MySQL 5.5 on Ubuntu 12.04 – Job Failed to Start

I migrated a web site from one host to another and as such upgraded to MySQL 5.5 running on Ubuntu 12.04.  Everything was moving along nicely until MySQL started to randomly crash.

Jul 23 07:06:38 domU-12-31-39-02-76-EA kernel: [236645.626405] init: mysql main process (21515) terminated with status 1
Jul 23 07:06:38 domU-12-31-39-02-76-EA kernel: [236645.626453] init: mysql main process ended, respawning
Jul 23 07:06:39 domU-12-31-39-02-76-EA kernel: [236646.617559] init: mysql post-start process (21516) terminated with status 1

Trying to start the process using the service command yields this message:

Job failed to start

I found several sites recommending that I uninstall and re-install mysqld – which I did to no avail.

I finally tried to run mysqld manually from command line and found a bit more of a clue:

120723 7:40:29 [Note] Plugin 'FEDERATED' is disabled.
120723 7:40:29 InnoDB: The InnoDB memory heap is disabled
120723 7:40:29 InnoDB: Mutexes and rw_locks use GCC atomic builtins
120723 7:40:29 InnoDB: Compressed tables use zlib 1.2.3.4
120723 7:40:29 InnoDB: Initializing buffer pool, size = 128.0M
InnoDB: mmap(137363456 bytes) failed; errno 12
120723 7:40:29 InnoDB: Completed initialization of buffer pool
120723 7:40:29 InnoDB: Fatal error: cannot allocate memory for the buffer pool
120723 7:40:29 [ERROR] Plugin 'InnoDB' init function returned error.
120723 7:40:29 [ERROR] Plugin 'InnoDB' registration as a STORAGE ENGINE failed.
120723 7:40:29 [ERROR] Unknown/unsupported storage engine: InnoDB
120723 7:40:29 [ERROR] Aborting
120723 7:40:29 [Note] /usr/sbin/mysqld: Shutdown complete

Aha!  Looks like something with the configuration of Innodb.

Checking some of these messages revealed that the default configuration for innodb_buffer_pool_size is 128M… for my small server this was simply too large.

From here, I simply modified /etc/mysql/my.cnf to include the following statement

innodb_buffer_pool_size = 16M

A much more reasonable number considering the size of my server memory. Now simply start your mysql server and you should be good to go!

Slow Wireless Download Speeds Solved – Disable WMM Support

I was completely frustrated with the speed of my network connection so I decided to do some investigation. I was convinced that Comcast was to blame and even placed a call to their support department to complain. They told me that the network speeds were as promised and everything checked out. They reset the connection and told me there was nothing they could do.

I ran speed tests (over at http://speedtest.net) and found the download speeds to be anywhere from .66Mbps to .99Mbps.

I tried disabling the security to no avail. I tried disabling the firewall and Upnp – again speeds hovered around 1Mbps. Finally, I disabled WMM support and POW! Speeds increased to over 35Mbps. Below is the screenshot of Cisco configuration.

To modify the configuration, login to your router and select Applications & Gaming, then click QoS and click Disable next to the WMM Support option.  WMM or Wireless Multi-Media Extensions were created to enable better performance (Quality of Service) for video and voice traffic but have the unintended effect of destroying wireless performance.

Disable WMM Support to Fix Slow Wireless Speeds

Disable WMM Support to Fix Slow Wireless Speeds

Graceful Sidebar Updated – Version 1.0.14 Released

The Graceful Sidebar is a WordPress plugin that enables you to display custom sidebar content for each of your posts or pages. This update fixes a problem that resulted in deleted sidebars.  As always, please remember to backup your wordpress database prior to installing this (or any) updated plugin.  Check out this guide to backing up your database for additional details on exactly how to do that.

Gantter Project – A Great, Free Way to Manage Projects

I’ve used OpenProj for several years. It’s a nice, free alternative to MS Project. The only problem is sharing the project plans with folks – rarely do people I work with have OpenProj installed. Fortunately, OpenProj gives you the option of saving as a MS Project XML file. This makes it easier but I was still looking for the ability to save the projects in PDF format. This is possible, but only with the paid version of OpenProj. This is when I found the Gantter Project.

Gantter is written to work with Google Apps. It enables you to import MS Project project plans, save them as PDF and even save them directly to Google Docs.

For me, Google Docs and the Gantter Project work best with my custom domain – mlynn.org – but you can use it even if you don’t have a custom domain. Visit Gantter.com to find out more information about this great, free tool to help you manage your projects.

How to Monitor your Mac Desktop with Dropbox

I’m a huge fan of the fabulous, free storage service called Dropbox so when I saw a recent episode of Hak5 which covered monitoring your desktop with Dropbox, obviously, I jumped right in. Turns out, however that the episode only covers how to do this using MS Windows. I decided to whip something up for the rest of us and this article covers how I accomplished it. However, I’m not really sure how realistic it is to think of this as a real security tool. First of all it’s unless you’ve enabled passwordless login, or someone has compromised your password, or you’ve left your mac unlocked… it’s highly unlikely that you’ll find this a much value beyond a science experiment. So that’s what I’m calling it… an experiment in Mac Desktop Monitoring using Dropbox.

