# Associate functions with distributions To use a function with a distribution, you associate the function with one or more cache behaviors in the distribution. You can associate a function with multiple cache behaviors in multiple distributions. You can associate a function with any of the following: + An existing cache behavior + A new cache behavior in an existing distribution + A new cache behavior in a new distribution When you associate a function with a cache behavior, you must choose an *event type*. The event type determines when CloudFront runs the function. You can choose the following event types: + **Viewer request** – The function runs when CloudFront receives a request from a viewer. + **Viewer response** – The function runs before CloudFront returns a response to the viewer. You can't use origin-facing event types (*origin request* and *origin response*) with CloudFront Functions. Instead you can use Lambda@Edge. For more information, see [CloudFront events that can trigger a Lambda@Edge function](lambda-cloudfront-trigger-events.md). **Note** Before you associate a function, you must [publish it](publish-function.md) to the `LIVE` stage. You can associate a function with a distribution in the CloudFront console or with the AWS Command Line Interface (AWS CLI). The following procedure shows how to associate a function with an existing cache behavior. ------ #### [ Console ] **To associate a function with an existing cache behavior** 1. Sign in to the CloudFront console at [https://console.aws.amazon.com/cloudfront/v4/home#/functions](https://console.aws.amazon.com/cloudfront/v4/home#/functions) and choose the **Functions** page. 1. Choose the function that you want to associate. 1. On the **Function** page, choose the **Publish** tab. 1. Choose **Publish function**. 1. Choose **Add association**. On the dialog box that appears, choose a distribution, an event type, and/or a cache behavior. For the event type, choose when you want this function to run: + **Viewer Request** – Run the function every time CloudFront receives a request. + **Viewer Response** – Run the function every time CloudFront returns a response. 1. To save the configuration, choose **Add association**. CloudFront associates the distribution with the function. Wait a few minutes for the associated distribution to finish deploying. You can choose **View distribution** on the function details page to check the progress. ------ #### [ CLI ] **To associate a function with an existing cache behavior** 1. Open a command line window. 1. Enter the following command to save the distribution configuration for the distribution whose cache behavior you want to associate with a function. This command saves the distribution configuration to a file named `dist-config.yaml`. To use this command, do the following: + Replace *`DistributionID`* with the distribution's ID. + Run the command on one line. In the example, line breaks are provided to make the example more readable. ``` aws cloudfront get-distribution-config \ --id DistributionID \ --output yaml > dist-config.yaml ``` When the command is successful, the AWS CLI returns no output. 1. Open the file named `dist-config.yaml` that you created. Edit the file to make the following changes. 1. Rename the `ETag` field to `IfMatch`, but don't change the field's value. 1. In the cache behavior, find the object named `FunctionAssociations`. Update this object to add a function association. The YAML syntax for a function association looks like the following example. + The following example shows a viewer request event type (trigger). To use a viewer response event type, replace `viewer-request` with `viewer-response`. + Replace *`arn:aws:cloudfront::111122223333:function/ExampleFunction`* with the Amazon Resource Name (ARN) of the function that you're associating with this cache behavior. To get the function ARN, you can use the **aws cloudfront list-functions** command. ``` FunctionAssociations: Items: - EventType: viewer-request FunctionARN: arn:aws:cloudfront::111122223333:function/ExampleFunction Quantity: 1 ``` 1. After making these changes, save the file. 1. Use the following command to update the distribution, adding the function association. To use this command, do the following: + Replace *`DistributionID`* with the distribution's ID. + Run the command on one line. In the example, line breaks are provided to make the example more readable. ``` aws cloudfront update-distribution \ --id DistributionID \ --cli-input-yaml file://dist-config.yaml ``` When the command is successful, you see output like the following that describes the distribution that was just updated with the function association. The following example output is truncated for readability. ``` Distribution: ARN: arn:aws:cloudfront::111122223333:distribution/EBEDLT3BGRBBW ... truncated ... DistributionConfig: ... truncated ... DefaultCacheBehavior: ... truncated ... FunctionAssociations: Items: - EventType: viewer-request FunctionARN: arn:aws:cloudfront::111122223333:function/ExampleFunction Quantity: 1 ... truncated ... DomainName: d111111abcdef8.cloudfront.net Id: EDFDVBD6EXAMPLE LastModifiedTime: '2021-04-19T22:39:09.158000+00:00' Status: InProgress ETag: E2VJGGQEG1JT8S ``` ------ The distribution's `Status` changes to `InProgress` while the distribution is redeployed. When the new distribution configuration reaches a CloudFront edge location, that edge location starts using the associated function. When the distribution is fully deployed, the `Status` changes back to `Deployed`. This indicates that the associated CloudFront function is live in all CloudFront edge locations worldwide. This typically takes a few minutes.