【go语言之thrift协议三之client端分析】

上一篇文章分析了thrift协议server端的实现，这边还是基于官方的示例去分析。

import ("crypto/tls""flag""fmt""os""github.com/apache/thrift/lib/go/thrift"
)func Usage() {fmt.Fprint(os.Stderr, "Usage of ", os.Args[0], ":\n")flag.PrintDefaults()fmt.Fprint(os.Stderr, "\n")
}func main() {flag.Usage = Usageserver := flag.Bool("server", false, "Run server")protocol := flag.String("P", "compact", "Specify the protocol (binary, compact, json, simplejson)")framed := flag.Bool("framed", false, "Use framed transport")buffered := flag.Bool("buffered", false, "Use buffered transport")addr := flag.String("addr", "localhost:9090", "Address to listen to")secure := flag.Bool("secure", false, "Use tls secure transport")flag.Parse()var protocolFactory thrift.TProtocolFactoryswitch *protocol {case "compact":protocolFactory = thrift.NewTCompactProtocolFactoryConf(nil)case "simplejson":protocolFactory = thrift.NewTSimpleJSONProtocolFactoryConf(nil)case "json":protocolFactory = thrift.NewTJSONProtocolFactory()case "binary", "":protocolFactory = thrift.NewTBinaryProtocolFactoryConf(nil)default:fmt.Fprint(os.Stderr, "Invalid protocol specified", protocol, "\n")Usage()os.Exit(1)}var transportFactory thrift.TTransportFactorycfg := &thrift.TConfiguration{TLSConfig: &tls.Config{InsecureSkipVerify: true,},}if *buffered {transportFactory = thrift.NewTBufferedTransportFactory(8192)} else {transportFactory = thrift.NewTTransportFactory()}if *framed {transportFactory = thrift.NewTFramedTransportFactoryConf(transportFactory, cfg)}if *server {if err := runServer(transportFactory, protocolFactory, *addr, *secure); err != nil {fmt.Println("error running server:", err)}} else {if err := runClient(transportFactory, protocolFactory, *addr, *secure, cfg); err != nil {fmt.Println("error running client:", err)}}
}

这里的代码因为是和server端是公用的，所以就不进行具体的分析，详情可以看上一篇。

runClient

还是先看一下具体的实现

func runClient(transportFactory thrift.TTransportFactory, protocolFactory thrift.TProtocolFactory, addr string, secure bool, cfg *thrift.TConfiguration) error {// 初始化transportvar transport thrift.TTransportif secure {transport = thrift.NewTSSLSocketConf(addr, cfg)} else {transport = thrift.NewTSocketConf(addr, cfg)}// 根据transportFactory获取transporttransport, err := transportFactory.GetTransport(transport)if err != nil {return err}defer transport.Close()// 根据地址获取连接if err := transport.Open(); err != nil {return err}// 获取inbound的protoiprot := protocolFactory.GetProtocol(transport)// 获取inbound的protooprot := protocolFactory.GetProtocol(transport)// 进行请求return handleClient(tutorial.NewCalculatorClient(thrift.NewTStandardClient(iprot, oprot)))
}

首先就是初始化client的transport，这里因为没有走https，所以这里走的是transport = thrift.NewTSocketConf(addr, cfg).然后和server一样，其实最终是初始化了TSocket这个结构体，如下

// NewTSocketFromAddrConf creates a TSocket from a net.Addr
func NewTSocketFromAddrConf(addr net.Addr, conf *TConfiguration) *TSocket {return &TSocket{addr: addr,cfg:  conf,}
}

然后调用transportFactory.GetTransport。这里的GetTransport其实还是原封不动的返回了，所以这里就是TSocket的这个结构体，然后就是open方法去根据地址获取连接。

Open

// Connects the socket, creating a new socket object if necessary.
func (p *TSocket) Open() error {if p.conn.isValid() {return NewTTransportException(ALREADY_OPEN, "Socket already connected.")}if p.addr == nil {return NewTTransportException(NOT_OPEN, "Cannot open nil address.")}if len(p.addr.Network()) == 0 {return NewTTransportException(NOT_OPEN, "Cannot open bad network name.")}if len(p.addr.String()) == 0 {return NewTTransportException(NOT_OPEN, "Cannot open bad address.")}var err error// 根据地址获取连接if p.conn, err = createSocketConnFromReturn(net.DialTimeout(p.addr.Network(),p.addr.String(),p.cfg.GetConnectTimeout(),)); err != nil {return &tTransportException{typeId: NOT_OPEN,err:    err,msg:    err.Error(),}}p.addr = p.conn.RemoteAddr()return nil
}

