# Using AWS Lambda to handle EventBridge events
<a name="using_lambda"></a>

You can use Amazon EBS and Amazon EventBridge to automate your data-backup workflow. This requires you to create an IAM policy, a AWS Lambda function to handle the event, and an EventBridge rule that matches incoming events and routes them to the Lambda function.

The following procedure uses the `createSnapshot` event to automatically copy a completed snapshot to another Region for disaster recovery. 

**To copy a completed snapshot to another Region**

1. Create an IAM policy, such as the one shown in the following example, to provide permissions to use the `CopySnapshot` action and write to the EventBridge log. Assign the policy to the user that will handle the EventBridge event.

------
#### [ JSON ]

****  

   ```
   {
     "Version":"2012-10-17",		 	 	 
     "Statement": [
       {
         "Effect": "Allow",
         "Action": [
           "logs:CreateLogGroup",
           "logs:CreateLogStream",
           "logs:PutLogEvents"
         ],
         "Resource": "arn:aws:logs:*:*:*"
       },
       {
         "Effect": "Allow",
         "Action": [
           "ec2:CopySnapshot"
         ],
         "Resource": "*"
       }
     ]
   }
   ```

------

1. Define a function in Lambda that will be available from the EventBridge console. The sample Lambda function below, written in Node.js, is invoked by EventBridge when a matching `createSnapshot` event is emitted by Amazon EBS (signifying that a snapshot was completed). When invoked, the function copies the snapshot from `us-east-2` to `us-east-1`.

   ```
   // Sample Lambda function to copy an EBS snapshot to a different Region
    
   var AWS = require('aws-sdk');
   var ec2 = new AWS.EC2();
    
   // define variables
   var destinationRegion = 'us-east-1';
   var sourceRegion = 'us-east-2';
   console.log ('Loading function');
    
   //main function
   exports.handler = (event, context, callback) => {
    
       // Get the EBS snapshot ID from the event details
       var snapshotArn = event.detail.snapshot_id.split('/');
       const snapshotId = snapshotArn[1];
       const description = `Snapshot copy from ${snapshotId} in ${sourceRegion}.`;
       console.log ("snapshotId:", snapshotId);
   
       // Load EC2 class and update the configuration to use destination Region to initiate the snapshot.
       AWS.config.update({region: destinationRegion});
       var ec2 = new AWS.EC2();
   
       // Prepare variables for ec2.modifySnapshotAttribute call
       const copySnapshotParams = {
           Description: description,
           DestinationRegion: destinationRegion,
           SourceRegion: sourceRegion,
           SourceSnapshotId: snapshotId
       };
    
       // Execute the copy snapshot and log any errors
       ec2.copySnapshot(copySnapshotParams, (err, data) => {
           if (err) {
               const errorMessage = `Error copying snapshot ${snapshotId} to Region ${destinationRegion}.`;
               console.log(errorMessage);
               console.log(err);
               callback(errorMessage);
           } else {
               const successMessage = `Successfully started copy of snapshot ${snapshotId} to Region ${destinationRegion}.`;
               console.log(successMessage);
               console.log(data);
               callback(null, successMessage);
           }
       });
   };
   ```

   To ensure that your Lambda function is available from the EventBridge console, create it in the Region where the EventBridge event will occur. For more information, see the [AWS Lambda Developer Guide](https://docs.aws.amazon.com/lambda/latest/dg/).

1. Open the Amazon EventBridge console at [https://console.aws.amazon.com/events/](https://console.aws.amazon.com/events/).

1. In the navigation pane, choose **Rules**, and then choose **Create rule**.

1. For **Step 1: Define rule detail**, do the following:

   1. Enter values for **Name** and **Description**.

   1. For **Event bus**, keep **default**.

   1. Ensure that **Enable the rule on the selected event bus** is toggled on.

   1. For **Event type**, select **Rule with an event pattern**.

   1. Choose **Next**.

1. For **Step 2: Build event pattern**, do the following:

   1. For **Event source**, select **AWS events or EventBridge partner events**.

   1. In the **Event pattern** section, for **Event source**, ensure that **AWS service** is selected, and for **AWS service**, select **EC2**.

   1. For **Event type**, select **EBS Snapshot Notification**, select **Specific event(s)**, and then choose **createSnapshot**.

   1. Select **Specific result(s)** and then choose **succeeded**.

   1. Choose **Next**.

1. For **Step 3: Select targets**, do the following:

   1. For **Target types**, choose **AWS service**.

   1. For **Select target**, choose **Lambda function**, and for **Function** select the function that you created earlier.

   1. Choose **Next**

1. For **Step 4: Configure tags**, specify tags for the rule if needed, and then choose **Next**.

1. For **Step 5: Review and create**, review the rule and then choose **Create rule**.

Your rule should now appear on the **Rules** tab. In the example shown, the event that you configured should be emitted by EBS the next time you copy a snapshot.