[Bug 60244] mod_http2 causes serialized requests if there are parallel long running requests on the same connection

[bugzilla]

https://bz.apache.org/bugzilla/show_bug.cgi?id=60244

--- Comment #6 from Laurence 'GreenReaper' Parry  ---
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

[bugzilla]

https://bz.apache.org/bugzilla/show_bug.cgi?id=60244

--- Comment #5 from Reno Reckling  ---
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

[bugzilla]

https://bz.apache.org/bugzilla/show_bug.cgi?id=60244

Stefan Eissing  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

[bugzilla]

https://bz.apache.org/bugzilla/show_bug.cgi?id=60244

--- Comment #4 from Stefan Eissing  ---
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

[bugzilla]

https://bz.apache.org/bugzilla/show_bug.cgi?id=60244

--- Comment #3 from Reno Reckling  ---
Created attachment 34368
  --> https://bz.apache.org/bugzilla/attachment.cgi?id=34368=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

[bugzilla]

https://bz.apache.org/bugzilla/show_bug.cgi?id=60244

Eric Covener  changed:

   What|Removed |Added

 Status|NEW |NEEDINFO

--- Comment #2 from Eric Covener  ---
loglevel trace8 of the situation pls?

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[Bug 60244] mod_http2 causes serialized requests if there are parallel long running requests on the same connection

[bugzilla]

https://bz.apache.org/bugzilla/show_bug.cgi?id=60244

--- Comment #1 from Reno Reckling  ---
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

[bugzilla]

https://bz.apache.org/bugzilla/show_bug.cgi?id=60244

e-apa...@wthack.de changed:

   What|Removed |Added

 CC||e-apa...@wthack.de

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