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Posted to httpclient-users@hc.apache.org by Tobias Gesellchen <ge...@gmail.com> on 2018/04/28 19:49:14 UTC

httpclient-cache caches HEAD requests with missing body

Hi all,

since httpclient-cache 4.4 HEAD requests can be cached with a `null` response body. Subsequent GET requests to the same target then use the headers "If-None-Match" and "If-Modified-Since" to leverage caching via HTTP protocol. In that case a server can respond with status code 304 and an empty response body, which leads to an invalid cache entry.

You can find example logs along with a mini app to demonstrate the issue at https://github.com/gesellix/httpclient-cache-demo.
I have already prepared a simple fix (based on httpclient-cache 4.5.5) at https://github.com/gesellix/httpcomponents-client/tree/disable-cache-for-null-resource.

My questions are:
1) did I miss some detail or use the cache library in a wrong way?
2) would the proposed fix be a good candidate for a pull request?

Thanks!
Tobias


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Re: httpclient-cache caches HEAD requests with missing body

Posted by Tobias Gesellchen <ge...@gmail.com>.
> On 29. Apr 2018, at 13:10, Oleg Kalnichevski <ol...@apache.org> wrote:
> 
> On Sat, 2018-04-28 at 21:49 +0200, Tobias Gesellchen wrote:
>> Hi all,
>> 
>> since httpclient-cache 4.4 HEAD requests can be cached with a `null`
>> response body. Subsequent GET requests to the same target then use
>> the headers "If-None-Match" and "If-Modified-Since" to leverage
>> caching via HTTP protocol. In that case a server can respond with
>> status code 304 and an empty response body, which leads to an invalid
>> cache entry.
>> 
>> You can find example logs along with a mini app to demonstrate the
>> issue at https://github.com/gesellix/httpclient-cache-demo.
>> I have already prepared a simple fix (based on httpclient-cache
>> 4.5.5) at https://github.com/gesellix/httpcomponents-client/tree/disa
>> ble-cache-for-null-resource.
>> 
>> My questions are:
>> 1) did I miss some detail or use the cache library in a wrong way?
>> 2) would the proposed fix be a good candidate for a pull request?
>> 
>> Thanks!
>> Tobias
> 
> Hi Tobias
> 
> The fix you are proposing looks good to me but I would like someone
> with a more in-depth knowledge of caching to take a look at it. Could
> you please raise a JIRA for this issue, raise a PR at GitHub and
> reference that PR from JIRA? I'll try to get Jon to take a quick look
> at your patch.
> 
> Cheers
> 
> Oleg

Hi Oleg,

I've raised https://issues.apache.org/jira/browse/HTTPCLIENT-1920 along with the PR https://github.com/apache/httpcomponents-client/pull/101

Thanks for the quick feedback!

Best,
Tobias


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Re: httpclient-cache caches HEAD requests with missing body

Posted by Oleg Kalnichevski <ol...@apache.org>.
On Sat, 2018-04-28 at 21:49 +0200, Tobias Gesellchen wrote:
> Hi all,
> 
> since httpclient-cache 4.4 HEAD requests can be cached with a `null`
> response body. Subsequent GET requests to the same target then use
> the headers "If-None-Match" and "If-Modified-Since" to leverage
> caching via HTTP protocol. In that case a server can respond with
> status code 304 and an empty response body, which leads to an invalid
> cache entry.
> 
> You can find example logs along with a mini app to demonstrate the
> issue at https://github.com/gesellix/httpclient-cache-demo.
> I have already prepared a simple fix (based on httpclient-cache
> 4.5.5) at https://github.com/gesellix/httpcomponents-client/tree/disa
> ble-cache-for-null-resource.
> 
> My questions are:
> 1) did I miss some detail or use the cache library in a wrong way?
> 2) would the proposed fix be a good candidate for a pull request?
> 
> Thanks!
> Tobias

Hi Tobias

The fix you are proposing looks good to me but I would like someone
with a more in-depth knowledge of caching to take a look at it. Could
you please raise a JIRA for this issue, raise a PR at GitHub and
reference that PR from JIRA? I'll try to get Jon to take a quick look
at your patch.

Cheers

Oleg

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