manager.localserver是创建的本地Unix socket，用来等待处理swarmctl发来的命令请求（源码在manager/controlapi目录）。Manager.Run()函数里localserver相关代码如下：
baseControlAPI := controlapi.NewServer(m.RaftNode.MemoryStore(), m.RaftNode, m.config.SecurityConfig.RootCA())
......
proxyOpts := []grpc.DialOption{
grpc.WithBackoffMaxDelay(time.Second),
grpc.WithTransportCredentials(m.config.SecurityConfig.ClientTLSCreds),
}
cs := raftpicker.NewConnSelector(m.RaftNode, proxyOpts...)
m.connSelector = cs
......
// localProxyControlAPI is a special kind of proxy. It is only wired up
// to receive requests from a trusted local socket, and these requests
// don't use TLS, therefore the requests it handles locally should
// bypass authorization. When it proxies, it sends them as requests from
// this manager rather than forwarded requests (it has no TLS
// information to put in the metadata map).
forwardAsOwnRequest := func(ctx context.Context) (context.Context, error) { return ctx, nil }
localProxyControlAPI := api.NewRaftProxyControlServer(baseControlAPI, cs, m.RaftNode, forwardAsOwnRequest)
......
api.RegisterControlServer(m.localserver, localProxyControlAPI)
（1）首先看一下controlapi.Server和controlapi.NewServer()的定义：
// Server is the Cluster API gRPC server.
type Server struct {
store *store.MemoryStore
raft *raft.Node
rootCA *ca.RootCA
}
// NewServer creates a Cluster API server.
func NewServer(store *store.MemoryStore, raft *raft.Node, rootCA *ca.RootCA) *Server {
return &Server{
store: store,
raft: raft,
rootCA: rootCA,
}
}
controlapi.NewServer()函数就是用来创建一个响应swarmctl程序发出的control命令请求的server。
其中store.MemoryStore是一个很重要的结构体：
// MemoryStore is a concurrency-safe, in-memory implementation of the Store
// interface.
type MemoryStore struct {
// updateLock must be held during an update transaction.
updateLock sync.Mutex
memDB *memdb.MemDB
queue *watch.Queue
proposer state.Proposer
}
而watch.Queue定义如下：
// Queue is the structure used to publish events and watch for them.
type Queue struct {
broadcast *events.Broadcaster
}
......
// Watch returns a channel which will receive all items published to the
// queue from this point, until cancel is called.
func (q *Queue) Watch() (eventq chan events.Event, cancel func()) {
return q.CallbackWatch(nil)
}
......
// Publish adds an item to the queue.
func (q *Queue) Publish(item events.Event) {
q.broadcast.Write(item)
}
简单地讲，就是当Server.store发生变化时，把数据更新到memDB的同时，也要发送消息到queue里，这样manager监听在相应channel的goroutine就可以收到并处理请求。
下面代码就是把当前cluster的信息填充到新创建的controlapi.Server变量里：
baseControlAPI := controlapi.NewServer(m.RaftNode.MemoryStore(), m.RaftNode, m.config.SecurityConfig.RootCA())
（2）
proxyOpts := []grpc.DialOption{
grpc.WithBackoffMaxDelay(time.Second),
grpc.WithTransportCredentials(m.config.SecurityConfig.ClientTLSCreds),
}
cs := raftpicker.NewConnSelector(m.RaftNode, proxyOpts...)
m.connSelector = cs
......
// localProxyControlAPI is a special kind of proxy. It is only wired up
// to receive requests from a trusted local socket, and these requests
// don't use TLS, therefore the requests it handles locally should
// bypass authorization. When it proxies, it sends them as requests from
// this manager rather than forwarded requests (it has no TLS
// information to put in the metadata map).
forwardAsOwnRequest := func(ctx context.Context) (context.Context, error) { return ctx, nil }
localProxyControlAPI := api.NewRaftProxyControlServer(baseControlAPI, cs, m.RaftNode, forwardAsOwnRequest)
上述代码创建出一个raftProxyControlServer类型的变量：
type raftProxyControlServer struct {
local ControlServer
connSelector *raftpicker.ConnSelector
cluster raftpicker.RaftCluster
ctxMods []func(context.Context) (context.Context, error)
}
localProxyControlAPI含义是如果收到swarmctl请求的manager是leader（swarmctl和manager当然位于同一台机器上），则会处理请求，否则就转发给这个cluster的leader。
（3）
api.RegisterControlServer(m.localserver, localProxyControlAPI)
上述代码则是把localserver所对应的Unix socket和raftProxyControlServer关联起来。