beego框架post参数默认长度限制64M

背景

使用beego做的一个http服务一个接口，接收logstash推送过来的日志数据，对日志进行报警和统计处理，一直稳定运行。但是最近开始该服务的日志显示经常收到logstash推送日志的请求，但是处理的日志数量为0条并且处理时间明显比正常的请求时间长（正常30ms以内，异常请求都是500ms以上）。正常情况下logstash会打包推送日志，也就是说根据需要推送的日志量不同一个http请求中包含1-1000条不等的日志。所以上面的情况就很不正常。

由下面这个连接（https://github.com/astaxie/beego/issues/2739）中提问的启发仔细看了一下相关源码

	// router.go 709行
	if r.Method != http.MethodGet && r.Method != http.MethodHead {
		if BConfig.CopyRequestBody && !context.Input.IsUpload() {
			context.Input.CopyBody(BConfig.MaxMemory)
		}
		context.Input.ParseFormOrMulitForm(BConfig.MaxMemory)
	}

// input.go 353行
// CopyBody returns the raw request body data as bytes.
func (input *BeegoInput) CopyBody(MaxMemory int64) []byte {
	if input.Context.Request.Body == nil {
		return []byte{}
	}

	var requestbody []byte
	safe := &io.LimitedReader{R: input.Context.Request.Body, N: MaxMemory}
	if input.Header("Content-Encoding") == "gzip" {
		reader, err := gzip.NewReader(safe)
		if err != nil {
			return nil
		}
		requestbody, _ = ioutil.ReadAll(reader)
	} else {
		requestbody, _ = ioutil.ReadAll(safe)
	}

	input.Context.Request.Body.Close()
	bf := bytes.NewBuffer(requestbody)
	input.Context.Request.Body = http.MaxBytesReader(input.Context.ResponseWriter, ioutil.NopCloser(bf), MaxMemory)
	input.RequestBody = requestbody
	return requestbody
}

// config.go 207行
func newBConfig() *Config {
	return &Config{
		AppName:             "beego",
		RunMode:             PROD,
		RouterCaseSensitive: true,
		ServerName:          "beegoServer:" + VERSION,
		RecoverPanic:        true,
		RecoverFunc:         recoverPanic,
		CopyRequestBody:     false,
		EnableGzip:          false,
		MaxMemory:           1 << 26, //64MB
		EnableErrorsShow:    true,
		EnableErrorsRender:  true,
		Listen: Listen{
			Graceful:      false,
			ServerTimeOut: 0,
			ListenTCP4:    false,
			EnableHTTP:    true,
			AutoTLS:       false,
			Domains:       []string{},
			TLSCacheDir:   ".",
			HTTPAddr:      "",
			HTTPPort:      8080,
			EnableHTTPS:   false,
			HTTPSAddr:     "",
			HTTPSPort:     10443,
			HTTPSCertFile: "",
			HTTPSKeyFile:  "",
			EnableAdmin:   false,
			AdminAddr:     "",
			AdminPort:     8088,
			EnableFcgi:    false,
			EnableStdIo:   false,
		},
		WebConfig: WebConfig{
			AutoRender:             true,
			EnableDocs:             false,
			FlashName:              "BEEGO_FLASH",
			FlashSeparator:         "BEEGOFLASH",
			DirectoryIndex:         false,
			StaticDir:              map[string]string{"/static": "static"},
			StaticExtensionsToGzip: []string{".css", ".js"},
			TemplateLeft:           "{{",
			TemplateRight:          "}}",
			ViewsPath:              "views",
			EnableXSRF:             false,
			XSRFKey:                "beegoxsrf",
			XSRFExpire:             0,
			Session: SessionConfig{
				SessionOn:                    false,
				SessionProvider:              "memory",
				SessionName:                  "beegosessionID",
				SessionGCMaxLifetime:         3600,
				SessionProviderConfig:        "",
				SessionDisableHTTPOnly:       false,
				SessionCookieLifeTime:        0, //set cookie default is the browser life
				SessionAutoSetCookie:         true,
				SessionDomain:                "",
				SessionEnableSidInHTTPHeader: false, // enable store/get the sessionId into/from http headers
				SessionNameInHTTPHeader:      "Beegosessionid",
				SessionEnableSidInURLQuery:   false, // enable get the sessionId from Url Query params
			},
		},
		Log: LogConfig{
			AccessLogs:       false,
			EnableStaticLogs: false,
			AccessLogsFormat: "APACHE_FORMAT",
			FileLineNum:      true,
			Outputs:          map[string]string{"console": ""},
		},
	}
}

结论

beego框架如果没有配置MaxMemory，那么post参数默认长度限制就是64M。
并且参数长度超过64M时框架没有任何报错，只是Ctx.Input.RequestBody或者Context.Request.Body里拿不到全部的参数（长度超出的部分被丢弃），后续的json操作也会失败。

参考

• https://github.com/astaxie/beego/issues/2739