Context Copy Problem getting data.

[JomperBytes]

• go version: 1.12

Description

Using FetRawData from an copied context delete the original context body

func RequestLogger() gin.HandlerFunc {

	return func(c *gin.Context) {

		c.Set("HostIP", c.ClientIP())
		cCp := c.Copy()

		go func() {
			logger := cCp.MustGet("logger").(utils.LogDataInterface)
			internalCode := msgmanager.CreateInternalCode(severities.INFO, services.PDF, sources.SAMESERVICE, operations.NA, entities.NA)

			if cCp.Request.Method == "POST" {
				data, _ := cCp.GetRawData()
				logger.LogData(0, cCp, "Request using POST Method", gelf.LOG_INFO, data, internalCode, nil)
			} else {
				logger.LogData(0, cCp, "Request using GET Method, look at URL for data", gelf.LOG_INFO, nil, internalCode, nil)
			}
		}()

		c.Next()
	}
}

data, _ := cCp.GetRawData() This line sometimes delete "c" body.

This happen just like in 10% of calls.

Changing GetRawData for ShouldBindBodyWith fix the problem.

func RequestLogger() gin.HandlerFunc {

	return func(c *gin.Context) {

		c.Set("HostIP", c.ClientIP())
		cCp := c.Copy()

		go func() {
			logger := cCp.MustGet("logger").(utils.LogDataInterface)
			internalCode := msgmanager.CreateInternalCode(severities.INFO, services.PDF, sources.SAMESERVICE, operations.NA, entities.NA)

			if cCp.Request.Method == "POST" {
				var data interface{}
				_ = cCp.ShouldBindBodyWith(&data, binding.JSON)
				logger.LogData(0, cCp, "Request using POST Method", gelf.LOG_INFO, data, internalCode, nil)
			} else {
				logger.LogData(0, cCp, "Request using GET Method, look at URL for data", gelf.LOG_INFO, nil, internalCode, nil)
			}
		}()

		c.Next()
	}
}

Screenshots

[dmarkham]

So I have not yet tried to reproduce this. But I have some ideas.

In short once someone reads c.Request.Body it is drained and empty, GetRawData in this case is racing for the data with other parts of the system your other middleware/handler or gin internals to read and close c.Request.Body

ShouldBindBodyWith is set up to be called more than once and saves a copy of the c.Request.Body. I'm not yet sure how it's fixing your issue, but as you report it is.

Guess in general rule for something that reads c.Request.Body means you have taken ownership of that data and need to be responsible for moving it to your next needed middleware or handlerFunc.

I'm not sure to many reasonable ways around this. when I get some time unless someone else does... I'll try to dig in at least enough to know for sure why.