If you’re not using Mac OS – you’ll want to head over to either the Hak5 episode or to this link on the Dropbox forum which covers how to accomplish this with windows.

Link to Script Download

[download id=”6″]

Requirements

  • First, you need a free dropbox account. I would encourage you to click here and sign-up if you don’t have one already. After you’ve installed Dropbox and have it running, you should have a folder that you’ll use to store files and make them available to multiple computers using the same Dropbox account. In this tutorial, we’ll leverage dropbox to share images of your computer’s desktop in the event that some activity is taking place.
  • Second, you need to install ImageMagick. This is a suite of tools that allows you to create, edit and manipulate graphic files from the command line. The installation is simple if you download the binary for Mac OS X, or you can use MacPorts to install it. Instructions on available on the ImageMagick Site.
  • Lastly, you’ll need to know your way around the terminal app. This script was written in shell and will need to be started via cron on a regular basis or you can enable the loop option by editing the code as directed (Around lines 172 and 242.) If you’re unfamiliar with the Mac OS Terminal or shell commands, Click Here. This package comes with an example crontab entry file called dbmon.crontab. You’ll need to add the contents of this file to your user crontab using the crontab command… eg: crontab -e or crontab < dbmon.crontab.

What’s in the script package?

  • ./dbmon.crontab – Example crontab to run the script every minute.
  • ./dbmon.sh – The monitoring script.
  • ./gpl.txt – GPL Text – this script is covered under the terms of the GNU Public License.
  • ./start – Start script to enable the script once you’ve set it to run via crontab.
  • ./status – Check whether or not the script is enabled or disabled.
  • ./stop – Stop the script – disable it from running.

How does it work?

The script works by taking periodic screenshots and comparing them to each other. Using ImageMagick’s compare utility, we can assign a value to the level of difference between two images. The script allows you to set a tolerance for the difference detection – the default seems to work well and is set at a level of 6. Any difference greater than the tolerance probably means that someone is on your desktop doing something. The script will move the screen captures to a configurable directory (typically under your dropbox folder) and send you an email with the screen capture to alert you.

If you’re using Dropbox from a computer other than the one you’re monitoring during the time an alert fires, you’ll be notified by the dropbox update daemon telling you that you’ve added several images to your dropbox folder.

Why do I need this?

Let’s say you’re a mobile worker, with several machines that you use on a regular basis. You probably have a desktop at work, a laptop and maybe several home computers that you use regularly. Dropbox allows you to have a common file share between all of these computers. This script allows you to leverage the communication and storage channels of dropbox to alert you when someone attempts to use one of your computers.

Combine Dropbox with a remote access tool such as Logmein and you’ve got a pretty good remote monitoring and access suite.

How do I install it?

The script was written in shell and can run pretty much from any directory. I would recommend something like the following to install it and test it out…

  1. Make a directory under your home directory
    mkdir /Users/you/dbmon
  2. Download the script package, untar it and place it in a file under that directory… call it something like dbmon.sh.
    tar zxvf dbmon-v1.0.tar.gz
  3. Make it executable
    chmod +x /Users/you/dbmon/dbmon.sh
    
  4. Edit the script or simply create a .dbmon configuration file in your home directory (~/.dbmon) and change the variables to reflect your specific environment.
    computer:dbmon mlynn$ vi ~/.dbmon
    

    ~/.dbmon

    DBMON_TOLERANCE=9
    DBMON_ACTIVE="1"
    DBMON_SCOUNT="2"
    DBMON_SLEEP="1"
    DBMON_VERBOSE='ON'
    DBMON_PROGNAME='DBMON'
    # LABEL="ON" doesn't work... bug in ImageMagick Version 6.6.3
    DBMON_LABEL="OFF"
    DBMON_LABELMESSAGE="Screen Capture $HOSTNAME "
    DBMON_DBPATH='/Users/you/Dropbox/dbmon'
    DBMON_TMPPATH='/Users/you/dbmon/tmp'
    DBMON_ALERTEMAIL='you@gmail.com'
    DBMON_REMOTEOFFSWITCH='/Users/you/Dropbox/dbmon/OFF'
    DBMON_CONVERT="$MAGICK_HOME/bin/convert"
    DBMON_COMPARE="$MAGICK_HOME/bin/compare"
    DBMON_SCAP="/usr/sbin/screencapture"
    
  5. Now you should be able to test the script out by simply running it.
    computer:dbmon you$ ./start 
    computer:dbmon you$ ./dbmon.sh 
    [08/09/2010 21:20:49] DBMON: Moving /Users/you/dbmon/tmp/alert/current.png to /Users/you/dbmon/tmp/alert/previous.png...
    [08/09/2010 21:20:49] DBMON: Snapping /Users/you/dbmon/tmp/alert/current.png...
    [08/09/2010 21:20:50] DBMON: Comparing /Users/you/dbmon/tmp/alert/current.png to /Users/you/dbmon/tmp/alert/previous.png...
    [08/09/2010 21:20:51] DBMON: Difference [2925] exceeds tolerance [9]!!
    [08/09/2010 21:20:51] DBMON: Copying /Users/you/dbmon/tmp/alert/current.png to /Users/you/Dropbox/dbmon/201008/20100809-212049.png...
    [08/09/2010 21:20:51] DBMON: Sending alert email to you@gmail.com...
    [08/09/2010 21:20:51] DBMON: Snapping 1
    [08/09/2010 21:20:54] DBMON: Snapping 2
    computer:dbmon you$ ./stop 
    
