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Filtered by popular tag bgdelivery, 1 - 3 of 3 Postings (all, summary)


Created by Emmanuelle Raffenne, last modified by Benjamin Brink 22 Oct 2016, at 02:59 AM

Package Specification Summary for Package: chat

Summary: Server based chat with an html and ajax client.
Description: Adapted by Peter Alberer 2006/03/25 to allow java and ajax to coexist. Adapted by Tekne 2006/03/01 to replace JAVA server with AJAX; make use of generalized chat class from xotcl-core.
Maturity: New Submission or Maturity Unknown
This package depends on: acs-kernel xotcl-core
Packages that depend on chat: chat-includelet chat-portlet dotlrn-chat
Package parameters:
Height of the applet (default 500, type number, scope instance)
width of the applet (default 700, type number, scope instance)
Default client interface to use (default ajax, type string, scope instance)
Chat server host (default , type string, scope instance)
Listening for chat connection on this port (default 8200, type number, scope instance)
A list of colors to assign to user names in the chat (default #006400 #0000ff #b8860b #bdb76b #8b0000, type string, scope instance)

Bug Tracker Summary for Package: chat

Open Bugs: 1
Latest Bug Opened: 2006-04-05 Ajax chat English language catalog incomplete
Latest Bug Fixed: 2015-07-25 Russian localization for package chat(HEAD).
Top Bug Submitters: Ryan Gallimore (3) Joel Aufrecht (1) v v (1)
Top Bug Fixers: Gustaf Neumann (4)

Code Metrics Summary for Package: chat

# Tcl Procs 30
# Tcl Lines 621
# Automated Tests 0
# Stored Procedures PG: 0 ORA: 0
# SQL Lines PG: 0 ORA: 0
# ADP pages 21
# ADP lines 445
# Include pages (chat/lib/) 3
# Documentation pages 0
# Documentation lines 0
Browse Source Not installed


The chat package is using currently two different chat engines:

  1. The Java applet and the Java chat server, or
  2. the Ajax based chat class from xotcl-core

If no xotcl-core is installed, one can only use the version with Java applet. If xotcl-core is installed, one has to option to choose between both engines via parameter.

In essence, the Ajax based variant is the chat implementation from xowiki plus chat room management and a list of the currently connected users. Originally, the ajax-based chat class (::xo::Chat) was developed for xowiki, but later moved to xotcl-core such that the chat package does not need a dependency on xotcl-core and xowiki.

Actually, the chat support in xowiki contains a different variety of ajax based communication strategies:

  1. Polling mode (the web browser queries via ajax in definable intervals the server, and checks, if there is some new information available), and
  2. Streaming mode (the client opens a connection to the server, the server pushes the information back to the client. xowiki chat supports two different submodes:
    1. streaming of JSON  objects via asynchronous AJAX sockets, or
    2. scripted streaming, where the browser loads HTML with embedded script tags in the background  from an hidden iframe

Both (2a) and (2b) require libthread support and a small patch for the aolserver, so they are currently not for beginners. However, the advantage of the streaming approaches is that they are much faster in the look and feel and that they are better scalable on sites with a high load. 2a works only on firefox (not in current versions of IE or Safari) and has the advantage over 2b that the browser does not show the background activity (no spinning wheel in Firefox). 2b is more robust and works with Safari, IE and Firefox (the information about the browser support is from 2006, and most probably different today). Both streaming modes implement, what is sometimes called COMET .


When the chat package uses the ::xo::Chat, it uses it only in currently only polling mode which has the  least requirements. This has been as well tested with (Firefox, IE and Safari).





Boost your application performance to serve large files!

Created by Rocael Hernández Rizzardini, last modified by Gustaf Neumann 16 Oct 2016, at 12:38 PM

In order to speed up file-deliveries, one can use the background delivery methods provided by xotcl-core. The main advantage is that with background delivery the costly connection threads are just used for permission checking and locating the file, and the time-consuming spooling of the file to the client is implemented in an asynchronous background delivery thread. Therefore, connection thread are not blocked, it is possible to spool simultaneously several hundred (thousand?) files with only a few connection threads configured.

We use this in production since several years. For example today (no semester yet) we had so far 150.000 file deliveries by background delivery.

The asynchrounous background delivery requires a small patch (2 changes, one is a backport from naviserver) and the tcl thread library (by zoran). The application code is in XOTcl is only a few lines of code and is included in xotcl-core (bgdelivery-procs.tcl).

One needs the following patch to

The patch is already included in the current head version of aolserver 4.5 and in NaviServer.

With this patch and xotcl-core, one can replace
   ns_returnfile 200 $mime_type $filename

   ad_returnfile_background 200 $mime_type $filename

e.g. in cr_write_content in acs-content-repository/tcl/revision-procs.tcl to activate it and to deliver files from the content-repository (file-store) in the background.

The connection thread is only used for permission management, localization of the file and writing the the reply header, the actual delivery of the file is performed via asynchronous io without using up many resources. This can handle probably a couple of thousand concurrent file deliveries without running out of resources.

Check the files that has been served since the last reboot of your NaviServer/aolserver using this method from the developer support shell:

   bgdelivery do set delivery_count

Original thread: 



Tcl Thread Library

Created by Gustaf Neumann, last modified by Monika Andergassen 05 Oct 2015, at 12:44 PM

Libthread is the standard Tcl thread library developed by Zoran Vasiljevic and provides optional functionality for OpenACS. Threads created by the Tcl thread library are executed in an event loop, which makes it easy to send commands to such threads. xotcl-core provides support for the the thread library and uses it for example for [background delivery] of large files. Also the chat package uses libthread when it is installed. The xotcl-request-monitor depends on libthread.


1. Get and install libthread:

    download thread2.6.5 from

 untar it and go to you platform specific directory (eg. thread2.6.5/unix)

# cd unix
# ../configure --enable-threads \
--prefix=/usr/local/aolserver \
--exec-prefix=/usr/local/aolserver \

use --prefix --exec-prefix --with-aolserver with the path pointing to the directory, where aolserver4 is installed. The flag --with-aolserver is essential. When multiple Tcls are installed on the system, it is recommended to use the flag pointing to it, like e.g. in --with-tclinclude=/usr/local/src/tcl8.4.16/unix/ --with-tcl=/usr/lib/

# check in output if there is following definition: -DNS_AOLSERVER=1
make install

You should now have installed (check for /usr/local/aolserver/lib/thread2.6.5/

2) Adjusting config.tcl for libthread service

    I would recommed to load libthread 2.6.5 as a "module" from the aolserver config file to avoid a mixup with the plain tcl libthread extension (which is most likely compiled without --with-aolserver)

  • open config.tcl (/var/lib/aolserver/${yourservice}/etc/config.tcl)
  • look for modules section: ns_section ns/server/${server}/modules
  • add libthread to modules section:

    ns_param libthread ${homedir}/lib/thread2.6.5/

restart the aolserver and check the error log, whether libthread2.6.5 was loaded successfully.

svc -t /service/${yourservice}


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