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Posted to bugs@httpd.apache.org by bu...@apache.org on 2016/10/12 11:59:33 UTC
[Bug 60244] New: mod_http2 causes serialized requests if there are
parallel long running requests on the same connection
https://bz.apache.org/bugzilla/show_bug.cgi?id=60244
Bug ID: 60244
Summary: mod_http2 causes serialized requests if there are
parallel long running requests on the same connection
Product: Apache httpd-2
Version: 2.4.23
Hardware: PC
OS: Linux
Status: NEW
Severity: normal
Priority: P2
Component: mod_http2
Assignee: bugs@httpd.apache.org
Reporter: e-apache@wthack.de
Hi, I just tried to move my webserver to use http2 and discovered the following
phenomenon.
This happens in chrome as well as in firefox with apache2 2.4.23.
If I open one tab to my http2 enabled domain (using h2) and it does background
ajax long-polling to a php script on the server (The script just does
sleep(30)).
While the longpoll is running, if i try to open a new tab to the same server,
the new request gets stuck in the "pending" state until the longpoll is
finished.
The second request can be against a static .html file (so no php processing)
and still gets stuck.
If I disable http2 for this setup, the requests finish in parallel just fine.
It seems to me that I somehow cause all requests to be serialized for the same
connection but different streams.
This does NOT happen for different connections, so longpoll in chrome and
second request in firefox is fine.
List of my used modules:
core.c, http_core.c, mod_access_compat.c, mod_actions.c, mod_alias.c,
mod_auth_basic.c, mod_authn_core.c, mod_authn_file.c, mod_authz_core.c,
mod_authz_groupfile.c, mod_authz_host.c, mod_authz_unixgroup.c,
mod_authz_user.c, mod_autoindex.c, mod_cgi.c, mod_dav.c, mod_dav_fs.c,
mod_deflate.c, mod_dir.c, mod_env.c, mod_filter.c, mod_headers.c, mod_http2.c,
mod_include.c, mod_info.c, mod_log_config.c, mod_logio.c, mod_mime.c,
mod_negotiation.c, mod_php7.c, mod_proxy.c, mod_proxy_http.c, mod_reqtimeout.c,
mod_rewrite.c, mod_setenvif.c, mod_so.c, mod_socache_shmcb.c, mod_ssl.c,
mod_status.c, mod_unixd.c, mod_version.c, mod_watchdog.c, mod_wsgi.c, prefork.c
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[Bug 60244] mod_http2 causes serialized requests if there are
parallel long running requests on the same connection
Posted by bu...@apache.org.
https://bz.apache.org/bugzilla/show_bug.cgi?id=60244
--- Comment #5 from Reno Reckling <e-...@wthack.de> ---
I went for mpm_event + mod_fcgid which works nicely for php. Thank you
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[Bug 60244] mod_http2 causes serialized requests if there are
parallel long running requests on the same connection
Posted by bu...@apache.org.
https://bz.apache.org/bugzilla/show_bug.cgi?id=60244
--- Comment #4 from Stefan Eissing <st...@eissing.org> ---
The problem is that you run 'prefork' as your mpm. In prefork there is only one
connection/request per process. So, when you browser reuses the h2 connection,
it ends up in the very same process that is working on the longpoll.
What can you do?
1. Disable http2
2. Switch to mpm_event
3. Enable more H2Workers per process (the default on prefork is 1, since
prefork is intended to not have multithreading).
2 would be my recommendation. 3 might not work if you really need prefork. 1
makes me sad.
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[Bug 60244] mod_http2 causes serialized requests if there are
parallel long running requests on the same connection
Posted by bu...@apache.org.
https://bz.apache.org/bugzilla/show_bug.cgi?id=60244
--- Comment #6 from Laurence 'GreenReaper' Parry <gr...@hotmail.com> ---
This behaviour should really be documented. It makes sense once you understand
the reason, but is unexpected nevertheless, and has the potential for
triggering hard-to-track bugs where it looks like the client may be at issue.
Current browsers show the connections as "stalled" even though they may in fact
have done their part in issuing the request.
While HTTP/2 is not doing anything "wrong", per-se, it is a case where it
breaks website workflows which worked fine with HTTP/1.1 on the same MPM.
Possible locations to mention it:
https://httpd.apache.org/docs/2.4/howto/http2.html
https://httpd.apache.org/docs/2.4/mod/mod_http2.html#h2maxworkers ("If this
directive is not used, mod_http2 will chose a value suitable for the mpm module
loaded." is not enough, because it does not specify a value or the
implications.)
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[Bug 60244] mod_http2 causes serialized requests if there are
parallel long running requests on the same connection
Posted by bu...@apache.org.
https://bz.apache.org/bugzilla/show_bug.cgi?id=60244
--- Comment #1 from Reno Reckling <e-...@wthack.de> ---
Additional insight:
This happens _only_ during requests that involve php.
If i have a long running download that shares a connection with another static
file requests, everything is fine.
Could it be that mod_php7 somehow gets an exclusive lock on the connection
except just on the stream?
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[Bug 60244] mod_http2 causes serialized requests if there are
parallel long running requests on the same connection
Posted by bu...@apache.org.
https://bz.apache.org/bugzilla/show_bug.cgi?id=60244
e-apache@wthack.de changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |e-apache@wthack.de
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[Bug 60244] mod_http2 causes serialized requests if there are
parallel long running requests on the same connection
Posted by bu...@apache.org.
https://bz.apache.org/bugzilla/show_bug.cgi?id=60244
--- Comment #3 from Reno Reckling <e-...@wthack.de> ---
Created attachment 34368
--> https://bz.apache.org/bugzilla/attachment.cgi?id=34368&action=edit
loglevel trace8 of a session that has the problem
This shows the following series of event:
Request to /test/first.html in tab #1, which loads the basic html and some
javascript.
The javascript of first.html then does an ajax request to /test/longpoll.php
which hangs for 30 seconds.
This phase is clearly visible because of the 30 second long period of:
OpenSSL: I/O error, 5 bytes expected to read on BIO#558423e82670
2 seconds after the longpoll.php request is initiated, i open another tab #2 to
/test/second.html. This one does not really show up in the log just yet.
After the longpoll in Tab #1 finished, the log says:
AH02034: Subsequent (No.3) HTTPS request received for child 2 (server
exi.wthack.de:443)
Which goes to /test/second.html and finished immediately.
Anything else i could provide to help solve this?
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[Bug 60244] mod_http2 causes serialized requests if there are
parallel long running requests on the same connection
Posted by bu...@apache.org.
https://bz.apache.org/bugzilla/show_bug.cgi?id=60244
Stefan Eissing <st...@eissing.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|NEEDINFO |RESOLVED
Resolution|--- |WORKSFORME
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[Bug 60244] mod_http2 causes serialized requests if there are
parallel long running requests on the same connection
Posted by bu...@apache.org.
https://bz.apache.org/bugzilla/show_bug.cgi?id=60244
Eric Covener <co...@gmail.com> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|NEW |NEEDINFO
--- Comment #2 from Eric Covener <co...@gmail.com> ---
loglevel trace8 of the situation pls?
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