    
  6. Once you’ve got it working, you can create a crontab entry to run it on a regular basis. Place the following in your crontab…
    * * * * * /Users/you/dbmon/dbmon.sh > /dev/null 2>&1
    

    Keep in mind – this will run EACH AND EVERY MINUTE OF EVERY HOUR OF EVERY DAY OF EVERY MONTH – unless of course you implement the remote off switch file. I created two scripts “start” and “stop” for use in conjunction with the crontab file. The start file simply removes the remote off switch and the stop script replaces it by “touch”ing that file.

    start

    #!/bin/sh
    #===========================================================================
    #= Script : Monitoring your Mac Desktop with Dropbox
    #= File   : start
    #= Version: 0.2
    #= Author : Mike Lynn
    #= Email  : merlynn@gmail.com
    #= Website: http://www.mlynn.org/2010/08/how-to-monitor-your-mac-desktop-with-dropbox/
    #===========================================================================
    #= Copyright (c) 2010 Mike Lynn
    #= You are free to use and modify this script as long as this header
    #= section stays intact
    #= This file is part of the "Monitoring your Mac Desktop with Dropbox" script
    #=
    #= This program is free software; you can redistribute it and/or modify
    #= it under the terms of the GNU General Public License as published by
    #= the Free Software Foundation; either version 2 of the License, or
    #= ( at your option ) any later version.
    #=
    #= This program is distributed in the hope that it will be useful,
    #= but WITHOUT ANY WARRANTY; without even the implied warranty of
    #= MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    #= GNU General Public License for more details.
    #=
    #= You should have received a copy of the GNU General Public License
    #= along with Mobile Detection Script ; if not, write to the Free Software
    #= Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
    #===========================================================================
    
    . ~/.dbmon
    if [ -z $DBMON_REMOTEOFFSWITCH ]; then
    	echo "No remote off switch set for dropbox monitor.  Exiting."
    	exit 1
    fi
    rm $DBMON_REMOTEOFFSWITCH
    
    

    stop

    #!/bin/sh
    #===========================================================================
    #= Script : Monitoring your Mac Desktop with Dropbox
    #= File   : stop
    #= Version: 0.2
    #= Author : Mike Lynn
    #= Email  : merlynn@gmail.com
    #= Website: http://www.mlynn.org/2010/08/how-to-monitor-your-mac-desktop-with-dropbox/
    #===========================================================================
    #= Copyright (c) 2010 Mike Lynn
    #= You are free to use and modify this script as long as this header
    #= section stays intact
    #= This file is part of the "Monitoring your Mac Desktop with Dropbox" script
    #=
    #= This program is free software; you can redistribute it and/or modify
    #= it under the terms of the GNU General Public License as published by
    #= the Free Software Foundation; either version 2 of the License, or
    #= ( at your option ) any later version.
    #=
    #= This program is distributed in the hope that it will be useful,
    #= but WITHOUT ANY WARRANTY; without even the implied warranty of
    #= MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    #= GNU General Public License for more details.
    #=
    #= You should have received a copy of the GNU General Public License
    #= along with Mobile Detection Script ; if not, write to the Free Software
    #= Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
    #===========================================================================
    . ~/.dbmon
    if [ -z $DBMON_REMOTEOFFSWITCH ]; then
            echo "No remote off switch set for dropbox monitor.  Exiting."
            exit 1
    fi
    touch $DBMON_REMOTEOFFSWITCH
    
    

    Be sure to edit the path’s to the REMOTEOFFSWITCH variable in the .dbmon configuration file located in your home directory.

You will probably want to make sure you have the start and stop scripts configured on several of your machines so that you can remotely control execution of the monitoring script. Keep in mind your environment (like where you have Dropbox installed) may change – so you will need to make sure you configure the REMOTEOFFSWITCH variable accordingly for each installed computer.

Notes and warnings

  • Dropbox offers free storage starting at 2GB – a lot of space… but keep in mind that if you accidentally leave this monitoring script running while you’re logged on you’re going to eventually fill it up and run out of space.
  • A note regarding multiple monitors: This script will only monitor the primary monitor so if you’re using multiple monitors, keep this in mind.
  • Make sure that when you’re testing, you’re haven’t configured the script to write your temporary screen capture files to a place that will visibly change the monitor – like the desktop for example.
  • This initial version of the script contains the configuration variables and might be difficult for someone to implement if they’re not command shell savvy. The next version will probably be a bit more sophisticated and might even incorporate a gui component… let me know if you’re interested in something like by leaving a comment or sending me an email.

