Etcd database source code analysis -- ServerV2 interface implementation

We know EtcdServer Realized Server Interface 、ServerV2 Interface and ServerV3 Interface , Let's first introduce ServerV2 Interface （ServerV2 Interfaces are used to operate v2 store Of API）. As shown in the figure above ServerV2 As shown in the code , It provides Leader()、Do() and ClientCertAuthEnabled() Function definition .EtcdServer The structure needs to realize ServerV2 Interface , To provide operation v2 store The ability of .

Do function

Here is Do Implementation of function , use first reqIDGen Generate a request id, Set to pb.Request Of ID Among members ; Then initialize reqV2HandlerEtcdServer Structure （ The structure in the right part of the above figure ）; And then call Request（RequestV2 Is defined as Request） Provided Handle function ; Finally, the current tenure of the node and commit raft log pos Set in response .

func (s *EtcdServer) Do(ctx context.Context, r pb.Request) (Response, error) {
    
	r.ID = s.reqIDGen.Next()
	h := &reqV2HandlerEtcdServer{
    
		reqV2HandlerStore: reqV2HandlerStore{
     store:   s.v2store, applier: s.applyV2, }, s: s,
	}
	rp := &r
	resp, err := ((*RequestV2)(rp)).Handle(ctx, h)
	resp.Term, resp.Index = s.Term(), s.CommittedIndex()
	return resp, err
}
func (r *RequestV2) Handle(ctx context.Context, v2api RequestV2Handler) (Response, error) {
    
	if r.Method == "GET" && r.Quorum {
     r.Method = "QGET" }
	switch r.Method {
    
	case "POST": return v2api.Post(ctx, r)
	case "PUT": return v2api.Put(ctx, r)
	case "DELETE": return v2api.Delete(ctx, r)
	case "QGET": return v2api.QGet(ctx, r)
	case "GET": return v2api.Get(ctx, r)
	case "HEAD": return v2api.Head(ctx, r)
	}
	return Response{
    }, errors.ErrUnknownMethod
}

Handle function Yes Request To analyze , according to Request.Method And other fields to perform corresponding operations . If Request.Method yes “POST”、“PUT”、“DELETE” or Quorum by true Of “QGET”, be Request Will be sent by consensus before performing its corresponding operation ,Do Function will block , Until the operation is performed or an error occurs .

reqV2HandlerEtcdServer

reqV2HandlerEtcdServer The structure contains reqV2HandlerStore and EtcdServer Two members ,reqV2HandlerStore Contains v2store.Store and ApplierV2 Two parts , From the above Do The function can see , These two members are EtcdServer Of v2store and applyv2, That is, follow-up reqV2HandlerStore Interface function implemented by structure , That's right EtcdServer Of v2store and applyv2 The operation of these two members .

type reqV2HandlerEtcdServer struct {
    
	reqV2HandlerStore
	s *EtcdServer
}

reqV2HandlerEtcdServer The structure realizes RequestV2Handler All interface functions of the interface . As can be seen below these Post、Put、Delete and QGet Methods are called processRaftRequest Realized , stay processRaftRequest Method will give the request to etcd-raft Module processing , And block waiting for the request processing to end .

type RequestV2Handler interface {
    
	Post(ctx context.Context, r *RequestV2) (Response, error)
	Put(ctx context.Context, r *RequestV2) (Response, error)
	Delete(ctx context.Context, r *RequestV2) (Response, error)
	QGet(ctx context.Context, r *RequestV2) (Response, error)
	Get(ctx context.Context, r *RequestV2) (Response, error)
	Head(ctx context.Context, r *RequestV2) (Response, error)
}
func (a *reqV2HandlerEtcdServer) Post(ctx context.Context, r *RequestV2) (Response, error) {
     return a.processRaftRequest(ctx, r) }
func (a *reqV2HandlerEtcdServer) Put(ctx context.Context, r *RequestV2) (Response, error) {
     return a.processRaftRequest(ctx, r) }
func (a *reqV2HandlerEtcdServer) Delete(ctx context.Context, r *RequestV2) (Response, error) {
     return a.processRaftRequest(ctx, r) }
func (a *reqV2HandlerEtcdServer) QGet(ctx context.Context, r *RequestV2) (Response, error) {
     return a.processRaftRequest(ctx, r) }
func (a *reqV2HandlerEtcdServer) processRaftRequest(ctx context.Context, r *RequestV2) (Response, error) {
    
	data, err := ((*pb.Request)(r)).Marshal()
	if err != nil {
     return Response{
    }, err }
	ch := a.s.w.Register(r.ID)
	start := time.Now()
	a.s.r.Propose(ctx, data)
	select {
    
	case x := <-ch:
		resp := x.(Response)
		return resp, resp.Err
	case <-ctx.Done():
		proposalsFailed.Inc()
		a.s.w.Trigger(r.ID, nil) // GC wait
		return Response{
    }, a.s.parseProposeCtxErr(ctx.Err(), start)
	case <-a.s.stopping:
	}
	return Response{
    }, errors.ErrStopped
}

reqV2HandlerStore

type reqV2HandlerStore struct {
    
	store   v2store.Store
	applier ApplierV2
}

reqV2HandlerStore The structure realizes RequestV2Handler All interface functions of the interface . from reqV2HandlerStore The implementation of these functions can be seen Post、Put、Delete、QGet In fact, it's all called ApplierV2 The corresponding function of ;Get and Head It's called v2store.Store Corresponding interface function ,Do Function for Request.Method by Get and Head The operation of is to call the following Get and Head function , perform v2store.Store The corresponding interface function obtains data .

func (a *reqV2HandlerStore) Post(ctx context.Context, r *RequestV2) (Response, error) {
     return a.applier.Post(r), nil }
func (a *reqV2HandlerStore) Put(ctx context.Context, r *RequestV2) (Response, error) {
     return a.applier.Put(r, membership.ApplyBoth), nil }
func (a *reqV2HandlerStore) Delete(ctx context.Context, r *RequestV2) (Response, error) {
     return a.applier.Delete(r), nil }
func (a *reqV2HandlerStore) QGet(ctx context.Context, r *RequestV2) (Response, error) {
     return a.applier.QGet(r), nil }

func (a *reqV2HandlerStore) Get(ctx context.Context, r *RequestV2) (Response, error) {
    
	if r.Wait {
    
		wc, err := a.store.Watch(r.Path, r.Recursive, r.Stream, r.Since)
		return Response{
    Watcher: wc}, err
	}
	ev, err := a.store.Get(r.Path, r.Recursive, r.Sorted)
	return Response{
    Event: ev}, err
}
func (a *reqV2HandlerStore) Head(ctx context.Context, r *RequestV2) (Response, error) {
    
	ev, err := a.store.Get(r.Path, r.Recursive, r.Sorted)
	return Response{
    Event: ev}, err
}

Get rid of v2sotre, It needs to be deleted ServerV2 Of Do Function implementation and updateClusterVersionV2 function , Delete server/etcdserver/apply.v2.go and server/etcdserver/v2.server.go file .