README.md

FAQ (Frequently Asked Questions)

Do I have to implement all 4 methods (Collect, Load, Unload, DefinePlugin) in order to enable plugin to work in snap environment?

No. In simple cases only Collect method is required.

However, implementing all of the methods gives the following benefits:

• Collect takes care of gathering measurements
• Load (in pair with Unload) is used for processing configuration, creating shared objects etc. and enables the plugin to handle more than one task simultaneously.
• DefinePlugin helps in plugin maintenance by: providing metadata of what collector may produce.

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Is there a template for a minimal collector?

You can take a look at collector's code from Chapter 1 (see: main.go)

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Should I handle error value from ctx.AddMetric()?

Generally, no. Notice that error may be returned in the following situations:

• you are trying to add metric not aligned with metrics set defined in DefinePlugin (developer error)
• you are trying to add metric with namespace containing disallowed characters (developer error)
• you are trying to add metric which is filtered out (due to using -plugin-filter flag or defining subset of requested metrics) - actually not a logical error

If you find yourself in a situation when you can't find why metric is not present in a result set you can check the value returned from AddMetric in debug mode (or temporarily printing it out).

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How can I test if my plugin is working correctly?

There are several ways to achieve that at different levels:

• you can write unit tests - library provides mock.Context if you want to test Collect method (take a look at ./collector/09-config/collector/*_test.go to see how it can be achieved)
• you can run a plugin in Debug mode
• you can run a plugin with Snap-mock
• you can run a plugin in the Snap environment

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• Table of contents

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