Strange issue with probes

[Håvard Alsaker Futsæter]

Hi! I have a problem with backend probes not beeing sent, that seems very
similar to what Luca Gervasi has reported(see below).
Luca: Did you ever figure out a fix?

I run varnish version 5.1.3-1~xenial on ubuntu/xenial with
kernel  4.4.0-109-generic.

The behaviour I see is that I start up varnish, varnish sends one backend
probe for each backend, bringing them up to Healthy status. After that, it
seems like there are no more backend probes sent.

The backend replies correctly when I use curl, and anyway there is not
indication that a probe fails. They are simply not sent in the first place,
as far as I can tell.

Here is an example of my backend configuration:
    .host = "foo1";
    .port = "8080";
    .connect_timeout = 0.4s;
    .first_byte_timeout = 12s;
    .between_bytes_timeout = 1s;
    .max_connections = 40;
    .probe = {
        .url        = "/healthcheck";
        .timeout    = 1s;
        .interval   = 6s;
        .window     = 5;
        .threshold  = 3;
     }
}

My backend.list looks like this:
boot.foo1          probe      Healthy             4/5 Fri, 12 Jan 2018
08:50:38 GMT
boot.foo2          probe      Healthy             4/5 Fri, 12 Jan 2018
08:50:38 GMT

and here is an extract from backend.list -p:
boot.foo1           probe      Healthy             4/5
  Current states  good:  4 threshold:  3 window:  5
  Average response time of good probes: 0.002105
  Oldest ================================================== Newest
  --------------------------------------------------------------44 Good IPv4
  --------------------------------------------------------------XX Good Xmit
  --------------------------------------------------------------RR Good Recv
  ------------------------------------------------------------HHHH Happy


And running "varnishlog -g raw -i Backend_health" gives me no results back.

I also tested the exact same config on 5.2,1~xenial, but I get the same
problem there.

I don't really understand what is going on here, or how I should proceed.
Any help would be greatly appreciated!

Best regards,
Håvard Futsæter


2017-10-19 8:44 GMT+02:00 Luca Gervasi <luca.gervasi at gmail.com>:

> 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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>
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