Thanks for the explanations Amos, much appreciated.
On Thu, 18 Jan 2024 at 16:24, Amos Jeffries <squid3@xxxxxxxxxxxxx> wrote:
On 19/01/24 03:53, Robin Carlisle wrote:
> Hi, Hoping someone can help me with this issue that I have been
> struggling with for days now. I am setting up squid on an ubuntu PC to
> forward HTTPS requests to an API and an s3 bucket under my control on
> amazon AWS. The reason I am setting up the proxy is two-fold...
>
> 1) To reduce costs from AWS.
> 2) To provide content to the client on the ubuntu PC if there is a
> networking issue somewhere in between the ubuntu PC and AWS.
>
> Item 1 is going well so far. Item 2 is not going well. Setup details ...
>
...
>
> When network connectivity is BAD, I get errors and a cache MISS. In
> this test case I unplugged the ethernet cable from the back on the
> ubuntu-pc ...
>
> *# /var/log/squid/access.log*
> 1705588717.420 11 127.0.0.1 NONE_NONE/200 0 CONNECT
> stuff.amazonaws.com:443 <http://stuff.amazonaws.com:443> -
> HIER_DIRECT/3.135.162.228 <http://3.135.162.228> -
> 1705588717.420 0 127.0.0.1 NONE_NONE/503 4087 GET
> https://stuff.amazonaws.com/api/v1/stuff/stuff.json
> <https://stuff.amazonaws.com/api/v1/stuff/stuff.json> - HIER_NONE/-
> text/html
>
> *# extract from /usr/bin/proxy-test output*
> < HTTP/1.1 503 Service Unavailable
> < Server: squid/5.7
> < Mime-Version: 1.0
> < Date: Thu, 18 Jan 2024 14:38:37 GMT
> < Content-Type: text/html;charset=utf-8
> < Content-Length: 3692
> < X-Squid-Error: ERR_CONNECT_FAIL 101
> < Vary: Accept-Language
> < Content-Language: en
> < X-Cache: MISS from ubuntu-pc
> < X-Cache-Lookup: NONE from ubuntu-pc:3129
> < Via: 1.1 ubuntu-pc (squid/5.7)
> < Connection: close
>
> I have also seen it error in a different way with a 502 but with the
> same ultimate result.
>
> My expectation/hope is that squid would return the cached object on any
> network failure in between ubuntu-pc and the AWS endpoint - and continue
> to return this cached object forever. Is this something squid can do?
> It would seem that offline_mode should do this?
>
FYI, offline_mode is not a guarantee that a URL will always HIT. It is
simply a form of "greedy" caching - where Squid will take actions to
ensure that full-size objects are fetched whenever it lacks one, and
serve things as stale HITs when a) it is not specifically prohibited,
and b) a refresh/fetch is not working.
The URL you are testing with should meet your expected behaviour due to
the "Cache-Control: public, stale-of-error" header alone.
Regardless of offline_mode configuration.
That said, getting a 5xx response when there is an object already in
cache seems like something is buggy to me.
A high level cache.log will be needed to figure out what is going on
(see https://wiki.squid-cache.org/SquidFaq/BugReporting#full-debug-output).
Be aware this list does not permit large posts so please provide a link
to download in your reply not attachment.
Cheers
Amos
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