Mobile Device Detection and Redirection with Perl and CGI

Last month, I took some time and wrote about Mobile Device Detection and Redirection with PHP. Well, it turns out that some folks can’t (or choose not to) make use of PHP and favor the Perl/CGI approach to web development. This article covers the same bases and presents a set of examples implemented using Perl and Lincoln Stein’s great CGI.pm module.

Download Code and Examples Here:
From Github: http://github.com/mrlynn/MobileBrowserDetectionExample

or locally:
Version 0.3 (Latest – includes perl/cgi AND PHP examples)
[download id=”2″]

Version 0.2 (Older version – PHP examples only)
[download id=”1″]

View the working example using Perl/CGI here: https://mlynn.org/uatest/cgi-bin/index.cgi

Redirecting a user based on the type of device they are using is not rocket science. In fact, it can be accomplished quite simply using an apache redirect in a .htaccess file.

RewriteCond %{HTTP_USER_AGENT} ^.*iPad.*$
RewriteRule ^(.*)$ http://ipad.yourdomain.com [R=301]

The issue with this approach is that users coming to your site using an iPad will never have the ability to see the other versions of your site. for many, that may be a satisfactory solution. However, if you want users to have the ability to view a version of your site designed specifically for their type of mobile device by default – but have the option to click a link and either view or optionally set a preference for another version of the site, this article is for you.

Perl and CGI have been around for many years and are in wide use on the web. Perl is extremely extensible and using the very popular CGI.pm Perl Module written by Lincoln Stein, it’s very easy to write code to dynamically manage your web site.

Where PHP has built-in variables designed to expose the server and apache session environment ($_SERVER, $_SESSION), Perl and CGI.pm make use of %ENV and module variables such as param(). Consider the following table which contrasts PHP and Perl/CGI.

User Agent

PHP

$_SERVER['HTTP_USER_AGENT']

Perl/CGI

$ENV{HTTP_USER_AGENT}

Reading Cookies

PHP

$cookievalue = $_COOKIE['COOKIENAME']

Perl/CGI

use CGI;
$query=new CGI;
$cookievalue = $query-&gt;cookie('COOKIENAME');

Setting Cookies

PHP

setcookie(name, value, expire, path, domain);

Perl/CGI

$cookie = $query-&gt;cookie(-name=&gt;'COOKIENAME',
			 -value=&gt;'COOKIEVALUE',
			 -expires=&gt;'+4h',
			 -path=&gt;'/');
print $query-&gt;header(-cookie=&gt;$cookie);

Now that we have the basics down, the rest is easy. We’ll want to check the users’ device type by querying the user agent, check the value of a cookie to see if they’ve specified a preference for something other than the site designed for their specific device and redirect accordingly.

The initial landing page does most of the heavy lifting.

index.cgi

#!/usr/bin/perl
require 'includes/config.inc.pl';
require 'includes/functions.inc.pl';

use CGI;
$query = new CGI; 

$useragent = $ENV{HTTP_USER_AGENT};
$sitepref = $query->cookie( 'SITEPREF' );

if ( ismobile( $useragent ) ) {
        if ( !$sitepref ) {
          if ( isipad( $useragent ) ) {
                  print $query->redirect( "$IPADURL" );
          } else {
              if ( isiphone( $useragent ) ) {
                          print $query->redirect( "$IPHONEURL" );
                  } else {
                          print $query->redirect( "$MOBILEURL" );
                  }
          }
        } else {
          if ( $sitepref=='MOBILE' ) {
                  print $query->redirect( "$MOBILEURL" );
          } else {
                  if ( $sitepref=='IPHONE' ) {
                          print $query->redirect( "$IPHONEURL" );
                  } else {
                          if ( $sitepref=='IPAD' ) {
                                  print $query->redirect( "$IPADURL" );
                          } else {
                                  print $query->redirect( "$NORMALURL" );
                          }
                  }
            }
        }
} else {
    if ( !$sitepref ) {
          print $query->redirect( "$NORMALURL" );
    } else {
      if ( $sitepref=='MOBILE' ) {
          print $query->redirect( "$MOBILEURL" );
      } else {
          if ( $sitepref=='IPAD' ) {
              print $query->redirect( "$IPADURL" );
          } else {
              if ( $sitepref=='IPHONE' ) {
                  print $query->redirect( "$IPHONEURL" );
              } else {
                  print $query->redirect( "$NORMALURL" );
              }
          }  
      }
    }
}

And the included files… which set the URL values and contain many of the functions.

functions.inc.pl

sub setcookiealive() {
        my ($name,$value,$expires,$redirect) = @_;
        $cookie = $query->cookie(-name=>"$name",
                         -value=>"$value",
                         -expires=>'+5d',
                         -path=>'/');
        if ($redirect) {
                print $query->redirect("$redirect","-cookie=>$cookie");
        } else {
                print $query->header(-cookie=>$cookie);
        }
}

sub in_array {
     my ($arr,$search_for) = @_;
     my %items = map {$_ => 1} @$arr; # create a hash out of the array values
     return (exists($items{$search_for}))?1:0;
}

sub ismobile {
        $useragent=lc(@_);
        $is_mobile = '0';

        if($useragent =~ m/(android|up.browser|up.link|mmp|symbian|smartphone|midp|wap|phone)/i) {
                $is_mobile=1;
        }

        if((index($ENV{HTTP_ACCEPT},'application/vnd.wap.xhtml+xml')>0) || ($ENV{HTTP_X_WAP_PROFILE} || $ENV{HTTP_PROFILE})) {
                $is_mobile=1;
        }

