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  • NMIS - Polling Policy - Configuring Variable Polling Polices

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Starting with NMIS 8.6.2a user-defined polling polices policies 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:

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The GUI presents a variety of time choices for these attributes, ranging from 1 minute (which is the minimum supported by NMIS) to 1 day; other selections could can be added by editing editing 

conf/Table-Polling-Policy.nmis and , fractional frequency settings (e.g. 3.5m or 1.5h) are supported.

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The policy named "default" is special: any node that is not assigned a particular polling policy is subject to this "default" policy. The "default" policy is always available and contains the old standard 5-minute frequency unless explicitely explicitly overridden.

To change a node's polling frequencies from the defaults supplied, that the node must be assigned a polling policy in its configuration.

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  1. it controls the candidate selection for collect and ping,
  2. and it defines critical parameters for the RRD files that store the collected information.

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Candidate selection

Whenever an NMIS collect cycle starts, only the nodes whose last poll was  longer ago was earlier 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 close as possible with their configured ping frequency.

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The  timing parameters cannot be changed for existing RRD files, and It 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.

When you switch a node to a different polling policy, all its existing RRD files are deleted and new RRD files are created that reflect the new polling policy.

(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 will 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).)

Configuration

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 policies may be added, viewed and deleted.   

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From the 'Polling Policy' drop down menu, the currently configured polling policies will be available for assignment. Once finished click , click the 'Edit and Update Node' button at the bottom of the Edit Node window.

Please note that a polling  polling policy can be deleted only if no nodes are associated with it.

Verification

This step is an optional step, use this 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.

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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.

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The "step" value represents the polling frequency in seconds, in the example above it's a 2-minute polling policy.

ICMP/Ping

In order to verify the ICMP/Ping polling frequency the simplest way is to restart fpingd with logging enabled , and observe its log in logs/fpingd.log:

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