聊聊dubbo-go的DubboInvoker

序

本文主要研究一下dubbo-go的DubboInvoker

Invoker

dubbo-go-v1.4.2/protocol/invoker.go

// Extension - Invoker
type Invoker interface {
    common.Node
    Invoke(context.Context, Invocation) Result
}

/////////////////////////////
// base invoker
/////////////////////////////

// BaseInvoker ...
type BaseInvoker struct {
    url       common.URL
    available bool
    destroyed bool
}

// NewBaseInvoker ...
func NewBaseInvoker(url common.URL) *BaseInvoker {
    return &BaseInvoker{
        url:       url,
        available: true,
        destroyed: false,
    }
}

// GetUrl ...
func (bi *BaseInvoker) GetUrl() common.URL {
    return bi.url
}

// IsAvailable ...
func (bi *BaseInvoker) IsAvailable() bool {
    return bi.available
}

// IsDestroyed ...
func (bi *BaseInvoker) IsDestroyed() bool {
    return bi.destroyed
}

// Invoke ...
func (bi *BaseInvoker) Invoke(context context.Context, invocation Invocation) Result {
    return &RPCResult{}
}

// Destroy ...
func (bi *BaseInvoker) Destroy() {
    logger.Infof("Destroy invoker: %s", bi.GetUrl().String())
    bi.destroyed = true
    bi.available = false
}

• Invoker定义了Invoke方法；BaseInvoker定义了url、available、destroyed属性；NewBaseInvoker方法实例化了BaseInvoker，其available为true，destroyed为false；Destroy方法设置available为false，destroyed为true

DubboInvoker

dubbo-go-v1.4.2/protocol/dubbo/dubbo_invoker.go

var (
    // ErrNoReply ...
    ErrNoReply          = perrors.New("request need @response")
    ErrDestroyedInvoker = perrors.New("request Destroyed invoker")
)

var (
    attachmentKey = []string{constant.INTERFACE_KEY, constant.GROUP_KEY, constant.TOKEN_KEY, constant.TIMEOUT_KEY}
)

// DubboInvoker ...
type DubboInvoker struct {
    protocol.BaseInvoker
    client   *Client
    quitOnce sync.Once
    // Used to record the number of requests. -1 represent this DubboInvoker is destroyed
    reqNum int64
}

• DubboInvoker定义了client、quitOnce、reqNum属性

NewDubboInvoker

dubbo-go-v1.4.2/protocol/dubbo/dubbo_invoker.go

// NewDubboInvoker ...
func NewDubboInvoker(url common.URL, client *Client) *DubboInvoker {
    return &DubboInvoker{
        BaseInvoker: *protocol.NewBaseInvoker(url),
        client:      client,
        reqNum:      0,
    }
}

• NewDubboInvoker方法实例化DubboInvoker

Invoke

dubbo-go-v1.4.2/protocol/dubbo/dubbo_invoker.go

// Invoke ...
func (di *DubboInvoker) Invoke(ctx context.Context, invocation protocol.Invocation) protocol.Result {
    var (
        err    error
        result protocol.RPCResult
    )
    if di.reqNum < 0 {
        // Generally, the case will not happen, because the invoker has been removed
        // from the invoker list before destroy,so no new request will enter the destroyed invoker
        logger.Warnf("this dubboInvoker is destroyed")
        result.Err = ErrDestroyedInvoker
        return &result
    }
    atomic.AddInt64(&(di.reqNum), 1)
    defer atomic.AddInt64(&(di.reqNum), -1)

    inv := invocation.(*invocation_impl.RPCInvocation)
    for _, k := range attachmentKey {
        if v := di.GetUrl().GetParam(k, ""); len(v) > 0 {
            inv.SetAttachments(k, v)
        }
    }

    // put the ctx into attachment
    di.appendCtx(ctx, inv)

    url := di.GetUrl()
    // async
    async, err := strconv.ParseBool(inv.AttachmentsByKey(constant.ASYNC_KEY, "false"))
    if err != nil {
        logger.Errorf("ParseBool - error: %v", err)
        async = false
    }
    response := NewResponse(inv.Reply(), nil)
    if async {
        if callBack, ok := inv.CallBack().(func(response common.CallbackResponse)); ok {
            result.Err = di.client.AsyncCall(NewRequest(url.Location, url, inv.MethodName(), inv.Arguments(), inv.Attachments()), callBack, response)
        } else {
            result.Err = di.client.CallOneway(NewRequest(url.Location, url, inv.MethodName(), inv.Arguments(), inv.Attachments()))
        }
    } else {
        if inv.Reply() == nil {
            result.Err = ErrNoReply
        } else {
            result.Err = di.client.Call(NewRequest(url.Location, url, inv.MethodName(), inv.Arguments(), inv.Attachments()), response)
        }
    }
    if result.Err == nil {
        result.Rest = inv.Reply()
        result.Attrs = response.atta
    }
    logger.Debugf("result.Err: %v, result.Rest: %v", result.Err, result.Rest)

    return &result
}

• Invoke方法先通过atomic.AddInt64递增reqNum，之后遍历attachmentKey设置到invocation；之后读取constant.ASYNC_KEY属性，若async为true，则执行di.client.AsyncCall或di.client.CallOneway；若async为false则执行di.client.Call；最后返回result

Destroy

dubbo-go-v1.4.2/protocol/dubbo/dubbo_invoker.go

// Destroy ...
func (di *DubboInvoker) Destroy() {
    di.quitOnce.Do(func() {
        for {
            if di.reqNum == 0 {
                di.reqNum = -1
                logger.Infof("dubboInvoker is destroyed,url:{%s}", di.GetUrl().Key())
                di.BaseInvoker.Destroy()
                if di.client != nil {
                    di.client.Close()
                    di.client = nil
                }
                break
            }
            logger.Warnf("DubboInvoker is to be destroyed, wait {%v} req end,url:{%s}", di.reqNum, di.GetUrl().Key())
            time.Sleep(1 * time.Second)
        }

    })
}

• Destroy方法在di.reqNum为0时执行di.BaseInvoker.Destroy()及di.client.Close()

小结

Invoker定义了Invoke方法；BaseInvoker定义了url、available、destroyed属性；NewBaseInvoker方法实例化了BaseInvoker，其available为true，destroyed为false；Destroy方法设置available为false，destroyed为true；DubboInvoker的Invoke方法先通过atomic.AddInt64递增reqNum，之后遍历attachmentKey设置到invocation；之后读取constant.ASYNC_KEY属性，若async为true，则执行di.client.AsyncCall或di.client.CallOneway；若async为false则执行di.client.Call；最后返回result

doc

• dubbo_invoker