        $mobile_ua = lc(substr $ENV{HTTP_USER_AGENT},0,4);
        @mobile_agents = ('w3c ','acs-','alav','alca','amoi','andr','audi','avan','benq','bird','blac','blaz','brew','cell','cldc','cmd-','dang','doco','eric','hipt','inno','ipaq','java','jigs','kddi','keji','leno','lg-c','lg-d','lg-g','lge-','maui','maxo','midp','mits','mmef','mobi','mot-','moto','mwbp','nec-','newt','noki','oper','palm','pana','pant','phil','play','port','prox','qwap','sage','sams','sany','sch-','sec-','send','seri','sgh-','shar','sie-','siem','smal','smar','sony','sph-','symb','t-mo','teli','tim-','tosh','tsm-','upg1','upsi','vk-v','voda','wap-','wapa','wapi','wapp','wapr','webc','winw','winw','xda','xda-');

        if(in_array(@mobile_agents,$mobile_ua)) {
                $is_mobile=1;
        }

        if ($ENV{ALL_HTTP}) {
                if (index(lc($ENV{ALL_HTTP}),'OperaMini')>0) {
                        $is_mobile=1;
                }
        }

        if (index(lc($ENV{HTTP_USER_AGENT}),'windows')>0) {
                $is_mobile=0;
        }
    return $is_mobile;
}

sub isiphone {

        $useragent = @_;
        $iphone=0;
        if (lc($useragent) =~ m/iphone/) {
                $iphone=1;
        }
        return $iphone;
}

sub isipad {

        $useragent = @_;
        $ipad=0;
        if (lc($useragent) =~ m/ipad/) {
                $ipad=1;
        }
        return $ipad;
}
1;

config.inc.pl

$SITEURL='https://mlynn.org/uatest/cgi-bin/index.cgi';
$LOGFILE='debug.log';
$MOBILEURL='https://mlynn.org/uatest/cgi-bin/mobile/index.cgi';
$IPHONEURL='https://mlynn.org/uatest/cgi-bin/iphone/index.cgi';
$IPADURL='https://mlynn.org/uatest/cgi-bin/ipad/index.cgi';
$NORMALURL='https://mlynn.org/uatest/cgi-bin/normal/index.cgi';
1;

Related Sites and Interesting Links

Have a site you’d like to add to this list? Send me an email or submit a comment.

SOLVED: My WordPress Thumbnails Stopped Thumbnailing

The server where I host this blog experienced some oddness and the web server daemon (httpd) had to be restarted.  Once it came back up and it was determined that the primary DNS server on which we rely had crapped out, we were able to point to another DNS server and things seemed to get back to normal.  With a few minor exceptions that is… most notably, thumbnails were no longer thumbnailing.

This WordPress theme uses a

TimThumb script created by Tim McDaniels and Darren Hoyt with tweaks by Ben Gillbanks

. To diagnose the problem, the first place I looked (like every good web administrator) is the logs.

[Wed Jul 14 05:41:11 2010] [error] [client xx.xx.xx.xx] PHP Fatal error:  Allowed memory size of 31457280 bytes exhausted (tried to allocate 12288 bytes) in /path/to/my/web/home/httpdocs/wp-content/themes/mytheme/thumb.php on line 271, referer: http://www.mlynn.org/wp-admin/post.php?post=127&amp;action=edit&amp;message=1

AHA! The problem became obvious and easy to solve. The problem appears to be that the memory_limit value in the php configuration file (php.ini) has been set to low. Sure enough it was set to 4M.

A quick edit of the php.ini file…

;;;;;;;;;;;;;;;;;;;
; Resource Limits ;
;;;;;;;;;;;;;;;;;;;

max_execution_time = 30     ; Maximum execution time of each script, in seconds
max_input_time = 60     ; Maximum amount of time each script may spend parsing request data
memory_limit = 48M      ; Maximum amount of memory a script may consume</pre>
And a quick restart of apache...
<pre>/etc/init.d/httpd graceful

and blam-o… we’re back in business…. thumbnail’s a thumb’n.

If you don’t have root permissions – or don’t have access to your own php.ini file, you may need to contact the support team where you host your web site. Questions? Comments?

Mobile Device Detection and Redirection with PHP

** Updated 04/26/2010 **  Added Google Mobile Crawling Detection
See also http://www.mlynn.org/2010/07/mobile-device-detection-and-redirection-with-perl-and-cgi/ for additional information on Mobile Browser Detection and Redirection using Perl / CGI.

Target Audience

Web Content Publishers, Web Server Administrators and anyone considering preparing and publishing content that may be consumed by users with mobile devices.

