Configuring high availability for Dispatcher
 Technote (troubleshooting)
 
Problem(Abstract)
The steps listed in the administration guide to configure high availability are incorrectly ordered.
 
Cause
When the configuration is saved, Load Balancer (also known as Network Dispatcher in earlier releases) places the commands in the correct order; however, if you write your own configurations, follow these updated steps to avoid problems with ServerUp ServerDown scripts and possible problems with ownership of the clusters that can lead to forwarding problems.
 
Resolving the problem
The following are the correct steps for configuring high availability for the Dispatcher component:
Note: For Network Dispatcher 4.0 (Edge Server 2.0), substitute the use of dscontrol with ndcontrol.
  1. Create alias script files on each of the 2 Dispatcher machines.


  2. Start the server on both Dispatcher server machines.


  3. Start the executor on both machines.


  4. Ensure that the nonforwarding address (NFA) of each Dispatcher machine is configured, and is a valid IP address for the subnet of the Dispatcher machines.

    Windows® platform: For Network Dispatcher versions 4.x and Load Balancer 5.x only:
    In addition, configure each nonforwarding address using the dsconfig command.

    For example:

    dsconfig en0 nfa_addr netmask netmask


  5. Add the heartbeat information on both machines:

    dscontrol highavailability heartbeat add sourceaddress destinationaddress

    Note: sourceaddress and destinationaddress are the IP addresses (either DNS names or dotted-decimal addresses) of the Dispatcher machines.

    The values are reversed on each machine.

    For example:

    Primary - highavailability heartbeat add 9.67.111.3 9.67.186.8
    Backup - highavailability heartbeat add 9.67.186.8 9.67.111.3
    At least one heartbeat pair must have the NFAs on the pair as the source and destination address.

    If possible, it is recommended that a least one of the heartbeat pairs be across a different subnet than the regular cluster traffic. Keeping the heartbeat traffic distinct helps prevent false takeovers during very heavy network loads and also improves complete recovery times after a failover.

    Note: This is unique for Load Balancer 5.1.1 and higher levels:

    Set the number of seconds that the executor uses to timeout high availability heartbeats.

    For example:

    dscontrol executor set hatimeout 3
    The default is 2 seconds.


  6. On both machines, configure the list of IP addresses that the Dispatcher must be able to reach to ensure full service, using the reach add command.

    For example:

    dscontrol highavailability reach add 9.67.125.18

    Reach targets are recommended but not required.


  7. Add the backup information to each machine.
    • For the primary machine:
      dscontrol highavailability backup add primary [auto|manual] port

    • For the backup machine:
      dscontrol highavailability backup add backup [auto|manual] port

    • For mutual high availability each Dispatcher has both primary and backup roles:
      dscontrol highavailability backup add both [auto|manual] port

      Note: Select an unused port on your machines as the port. Your two machines will communicate over this port.


  8. Check the high availability status on each machine:

    dscontrol highavailability status

    The machines must each have the correct role (backup, primary, or both), states, and substates. The primary must be active and synchronized; the backup must be in a standby mode and must be synchronized within a short time. The strategies must be the same.


  9. Set up the cluster, port, and server information on both machines.


  10. Start the manager and advisors on both machines.
 
 
Cross Reference information
Segment Product Component Platform Version Edition
Application Servers Network Dispatcher Multi-Platform 4.0
Application Servers Runtimes for Java Technology Java SDK
 
 


Document Information


Product categories: Software > Application Servers > Distributed Application & Web Servers > WebSphere Application Server > Edge Component
Operating system(s): Windows
Software version: 6.0
Software edition:
Reference #: 1190905
IBM Group: Software Group
Modified date: Sep 3, 2007