Chapter 4: Installation Up Main page

5 The Load Balancer

The load balancer works by having all nodes in the cluster share one or more IP addresses, which InterWorx Control Panel uses to host websites as it normally does. This sharing is managable since none of the Clustered Nodes answer ARP requests from your network infrastructure. The Cluster Manager answers any ARP requests for the clustered IP address and then decides which of the Clustered Nodes will actually be servicing the request. The Cluster Manager then forwards the request to the Node which will service it by doing address translation.
It is possible to change which services a given node provides by manipulating the load-balancer policies for various services. This is done from the Cluster Manager, and is not possible to do from a Node.

5.3.1 Changing the Default Load-Balancing Policy

  1. In NodeWorx, open the Clustering menu item if it is not already open.
  2. Click the Load Balancing menu item.
  3. Select the new default policy you would like to set from the drop-down list in the Load Balancer Information table.
  4. Press the Update button to commit your changes.

5.3.2 Adding a Load-Balanced Service

figure images/clustering/cl1-service-add.png
Figure 5.1 The Add Service Dialog, Part 1
figure images/clustering/cl1-service-add2.png
Figure 5.2 The Add Service Dialog, Part 2
  1. In NodeWorx, open the Clustering menu item if it is not already open.
  2. Click the Load Balancing menu item.
  3. Click ’Add Service’ next to Load Balanced Services.
  4. Select the service you wish to balance from the dropdown.
  5. Select the Virtual IP you wish to load-balance the service for from the dropdown.
  6. Choose the Load Balancing Policy from the dropdown.
  7. Select your persistence value from the radio button list.
  8. Press the Continue button to proceed to node selection.
  9. Enable or disable nodes that will serve requests.
  10. Click ’Save’ to commit your changes.

5.3.3 Deleting a Load-Balanced Service

figure images/clustering/cl1-service-del.png
Figure 5.3 The Delete Service Confirmation Dialog.
  1. In NodeWorx, open the Clustering menu item if it is not already open.
  2. Click the Load Balancing menu item.
  3. Select the check box next to the service you wish to delete.
  4. Press the ’Delete Selected Services’ button.
  5. Press ’Delete’ to commit your changes.

Footnotes

[A]More information on LVS-NAT can be found at http://www.linuxvirtualserver.org/VS-NAT.html
[B]More information on LVS-DR can be found at http://www.linuxvirtualserver.org/VS-DRouting.html
[C]More information on LVS-TUN can be found at http://www.linuxvirtualserver.org/VS-IPTunneling.html
[D]Note: If this shared storage device is mounted after InterWorx is installed, you may need to create the following symlinks:
  • /home/interworx to /usr/local/interworx
/home/vpopmail to /var/vpopmail
[E]This can be done after the cluster is setup if you wish.
[F]Doing a pre-addition test weeds out 90% of Node addition errors that can occur.
[G]Successful tests are denoted by the message: “» Node passed all pre-cluster tests” at the top of the screen.
[H]Node addition may take from several seconds to many minutes depending on the network speed and Manager/Node server speed.

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