On 12/20/23 4:08 PM, Yann Ylavic wrote:
> On Wed, Dec 20, 2023 at 2:40 PM Joe Orton <jor...@redhat.com> wrote:
>>
>> I was surprised this made a difference to the behaviour on the wire. It
>> seems like the chunk filter has suboptimal behaviour here. If you take
>> an output brigade like either:
>>
>> a) [HEAP FLUSH EOS]
>> b) [HEAP FLUSH EOS FLUSH]
>>
>> in both cases the chunk filter would output two brigades:
>>
>> [chunk-hdr HEAP crlf FLUSH] [last-chunk EOS]
>>
>> Significantly there is no FLUSH in the second brigade even for case (b),
>> because the chunk filter also drops everything after EOS. It would be
>> clearly better/correct if the chunk filter produces a single brigade for
>> this very common output pattern:
>>
>> [chunk-hdr HEAP crlf last-chunk FLUSH EOS]
>>
>> correctly preserving the semantics of the FLUSH. I've tried this here:
>>
>> https://github.com/apache/httpd/pull/400
>
> Thanks, looks good to me.
+1
>
>>>
>>> On Mon, Oct 9, 2023 at 2:50 PM Eric Norris <enor...@etsy.com> wrote:
>>>>
>>>> At Etsy, we use mod_php and were investigating what we thought was
>>>> surprising behavior - that code executed during PHP's shutdown phase
>>>> prevented the request from terminating, even if we didn't expect to send
>>>> any additional output to the client.
>>>>
>>>> We determined that this was not surprising given mod_php's
>>>> implementation, but after we developed a proof-of-concept patch that
>>>> sent an EOS bucket and a flush bucket via a "userland" PHP function, we
>>>> were surprised that it didn't work when compression was enabled for the
>>>> request.
>
> I'm wondering if these cases are valid/supported though:
> c) [HEAP EOS FLUSH]
> d) [HEAP EOS] [FLUSH] (with separate FLUSH but on r->output_filters still)
> which seems to be what mod_php and the "userland" POC do?
>
> I thought nothing should be sent on r->output_filters after EOS (only
> c->output_filters might forward metadata in between requests), and at
> least in ap_http_chunk_filter() this won't work since, as Joe said,
> everything after EOS being dropped breaks c) and the filter not
> removing itself after EOS breaks d).
>
> So I think what the POC or mod_php should be doing is [FLUSH EOS] or
> something might not work in the chain sooner or later?
+1
Regards
Rüdiger