这里的逻辑其实也是比较简单，通过官方的net.DialTimeout方法去获取一个链接。

protocolFactory.GetProtocol

这里的实现是和server端一样，根据compact的proto去返回一个TProtocol。

func (p *TCompactProtocolFactory) GetProtocol(trans TTransport) TProtocol {return NewTCompactProtocolConf(trans, p.cfg)
}
func NewTCompactProtocolConf(trans TTransport, conf *TConfiguration) *TCompactProtocol {PropagateTConfiguration(trans, conf)p := &TCompactProtocol{origTransport: trans,cfg:           conf,}if et, ok := trans.(TRichTransport); ok {p.trans = et} else {p.trans = NewTRichTransport(trans)}return p
}

handleClient

注意这里首先是需要初始化client的方法也就是 tutorial.NewCalculatorClient(thrift.NewTStandardClient(iprot, oprot))。接下来进行逐步的解析

NewTStandardClient

// TStandardClient implements TClient, and uses the standard message format for Thrift.
// It is not safe for concurrent use.
func NewTStandardClient(inputProtocol, outputProtocol TProtocol) *TStandardClient {return &TStandardClient{iprot: inputProtocol,oprot: outputProtocol,}
}type TClient interface {Call(ctx context.Context, method string, args, result TStruct) (ResponseMeta, error)
}

首先需要注意的是这个TStandardClient结构体实现了TClient 这个interface，这个也是这个结构体核心的功能，在后面的很多地方也都有使用。然后看一下call这个方法

type TStruct interface {Write(ctx context.Context, p TProtocol) errorRead(ctx context.Context, p TProtocol) error
}
func (p *TStandardClient) Call(ctx context.Context, method string, args, result TStruct) (ResponseMeta, error) {p.seqId++seqId := p.seqIdif err := p.Send(ctx, p.oprot, seqId, method, args); err != nil {return ResponseMeta{}, err}// method is onewayif result == nil {return ResponseMeta{}, nil}err := p.Recv(ctx, p.iprot, seqId, method, result)var headers THeaderMapif hp, ok := p.iprot.(*THeaderProtocol); ok {headers = hp.transport.readHeaders}return ResponseMeta{Headers: headers,}, err
}

这里的seqId每次调用都会自增一次。
然后可以看出来这个方法的主要是由Send 和Recv这两个方法构成。分别看一下Send方法和Recv方法，

func (p *TStandardClient) Send(ctx context.Context, oprot TProtocol, seqId int32, method string, args TStruct) error {// Set headers from context object on THeaderProtocolif headerProt, ok := oprot.(*THeaderProtocol); ok {headerProt.ClearWriteHeaders()for _, key := range GetWriteHeaderList(ctx) {if value, ok := GetHeader(ctx, key); ok {headerProt.SetWriteHeader(key, value)}}}// 注意这里的oprot就是compact所生成的TProtocol。if err := oprot.WriteMessageBegin(ctx, method, CALL, seqId); err != nil {return err}// 因为这里的args是一个interface，所以后面根据具体的实现分析if err := args.Write(ctx, oprot); err != nil {return err}// 这里compact的WriteMessageEnd方法if err := oprot.WriteMessageEnd(ctx); err != nil {return err}// 调用compact的Flush方法return oprot.Flush(ctx)
}

这里没有多余的逻辑主要就是调用compact中的WriteMessageBegin，WriteMessageEnd方法，然后调用args的args方法。
然后看一下recv方法。

func (p *TStandardClient) Recv(ctx context.Context, iprot TProtocol, seqId int32, method string, result TStruct) error {// 读取compact的ReadMessageBegin方法 并且获取对应的参数rMethod, rTypeId, rSeqId, err := iprot.ReadMessageBegin(ctx)if err != nil {return err}// 判断是不是自己指定的方法if method != rMethod {return NewTApplicationException(WRONG_METHOD_NAME, fmt.Sprintf("%s: wrong method name", method))} else if seqId != rSeqId {return NewTApplicationException(BAD_SEQUENCE_ID, fmt.Sprintf("%s: out of order sequence response", method))} else if rTypeId == EXCEPTION {var exception tApplicationExceptionif err := exception.Read(ctx, iprot); err != nil {return err}if err := iprot.ReadMessageEnd(ctx); err != nil {return err}return &exception} else if rTypeId != REPLY {return NewTApplicationException(INVALID_MESSAGE_TYPE_EXCEPTION, fmt.Sprintf("%s: invalid message type", method))}// result读取结果if err := result.Read(ctx, iprot); err != nil {return err}// 调用compact的ReadMessageEnd方法return iprot.ReadMessageEnd(ctx)
}

