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			105 lines
		
	
	
		
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			Markdown
		
	
	
	
	
	
			
		
		
	
	
			105 lines
		
	
	
		
			4.9 KiB
		
	
	
	
		
			Markdown
		
	
	
	
	
	
---
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title: Impression data
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---
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:::info Availability
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The impression data feature was introduced in **Unleash 4.7**. Listening for events requires [an SDK that supports impression data events](../sdks/index.md#server-side-sdk-compatibility-table). Currently, it's only supported in the [Unleash Proxy client](../sdks/proxy-javascript.md) and [React Proxy client](../sdks/proxy-react.md).
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:::
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Unleash can provide you with **impression data** about the toggles in your application. Impression data contains information about a specific feature toggle activation check: The client SDK will emit an **impression event** whenever it calls `isEnabled` or `getVariant`.
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Impression data was designed to make it easier for you to **collect analytics data**, **perform A/B tests**, and **enrich experiments** in your applications. It contains information about the feature toggle and the related [Unleash Context](../user_guide/unleash-context.md).
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Impression data is **opt-in on a per-toggle basis**. Unleash will not emit impression events for toggles not marked as such. Once you've turned impression data on for a toggle, you can start listening for impression events in your client SDK.
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## Impression event data
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There's two types of impression events you can listen for:
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- [`isEnabled` events](#example-isenabled)
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- [`getVariant` events](#example-getvariant)
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The `getVariant` event contains all the information found in an `isEnabled` event in addition to extra data that's only relevant to `getVariant` calls.
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This table describes all the properties on the impression events:
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| Property name | Description                                                                          | Event type               |
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|---------------|--------------------------------------------------------------------------------------|--------------------------|
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| `eventType`   | The type of the event: `isEnabled` or `getVariant`                                   | All                      |
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| `eventId`     | A globally unique id (GUID) assigned to this event.                                  | All                      |
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| `context`     | A representation of the current [Unleash Context](../user_guide/unleash-context.md). | All                      |
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| `enabled`     | Whether the toggle was enabled or not at when the client made the request.           | All                      |
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| `featureName` | The name of the feature toggle.                                                      | All                      |
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| `variant`     | The name of the active variant                                                       | `getVariant` events only |
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### Example `isEnabled`  event {#example-isenabled}
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```js
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{
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  eventType: 'isEnabled',
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  eventId: '84b41a43-5ba0-47d8-b21f-a60a319607b0',
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  context: {
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    sessionId: 54085233,
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    appName: 'my-webapp',
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    environment: 'default'
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  },
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  enabled: true,
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  featureName: 'my-feature-toggle',
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}
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```
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### Example `getVariant` event {#example-getvariant}
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```js
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{
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  eventType: 'getVariant',
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  eventId: '84b41a43-5ba0-47d8-b21f-a60a319607b0',
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  context: {
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    sessionId: 54085233,
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    appName: 'my-webapp',
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    environment: 'default'
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  },
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  enabled: true,
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  featureName: 'my-feature-toggle',
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  variant: 'variantA'
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}
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```
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## Enabling impression data
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Impression data is strictly an **opt-in** feature and must be enabled on a **per-toggle basis**.
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You can enable and disable it both when you create a toggle and when you edit a toggle.
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You can enable impression data via the impression data toggle in the admin UI's toggle creation form. You can also go via the [the API, using the `impressionData` option](../api/admin/feature-toggles-api-v2.md#create-toggle). For more detailed instructions, see [the section on enabling impression data in the how-to guide for capturing impression data](../how-to/how-to-capture-impression-data.mdx#step-1).
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## Example setup
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:::caution
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This functionality is currently only supported in the [Unleash Proxy client](../sdks/proxy-javascript.md) and [React Proxy client](../sdks/proxy-react.md).
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:::
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The exact setup will vary depending on your [client SDK](../sdks/index.md). The below example configures the [Unleash Proxy client](/sdks/proxy-javascript) to listen for impression events and log them to the console. If "my-feature-toggle" is configured to emit impression data, then it will trigger an impression event as soon as Unleash is ready.
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```js
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const unleash = new UnleashClient({
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  url: 'https://eu.unleash-hosted.com/hosted/proxy',
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  clientKey: 'your-proxy-key',
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  appName: 'my-webapp',
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});
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unleash.start();
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unleash.on("ready", () => {
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  unleash.isEnabled("my-feature-toggle");
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})
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unleash.on("impression", (event) => {
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  // Capture the event here and pass it internal data lake or analytics provider
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  console.log(event);
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})
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```
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