Mailing-List: contact dev-help@httpd.apache.org; run by ezmlm
Precedence: bulk
Reply-To: dev@httpd.apache.org
Content-Type: text/plain; charset=us-ascii
Mime-Version: 1.0 (Mac OS X Mail 9.3 \(3124\))
Subject: Re: Detecting client aborts and stream resets
From: Stefan Eissing <stefan.eissing@greenbytes.de>
In-Reply-To: <CACsi253h9r0VE0RaSS03MKBKReCv_OP6CO=V_v06s27r+ngg2g@mail.gmail.com>
Date: Wed, 4 May 2016 09:51:02 +0200
Content-Transfer-Encoding: quoted-printable
Message-Id: <CACD9AFB-6811-4FF0-831F-C3C25E64580E@greenbytes.de>
References: <20160503163109.Horde.dDuX6tl_vMFkpJE75Qne6Q0@webmail.michael-kaufmann.ch> <CACsi253h9r0VE0RaSS03MKBKReCv_OP6CO=V_v06s27r+ngg2g@mail.gmail.com>
To: dev@httpd.apache.org
archived-at: Wed, 04 May 2016 07:51:15 -0000


> Am 03.05.2016 um 17:35 schrieb William A Rowe Jr =
<wrowe@rowe-clan.net>:
>=20
> On Tue, May 3, 2016 at 9:31 AM, Michael Kaufmann =
<mail@michael-kaufmann.ch> wrote:
> Hi all,
>=20
> a content generator module can detect client aborts and stream resets =
while it reads the request body. But how can it detect this afterwards, =
while the response is being generated?
>=20
> This is important for HTTP/2, because the client may reset a stream, =
and mod_http2 needs to wait for the content generator to finish. =
Therefore the content generator should stop generating the response when =
it is no longer needed.
>=20
> Is there any API for this? The "conn_rec->aborted" flag exists, but =
which Apache function sets this flag?

conn_rec->aborted is currently not set by mod_http2 on slave =
connections, but should. I'll add that.

> If there is no API, maybe an optional function for mod_http2 would be =
a solution.
>=20
> Nope - an optional function in mod_http2 is too special case, =
generators
> must remain protocol (socket or other transport) agnostic.
>=20
> In the case of mod_cache'd content, the generator can't quit, it is =
already
> populating a cache, which means you'll generate an invalid cached =
object.
>=20
> But if you knew that the cache module wasn't collecting info, =
r->c->aborted
> tells you if anyone is still listening, right?

William is right, this is not a good idea. The ->aborted flag should =
serve this purpose of telling anyone interested that this connection is =
not longer delivering. I will make a github release soon where that is =
working and you can test.

-Stefan=