current RPS is not accurate

[debugtalk]

Describe the bug

When running in standalone mode, the ConsoleOutput will print each (method, name) group's current RPS. And I found that the data is not accurate. The report interval is 3s, the requests number of get with params is 20, the rps should be 20/3=6.67, which is much bigger than the actual 5.

Current time: 2021/12/01 12:06:26, Users: 10, Total RPS: 15, Total Fail Ratio: 0.0%
+--------------+-----------------+------------+---------+--------+---------+-----+------+--------------+------------+-------------+
|     TYPE     |      NAME       | # REQUESTS | # FAILS | MEDIAN | AVERAGE | MIN | MAX  | CONTENT SIZE | # REQS/SEC | # FAILS/SEC |
+--------------+-----------------+------------+---------+--------+---------+-----+------+--------------+------------+-------------+
| request-GET  | get with params |         20 |       0 |    970 |  977.15 | 954 | 1089 |          300 |          5 |           0 |
| request-POST | post json data  |         20 |       0 |    250 |  244.70 | 238 |  251 |          420 |          5 |           0 |
| request-POST | post form data  |         20 |       0 |    250 |  245.20 | 240 |  253 |          441 |          5 |           0 |
+--------------+-----------------+------------+---------+--------+---------+-----+------+--------------+------------+-------------+

This issue maybe resulted from the algorithm of calculating current rps. As the keys of numReqsPerSecond is timestamps, while mostly the interval may span 4 seconds, e.g. starts from 0.5s and ends at 3.5s.

func getCurrentRps(numRequests int64, numReqsPerSecond map[int64]int64) (currentRps int64) {
	currentRps = int64(0)
	numReqsPerSecondLength := int64(len(numReqsPerSecond))
	if numReqsPerSecondLength != 0 {
		currentRps = numRequests / numReqsPerSecondLength
	}
	return currentRps
}

[orange]

看起来可以把 slaveReportInterval 传给 output ，用于计算 CurrentRps 。不知是否可以提pr

[myzhan]

@MyNextWeekend 不太清楚你要怎么实现，可以先提 PR 看看。