Operations by the HA for Oracle Web Tier Fault Monitors

Language:

The two resource types, ORCL.ohs and ORCL.opmn, contain separate fault probes that query the health of the Oracle HTTP Server and Oracle Process Management and Notification Server components, respectively.

Operations by the Oracle Process Management and Notification Server Fault Monitor

The ORCL.opmn fault probe for the Oracle Process Management and Notification Server component performs the following steps:

Checks that the opmnctl command exists in the /ORACLE-HOME/instances/INSTANCE-NAME/bin directory, and that the script is executable.
Checks that the opmn.xml file is valid by using the following command:
```
$ opmnctl validate
```

If either of these two checks fail, then an attempt is made to fail over (give over) the service to another node.
If both checks succeed, then the command opmnctl ping is run.
- If this command succeeds, the resource status is set to OK and the probe returns with an exit code of 0.
- If this command fails, the resource status is set to FAULTED and the probe returns with an exit code of 100, causing the resource to attempt to restart.

Operations by the Oracle HTTP Server Fault Monitor

Because the Oracle HTTP Server component is under the control of Oracle Process Management and Notification Server component, the ORCL.opmn fault probe obtains the status of the Oracle HTTP Server component from the Oracle Process Management and Notification Server component. This is done in two stages:

Checks that an Oracle HTTP Server component with type OHS is found in the output of the following command:
```
$ opmnctl status ias-component=COMPONENT-INSTANCE -noheaders -fmt "%typ"
```
Checks that the Oracle HTTP Server component is reported as ALIVE by the following command:
```
$ opmnctl status ias-component=COMPONENT-INSTANCE -noheaders -fmt "%sta"
```

If the fault probe is successful, the resource status is set to OK and the probe returns with an exit code of 0. If the fault probe fails, the resource status is set to FAULTED and the probe returns with an exit code of 100, causing the resource to attempt to restart.

Note - If the Oracle HTTP Server component is used as a load-balancer through the mod_wl_ohs plugin, then the Oracle Process Management and Notification Server component can declare that the Oracle HTTP Server component is DOWN if none of the load-balancing targets are available. In these circumstances, the fault probe for the Oracle HTTP Server component attempts to restart the service. You can avoid such behavior by creating a dependency between the load-balancer resource and the target resources.