Tarantella Administration Guide > Arrays, servers and load balancing > Troubleshooting CPU/memory-based application server load balancing

Troubleshooting CPU/memory-based application server load balancing

If you experience problems with CPU or memory-based application server load balancing, you can get information from various places to help you understand what is happening:

• Tarantella server log files - add the following filters on the Array properties panel in Array Manager:
  

  server/tier3loadbalancing/*:t3loadbal%%PID%%.log
  server/tier3loadbalancing/*:t3loadbal%%PID%%.jsl

  This provides detailed information about the decision to launch an application and the data being sent by the application server.
• application server log files - for UNIX application servers these will be in the same directory as the Tarantella Enhancement Module, by default this is /opt/tta-tem. For Windows application servers, this information displays in the Event Viewer.
• load balancing service connection cgi program - visit the following URL:
  http://application_server_DNS_name:3579?get&ttalbinfo

You can use this information to troubleshoot the following symptoms:

The load balancing service isn't working

• If you are using Tarantella Enterprise 3, have you added an Advanced Load Management license key to your array?
  If you have, have you also done a warm restart of the primary Tarantella server (tarantella restart --warm)?
  You must do both of these things to start using the Tarantella load balancing service.
• Has the Tarantella Enhancement Module been installed on all application servers and is it running?
  Use the load balancing service connection cgi program to check.
• Is the primary Tarantella server running?
  The load balancing service on the application server sends load information to the primary Tarantella server. If the primary is not available, Tarantella uses Fewest application sessions as the method for load balancing application servers.
• Is your firewall blocking the load balancing service?
  For the load balancing service to work, the firewall must allow:
  • a TCP connection on port 3579 between the Tarantella server and the application server.
  • a UDP connection on port 3579 between the application server and the Tarantella server.

  Note These connections do not need to be authenticated.

• What do the Tarantella server log files show?

Tarantella ignores a server-specific load balancing properties file

After creating a server-specific load balancing properties file, you must do a warm restart of the primary Tarantella server (tarantella restart --warm).

One application server is never picked

• Has the Tarantella Enhancement Module been installed and is it running?
  Use the load balancing service connection cgi program to check.
• Is the application server available to launch applications?
  Check the host object in Object Manager.

One application server is always picked regardless of its load

• Is more than one application server configured to run the application?
  Check the hosts tab for the application object.
• Are the other application servers available to launch applications?
  Check the host objects in Object Manager.
• Are you using the correct algorithm?
  Check the array-wide and application object settings.
• Are you using server affinity?
  Server affinity is on by default.
• What do the Tarantella server log files show?
• What do the application server log files show?
• Has the Tarantella Enhancement Module has been installed?
  Use the load balancing service connection to check.

Two identical application servers, but one launches more applications than the other

• Is the server weighting value for the servers the same?

The server log file shows an update received for an unknown id

If the Tarantella server log file shows an information message which contains the text 'Got an update for unknown id id from machine application server DNS name' this can be ignored. It occurs only when the primary Tarantella server is restarted.