vendor/github.com/docker/swarmkit/manager/watchapi/server.go

package watchapi

import (
	"errors"
	"sync"

	"github.com/docker/swarmkit/manager/state/store"
	"golang.org/x/net/context"
)

var (
	errAlreadyRunning = errors.New("broker is already running")
	errNotRunning     = errors.New("broker is not running")
)

// Server is the store API gRPC server.
type Server struct {
	store     *store.MemoryStore
	mu        sync.Mutex
	pctx      context.Context
	cancelAll func()
}

// NewServer creates a store API server.
func NewServer(store *store.MemoryStore) *Server {
	return &Server{
		store: store,
	}
}

// Start starts the watch server.
func (s *Server) Start(ctx context.Context) error {
	s.mu.Lock()
	defer s.mu.Unlock()

	if s.cancelAll != nil {
		return errAlreadyRunning
	}

	s.pctx, s.cancelAll = context.WithCancel(ctx)
	return nil
}

// Stop stops the watch server.
func (s *Server) Stop() error {
	s.mu.Lock()
	defer s.mu.Unlock()

	if s.cancelAll == nil {
		return errNotRunning
	}
	s.cancelAll()
	s.cancelAll = nil

	return nil
}