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From: David Carlin <dcarlin@oath.com>
Date: Thu, 23 Nov 2017 10:52:20 -0500
Message-ID: <CAJVuqmEmh6r1F6+HAEpwmus7gcm3P0W8kSazR=AFtV6aqtCF+w@mail.gmail.com>
Subject: Re: Avoiding TCP_REFRESH_HIT
To: users@trafficserver.apache.org
Content-Type: multipart/alternative; boundary="f403045c117cea0bbc055ea86b71"
archived-at: Thu, 23 Nov 2017 15:52:28 -0000

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Have you considered adding "Cache-Control: Immutable" to these objects
which will never require re-validation?  This will prevent the browser from
attempting an If-Modified-Since request.

https://hacks.mozilla.org/2017/01/using-immutable-caching-to-speed-up-the-web/

David

On Thu, Nov 23, 2017 at 10:07 AM, Veiko Kukk <veiko.kukk@gmail.com> wrote:

> In addition to my previous e-mail, headers that are provided by source to
> ATS:
>
> < HTTP/1.1 200 OK
> < Content-Length: 1185954
> < Accept-Ranges: bytes
> < Last-Modified: Mon, 02 Nov 2015 17:56:12 GMT
> < Etag: 92ef40097ba87bdf09efcf7e1cefd32a
> < X-Timestamp: 1446486971.39466
> < Content-Type: application/octet-stream
> < Content-Disposition: attachment; filename="ABIYohNyPrJNjvFsAdgN5wc8D-8Yo4ZO.m4s";
> filename*=UTF-8''ABIYohNyPrJNjvFsAdgN5wc8D-8Yo4ZO.m4s
> < Expires: Thu, 23 Nov 2017 15:27:30 GMT
> < X-Trans-Id: tx3a0af5473d5c41d38195c-005a16e30d
> < X-Openstack-Request-Id: tx3a0af5473d5c41d38195c-005a16e30d
> < Date: Thu, 23 Nov 2017 15:02:37 GMT
> < X-IPLB-Instance: 12631
>
> I assume, Expires header is here to blame and must be overriden in ATS
> config, but how? I don't have control over source, its Openstack Swift
> object storage.
>
> Veiko
>
>
> 2017-11-23 16:35 GMT+02:00 Veiko Kukk <veiko.kukk@gmail.com>:
>
>> Hi,
>>
>> Could ATS in reverse proxy mode be configured such way that it would
>> never try to revalidate from source? It is known that in our case, object
>> never changes (and is never refetched from source) and it is desirable to
>> avoid any source validation. Validation verification adds significant
>> overhead and we need to avoid it. Response to client with TCP_REFRESH_HIT
>> would take 100-200ms instead of 0-10 in case of direct local TCP_HIT.
>>
>> I've configured following:
>> dest_domain=.*.source.tld action=ignore-no-cache
>> dest_domain=.*.source.tld revalidate=9999d
>> dest_domain=.*.source.tld ttl-in-cache=9999d
>>
>> CONFIG proxy.config.http.cache.when_to_revalidate INT 3
>> CONFIG proxy.config.http.cache.required_headers INT 0
>>
>> But i still get TCP_REFRESH_HIT even when 9999 days have not passed
>> (obviously).
>>
>> NB! ATS is used as internal cache and our 'client' never explicitly
>> requests revalidation.
>>
>> Thanks,
>> Veiko
>>
>>
>

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Content-Transfer-Encoding: quoted-printable

