Using HP Serviceguard for Linux to Provide High Availability for LAMP, December 2005

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Using HP Serviceguard for Linux to Provide High

Availability for LAMP

December 2005

Executive Summary...................................................................... 2

Introduction ................................................................................ 2

Audience ................................................................................. 3

Providing high availability to the LAMP stack .................................. 3

Background.............................................................................. 3

Separate LAMP configuration................................................... 3

Consolidated LAMP configuration............................................. 3

Package Configuration............................................................ 3

Approach ................................................................................ 4

High availability for Consolidated LAMP configuration ................ 4

High availability for Separate LAMP configuration ...................... 5

Configuring LAMP for high availability........................................... 5

Separate LAMP configuration ..................................................... 5

Consolidated LAMP configuration ............................................... 6

Additional configuration steps .................................................... 9

SELinux Considerations .............................................................. 10

Toolkit Script Modifications......................................................... 11

Conclusion ............................................................................... 12

Related Materials ...................................................................... 12

Summary of content (12 pages)

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Using HP Serviceguard for Linux to Provide High Availability for LAMP December 2005 Executive Summary...................................................................... 2 Introduction ................................................................................ 2 Audience ................................................................................. 3 Providing high availability to the LAMP stack .................................. 3 Background.......................................................
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Executive Summary LAMP is an open source web server solution which is both powerful and stable that can be used to create business applications. The acronym LAMP stands for Linux, Apache, MySQL, and PHP/Perl/Python where Apache is the web server, MySQL the database, and PHP/Perl/Python are server side scripting languages for creating dynamic web pages. All these applications running on the open source OS, Linux, constitute the LAMP stack.
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except where explicitly mentioned in this white paper. The instructions in this white paper are based on the tests that were conducted on various configurations. Audience This document is for users of HP Serviceguard on Linux who want to take advantage of a complete web based database solution in the form of the LAMP stack running on a cluster which is highly available. It is assumed that the reader has a general understanding of HP Serviceguard for Linux and the LAMP components and features.
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Approach The existing Toolkits for Apache and MySQL have been leveraged to package the LAMP setup with HP Serviceguard for Linux. The Apache and MySQL toolkits for HP Serviceguard for Linux consist of sets of shell scripts that startup, shutdown and monitor the Apache web server and the MySQL database applications. These two toolkits can be used to simplify the packaging of Apache and MySQL with HP Serviceguard for Linux. In the LAMP “Separate packages” configuration, these toolkits are employed as is.
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High availability for Separate LAMP configuration Web Pkg A Apache Server A Pkg B MySQL data MySQL Server B Figure 2: Apache and MySQL running as separate packages in a Separate LAMP configuration In this configuration, the MySQL database and Apache Web server (with PHP) can run on separate machines. Failure of one application or node results in a restart of only that application on its adoptive node. Here Apache and MySQL would run as separate Serviceguard packages.
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Consolidated LAMP configuration In this configuration, since Apache and MySQL will run as a single Serviceguard for Linux package, only a single package configuration file and a single package control script need to be created. This package control script would make use of the toolkit scripts of both Apache and MySQL to start, monitor, and stop the respective services.
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Edit the package configuration file (lamp_single_pkg.config) and change the PACKAGE_NAME and NODE_NAME fields according to the comments given in that file template. The next set of editable fields in the package configuration file defines the path to the package control file. Enter the path to the package control script for both the RUN_SCRIPT and HALT_SCRIPT. In the package configuration file used in the development of this white paper, these entries look as follows.
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LV[1]="/dev/vg02/lvol0"; FS[1]="/MySQL_1"; FS_TYPE[1]="ext3"; FS_MOUNT_OPT[1]="-o rw" LV[0] is the logical volume of Apache’s mount point and FS[0] is the mount point for the shared Apache directory, whereas LV[1] is the logical volume of MySQL’s mount point and FS[1] is the mount point for the shared MySQL directory. IP[0]="15.70.191.61" SUBNET[0]="15.70.191.0" IP[0] is the virtual IP for the package lamp_single HA_APP_SERVER="post-IP" Enabling this variable initiates a call to the toolkit.
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A sample hahttp.conf file and hamysql.conf changes for the above example is shown below. For a complete description of all variables listed in the hahttp.conf and hamysql.conf files and their sample values, please refer to the respective toolkit README files. hahttp.conf SERVER_ROOT="/etc/httpd" PID_FILE="/var/run/httpd.pid" HTTP_SERVICE_NAME="http.monitor" HTTP_SERVICE_CMD="/usr/local/cmcluster/conf/http_pkg/hahttp.
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Listen 15.70.191.61:80 DocumentRoot "/Apache" # This should be changed to whatever you set DocumentRoot to. # Options Indexes FollowSymLinks AllowOverride None Order allow, deny Allow from all my.cnf [mysqld] datadir=/MySQL_1/mysql socket=/MySQL_1/mysql/mysql.sock port=3306 # Default to using old password format for compatibility with mysql 3.x # clients (those using the mysqlclient10 compatibility package). # old_passwords=1 [mysql.
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Toolkit Script Modifications The “hamysql.sh” also known as Toolkit Main Script contains the internal functions that support start/stop of a MySQL instance. While stopping the MySQL instance, this script terminates the process first and immediately afterwards unmounts the shared volume. Unmount occurs cleanly only if the instance is properly terminated. The time required to stop the MySQL instance however varies with the size of the database.
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Conclusion HP Serviceguard for Linux provides high availability to the LAMP stack in business critical environments. By following the recommended procedures one can get a highly available LAMP stack in an environment where both the database and the web server run in a consolidated environment on a single server and also in an environment where the web server and the database run on separate servers. This white paper has given guidelines on two possible configurations.