Description

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The Sampling Function filters out events, based on an expression and a sampling rate.

Usage

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Filter: Filter expression (JS) that selects data to be fed through the Function. Defaults to true, meaning that all events will be evaluated.

Description: Simple description of this Function. Defaults to empty.

Final: If true, stops data from being fed to downstream Functions. Defaults to No.

Sampling rules: Events matching these rules will be sampled at the rates you specify:

• Filter: Filter expression matching events to be sampled. Use true to match all.

• Sampling rate: Enter an integer N. (Defaults to 1.) Sampling will pick 1/N events matching this rule.

How It Works

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Setting this Function’s Sampling rate to 30 would mean that only 1 of every 30 events would be kept.

Let’s assume that we save this setting, and then capture data from a datagen Source by selecting Preview > Start a Capture > Capture. In the Capture Sample Data modal, select: 100 seconds, 100 events, and As they come in. Then start the capture, and Save as Sample File.

Next, in the Preview pane, click Simple beside the new file’s name. If you then click the Basic Statistics (chart) button, you should see that we’ve kept about 4 of the original 100 events, or close to 1 in 30.

Examples

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See Sampling for examples.