<div dir=3D"ltr"><div>Have you considered adding &quot;Cache-Control: Immut=
able&quot; to these objects which will never require re-validation?=C2=A0 T=
his will prevent the browser from attempting an If-Modified-Since request. =
<br></div><div><br></div><div><a href=3D"https://hacks.mozilla.org/2017/01/=
using-immutable-caching-to-speed-up-the-web/">https://hacks.mozilla.org/201=
7/01/using-immutable-caching-to-speed-up-the-web/</a></div><div><br></div><=
div>David<br></div></div><div class=3D"gmail_extra"><br><div class=3D"gmail=
_quote">On Thu, Nov 23, 2017 at 10:07 AM, Veiko Kukk <span dir=3D"ltr">&lt;=
<a href=3D"mailto:veiko.kukk@gmail.com" target=3D"_blank">veiko.kukk@gmail.=
com</a>&gt;</span> wrote:<br><blockquote class=3D"gmail_quote" style=3D"mar=
gin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir=3D"ltr=
">In addition to my previous e-mail, headers that are provided by source to=
 ATS:<div><br><div><div>&lt; HTTP/1.1 200 OK</div><div>&lt; Content-Length:=
 1185954</div><div>&lt; Accept-Ranges: bytes</div><div>&lt; Last-Modified: =
Mon, 02 Nov 2015 17:56:12 GMT</div><div>&lt; Etag: 92ef40097ba87bdf09efcf7e=
1cefd3<wbr>2a</div><div>&lt; X-Timestamp: 1446486971.39466</div><div>&lt; C=
ontent-Type: application/octet-stream</div><div>&lt; Content-Disposition: a=
ttachment; filename=3D&quot;<wbr>ABIYohNyPrJNjvFsAdgN5wc8D-<wbr>8Yo4ZO.m4s&=
quot;; filename*=3DUTF-8&#39;&#39;<wbr>ABIYohNyPrJNjvFsAdgN5wc8D-<wbr>8Yo4Z=
O.m4s</div><div>&lt; Expires: Thu, 23 Nov 2017 15:27:30 GMT</div><div>&lt; =
X-Trans-Id: tx3a0af5473d5c41d38195c-<wbr>005a16e30d</div><div>&lt; X-Openst=
ack-Request-Id: tx3a0af5473d5c41d38195c-<wbr>005a16e30d</div><div>&lt; Date=
: Thu, 23 Nov 2017 15:02:37 GMT</div><div>&lt; X-IPLB-Instance: 12631</div>=
</div></div><div><br></div><div>I assume, Expires header is here to blame a=
nd must be overriden in ATS config, but how? I don&#39;t have control over =
source, its Openstack Swift object storage.</div><div><br></div><div>Veiko<=
/div><div><br></div></div><div class=3D"gmail_extra"><br><div class=3D"gmai=
l_quote">2017-11-23 16:35 GMT+02:00 Veiko Kukk <span dir=3D"ltr">&lt;<a hre=
f=3D"mailto:veiko.kukk@gmail.com" target=3D"_blank">veiko.kukk@gmail.com</a=
>&gt;</span>:<br><blockquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8=
ex;border-left:1px #ccc solid;padding-left:1ex"><div dir=3D"ltr">Hi,<div><b=
r></div><div>Could ATS in reverse proxy mode be configured such way that it=
 would never try to revalidate from source? It is known that in our case, o=
bject never changes (and is never refetched from source) and it is desirabl=
e to avoid any source validation. Validation verification adds significant =
overhead and we need to avoid it. Response to client with TCP_REFRESH_HIT w=
ould take 100-200ms instead of 0-10 in case of direct local TCP_HIT.</div><=
div><br></div><div>I&#39;ve configured following:</div><div><div>dest_domai=
n=3D.*.source.tld action=3Dignore-no-cache</div><div>dest_domain=3D.*.sourc=
e.tld revalidate=3D9999d</div><div>dest_domain=3D.*.source.tld ttl-in-cache=
=3D9999d</div></div><div><br></div><div>CONFIG proxy.config.http.cache.when=
_t<wbr>o_revalidate INT 3<br></div><div>CONFIG proxy.config.http.cache.requ=
ir<wbr>ed_headers INT 0<br></div><div><br></div><div>But i still get TCP_RE=
FRESH_HIT even when 9999 days have not passed (obviously).</div><div><br></=
div><div>NB! ATS is used as internal cache and our &#39;client&#39; never e=
xplicitly requests revalidation.</div><div><br></div><div>Thanks,</div><div=
>Veiko</div><div><br></div></div>
</blockquote></div><br></div>
</blockquote></div><br></div>

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