Mailing List Archive

varnish health probe errors
Hello all,

a successful health probe will log this flags `4--X-RH` and from the
documentation the flags are:
4 -- IPv4 connection established
X -- Request transmit succeeded
R -- Read response succeeded
H -- Happy with the result

The issue I'm facing is that sometimes the health probe returns the flags
`4--X---` marking the backend as sick.

Can someone please explain to me when a varnish health probe will not log
an `R` (Read response succeeded)? Is this related to the health probe's
timeout value? Does this mean that the TCP connection failed before the
backend sent the response? The backend doesn't even log the request in its
access log, so from my understanding, the backend never received that
request, however, varnish says the request was successfully transmitted
(the `X` flag).

Thank you for your time.

--
Giannis
Re: varnish health probe errors [ In reply to ]
Hi,

I think you got everything right: on the Varnish side, the connection was
established (4) and successfully transmitted (X), we just never received a
response, so yes, this has to do with timing out, most probably.

--
Guillaume Quintard


On Thu, Aug 29, 2019 at 12:34 AM Giannis Zach <i.zachari@gmail.com> wrote:

> Hello all,
>
> a successful health probe will log this flags `4--X-RH` and from the
> documentation the flags are:
> 4 -- IPv4 connection established
> X -- Request transmit succeeded
> R -- Read response succeeded
> H -- Happy with the result
>
> The issue I'm facing is that sometimes the health probe returns the flags
> `4--X---` marking the backend as sick.
>
> Can someone please explain to me when a varnish health probe will not log
> an `R` (Read response succeeded)? Is this related to the health probe's
> timeout value? Does this mean that the TCP connection failed before the
> backend sent the response? The backend doesn't even log the request in its
> access log, so from my understanding, the backend never received that
> request, however, varnish says the request was successfully transmitted
> (the `X` flag).
>
> Thank you for your time.
>
> --
> Giannis
> _______________________________________________
> varnish-misc mailing list
> varnish-misc@varnish-cache.org
> https://www.varnish-cache.org/lists/mailman/listinfo/varnish-misc
>
Re: varnish health probe errors [ In reply to ]
Hi,

to avoid a common pitfall, if you use .request, remember to add "Connection: close"


_______________________________________________
varnish-misc mailing list
varnish-misc@varnish-cache.org
https://www.varnish-cache.org/lists/mailman/listinfo/varnish-misc
Re: varnish health probe errors [ In reply to ]
Thank you Guillaume for the confirmation, I've done some tests by
increasing the timeout and the failed health probes were decreased,
unfortunately, I've had to increase the timeout to 15 seconds which makes
me think that something is wrong with the network.

--
Giannis

On Thu, 29 Aug 2019 at 17:17, Guillaume Quintard <
guillaume@varnish-software.com> wrote:

> Hi,
>
> I think you got everything right: on the Varnish side, the connection was
> established (4) and successfully transmitted (X), we just never received a
> response, so yes, this has to do with timing out, most probably.
>
> --
> Guillaume Quintard
>
>
> On Thu, Aug 29, 2019 at 12:34 AM Giannis Zach <i.zachari@gmail.com> wrote:
>
>> Hello all,
>>
>> a successful health probe will log this flags `4--X-RH` and from the
>> documentation the flags are:
>> 4 -- IPv4 connection established
>> X -- Request transmit succeeded
>> R -- Read response succeeded
>> H -- Happy with the result
>>
>> The issue I'm facing is that sometimes the health probe returns the flags
>> `4--X---` marking the backend as sick.
>>
>> Can someone please explain to me when a varnish health probe will not log
>> an `R` (Read response succeeded)? Is this related to the health probe's
>> timeout value? Does this mean that the TCP connection failed before the
>> backend sent the response? The backend doesn't even log the request in its
>> access log, so from my understanding, the backend never received that
>> request, however, varnish says the request was successfully transmitted
>> (the `X` flag).
>>
>> Thank you for your time.
>>
>> --
>> Giannis
>> _______________________________________________
>> varnish-misc mailing list
>> varnish-misc@varnish-cache.org
>> https://www.varnish-cache.org/lists/mailman/listinfo/varnish-misc
>>
>

--
Giannis Zachariadis