Appendix C. Probes
As described in Section 6.9 Monitoring — 
, systems entitled with
Monitoring can have probes applied against them to constantly confirm their
health and full operability. This appendix lists the available probes
broken down by command group, such as Apache.
Many probes that monitor internal aspects of your systems, rather than externally facing components such as httpd, require the installation of the Red Hat Network Monitoring Daemon (rhnmd). This requirement is noted within the individual probe reference.
Each probe has its own reference that identifies required fields (marked with *), default values, and the thresholds that may be set to trigger alerts. Similarly, the beginning of each command group's section contains information applicable to all probes in that group. But before we begin examining individual probes, let's cover general guidelines for them all.
 | Note |
|---|---|
Nearly all of the probes use Transmission Control Protocol (TCP) as their transport protocol. Exceptions to this are noted within the individual probe references. |
C.1. Probe guidelines
The purpose of each probe is to obtain metrics from and identify the status of the
system or application being monitored. To accomplish this, first review the probe
descriptions in this appendix. Then apply relevant probes to Monitoring-entitled
systems within your organization, as described in Section 6.9 Monitoring — .
While adding those probes, select meaningful thresholds that when crossed notify you and your administrators of problems within your infrastructure. All probes that have been scheduled but are not yet running show a PENDING status in the Status Bar, while those with successful results not exceeding any thresholds display an OK status. Note that thresholds can be minimums, maximums, or both, depending on the probe.
A CRITICAL status is reported for the probe if it returns a value exceeding its critical threshold, while a WARNING status is returned for metrics beyond the warning threshold. Probes not run on the target system within the selected timeout period usually result in an UNKNOWN status, but not always. Timeout periods are entered in seconds, unless otherwise indicated. Exceptions to these rules are noted within the individual probe references.
 | Important |
|---|---|
Some probes have thresholds based upon time. In order for CRITICAL and WARNING thresholds based upon time to work as intended, their values cannot exceed the amount of time allotted to the timeout period. Otherwise, an UNKNOWN status will be returned in all instances of extended latency, thereby nullifying the thresholds. For this reason, Red Hat strongly recommends ensuring timeout periods exceed all timed thresholds. |