Re: proxy.config.http.no_dns_just_forward_to_parent but still DNS lookups?

[Theo Hoogerheide <th...@h2b.nl>]

Hi John,

Thanks for your reply.

I have done some testing.
When I adjust remap.conf to remap the URL’s to a destination not configured in the parent.config, I receive a 'HTTP/1.1 502 Next Hop Connection Failed’, and no DNS-queries are seen on the wire.
Disabling proxy.config.http.no_dns_just_forward_to_parent, with the adjusted remap.config entires, does show the adjusted DNS-entries.
So it seems the stuff in parent.config (dest_host) like you mentioned is responsible for the DNS query. 

This behaviour definitely changed, since 5.x and at leat up to version 6.2 the configuration I emailed earlier works without any DNS lookup.

We use the parent.config to load-balance between different origins and I do not see any other way to configure this in ATS.
If this is the intended behaviour, how can I then remap a url, and select a parent that needs to be used, without doing any DNS lookups?

-- 
Kind regards,

Theo Hoogerheide
Lead Infrastructure Architect

> On 12 Dec 2018, at 01:26, John Rushford <jj...@gmail.com> wrote:
> 
> Hi Theo,
> 
> I don’t see that ATS is doing DNS lookups on the parents.  Your showing that ATS is doing DNS lookups on
> the remapped origin hostname, aka dest_host.  I think that it has always done so and the origin hostname should be resolvable
> 
> John
> 
>> On Dec 11, 2018, at 10:23 AM, Theo Hoogerheide <th...@h2b.nl> wrote:
>> 
>> Hello List,
>> 
>> I’m having difficulties to configure ATS to *not* do any DNS lookups for parents.
>> 
>> Relevant configuration:
>> 
>> ** records.conf:
>> CONFIG proxy.config.http.parent_proxy_routing_enable INT 1
>> CONFIG proxy.config.admin.user_id STRING trafficserver
>> CONFIG proxy.config.http.no_dns_just_forward_to_parent INT 1
>> 
>> ** parent.conf
>> dest_host=liveshieldgroup001 method=GET parent=“1.1.1.1:80;" round_robin=consistent_hash qstring=ignore
>> dest_host=vodshieldgroup001 method=GET parent=“1.1.1.1:80;" round_robin=consistent_hash qstring=ignore
>> 
>> ** remap.conf
>> map http://trafficserver_ram/ http://liveshieldgroup001/
>> map http://trafficserver_disk/ http://vodshieldgroup001/
>> 
>> If I do a GET-request, it fails in a “502 Server not found”:
>> 
>> T 127.0.0.1:39062 -> 127.0.0.1:8080 [AP] #24
>> GET /test HTTP/1.1.
>> Host: trafficserver_ram.
>> X-Real-IP: 2.2.2.2.
>> X-Forwarded-For: 2.2.2.2.
>> Connection: upgrade.
>> Accept: */*.
>> .
>> 
>> T 127.0.0.1:8080 -> 127.0.0.1:39062 [AP] #26
>> HTTP/1.1 502 Cannot find server..
>> Date: Tue, 11 Dec 2018 17:18:18 GMT.
>> Connection: keep-alive.
>> Server: ATS/7.1.2.
>> Cache-Control: no-store.
>> Content-Type: text/html.
>> Content-Language: en.
>> Content-Length: 2.
>> .
>> 
>> During this request I *do* see ATS doing DNS requests:
>>   1 0.000000000 x.x.x.x → 8.8.8.8      DNS 78 Standard query 0x6a81 AAAA liveshieldgroup001
>>   2 0.005837695      8.8.8.8 → x.x.x.x DNS 153 Standard query response 0x6a81 No such name AAAA liveshieldgroup001 SOA a.root-servers.net
>>   3 0.005899611 x.x.x.x → 8.8.8.8      DNS 78 Standard query 0xf4f3 AAAA liveshieldgroup001
>>   4 0.011621809      8.8.8.8 → x.x.x.x DNS 153 Standard query response 0xf4f3 No such name AAAA liveshieldgroup001 SOA a.root-servers.net
>> 
>> I have checked with "traffic_ctl config diff” and see only the entries above as non-standard.
>> Software used is the stock ATS from Ubuntu 18.04: trafficserver 7.1.2+ds-3
>> 
>> Am I hitting a bug, or missing something obvious?
>> Thanks for any replies.
>> 
>> -- 
>> Met vriendelijke groet,
>> 
>> Theo Hoogerheide
>> Lead Infrastructure Architect
>> 
>