How to configure ATS to support X-Cache-Tags header?

[Vaughan, Wendre]

I have ATS 7.1 setup as a reverse proxy for a Drupal-Managed Website. My Drupal Development Team wants to use a feature called Cache Tags (https://www.drupal.org/docs/8/api/cache-api/cache-tags-varnish ) that is designed specifically for Varnish.

The Drupal system would send a Request with method ‘BAN’ to the ATS servers expecting the ATS servers to read the X-Cache-Tags headers (a list of pages to not cache) and have ATS do the following:


1. Purge the ATS cache of any of the items in the X-Cache-Tags list
2. Dynamically update a list of ‘Never Cache’ to the items in the X-Cache-Tag list.
3. Remove these four headers from origin responses before sending the response to the requestor: X-Url, X-Host, X-Cache-Tags, X-Cache-Contexts (can do this with the headers plugin)

So I have a few questions. Can I setup a method called ‘BAN’ on the ATS servers? I think I can use the headers plugin and possibly a lua script to do the purging and update the cache.config file. If I can get the ‘BAN’ method to be accepted by ATS.

I am pretty new to extending ATS with lua. Any help is appreciated.

Wendre Vaughan
Senior Software Engineer, Operations | Finance & Information Technology | Sound Transit
P: 206.903.7270 | F: 206.398.5223 | e: ***@soundtransit.org<mailto:***@soundtransit.org>

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[Shu Kit Chan]

I think as long as you allowed it in ip_allow.config properly, "BAN" method
works.

I think last time the community discussed about this feature, the
conclusion is that you can probably achieve similar effect with the
regex_revalidate plugin -
https://docs.trafficserver.apache.org/en/latest/admin-guide/plugins/regex_revalidate.en.html
or the purge remap plugin -
https://docs.trafficserver.apache.org/en/latest/admin-guide/plugins/remap_purge.en.html


I think you should be able to implement the mechanism you mentioned using
lua. Although i am not too sure why you want to update cache.config. Since
i thought the "ban" is just to invalidate the cache entry once and not
indefinitely.

Thanks

kit


On Thu, Oct 11, 2018 at 9:35 AM Vaughan, Wendre <

Post by Vaughan, Wendre
I have ATS 7.1 setup as a reverse proxy for a Drupal-Managed Website. My
Drupal Development Team wants to use a feature called Cache Tags (
https://www.drupal.org/docs/8/api/cache-api/cache-tags-varnish ) that is
designed specifically for Varnish.
The Drupal system would send a Request with method ‘BAN’ to the ATS
servers expecting the ATS servers to read the X-Cache-Tags headers (a list
1. Purge the ATS cache of any of the items in the X-Cache-Tags list
2. Dynamically update a list of ‘Never Cache’ to the items in the
X-Cache-Tag list.
3. Remove these four headers from origin responses before sending the
response to the requestor: X-Url, X-Host, X-Cache-Tags, X-Cache-Contexts
(can do this with the headers plugin)
So I have a few questions. Can I setup a method called ‘BAN’ on the ATS
servers? I think I can use the headers plugin and possibly a lua script to
do the purging and update the cache.config file. If I can get the ‘BAN’
method to be accepted by ATS.
I am pretty new to extending ATS with lua. Any help is appreciated.
Wendre Vaughan
Senior Software Engineer, Operations | Finance & Information Technology | Sound Transit
Connect with us
https://www.facebook.com/SoundTransit | https://twitter.com/SoundTransit

[Shu Kit Chan]

I wrote a small prototype lua script here for supporting cache invalidation
through cache tags -

https://github.com/shukitchan/ats_lua_scripts/blob/master/cache_tags.lua

Should be a good starting point.

Kit

Post by Shu Kit Chan
I think as long as you allowed it in ip_allow.config properly, "BAN"
method works.
I think last time the community discussed about this feature, the
conclusion is that you can probably achieve similar effect with the
regex_revalidate plugin -
https://docs.trafficserver.apache.org/en/latest/admin-guide/plugins/regex_revalidate.en.html
or the purge remap plugin -
https://docs.trafficserver.apache.org/en/latest/admin-guide/plugins/remap_purge.en.html
I think you should be able to implement the mechanism you mentioned using
lua. Although i am not too sure why you want to update cache.config. Since
i thought the "ban" is just to invalidate the cache entry once and not
indefinitely.
Thanks
kit
On Thu, Oct 11, 2018 at 9:35 AM Vaughan, Wendre <

Post by Vaughan, Wendre
I have ATS 7.1 setup as a reverse proxy for a Drupal-Managed Website. My
Drupal Development Team wants to use a feature called Cache Tags (
https://www.drupal.org/docs/8/api/cache-api/cache-tags-varnish ) that is
designed specifically for Varnish.
The Drupal system would send a Request with method ‘BAN’ to the ATS
servers expecting the ATS servers to read the X-Cache-Tags headers (a list
1. Purge the ATS cache of any of the items in the X-Cache-Tags list
2. Dynamically update a list of ‘Never Cache’ to the items in the
X-Cache-Tag list.
3. Remove these four headers from origin responses before sending the
response to the requestor: X-Url, X-Host, X-Cache-Tags, X-Cache-Contexts
(can do this with the headers plugin)
So I have a few questions. Can I setup a method called ‘BAN’ on the ATS
servers? I think I can use the headers plugin and possibly a lua script to
do the purging and update the cache.config file. If I can get the ‘BAN’
method to be accepted by ATS.
I am pretty new to extending ATS with lua. Any help is appreciated.
Wendre Vaughan
Senior Software Engineer, Operations | Finance & Information Technology | Sound Transit
Connect with us
https://www.facebook.com/SoundTransit | https://twitter.com/SoundTransit