Strange issue with probes

[Luca Gervasi]

Hi,
i have a strange issue where varnish suddenly stops sending probes thus
declaring a backend healthy or sick till a next restart and i'm unable to
determine why. Please note that my backend is able to receive my probes
(and actually receives it), and i'm able to get a response every time i go
with a curl -H "Host: healthcheck" 10.32.161.89/balance_me, so i'll
consider my backend ultimately "good" and "able to respond".

Thanks a lot for every hint!
Luca

This is my backend configuration:

probe backend_check {
  .request =  "GET /balance_me HTTP/1.1"
  "Host: healthcheck"
  "Connection: close";
  .timeout = 1s;
  .interval = 2s;
  .window = 5;
  .threshold = 2;
}
backend othaph {
    .host = "10.32.161.89";
    .port = "80";
    .connect_timeout = 1s;
    .first_byte_timeout    = 20s;
    .between_bytes_timeout = 20s;
    .probe = backend_check;
}

This is my "varnishadm backend.list"
boot.othaph                    probe      Healthy 3/5

This is the total log of 20 minutes of  "varnishlog -g raw -i
Backend_health" (please note that above it shows 3/5 while i have only 2
probes sent, apparently)
         0 Backend_health - boot.othaph Back healthy 4--X-RH 2 2 5 0.067021
0.033510 HTTP/1.1 200 OK
         0 Backend_health - boot.othaph Still healthy 4--X-RH 3 2 5
0.015176 0.027399 HTTP/1.1 200 OK

And this is my "varnishadm backend.list -p"
Backend name                   Admin      Probe
boot.othaph                    probe      Healthy 3/5
  Current states  good:  3 threshold:  2 window:  5
  Average response time of good probes: 0.027399
  Oldest ================================================== Newest
  --------------------------------------------------------------44 Good IPv4
  --------------------------------------------------------------XX Good Xmit
  --------------------------------------------------------------RR Good Recv
  -------------------------------------------------------------HHH Happy
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