d76645680f
Bump containers/image (pulling in its new dependency on ostree-go), containers/storage, and updated image-spec. This pulls in the OCI v1.0 specifications and code that allows us to support 1.0 images. Signed-off-by: Dan Walsh <dwalsh@redhat.com> Signed-off-by: Nalin Dahyabhai <nalin@redhat.com>
271 lines
6 KiB
Go
271 lines
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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// Storage 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/containers/storage/plugins, whereas spec files can be
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// located either under /etc/containers/storage/plugins or
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// /usr/lib/containers/storage/plugins. This is handled by the Registry
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// interface, which lets you list all plugins or get a plugin by its name if it
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// 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 subsystems which this plugin implements. As of
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// this writing, the known subsystem is "GraphDriver".
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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
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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/Sirupsen/logrus"
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"github.com/docker/go-connections/tlsconfig"
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)
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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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var (
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storage = plugins{plugins: make(map[string]*Plugin)}
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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 storage 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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// error produced by activation
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activateErr error
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// specifies if the activation sequence is completed (not if it is successful or not)
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activated bool
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// wait for activation to finish
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activateWait *sync.Cond
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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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// 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.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.activated = true
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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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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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for _, iface := range m.Implements {
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handler, handled := extpointHandlers[iface]
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if !handled {
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continue
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}
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handler(p.name, p.client)
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}
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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 {
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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 err := p.waitActive(); err != 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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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 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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extpointHandlers[iface] = fn
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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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if pl, ok := storage.plugins[name]; 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 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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