Swarmkit筆記（11）——manager建立處理swarmctl請求的server

這是一個建立於 的文章，其中的資訊可能已經有所發展或是發生改變。

manager.localserver是建立的本地Unix socket，用來等待處理swarmctl發來的命令請求（源碼在manager/controlapi目錄）。Manager.Run()函數裡localserver相關代碼如下：

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()的定義：

// 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()函數就是用來建立一個響應swarmctl程式發出的control命令請求的server。

其中store.MemoryStore是一個很重要的結構體：

// 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定義如下：

// 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)}

簡單地講，就是當Server.store發生變化時，把資料更新到memDB的同時，也要發送訊息到queue裡，這樣manager監聽在相應channel的goroutine就可以收到並處理請求。

下面代碼就是把當前cluster的資訊填充到新建立的controlapi.Server變數裡：

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)

上述代碼建立出一個raftProxyControlServer類型的變數：

type raftProxyControlServer struct {    local        ControlServer    connSelector *raftpicker.ConnSelector    cluster      raftpicker.RaftCluster    ctxMods      []func(context.Context) (context.Context, error)}

localProxyControlAPI含義是如果收到swarmctl請求的manager是leader（swarmctl和manager當然位於同一台機器上），則會處理請求，否則就轉寄給這個cluster的leader。

（3）

api.RegisterControlServer(m.localserver, localProxyControlAPI)

上述代碼則是把localserver所對應的Unix socket和raftProxyControlServer關聯起來。