varnish health probe errors

Guillaume Quintard guillaume at
Thu Aug 29 14:16:59 UTC 2019


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 at> 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
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> varnish-misc mailing list
> varnish-misc at
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