[wp-trac] [WordPress Trac] #18239: wp_ob_end_flush_all() hangs the output buffering, during plugin update/install

[WordPress Trac]

#18239: wp_ob_end_flush_all() hangs the output buffering, during plugin
update/install
-----------------------------+-----------------------------
 Reporter:  mamborambo       |      Owner:
     Type:  defect (bug)     |     Status:  new
 Priority:  normal           |  Milestone:  Awaiting Review
Component:  Upgrade/Install  |    Version:  3.2.1
 Severity:  minor            |   Keywords:  output hangs
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 Symptom: During plugin update process, the screen displays "Downloading
 {plugin}" then appears to hang.

 System: Apache2 on LinuxMint-11

 I traced the fault to the following function:
 send_message() in /wp-admin/includes/misc.php

 this function writes out the message, then tries to flush
 the buffers by calling wp_ob_end_flush_all()

 the mechanism of the ob_flush is to repeatedly call ob_end_flush until
 there is no more levels.

 On the default configuration of LinuxMint / Debian,
 zlib.output_compression is ON, and this interferes with ob_end_flush

 Based on notes from php.net, ob flushing is not necessary.

 SOLUTION:

 1) Either change php.ini to set zlib.output_compression to OFF, or

 2) shortcircuit the wp_ob_end_flush_all() by adding an immediate return to
 the first line.

 RECOMMENDATION:

 In future versions of Wordpress, the interaction between ob and zlib
 should be studied carefully to derive the most universal solution.

-- 
Ticket URL: <http://core.trac.wordpress.org/ticket/18239>
WordPress Trac <http://core.trac.wordpress.org/>
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