Amazon AWS: The Simplest Load Balancing Cluster with Failover on Windows and Linux

Manual installation on existing VMs in Amazon AWS of a load balancing cluster with failover (Windows or Linux)

• Configuration of the Amazon AWS load balancer
• Configuration of the Amazon AWS network security
• Package installation on Windows
• Package installation on Linux
• Configuration of SafeKit
• Tests

Configuration of the Amazon AWS load balancer

The load balancer must be configured to periodically send health packets to virtual machines. For that, SafeKit provides a health check which runs inside the virtual machines and which

• returns OK when the farm module state is UP (green)
• returns NOT FOUND in all other states

You must configure the Amazon AWS load balancer with:

• HTTP protocol
• port 9010, the SafeKit web server port
• URL /var/modules/farm/ready.txt (if farm is the module name that you will deploy later)

For more information, see the configuration of the Amazon AWS load balancer.

Configuration of the Amazon AWS network security

The network security must be configured to enable communications for the following protocols and ports:

• UDP - 4800 for the safeadmin service (between SafeKit nodes)
• TCP – 9010 for the load-balancer health check and for the SafeKit web console running the http mode
• TCP – 9001 to configure the https mode for the console
• TCP – 9453 for the SafeKit web console running in the https mode

Package installation on Windows

On both Windows servers

• Install the free version of SafeKit for Cloud (click here) on 2 Windows nodes
• The module farm.safe is delivered inside the package.
• To open firewall, start a command line as administrator, goto C:\safekit\private\bin and type  .\firewallcfg.cmd add on both nodes

Package installation on Linux

On both Linux servers

• Install the free version of SafeKit for Cloud (click here) on 2 Linux nodes
• After the download of safekit_xx.bin package, execute it to extract the rpm and the safekitinstall script and then execute the safekitinstall script
• Answer yes to firewall automatic configuration
• The module farm.safe is delivered inside the package.

Configuration of SafeKit

The configuration is presented with the web console connected to 2 Windows servers but it is the same thing with 2 Linux servers.

Important: all the configuration must be done from a single browser.

It is recommended to configure the web console in the https mode by connecting to https://<IP address of 1 VM>:9453 (next image). In this case, you must configure before the https mode by using the wizard described in the User's Guide: see "11.1 HTTPS Quick Configuration with the Configuration Wizard".

Or you can use the web console in the http mode by connecting to http://<IP address of 1 VM>:9010 (next image).

Note that you can also make a configuration with DNS names, especially if the IP addresses are not static.

Enter IP address of the first node and click on Confirm (next image)

Click on New node and enter IP address of the second node (next image)

Click on the red floppy disk to save the configuration (previous image)

In the Configuration tab, click on farm.safe then enter farm as the module name and Confirm (next images with farm instead of xxx)

Click on Validate (next image)

Do not configure a virtual IP address (next image) because this configuration is already made in the Amazon AWS load balancer. This section is useful for on-premise configuration only.

If a process is defined in the Process Checker section (next image), it will be monitored with the action restart in case of failure. The services will be stopped an restarted locally on the local server if this process disappears from the list of running processes. After 3 unsuccessful local restarts, the module is stopped on the local server. As a consequence, the health check answers NOT FOUND to the Amazon AWS load balancer and the load balancing is reconfigured to load balance the traffic on the remaining servers of the farm.

start_both and stop_both (next image) contain the start and the stop of services.

Click on Validate (previous image)

Click on Configure (previous image)

Check the success green message on both servers and click on Next (previous image)

Start the cluster on both nodes (previous image). Check that the status becomes UP (green) - UP (green) (next image).

The cluster is operational with services running on both UP nodes (previous image).

Be careful, components which are clients of the services must be configured with the virtual IP address. The configuration can be made with a DNS name (if a DNS name has been created and associated with the virtual IP address).

Tests

Check with Windows Microsoft Management Console (MMC) or with Linux command lines that the services are started on both UP nodes. Put  services with Boot Startup Type = Manual (SafeKit controls start of services).

Stop one UP node by scrolling down the menu of the node and by clicking on Stop. Check that the load balancing is reconfigured with only the other node taking all TCP connections. And check that the services are stopped on the STOP node with Windows Microsoft Management Console (MMC) or with Linux command lines.

