Re: [squid-users] Debuging ERR_CONNECT_FAIL with SYSERR=110

On 13/02/2014 1:59 a.m., Pawel Mojski wrote:
> W dniu 2014-02-12 13:54, Kinkie pisze:
>> On Wed, Feb 12, 2014 at 1:49 PM, Pawel Mojski <pawcio_at_pawcio.net> wrote:
>>> W dniu 2014-02-12 13:30, Kinkie pisze:
>>>> On Wed, Feb 12, 2014 at 12:40 PM, Pawel Mojski <pawcio_at_pawcio.net> wrote:
>>>>> Hi All;
>>>>>
>>>>> I have pretty loaded squid server working in interception mode.
>>>>> In about 0.5% of total http request I have an ERR_CONNECT_FAIL with
>>>>> additional error SYSERR=110.
>>>>> How can I debug a reason of those errors?
>>>>>
>>>>> The thing which consider me a lot is the URL and remote server of those
>>>>> requests.
>>>>> For example, I found three same requests for the same URL hosted on the
>>>>> same IP request.
>>>>> The first one finished with response 200, the second with 503 and
>>>>> ERR_CONNECT_FAIL(SYSERR=110) and the third with 200 again.
>>>>>
>>>>> Also, my customers complains that sometimes "they have problems surfing
>>>>> the web".
>>>>>
>>>>> What can I do to debug the problem?
>>>> Hi Pawel,
>>>> SYSERR 110 on Linux is connection timeout (ETIMEOUT).
>>>> It would seem to indicate network issues somewhere, or a severely
>>>> overloaded server (which has used all its syn backlog)
>>>>
>>>>
>>> Hi Kinkie;
>>>
>>> I thought the same, but, I have huge net.core.netdev_max_backlog and
>>> net.ipv4.tcp_max_syn_backlog and there are no network related problems
>>> at all.
>> The error is reported by squid, but the issue is on the origin server, if any.
>>
>>> At the same time when squid reports a problem I can connect manually
>>> from squid box to the same ip address (through telnet, wget, etc) and
>>> nothing wrong occurs.
>>> I even can belive somewhere somekind of timeout happened but how can I
>>> find out what type of timeout it is? syn/ack, wait, whatever?
>> It should be waiting for syn/ack.
> So. Just to clarify.
> From tcp point of view: squid is not able to establish connection with
> origin server. Thats all.
> After sending SYN packet no ACK is reponded. SYSERR=100 cannot means
> that squid was able to connect but no response was returned in some
> period of time. Am I right?

Whether or not that is right the ERR_CONNECT_FAIL is only produced on
SYN errors.

If Squid were able to connect but no HTTP response it would be a
ERR_READ_ERROR, ERR_READ_TIMEOUT or ERR_ZERO_SIZE_OBJECT.

Amos
Received on Wed Feb 12 2014 - 13:11:19 MST