87 lines
2.0 KiB
Go
87 lines
2.0 KiB
Go
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package zk
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import (
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"github.com/samuel/go-zookeeper/zk"
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"github.com/go-kit/kit/endpoint"
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"github.com/go-kit/kit/log"
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"github.com/go-kit/kit/sd"
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"github.com/go-kit/kit/sd/cache"
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)
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// Subscriber yield endpoints stored in a certain ZooKeeper path. Any kind of
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// change in that path is watched and will update the Subscriber endpoints.
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type Subscriber struct {
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client Client
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path string
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cache *cache.Cache
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logger log.Logger
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quitc chan struct{}
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}
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var _ sd.Subscriber = &Subscriber{}
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// NewSubscriber returns a ZooKeeper subscriber. ZooKeeper will start watching
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// the given path for changes and update the Subscriber endpoints.
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func NewSubscriber(c Client, path string, factory sd.Factory, logger log.Logger) (*Subscriber, error) {
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s := &Subscriber{
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client: c,
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path: path,
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cache: cache.New(factory, logger),
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logger: logger,
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quitc: make(chan struct{}),
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}
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err := s.client.CreateParentNodes(s.path)
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if err != nil {
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return nil, err
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}
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instances, eventc, err := s.client.GetEntries(s.path)
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if err != nil {
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logger.Log("path", s.path, "msg", "failed to retrieve entries", "err", err)
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return nil, err
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}
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logger.Log("path", s.path, "instances", len(instances))
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s.cache.Update(instances)
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go s.loop(eventc)
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return s, nil
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}
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func (s *Subscriber) loop(eventc <-chan zk.Event) {
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var (
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instances []string
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err error
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)
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for {
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select {
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case <-eventc:
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// We received a path update notification. Call GetEntries to
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// retrieve child node data, and set a new watch, as ZK watches are
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// one-time triggers.
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instances, eventc, err = s.client.GetEntries(s.path)
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if err != nil {
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s.logger.Log("path", s.path, "msg", "failed to retrieve entries", "err", err)
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continue
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}
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s.logger.Log("path", s.path, "instances", len(instances))
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s.cache.Update(instances)
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case <-s.quitc:
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return
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}
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}
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}
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// Endpoints implements the Subscriber interface.
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func (s *Subscriber) Endpoints() ([]endpoint.Endpoint, error) {
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return s.cache.Endpoints(), nil
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}
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// Stop terminates the Subscriber.
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func (s *Subscriber) Stop() {
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close(s.quitc)
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}
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