看起来Recv方法其实和Send类似，读取的是compact的ReadMessageBegin和ReadMessageEnd方法，然后就是调用args的write和result.Read方法。

NewCalculatorClient

需要注意这个是通过thrift实现的方法，入参就是上面实现的TStandardClient结构体，然后实现了TClient这个interface也就是Call方法。

func NewCalculatorClient(c thrift.TClient) *CalculatorClient {return &CalculatorClient{SharedServiceClient: shared.NewSharedServiceClient(c),}
}
func NewSharedServiceClient(c thrift.TClient) *SharedServiceClient {return &SharedServiceClient{c: c,}
}

handleClient的具体实现

func handleClient(client *tutorial.CalculatorClient) (err error) {// 调用ping方法client.Ping(defaultCtx)fmt.Println("ping()")// 调用Add方法sum, _ := client.Add(defaultCtx, 1, 1)fmt.Print("1+1=", sum, "\n")// 调用Calculate方法work := tutorial.NewWork()work.Op = tutorial.Operation_DIVIDEwork.Num1 = 1work.Num2 = 0quotient, err := client.Calculate(defaultCtx, 1, work)if err != nil {switch v := err.(type) {case *tutorial.InvalidOperation:fmt.Println("Invalid operation:", v)default:fmt.Println("Error during operation:", err)}} else {fmt.Println("Whoa we can divide by 0 with new value:", quotient)}// 调用Calculate方法 work.Op = tutorial.Operation_SUBTRACTwork.Num1 = 15work.Num2 = 10diff, err := client.Calculate(defaultCtx, 1, work)if err != nil {switch v := err.(type) {case *tutorial.InvalidOperation:fmt.Println("Invalid operation:", v)default:fmt.Println("Error during operation:", err)}return err} else {fmt.Print("15-10=", diff, "\n")}// 调用GetStruct方法log, err := client.GetStruct(defaultCtx, 1)if err != nil {fmt.Println("Unable to get struct:", err)return err} else {fmt.Println("Check log:", log.Value)}return err
}

这个方法从使用上来看是好理解的，主要作用就是组装参数，调用client所实现的方法，接下来看一下这些方法在thrift中的实现。因为这里的实现都是大同小异的，所以这里看一下Add这个方法，代码如下

type CalculatorAddArgs struct {Num1 int32 `thrift:"num1,1" db:"num1" json:"num1"`Num2 int32 `thrift:"num2,2" db:"num2" json:"num2"`
}// Attributes:
//   - Success
type CalculatorAddResult struct {Success *int32 `thrift:"success,0" db:"success" json:"success,omitempty"`
}// ResponseMeta represents the metadata attached to the response.
type ResponseMeta struct {// The headers in the response, if any.// If the underlying transport/protocol is not THeader, this will always be nil.Headers THeaderMap
}// Parameters:
//   - Num1
//   - Num2
func (p *CalculatorClient) Add(ctx context.Context, num1 int32, num2 int32) (_r int32, _err error) {var _args3 CalculatorAddArgs_args3.Num1 = num1_args3.Num2 = num2var _result5 CalculatorAddResultvar _meta4 thrift.ResponseMeta_meta4, _err = p.Client_().Call(ctx, "add", &_args3, &_result5)p.SetLastResponseMeta_(_meta4)if _err != nil {return}return _result5.GetSuccess(), nil
}

这里的CalculatorAddArgs，CalculatorAddResult和ResponseMeta都如上所示，然后也是调用的Call方法。之所以要传入add是因为在server那边根据方法名称去获取不同的的handler，所以method名称是add。然后就是获取结果，然后调用CalculatorAddResult 中的success的成员，当然这里就是int32。

到这里基本上就说完了，当然这还远远不够，因为接下来需要说一下thrift中不同的proto对于TProtocol的具体实现。