Overview

The mobile phone and computing market is exploding. With more and more phones and hand held devices gaining web browsing capability, it only makes sense to ensure that your site is at least viewable by these mobile browsers. In this article, I present one possible solution for detecting and redirecting incoming mobile browsers so you can customize and enhance the mobile users’ experience.

In this article, I’ll discuss an example web site where we want to present customized web content to four distinct types of user based on the browser device their using when they visit the site. I’ll also discuss how to enable the users to specify a preference for one of the other versions of the site. For example, if I’m an iphone user but I really want to see the full site.

Redirecting a user based on the type of device they are using is not rocket science. In fact, it can be accomplished quite simply using an apache redirect in a .htaccess file.

RewriteCond %{HTTP_USER_AGENT} ^.*iPad.*$
RewriteRule ^(.*)$ http://ipad.yourdomain.com [R=301]

The issue with this approach is that users coming to your site using an iPad will never have the ability to see the other versions of your site. for many, that may be a satisfactory solution. However, if you want users to have the ability to view a version of your site designed specifically for their type of mobile device by default – but have the option to click a link and either view or optionally set a preference for another version of the site, this article is for you.

Examples and Source Code

I know – you’re in a hurry… you’ve read the intro and you know this is what you’re after… well, here you go… The examples for this site are available for demonstration at https://mlynn.org/uatest/ and the code for this is available for download from the following link:

Version 0.3 – Includes PHP and Perl/CGI Examples
[download id=”2″ format=”1″ autop=”false”]

Version 0.2 – Includes only PHP Examples
[download id=”1″ format=”1″ autop=”false”]

You may additionally download or review the source for this example at github:
http://github.com/mrlynn/MobileBrowserDetectionExample

Before diving in to my solution, let’s cover some of the background and key factors. If you’re a seasoned web publisher and you already understand the basics of the web and how it works, you’ll probably want to skip down a bit.

There are several components involved in any web user interaction.

Web Browsing Device (Device)

This can be any device running some form of browser.  Desktop computers are the most popular devices browsing the web today but mobile devices are swiftly increasing in numbers.  According to statcounter.com, mobile browsers have experienced a 3 percent increase since 2008 and with the advent of hybrid devices such as the ipad and netbook, you can bet this number will continue to grow.

Web Browsing Program (Browser)

This refers to the program being run by the device for the purpose of browsing web content.  Popular browsers include Firefox, Google Chrome, Microsoft Internet Explorer and Opera.  Each browser communicates with web servers in a similar manner.  When the web browser contacts a web server, it sends several pieces of data identifying its program, version and even the device being used for this browsing session.

Web Server (Server)

The web server is responsible for presenting web content to the browsers.  Apache HTTPD and Microsoft Internet Information Server (IIS) are the two most popular web servers.

Web Content

This is the stuff you’re sending to the browser… the stuff you’re reading right now.  Depending on the type of site and your intended audience, you’re likely to have several types of content being delivered to your browsers.

The Conversation

When you type an address into your browser, or click on a link to a web site, the browser initiates a conversation with the target web server.  Much of this conversation is handled by the browser and hidden from you, the viewer.  The following is an example of a conversation initiated by a browser.

GET /uatest/index.php HTTP/1.1
Host: www.mlynn.org
User-Agent: Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.1)

In this example, a user is requesting the following url: http://www.mlynn.org/uatest/index.php from an instance of Firefox browser running on a windows device.

Here’s a list of other possible values sent along with a request for web content.

Header Value
Host http://www.mlynn.org
Connection keep-alive
User-Agent Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10_6_3; en-US) AppleWebKit/533.4 (KHTML, like Gecko) Chrome/5.0.375.86 Safari/533.4
Referer mlynn.org
Accept application/xml,application/xhtml+xml,text/html;q=0.9,text/plain;q=0.8,image/png,*/*;q=0.5
Accept-Encoding gzip,deflate,sdch
Accept-Language en-US,en;q=0.8
Accept-Charset ISO-8859-1,utf-8;q=0.7,*;q=0.3
Cookie __utma=2051572.1472781444.1277919157.1277919157.1277919157.1; __utmc=2051572; __utmb=2051572.1.10.1277919157

Here’s a look at what your actual request headers look like when you’re browser requested this page:

And this is the response sent back to your browser from the instance of apache httpd running on my server:

Apache’s httpd server exposes the values of some of these request and response headers.  If you’re using the Pre-Hypertext Programming language – or PHP as it’s better known, you can access these values using built-in functions.  See PHP: apache_request_headers and PHP: apache_response_headers for more information.

Identifying Mobile Devices

Now that we have a good understanding of the conversation between the browser and the server, let’s focus on identifying mobile devices and redirection.  As I briefly explained earlier, the web browser identifies the browser program and version along with any requests for content from your web server.  The browser identifies these items using the string “User-Agent.”  The trick to identifying mobile devices is all about knowing what is sent in the User-Agent request field by each and every mobile device.  The following is an example sent by a mobile device.

