Miles Libbey commented on TS-4829:

Changed Documentation to note that any previous hierarchy data is cached. 

> Via: header string should not be cached
> ---------------------------------------
>                 Key: TS-4829
>                 URL: https://issues.apache.org/jira/browse/TS-4829
>             Project: Traffic Server
>          Issue Type: Bug
>            Reporter: Miles Libbey
>             Fix For: sometime
> We use a cache hierarchy.  In theory the Via: string shows the path the 
> request took through proxies, and with 
> proxy.config.http.insert_response_via_str set to 3, a lot of info is 
> presented -- cache hit, etc. (The Via header is described in 
> https://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#sec14.45)
> However, the string is cached, so it doesn't accurately reflect the path that 
> *this* request took. Instead, it shows the path of the original request.
> For instance, imagine 2 servers, conveniently named child.example.com and 
> parent.example.com, which also represents their roles in the cache hierarchy. 
> The object is cacheable for a long time.
> The first request for the object might look like:
> Via: http/1.1 parent.example.com (ApacheTrafficServer/6.2.1 [uScMsSfWpSeN:t 
> cCMi p sS]), http/1.1 child.example.com (ApacheTrafficServer/6.2.1 [uScMsSf 
> pSeN:t cCMi pSs ])
> (with the cM meaning cache miss). The second request, a cache hit that just 
> goes through child.example.com might show:
> Via: http/1.1 parent.example.com (ApacheTrafficServer/6.2.1 [uScMsSfWpSeN:t 
> cCMi p sS]), http/1.1 child.example.com (ApacheTrafficServer/6.2.1[uScHs f p 
> eN:t cCHi p s ])
> eg, cache Hit for child, but cache Miss for parent -- even though the parent 
> wasn't involved in the request, and, if it were, it would be a Hit.  The 
> parent portion was cached by child.example.com.
> The expected behavior is that the 2nd request would yield:
> Via: http/1.1 child.example.com (ApacheTrafficServer/6.2.1[uScHs f p eN:t 
> cCHi p s ])

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