dnsdist: exclude TO's from average latency in showResponseLatency()

[bjoe2k4]

• Program: dnsdist
• Issue type: Bug report

Short description

Apparently T.O queries are assigned a latency of ~4200000ms (max unsigned 32bit integer in µseconds) in the ringbuffer. The same ringbuffer is used to compute the average latency in showResponseLatency(). As suggested by @rgacogne these T.O's should be excluded when calculating the average latency.

Environment

• Operating system: Arch Linux
• Software version: latest git
• Software source: Arch AUR

Steps to reproduce

1. setup dnsdist and simulate a timeout
2. look at statistics in dnsdist console by executing showResponseLatency()

Expected behaviour

The timeout not affecting the average latency.

Actual behaviour

Statistics with 19 successful and one TO query.

showServers()
#   Name                 Address                       State     Qps    Qlim Ord Wt    Queries   Drops Drate   Lat Outstanding Pools
0                        127.0.0.1:8443                   up     0.0       0   1  1         20       1   0.0   4.3           0
All                                                              0.0                        20       1
showResponseLatency()
Average response latency: 214777.80 msec
   msec
   0.10
   0.20
   0.40
   0.80
   1.60
   3.20
   6.40
  12.80
  25.60
  51.20 **********************************************************************
 102.40
 204.80
 409.60
 819.20
1638.40