User's Manual

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. Excep-

tions 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 ad-

ministrators 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 ex-

ceeding 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.