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Opened 12 years ago

Last modified 3 years ago

#18239 closed defect (bug)

wp_ob_end_flush_all() hangs the output buffering, during plugin update/install — at Initial Version

Reported by: mamborambo's profile mamborambo Owned by:
Milestone: Priority: normal
Severity: minor Version: 3.2.1
Component: Upgrade/Install Keywords: output hangs
Focuses: Cc:


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, ob flushing is not necessary.


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.


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

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