In a deployment that provides high availability, multiple Liberty servers are used to provide active/active availability. The active/active pattern allows multiple Liberty servers to allow connections from clients and continue to function when some of the Liberty servers fail.
Detecting server failure
To detect if a Liberty server has failed, you
can use logs in your load balancer. In the load
balancer, monitor the response where you use the
health/live endpoint to determine
which Liberty servers to route clients to. If the
response from the
endpoint for a particular Liberty server is
503, that Liberty server may have
For more information about the endpoint and its responses, see The health/live endpoint.
503if it is not started, in the startup process, or there is a temporary loss of connection to another component. Liberty can restart as a non-leader if it temporarily loses the connection to a component and loses leadership. If this is the reason for the
503, the following message is displayed in the IBM_i2_Component_Availability.log file:
For more information about the log file, see Monitor the system availability.
INFO ApplicationStateHandler - I2ANALYZE_STATUS:0066 - Application is entering non-leader mode to serve requests
If a Liberty server fails, the other Liberty servers continue to function as usual. If a client was connected to the failed Liberty server, the analyst might have to log out from the client and log in again for the load balancer to route the request to one of the live Liberty servers.
If it was the leader Liberty server that failed, one of the remaining Liberty servers is elected leader. For more information about the leadership process, see Liberty leadership configuration.
Recovering failed serversThere are a number of reasons why a server might fail. Use the logs from the failed server to diagnose and solve the issue. For example, you might need to restart the server, increase the hardware specification, or replace hardware components.
- The Liberty logs are in the deploy\wlp\usr\servers\opal-server\logs directory.
- The deployment toolkit logs are in the toolkit\configuration\logs directory.
For more information about the different log files and their contents, see Deployment log files.
Reinstating high availability
On the recovered Liberty server, run
setup -t startLiberty to restart
the server and i2 Analyze application.
You can use the load balancer logs to ensure
that the Liberty server is now returning
200 from the