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For 2021 - online Python 3 training - see ((here)).

Our plans were to retire in summer 2020 and see the world, but Coronavirus has lead us into a lot of lockdown programming in Python 3 and PHP 7.
We can now offer tailored online training - small groups, real tutors - works really well for groups of 4 to 14 delegates. Anywhere in the world; course language English.

Please ask about private 'maintenance' training for Python 2, Tcl, Perl, PHP, Lua, etc.
Server overloading - turns out to be feof in PHP

From the manual page on feof:

Warning - If passed file pointer is not valid you may get an infinite loop, because EOF fails to return TRUE.

From a script on our server:

while (1) {
  $nlines ++;
  $line = fgets($fh,1024);
  if (feof($fh)) break;


OOps! ... the file that's being analysed is our spam log, which is hard coded into the page that draws an email graph. And the slight (!) problem with the code above is that now that we have separated our email server from our web server, there is no such file.

Our new web server has been running fine ... except ... that occasionally and inexplicably, it has "maxed out" for a few minutes. And it was very hard to find (across many thousand pages!) what was happening. In the end, a top report showed me that we had one or two httpd threads grabbing all the cpu resource at 'event' time ... and a Perl script run against the log file to report only on the slowly served pages:

open (FH,"access_log");
$osid = 0;
while (<FH>) {
  $l++;
  ($h, $m, $s) = /(\d\d):(\d\d):(\d\d)/;
  $sid =$s + 60*$m + 3600 * $h;
  if ($osid) {
    $moved = $sid - $osid;
    if ($moved < -10) {
      print "$l ";
      print;
    }
  }
  $osid = $sid;
}


gave me the clue. (Isn't Perl a marvellous tool - even when helping debug PHP!)
(written 2008-09-01)

 
Associated topics are indexed as below, or enter http://melksh.am/nnnn for individual articles
H109 - PHP - Input / Output
  [114] Relative or absolute milkman - (2004-11-10)
  [616] printf - a flawed but useful function - (2006-02-22)
  [653] Easy feed! - (2006-03-21)
  [709] Handling huge data files in PHP - (2006-05-04)
  [997] Most recent file in a directory - PHP - (2006-12-18)
  [1094] PHP fread - truncated data - (2007-02-27)
  [1096] Sample script - FTP to get a file from within PHP - (2007-03-01)
  [1113] File and URL reading in PHP - (2007-03-20)
  [1442] Reading a file multiple times - file pointers - (2007-11-23)
  [2964] An introduction to file handling in programs - buffering, standard in and out, and file handles - (2010-09-21)
  [3029] PHP data sources - other web servers, large data flows, and the client (browser) - (2010-11-04)
  [3159] Returning multiple values from a function call in various languages - a comparison - (2011-02-06)
  [3424] Divide 10000 by 17. Do you get 588.235294117647, 588.24 or 588? - Ruby and PHP - (2011-09-08)
  [4483] Moving from mysql to mysqli - simple worked example - (2015-05-03)

A606 - Web Application Deployment - Apache httpd - log files and log tools
  [376] What brings people to my web site? - (2005-07-13)
  [1237] What proportion of our web traffic is robots? - (2007-06-19)
  [1503] Web page (http) error status 405 - (2008-01-12)
  [1598] Every link has two ends - fixing 404s at the recipient - (2008-04-02)
  [1656] Be careful of misreading server statistics - (2008-05-28)
  [1761] Logging Cookies with the Apache httpd web server - (2008-08-20)
  [1796] libwww-perl and Indy Library in your server logs? - (2008-09-13)
  [3015] Logging the performance of the Apache httpd web server - (2010-10-25)
  [3019] Apache httpd Server Status - monitoring your server - (2010-10-28)
  [3027] Server logs - drawing a graph of gathered data - (2010-11-03)
  [3087] Making the most of critical emails - reading behind the scene - (2010-12-16)
  [3443] Getting more log information from the Apache http web server - (2011-09-16)
  [3447] Needle in a haystack - finding the web server overload - (2011-09-18)
  [3491] Who is knocking at your web site door? Are you well set up to deal with allcomers? - (2011-10-21)
  [3554] Learning more about our web site - and learning how to learn about yours - (2011-12-17)
  [3670] Reading Google Analytics results, based on the relative populations of countries - (2012-03-24)
  [3974] TV show appearance - how does it effect your web site? - (2013-01-13)
  [3984] 20 minutes in to our 15 minutes of fame - (2013-01-20)
  [4307] Identifying and clearing denial of service attacks on your Apache server - (2014-09-27)
  [4404] Which (virtual) host was visited? Tuning Apache log files, and Python analysis - (2015-01-23)
  [4491] Web Server Admin - some of those things that happen, and solutions - (2015-05-10)


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Some other Articles
Global - Tcl, PHP, Python
Think before you send
Calling procs in Tcl and how it compares to Perl
Reception
Server overloading - turns out to be feof in PHP
Injection Attacks - avoiding them in your PHP
Pointing all the web pages in a directory at a database
The Rise and Rise of First Bus Fares
Does fruit and veg drag on?
Easterholic
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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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