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Starting with NMIS 8.6.2a user-defined polling polices are supported, which allows particular nodes to be polled more or less frequently than the normal 5 minute default. Administrators can define the following attributes when configuring a polling policy:
For nodes that are polled with SNMP and WMI concurrently, the shorter of the two polling frequencies will control overall polling of the node, but data collection with each source type will be attempted based on its frequency settings. This can lead to visually confusing results. It's not recommended to create policies with different timings for SNMP and WMI.
Polling for Service monitoring has supported variable frequencies for quite some time, and is configured independently from nodes: when defining the service parameters in
Services.nmis, you can set the service polling frequency for that particular service.
Polling Interval Defaults, If no policy is assigned or the automatic "default" policy is used:
- ICMP: 1 Minute
- SNMP: 5 Minutes
- WMI: 5 Minutes
Limitations and Caveats
When and how are Polling Policies evaluated?
A polling policy has two effects:
- it controls the candidate selection for collect and ping,
- and it defines critical parameters for the RRD files that store the collected information.
Whenever an NMIS collect cycle starts, only the nodes whose last poll was longer ago than their SNMP/WMI collect frequency are chosen.
(NMIS's nmis.pl starts once every minute, so the interval granularity is 60s. If your policy indicates a frequency of
1.5m (= 90 seconds), then NMIS will poll this node at time T, T+2m, T+4m and so on.)
For PING/ICMP, the NMIS
fpingd component runs always and will try to ping nodes as closely as possible with their configured ping frequency.
RRD parameter setting
Polling policies are also evaluated when a new RRD file is created, because the expected frequency of new data to enter the storage is vital knowledge for the RRD subsystem's functioning.
However, these RRD parameters cannot be modified for an existing RRD file - they can only be given on creation.
Changing the later would have no effect for existing RRD files, and Polling policies can therefore not be modified after having been created.
Changing a node's polling policy discards all of the node's data
The timing parameters cannot be changed for existing RRD files, and It is not feasible to retroactively rework the data in an existing RRD file, therefore switching policies implies a complete loss of all of the node's historic data
(The RRD file deletion does not happen instantly: assuming your node is named X, its rrd directory
database/nodes/X is renamed to
X.policy-<oldpolicy>-<timestamp>, which would then be deleted eventually. To back out of an inadvertent policy change you could remove the new node directory and rename the backup one, after having reset the polling policy associated with the node.)
Configure a Polling Policy
From the NMIS8 home dashboard using the top menu bar navigate to Setup -> Polling Policy. This will render the 'Polling Policy' overview window. From this this window polling polices may be added, viewed and deleted.
In this window enter a 'Policy Name', select the polling frequencies, and optionally add a Description. When finished click the 'Add' button.
Assign the Polling Policy
Polling Policy assignment is done via the Edit Node window. From the NMIS8 top menu bar navigate to System -> System Configuration -> NMIS Nodes (Devices). 'Table Nodes' will render. Click the 'edit' link for a node. The node edit window will render. In the 'Advanced Options' section look for the 'Polling Policy' attribute.
Please note that a polling policy can be deleted only if no nodes are associated with it.
This step is optional, if you need to show and see the verification that the activities are happening with higher or lower frequency. The easiest way is to zoom into one of the graphs for the node, then click on the "Stats" link in the quick access link bar: The column "step" should reflect your polling policy's frequency in seconds. For the default policy you'll see a step of 300 (seconds or 5 minutes). Please note that you will see the true "step" value only if you zoom into the graph.
In order to verify that the polling interval is occurring at the dictated frequency you can request status information from rrdtool. Likely candidate rrd files for each type of polling are listed below.
The "step" value represents the polling frequency in seconds, in the example above it's a 2 minute polling policy.
In order to verify the ICMP/Ping polling frequency the simplest way is to restart fpingd with logging enabled, and observe its log in