandlers[iface]
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if !handled {
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continue
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}
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for _, handler := range hdlrs {
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handler(p.name, p.client)
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}
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}
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p.handlersRun = true
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}
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handlers.RUnlock()
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}
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// activated returns if the plugin has already been activated.
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// This should only be called with the activation lock held
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func (p *Plugin) activated() bool {
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return p.Manifest != nil
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}
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func (p *Plugin) activateWithLock() error {
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c, err := NewClient(p.Addr, p.TLSConfig)
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if err != nil {
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return err
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}
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p.client = c
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m := new(Manifest)
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if err = p.client.Call("Plugin.Activate", nil, m); err != nil {
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return err
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}
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p.Manifest = m
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return nil
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}
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func (p *Plugin) waitActive() error {
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p.activateWait.L.Lock()
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for !p.activated() && p.activateErr == nil {
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p.activateWait.Wait()
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}
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p.activateWait.L.Unlock()
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return p.activateErr
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}
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func (p *Plugin) implements(kind string) bool {
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if p.Manifest == nil {
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return false
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}
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for _, driver := range p.Manifest.Implements {
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if driver == kind {
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return true
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}
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}
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return false
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}
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func load(name string) (*Plugin, error) {
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return loadWithRetry(name, true)
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}
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func loadWithRetry(name string, retry bool) (*Plugin, error) {
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registry := newLocalRegistry()
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start := time.Now()
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var retries int
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for {
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pl, err := registry.Plugin(name)
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if err != nil {
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if !retry {
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return nil, err
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}
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timeOff := backoff(retries)
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if abort(start, timeOff) {
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return nil, err
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}
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retries++
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logrus.Warnf("Unable to locate plugin: %s, retrying in %v", name, timeOff)
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time.Sleep(timeOff)
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continue
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}
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storage.Lock()
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if pl, exists := storage.plugins[name]; exists {
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storage.Unlock()
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return pl, pl.activate()
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}
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storage.plugins[name] = pl
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storage.Unlock()
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err = pl.activate()
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if err != nil {
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storage.Lock()
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delete(storage.plugins, name)
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storage.Unlock()
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}
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return pl, err
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}
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}
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func get(name string) (*Plugin, error) {
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storage.Lock()
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pl, ok := storage.plugins[name]
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storage.Unlock()
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if ok {
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return pl, pl.activate()
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}
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return load(name)
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}
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// Get returns the plugin given the specified name and requested implementation.
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func Get(name, imp string) (*Plugin, error) {
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pl, err := get(name)
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if err != nil {
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return nil, err
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}
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if err := pl.waitActive(); err == nil && pl.implements(imp) {
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logrus.Debugf("%s implements: %s", name, imp)
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return pl, nil
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}
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return nil, ErrNotImplements
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}
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// Handle adds the specified function to the extpointHandlers.
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func Handle(iface string, fn func(string, *Client)) {
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handlers.Lock()
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hdlrs, ok := handlers.extpointHandlers[iface]
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if !ok {
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hdlrs = []func(string, *Client){}
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}
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hdlrs = append(hdlrs, fn)
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handlers.extpointHandlers[iface] = hdlrs
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storage.Lock()
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for _, p := range storage.plugins {
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p.activateWait.L.Lock()
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if p.activated() && p.implements(iface) {
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p.handlersRun = false
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}
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p.activateWait.L.Unlock()
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}
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storage.Unlock()
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handlers.Unlock()
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}
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// GetAll returns all the plugins for the specified implementation
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func GetAll(imp string) ([]*Plugin, error) {
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pluginNames, err := Scan()
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if err != nil {
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return nil, err
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}
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type plLoad struct {
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pl *Plugin
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err error
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}
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chPl := make(chan *plLoad, len(pluginNames))
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var wg sync.WaitGroup
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for _, name := range pluginNames {
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storage.Lock()
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pl, ok := storage.plugins[name]
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storage.Unlock()
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if ok {
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chPl <- &plLoad{pl, nil}
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continue
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}
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wg.Add(1)
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go func(name string) {
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defer wg.Done()
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pl, err := loadWithRetry(name, false)
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chPl <- &plLoad{pl, err}
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}(name)
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}
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wg.Wait()
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close(chPl)
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var out []*Plugin
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for pl := range chPl {
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if pl.err != nil {
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logrus.Error(pl.err)
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continue
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}
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if err := pl.pl.waitActive(); err == nil && pl.pl.implements(imp) {
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out = append(out, pl.pl)
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}
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}
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return out, nil
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}
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