SafeKit quick installation guide for a new Linux application (farm.safe module for network load balancing and failover))

SafeKit quick installation guide for a new application Linux (farm.safe)

Step by step configuration

2. Configure node addresses

Enter the node IP addresses, press the Tab key to check connectivity and fill node names.
Then, click on Save and apply to save the configuration.

If either node1 or node2 has a red color, check connectivity of the browser to both nodes and check firewall on both nodes for troubleshooting.

In a farm architecture, you can define more than 2 nodes.

If you want, you can add a new LAN for a second heartbeat.

This operation will place the IP addresses in the cluster.xml file on both nodes (more information in the training with the command line).

4. Configure the module

Choose an Automatic start of the module at boot without delay in Module startup at boot.
Normally, you have a single Heartbeat network (except if you add a LAN at step 2).
Enter a Virtual IP address. A virtual IP address is a standard IP address in the same IP network (same subnet) as the IP addresses of both nodes.
Application clients must be configured with the virtual IP address (or the DNS name associated with the virtual IP address).
Set the service port to load balance (ex.: TCP 80 for HTTP, TCP 443 for HTTPS, TCP 9010 in the example).
Set the load balancing rule, Source address or Source port:
- with the source IP address of the client, the same client will be connected to the same node in the farm on multiple TCP sessions and retrieve its context on the node.
- with the source TCP port of the client, the same client will be connected to different nodes in the farm on multiple TCP sessions (without retrieving a context).
Note that if a process name is displayed in Monitored processes/services, it will be monitored with a restart action in case of failure. Configuring a wrong process name will cause the module to stop right after its start.

5. Edit scripts (optional)

start_both and stop_both must contain starting and stopping of the Linux application (example provided for Microsoft IIS on the right).
You can add new services in these scripts.
Check that the names of the services started in these scripts are those installed on both nodes, otherwise modify them in the scripts.
On Windows and on both nodes, with the Windows services manager, set Boot Startup Type = Manual for all the services registered in start_both (SafeKit controls the start of services in start_both).

8. Wait for the transition to UP (green) / UP (green)

Node 1 and node 2 should reach the UP (green) state, which means that the start_both script has been executed on node 1 and node 2.

If UP (green) is not reached or if the application is not started, analyze why with the module log of node 1 or node 2.

click the "log" icon of node1 or node2 to open the module log and look for error messages such as a checker detecting an error and stopping the module.
click on start_both in the log: output messages of the script are displayed on the right and errors can be detected such as a service incorrectly started.

9. Testing

SafeKit brings a built-in test in the product:

Configure a rule for TCP port 9010 with a load balancing on source TCP port.
Connect an external workstation outside the farm nodes.
Start a browser on http://virtual-ip:9010/safekit/mosaic.html.

You should see a mosaic of colors depending on nodes answering to HTTP requests.

Stop one UP (green) node by scrolling down its contextual menu and clicking Stop.
Check that there is no more TCP connections on the stopped node and on the virtual IP address.

More information on tests in the User's Guide.

Internals

Internal files of a SafeKit / Linux load balancing cluster with failover

Go to the Advanced Configuration tab in the console, for editing these files

Internal files of the Linux farm.safe module

userconfig.xml (description in the User's Guide)

<!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>
  <!-- Virtual IP Configuration -->
  <!-- Replace
     * VIRTUAL_IP_ADDR_TO_BE_DEFINED by the IP address of your virtual server 
  -->
  <vip>
    <interface_list>
      <interface check="on" arpreroute="on">
        <virtual_interface type="vmac_directed">
          <virtual_addr addr="VIRTUAL_IP_ADDR_TO_BE_DEFINED" where="alias"/>
        </virtual_interface>
      </interface>
    </interface_list>
    <loadbalancing_list>
      <group name="Windows_Appli">
        <!-- Set load-balancing rule on the TCP port of the service to load balance -->
        <rule port="TCP_PORT_TO_BE_DEFINED" proto="tcp" filter="on_addr"/>
      </group>
    </loadbalancing_list>
  </vip>
  <!-- TCP Checker Configuration -->
  <!-- Replace
     * VIRTUAL_IP_ADDR_TO_BE_DEFINED by the IP address of your virtual server 
     * TCP_PORT_TO_BE_DEFINED by the TCP port of the service to check
  -->
  <check>
    <tcp ident="Check_Appli" when="both">
      <to
         addr="VIRTUAL_IP_ADDR_TO_BE_DEFINED"
         port="TCP_PORT_TO_BE_DEFINED"
         interval="10"
         timeout="5"
       />
    </tcp>
  </check>
  <!-- User scripts activation -->
  <user nicestoptimeout="300" forcestoptimeout="300" logging="userlog" />
</service>
</safe>

start_both

#!/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

stop_both

#!/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"