More information on tests in the User's Guide

Automatic start of the module at boot

Configure boot start (next image on the right side) configures the automatic boot of the module when the server boots. Do this configuration on both nodes once the load balancing and failover solution is correctly running.

Note that for synchronizing SafeKit at boot and at shutdown on Windows, we assume that a command line has been run on both nodes during installation as administrator: .\addStartupShutdown.cmd in C:\safekit\private\bin (otherwise dot it now).

For reading the SafeKit logs, go to the Troubleshooting tab

For editing userconfig.xml, start_both and stop_both, go to the Advanced Configuration tab

Internal files of a SafeKit / Microsoft Azure load balancing cluster with failover

Internal files of the Windows farm.safe module

<!DOCTYPE safe>
<safe>
<service mode="farm" maxloop="3" loop_interval="24">
  <!-- Farm topology configuration -->
  <!-- Names or IP addresses on the default network are set during initialization in the console -->
  <farm>
    <lan name="default" />
  </farm>
  <!-- Software Error Detection Configuration -->
  <!-- Replace
       * PROCESS_NAME by the name of the process to monitor
  -->
  <errd polltimer="10">
    <proc name="PROCESS_NAME" atleast="1" action="restart" class="both" />
  </errd>
  <!-- User scripts activation -->
  <user nicestoptimeout="300" forcestoptimeout="300" logging="userlog" />
</service>
</safe>

@echo off

rem Script called on all servers for starting applications

rem For logging into SafeKit log use:
rem "%SAFE%\safekit" printi | printe "message"

rem stdout goes into Application log
echo "Running start_both %*" 

set res=0

rem Fill with your services start call

set res=%errorlevel%
if %res% == 0 goto end

:stop
set res=%errorlevel%
"%SAFE%\safekit" printe "start_both failed"

rem uncomment to stop SafeKit when critical
rem "%SAFE%\safekit" stop -i "start_both"

:end

@echo off

rem Script called on all servers for stopping application

rem For logging into SafeKit log use:
rem "%SAFE%\safekit" printi | printe "message"

rem ----------------------------------------------------------
rem
rem 2 stop modes:
rem
rem - graceful stop
rem   call standard application stop with net stop
rem
rem - force stop (%1=force)
rem   kill application's processes
rem
rem ----------------------------------------------------------

rem stdout goes into Application log
echo "Running stop_both %*" 

set res=0

rem default: no action on forcestop
if "%1" == "force" goto end

rem Fill with your services stop call

rem If necessary, uncomment to wait for the real stop of services
rem "%SAFEBIN%\sleep" 10

if %res% == 0 goto end

"%SAFE%\safekit" printe "stop_both failed"

:end

Internal files of the Linux farm.safe module

<!DOCTYPE safe>
<safe>
<service mode="farm" maxloop="3" loop_interval="24">
  <!-- Farm topology configuration for the membership protocol -->
  <!-- Names or IP addresses on the default network are set during initialization in the console -->
  <farm>
    <lan name="default" />
  </farm>
  <!-- Software Error Detection Configuration -->
  <!-- Replace
       * PROCESS_NAME by the name of the process to monitor
  -->
  <errd polltimer="10">
    <proc name="PROCESS_NAME" atleast="1" action="restart" class="both" />
  </errd>
  <!-- User scripts activation -->
  <user nicestoptimeout="300" forcestoptimeout="300" logging="userlog" />
</service>
</safe>

#!/bin/sh
# Script called on the primary server for starting application

# For logging into SafeKit log use:
# $SAFE/safekit printi | printe "message" 

# stdout goes into Application log
echo "Running start_both $*" 

res=0

# Fill with your application start call

if [ $res -ne 0 ] ; then
  $SAFE/safekit printe "start_both failed"

  # uncomment to stop SafeKit when critical
  # $SAFE/safekit stop -i "start_both"
fi

#!/bin/sh
# Script called on the primary server for stopping application

# For logging into SafeKit log use:
# $SAFE/safekit printi | printe "message" 

#----------------------------------------------------------
#
# 2 stop modes:
#
# - graceful stop
#   call standard application stop
#
# - force stop ($1=force)
#   kill application's processes
#
#----------------------------------------------------------

# stdout goes into Application log
echo "Running stop_both $*" 

res=0

# default: no action on forcestop
[ "$1" = "force" ] && exit 0

# Fill with your application stop call

[ $res -ne 0 ] && $SAFE/safekit printe "stop_both failed"