User-Agent: Mozilla/5.0 (iPhone; U; CPU iPhone OS 3_0 like Mac OS X; en-us) AppleWebKit/528.18 (KHTML, like Gecko) Version/4.0 Mobile/7A341 Safari/528.16

Redirecting Based on User Agent

So now we understand that the browser identifies itself, and if we’re using Apache httpd, we can access the value of that identifier. Let’s take a look a simple redirection example written in PHP.

[php]
if (preg_match(‘/iphone|ipad/’,strtolower($_SERVER[‘HTTP_USER_AGENT’]))) {
header("Location: http://mobile.mlynn.org&quot;);
} else {
header("Location: http://www.mlynn.org&quot;);
}
[/php]

This example interrogates the user agent variable using a php regular expression function and redirects accordingly. This redirection is facilitated using the PHP header() function.

There are several other mechanisms to accomplish similar redirection. For example, you could implement this redirection using a .htaccess file which would be parsed by Apache. This mechanism is discussed in detail on this blog entry. For now however, let’s stick to our PHP implementation.

If all you’re concerned about is redirecting users to another version of the site, this will probably work for you. You’ll simply need to understand and test for the right user-agent values.

However, let’s assume that we want to get a bit trickier. Let’s say we want to have different content or formatting for four separate versions of our site – one for each variant of browsing device that we want to support. One for normal desktop computer browsers, another for iPhone browsers, another for iPad users and one more for all other mobile browsing devices. The reasons for this are many and varied. You may want simply to vary the advertising code you expose to each user based on the type of device or browser they’re using.

To make this type of implementation work, I’ve created a configuration file to initialize some variables for our site. For each distinct version of the site, I’ll create a variable with the appropriate url. I’ll use these later when we write the code for our redirection script.

config.inc.php

[php]
$SITEURL=’https://mlynn.org/uatest/&#8217;;
$LOGFILE=’debug.log’;
$MOBILEURL=’https://mlynn.org/uatest/mobile/&#8217;; // Generic Mobile Device URL
$IPHONEURL=’https://mlynn.org/uatest/iphone/&#8217;; // iPhone URL
$IPADURL=’https://mlynn.org/uatest/ipad/&#8217;; // iPad URL
$NORMALURL=’https://mlynn.org/uatest/normal/&#8217;; // Normal – Full site URL
[/php]

Now let’s take a look at what our main index page or landing site will look like. This will be the initial page visited by users before being automatically redirected based on their browser device type.

[php]
$useragent=$_SERVER[‘HTTP_USER_AGENT’];
if (ismobile($useragent)) {
if (isipad($_SERVER[‘HTTP_USER_AGENT’])) {
header("Location: $IPADURL");
} else {
if (isiphone($_SERVER[‘HTTP_USER_AGENT’])) {
header("Location: $IPHONEURL");
} else {
header("Location: $MOBILEURL");
}
}
} else {
header("Location: $NORMALURL");
}
[/php]

This code snippet relies on several important custom functions: ismobile(), isiphone(), and isipad().

The first function examines the user agent value and returns a ‘0’ if the device is not recognized as a mobile device and a ‘1’ if it is mobile.

[php]
function ismobile() {
$is_mobile = ‘0’;

if(preg_match(‘/(googlebot-mobile|android|up.browser|up.link|mmp|symbian|smartphone|midp|wap|phone)/i’, strtolower($_SERVER[‘HTTP_USER_AGENT’]))) {
$is_mobile=1;
}

if((strpos(strtolower($_SERVER[‘HTTP_ACCEPT’]),’application/vnd.wap.xhtml+xml’)>0) or ((isset($_SERVER[‘HTTP_X_WAP_PROFILE’]) or isset($_SERVER[‘HTTP_PROFILE’])))) {
$is_mobile=1;
}

$mobile_ua = strtolower(substr($_SERVER[‘HTTP_USER_AGENT’],0,4)); $mobile_agents = array(‘w3c ‘,’acs-‘,’alav’,’alca’,’amoi’,’andr’,’audi’,’avan’,’benq’,’bird’,’blac’,’blaz’,’brew’,’cell’,’cldc’,’cmd-‘,’dang’,’doco’,’eric’,’hipt’,’inno’,’ipaq’,’java’,’jigs’,’kddi’,’keji’,’leno’,’lg-c’,’lg-d’,’lg-g’,’lge-‘,’maui’,’maxo’,’midp’,’mits’,’mmef’,’mobi’,’mot-‘,’moto’,’mwbp’,’nec-‘,’newt’,’noki’,’oper’,’palm’,’pana’,’pant’,’phil’,’play’,’port’,’prox’,’qwap’,’sage’,’sams’,’sany’,’sch-‘,’sec-‘,’send’,’seri’,’sgh-‘,’shar’,’sie-‘,’siem’,’smal’,’smar’,’sony’,’sph-‘,’symb’,’t-mo’,’teli’,’tim-‘,’tosh’,’tsm-‘,’upg1′,’upsi’,’vk-v’,’voda’,’wap-‘,’wapa’,’wapi’,’wapp’,’wapr’,’webc’,’winw’,’winw’,’xda’,’xda-‘);

if(in_array($mobile_ua,$mobile_agents)) {
$is_mobile=1;
}

if (isset($_SERVER[‘ALL_HTTP’])) {
if (strpos(strtolower($_SERVER[‘ALL_HTTP’]),’OperaMini’)>0) {
$is_mobile=1;
}
}

if (strpos(strtolower($_SERVER[‘HTTP_USER_AGENT’]),’windows’)>0) {
$is_mobile=0;
}

return $is_mobile;
}
[/php]

The following functions are used to detect specific device types.

