# Create an EventBridge rule for a CodeCommit source (CloudFormation template)
To use CloudFormation to create a rule, update your template as shown here.
**To update your pipeline CloudFormation template and create EventBridge rule**
1. In the template, under `Resources`, use the `AWS::IAM::Role` CloudFormation resource to configure the IAM role that allows your event to start your pipeline. This entry creates a role that uses two policies:
+ The first policy allows the role to be assumed.
+ The second policy provides permissions to start the pipeline.
**Why am I making this change?** Adding the `AWS::IAM::Role` resource enables CloudFormation to create permissions for EventBridge. This resource is added to your CloudFormation stack.
------
#### [ YAML ]
```
EventRole:
Type: AWS::IAM::Role
Properties:
AssumeRolePolicyDocument:
Version: 2012-10-17
Statement:
-
Effect: Allow
Principal:
Service:
- events.amazonaws.com
Action: sts:AssumeRole
Path: /
Policies:
-
PolicyName: eb-pipeline-execution
PolicyDocument:
Version: 2012-10-17
Statement:
-
Effect: Allow
Action: codepipeline:StartPipelineExecution
Resource: !Join [ '', [ 'arn:aws:codepipeline:', !Ref 'AWS::Region', ':', !Ref 'AWS::AccountId', ':', !Ref AppPipeline ] ]
```
------
#### [ JSON ]
```
"EventRole": {
"Type": "AWS::IAM::Role",
"Properties": {
"AssumeRolePolicyDocument": {
"Version": "2012-10-17",
"Statement": [
{
"Effect": "Allow",
"Principal": {
"Service": [
"events.amazonaws.com"
]
},
"Action": "sts:AssumeRole"
}
]
},
"Path": "/",
"Policies": [
{
"PolicyName": "eb-pipeline-execution",
"PolicyDocument": {
"Version": "2012-10-17",
"Statement": [
{
"Effect": "Allow",
"Action": "codepipeline:StartPipelineExecution",
"Resource": {
"Fn::Join": [
"",
[
"arn:aws:codepipeline:",
{
"Ref": "AWS::Region"
},
":",
{
"Ref": "AWS::AccountId"
},
":",
{
"Ref": "AppPipeline"
}
]
...
```
------
1. In the template, under `Resources`, use the `AWS::Events::Rule` CloudFormation resource to add an EventBridge rule. This event pattern creates an event that monitors push changes to your repository. When EventBridge detects a repository state change, the rule invokes `StartPipelineExecution` on your target pipeline.
**Why am I making this change? ** Adding the `AWS::Events::Rule` resource enables CloudFormation to create the event. This resource is added to your CloudFormation stack.
------
#### [ YAML ]
```
EventRule:
Type: AWS::Events::Rule
Properties:
EventPattern:
source:
- aws.codecommit
detail-type:
- 'CodeCommit Repository State Change'
resources:
- !Join [ '', [ 'arn:aws:codecommit:', !Ref 'AWS::Region', ':', !Ref 'AWS::AccountId', ':', !Ref RepositoryName ] ]
detail:
event:
- referenceCreated
- referenceUpdated
referenceType:
- branch
referenceName:
- main
Targets:
-
Arn:
!Join [ '', [ 'arn:aws:codepipeline:', !Ref 'AWS::Region', ':', !Ref 'AWS::AccountId', ':', !Ref AppPipeline ] ]
RoleArn: !GetAtt EventRole.Arn
Id: codepipeline-AppPipeline
```
------
#### [ JSON ]
```
"EventRule": {
"Type": "AWS::Events::Rule",
"Properties": {
"EventPattern": {
"source": [
"aws.codecommit"
],
"detail-type": [
"CodeCommit Repository State Change"
],
"resources": [
{
"Fn::Join": [
"",
[
"arn:aws:codecommit:",
{
"Ref": "AWS::Region"
},
":",
{
"Ref": "AWS::AccountId"
},
":",
{
"Ref": "RepositoryName"
}
]
]
}
],
"detail": {
"event": [
"referenceCreated",
"referenceUpdated"
],
"referenceType": [
"branch"
],
"referenceName": [
"main"
]
}
},
"Targets": [
{
"Arn": {
"Fn::Join": [
"",
[
"arn:aws:codepipeline:",
{
"Ref": "AWS::Region"
},
":",
{
"Ref": "AWS::AccountId"
},
":",
{
"Ref": "AppPipeline"
}
]
]
},
"RoleArn": {
"Fn::GetAtt": [
"EventRole",
"Arn"
]
},
"Id": "codepipeline-AppPipeline"
}
]
}
},
```
------
1. (Optional) To configure an input transformer with source overrides for a specific image ID, use the following YAML snippet. The following example configures an override where:
+ The `actionName`, `Source` in this example, is the dynamic value, defined at pipeline creation, not derived from the source event.
+ The `revisionType`, `COMMIT_ID` in this example, is the dynamic value, defined at pipeline creation, not derived from the source event.
+ The `revisionValue`, <*revisionValue*> in this example, is derived from the source event variable.
+ The output variables for `BranchName` and `Value` are specified.
```
Rule: my-rule
Targets:
- Id: MyTargetId
Arn: pipeline-ARN
InputTransformer:
sourceRevisions:
actionName: Source
revisionType: COMMIT_ID
revisionValue:
variables:
- name: BranchName
value: value
```
1. Save the updated template to your local computer, and then open the CloudFormation console.
1. Choose your stack, and then choose **Create Change Set for Current Stack**.
1. Upload the template, and then view the changes listed in CloudFormation. These are the changes to be made to the stack. You should see your new resources in the list.
1. Choose **Execute**.
**To edit your pipeline's PollForSourceChanges parameter**
**Important**
In many cases, the `PollForSourceChanges` parameter defaults to true when you create a pipeline. When you add event-based change detection, you must add the parameter to your output and set it to false to disable polling. Otherwise, your pipeline starts twice for a single source change. For details, see [Valid settings for the `PollForSourceChanges` parameter](PollForSourceChanges-defaults.md).
+ In the template, change `PollForSourceChanges` to `false`. If you did not include `PollForSourceChanges` in your pipeline definition, add it and set it to `false`.
**Why am I making this change?** Changing this parameter to `false` turns off periodic checks so you can use event-based change detection only.
------
#### [ YAML ]
```
Name: Source
Actions:
-
Name: SourceAction
ActionTypeId:
Category: Source
Owner: AWS
Version: 1
Provider: CodeCommit
OutputArtifacts:
- Name: SourceOutput
Configuration:
BranchName: !Ref BranchName
RepositoryName: !Ref RepositoryName
PollForSourceChanges: false
RunOrder: 1
```
------
#### [ JSON ]
```
{
"Name": "Source",
"Actions": [
{
"Name": "SourceAction",
"ActionTypeId": {
"Category": "Source",
"Owner": "AWS",
"Version": 1,
"Provider": "CodeCommit"
},
"OutputArtifacts": [
{
"Name": "SourceOutput"
}
],
"Configuration": {
"BranchName": {
"Ref": "BranchName"
},
"RepositoryName": {
"Ref": "RepositoryName"
},
"PollForSourceChanges": false
},
"RunOrder": 1
}
]
},
```
------