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Python and Tcl - public course schedule [here]
Private courses on your site - see [here]
Please ask about maintenance training for Perl, PHP, Lua, etc
 
Heartbeat script in Perl

Scenario ... an Apache httpd web server is distributing requests around between a number of Apache Tomcat instances on different computers (perhaps using mod_rewrite to allocate the requests). If a Tomcat instance become unavailable (i.e. if the host running it is taken offline) then it's to be removed from the pool, and if it comes back on line it's to be added to the pool again.

Sound complex? The basis can be quite a simple Perl script such as the one we wrote during today's course - source code here.

A regular ping around the machines that may be in the pool establishes which are present, and if the availabiity has changed the RewriteMap is rewritten. Place a pause of a few seconds into the loop and try again ....
(written 2007-02-09)

 
Associated topics are indexed as below, or enter http://melksh.am/nnnn for individual articles
A163 - Web Application Deployment - Network Configuration and Security
  [4134] Setting up your MacBook Air as a mobile broadband router - (2013-07-07)
  [3448] Checking all the systems on a subnet, using Expect and Tk - (2011-09-18)
  [2489] Parallel Pinging, using Python Threads or Expect spawn lists - (2009-11-02)
  [2052] How was my web site compromised? - (2009-02-24)
  [1904] Ruby, Perl, Linux, MySQL - some training notes - (2008-11-23)
  [1712] As different as night and tyres - (2008-07-18)
  [1666] Slow boot and terminal start on Linux boxes - (2008-06-05)
  [1408] Wireless hotel tips - FTP and Skype connections failing - (2007-10-26)
  [511] Domain Forwarding - 2 ways of doing it - (2005-11-29)
  [506] What are DHCP and DNS? - (2005-11-27)
  [332] Looking up IP addresses - (2005-06-01)
  [267] Searching security holes - (2005-04-04)
  [37] Security and Safety - (2004-09-03)
  [11] A bolt of lightning on Multicasting - (2004-08-11)

P224 - Perl - Intersystem Communications
  [2970] Perl - doing several things at the same time - (2010-09-25)
  [2876] Different perl examples - some corners I rarely explore - (2010-07-18)
  [2695] TCP v UDP / Client v Server - Python examples - (2010-03-25)
  [2402] Automated Browsing in Perl - (2009-09-11)
  [1918] Perl Socket Programming Examples - (2008-12-02)
  [604] Perl - multiprocess applications - (2006-02-13)


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I'm not the father
Java beans and classes, .war and .jar files
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Making a mountain out of a molehill
Java Deployment course - lunch break
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This is a page archived from The Horse's Mouth at http://www.wellho.net/horse/ - the diary and writings of Graham Ellis. Every attempt was made to provide current information at the time the page was written, but things do move forward in our business - new software releases, price changes, new techniques. Please check back via our main site for current courses, prices, versions, etc - any mention of a price in "The Horse's Mouth" cannot be taken as an offer to supply at that price.

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