[squid-users] URL sometimes reurns empty response

Ralf Hildebrandt Ralf.Hildebrandt at charite.de
Tue May 2 11:59:38 UTC 2017

In some cases, our proxies (got 4 of them) return a empty result when
querying "http://www.msftconnecttest.com/ncsi.txt" (whcih is used by
Microsoft Brwosers to check if they're online).

I'm using this incantation to check the URL:

watch -d curl --silent -v -x "http://proxy-cvk-1.charite.de:8080" http://www.msftconnecttest.com/ncsi.txt

Usually, the URL should just return "Microsoft NCSI".
In some cases I get an empyt response, but curl reports:

< Age: 5
< X-Cache: HIT from proxy-cvk-1
< Via: 1.1 proxy-cvk-1 (squid/5.0.0-20170421-r15126)
< Connection: keep-alive
* Excess found in a non pipelined read: excess = 14 url = /ncsi.txt (zero-length body)
* Curl_http_done: called premature == 0
* Connection #0 to host (nil) left intact

As you can see, something is producing an excess of 14 Bytes (which
coincides with the 14 bytes length of "Microsoft NCSI").

< Cache-Control: max-age=30,must-revalidate

Immediatly after revalidating, the problem occurs.

I tried this with 5.0.0-20170421-r15126 as well as 4.0.19 - same result.

Ralf Hildebrandt                   Charite Universitätsmedizin Berlin
ralf.hildebrandt at charite.de        Campus Benjamin Franklin
https://www.charite.de             Hindenburgdamm 30, 12203 Berlin
Geschäftsbereich IT, Abt. Netzwerk fon: +49-30-450.570.155

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