Liveness and readiness probes customization

This document describes how to customize the liveness and readiness probes for WebLogic Server instance Pods.

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Liveness probe customization

The liveness probe is configured to check that a server is alive by querying the Node Manager process. By default, the liveness probe is configured to check liveness every 45 seconds and to timeout after 5 seconds. If a pod fails the liveness probe, Kubernetes will restart that container.

You can customize the liveness probe interval and timeout using the livenessProbe attribute under the serverPod element of the domain resource.

Following is an example configuration to change the liveness probe interval and timeout value.

  serverPod:
    livenessProbe:
      periodSeconds: 30
      timeoutSeconds: 10

After the liveness probe script (livenessProbe.sh) performs its normal checks, you can customize the liveness probe by specifying a custom script, which will be invoked by livenessProbe.sh. You can specify the custom script either by using the livenessProbeCustomScript attribute in the domain resource or by setting the LIVENESS_PROBE_CUSTOM_SCRIPT environment variable using the env attribute under the serverPod element (see the configuration examples below). If the custom script fails with a non-zero exit status, the liveness probe will fail and Kubernetes will restart the container.

  • The spec.livenessProbeCustomScript domain resource attribute affects all WebLogic Server instance Pods in the domain.
  • The LIVENESS_PROBE_CUSTOM_SCRIPT environment variable takes precedence over the spec.livenessProbeCustomScript domain resource attribute when both are configured, and, like all domain resource environment variables, can be customized on a per domain, per cluster, or even a per server basis.
  • Changes to either the domain resource attribute or the environment variable on a running domain take effect on running WebLogic Server instance Pods when such Pods are restarted (rolled).

Note: The liveness probe custom script option is for advanced usage only and its value is not set by default. If the specified script is not found, then the custom script is ignored and the existing liveness script will perform its normal checks.

Note: Oracle recommends against having any long running calls (for example, any network calls or executing wlst.sh) in the liveness probe custom script.

Use the following configuration to specify a liveness probe custom script using the livenessProbeCustomScript domain resource field.

spec:
  livenessProbeCustomScript: /u01/customLivenessProbe.sh

Use the following configuration to specify the liveness probe custom script using the LIVENESS_PROBE_CUSTOM_SCRIPT environment variable.

    serverPod:
      env:
      - name: LIVENESS_PROBE_CUSTOM_SCRIPT
        value: /u01/customLivenessProbe.sh

The following operator-populated environment variables are available for use in the liveness probe custom script, which will be invoked by livenessProbe.sh.

ORACLE_HOME or MW_HOME: The Oracle Fusion Middleware software location as a file system path within the container.

WL_HOME: The Weblogic Server installation location as a file system path within the container.

DOMAIN_HOME: The domain home location as a file system path within the container.

JAVA_HOME: The Java software installation location as a file system path within the container.

DOMAIN_NAME: The WebLogic Server domain name.

DOMAIN_UID: The domain unique identifier.

SERVER_NAME: The WebLogic Server instance name.

LOG_HOME: The WebLogic log location as a file system path within the container. This variable is available only if its value is set in the configuration.

NOTES:

  • Additional operator-populated environment variables that are not listed above, are not supported for use in the liveness probe custom script.

  • The custom liveness probe script can call source $DOMAIN_HOME/bin/setDomainEnv.sh if it needs to set up its PATH or CLASSPATH to access WebLogic utilities in its domain.

  • A custom liveness probe must not fail (exit non-zero) when the WebLogic Server instance itself is unavailable. This could be the case when the WebLogic Server instance is booting or about to boot.

Readiness probe customization

By default, the readiness probe is configured to use the WebLogic Server ReadyApp framework. The ReadyApp framework allows fine customization of the readiness probe by the application’s participation in the framework. For more details, see Using the ReadyApp Framework. The readiness probe is used to determine if the server is ready to accept user requests. The readiness is used to determine when a server should be included in a load balancer’s endpoints, in the case of a rolling restart, when a restarted server is fully started, and for various other purposes.

By default, the readiness probe is configured to check readiness every 5 seconds and to timeout after 5 seconds. You can customize the readiness probe interval and timeout using the readinessProbe attribute under the serverPod element of the domain resource.

Following is an example configuration to change readiness probe interval and timeout value.

  serverPod:
    readinessProbe:
      periodSeconds: 10
      timeoutSeconds: 10