[php]
function isiphone($useragent) {
$iphone=0;
if (preg_match(‘/iphone/’,strtolower($useragent))) {
$iphone=1;
}
return $iphone;
}

function isipad($useragent) {
$ipad=0;
if (preg_match(‘/ipad/’,strtolower($useragent))) {
$ipad=1;
}
return $ipad;
}
[/php]

Now when a user visits our site, they will be redirected automatically based on the specific device they are using. This works in most cases, but let’s assume we want to give users the option of visiting a site other than the default for their device? Let’s say I’m on an iPhone – but I want to see what the real, full site looks like with my browser. To implement this, we’ll need some way for the user to specify a preference for a specific version of the site.

One way to accomplish this is using cookies. Cookies are small bits of data stored on your computer and referenced when you visit or revisit a web site.

There are several ways to set and get the value of cookies. Javascript can be used but depends heavily on the implementation of javascript on the device. Additionally, you must be certain that the user has not disabled javascript on their device in order for this to work.

Fortunately, cookies can be maintained using server-side code such as php. For our example, we’ll stick with PHP.

To accomplish setting and maintaining cookies via php for our users’ site preference, I created the following php script called setpref.php.

[php]
include_once(‘includes/config.inc.php’);
include_once(‘includes/functions.inc.php’);

$pref = (isset($_POST[‘SITEPREF’]) ? $_POST[‘SITEPREF’] : $_GET[‘SITEPREF’]);
switch ($pref) {
case ‘MOBILE’:
setcookiealive(‘SITEPREF’,’MOBILE’,time()+3600);
header("Location: $MOBILEURL");
break;
case ‘IPHONE’:
setcookiealive(‘SITEPREF’,’IPHONE’,time()+3600);
header("Location: $IPHONEURL");
break;
case ‘IPAD’:
setcookiealive(‘SITEPREF’,’IPAD’,time()+3600);
header("Location: $IPADURL");
break;
case ‘NORMAL’:
setcookiealive(‘SITEPREF’,’NORMAL’,time()+3600);
header("Location: $NORMALURL");
break;
default:
setcookiealive(‘SITEPREF’,’NORMAL’,time()+3600);
header("Location: $NORMALURL");
}
[/php]

This function relies on another function called setcookiealive which simply creates the cookie using php’s setcookie() function and also sets the value of the $_COOKIE variable so that the value is available immediately.

[php]
function setcookiealive($name,$value,$expires) {
$_COOKIE[$name] = $value;
setcookie($name,$value,$expires);
}
[/php]

In order for this to work, we need to give the user’s links to the alternate versions of the sites. Let’s look at one of the example site versions.

[php]
<?php
// Main iPad landing Page
include_once(‘../includes/config.inc.php’);
?>
<html>
<head>
<title>iPad Site</title>
</head>
<body>
<h1>iPad Site</h1>
<div id=’content’>
<h2>This is the iPad site. You got here because you are either using an iPad device or you specified a preference for the iPad site.</h2>
<p>
<?
echo "User Agent: ".$_SERVER[‘HTTP_USER_AGENT’];
?>
<p>
</div>
<div id=’footer’>
Visit Other Site Versions:
<a href="<? echo $NORMALURL;?>"/>Full Site</a> ||
<a href="<? echo $MOBILEURL;?>"/>Generic Mobile Site</a> ||
<a href="<? echo $IPHONEURL;?>"/>iPhone Site</a>
<p>
Set your Preference to other site versions:
<a href="/uatest/setpref.php?SITEPREF=NORMAL"/>Full Site</a> ||
<a href="/uatest/setpref.php?SITEPREF=MOBILE"/>Generic Mobile Site</a> ||
<a href="/uatest/setpref.php?SITEPREF=IPHONE"/>iPhone Site</a>
<p>
<?
if (isset($_COOKIE[‘SITEPREF’])) {
$sitepref=$_COOKIE[‘SITEPREF’];
} else {
$sitepref=’UNSET’;
}
print "YOUR CURRENT SITE PREFERENCE: ".$sitepref;

?>
</div>
</html>
[/php]

I’ve explained the components involved in any standard web user interaction, how they relate specifically to device detection, and I’ve showed one implementation of detection and redirection. If you’d like to implement something similar, feel free to download the code using the following link.
[download id=”1″ format=”1″ autop=”false”]

If you do end up using these scripts, drop me an email or log a comment to let me know how you made out. You can also try out this working example.

Example Site Links:

Related Sites and Interesting Links

Have a site you’d like to add to this list? Send me an email or submit a comment.