(aws-s3): retention on S3 autoDeleteObjects lambda CloudWatch log group is Never expire

[ozeebee]

Describe the bug

Currently, when setting autoDeleteObjects on a S3 bucket to true, the lambda creates a log group whose retention is set to 'Never expire'.
When deploying/destroying a lot of stacks (typically during development), this generates a lot of log groups (with pattern /aws/lambda/$StackName-CustomS3AutoDeleteObjects-$someid) that will stay there forever unless manually cleaned up.

Expected Behavior

We should be able to override the default log group retention or have a reasonable log retetion period for those logs (for instance 3 months).

Current Behavior

The log group is kept forever, retention is 'Never expire'.

Reproduction Steps

Create a bucket with autoDeleteObjects such as:

const bucket = new s3.Bucket(this, 'MyTempFileBucket', {
  removalPolicy: cdk.RemovalPolicy.DESTROY,
  autoDeleteObjects: true,
});

Then deploy/destroy the stack mulitple times, this will generate a different log group for each cycle, and all of them will be on CW logs forever unitl manually deleted.

Possible Solution

Either expose a log retention period for the lambda, for instance:

const bucket = new s3.Bucket(this, 'MyTempFileBucket', {
  removalPolicy: cdk.RemovalPolicy.DESTROY,
  autoDeleteObjects: true,
  autoDeleteObjectsLambdaLogRetention: logs.RetentionDays.THREE_MONTHS
});

or set a default log retention period other than 'Never expire' (3 months seems reasonnable).

Additional Information/Context

No response

CDK CLI Version

2.69.0 (build 60a5b2a)

Framework Version

No response

Node.js Version

v18.12.0

OS

macOS 12.6

Language

Typescript

Language Version

4.9.5

Other information

No response

[peterwoodworth]

This makes sense, thanks for the request.

We take contributions 🙂 We probably won't be able to get to this for a long time if this issue doesn't get enough 👍🏻 support

[FelixFeliciant]

Hello, we are facing the same issue, any workaround for this?
ideally I would prefer that such log group would not be created at all if possible, but setting it for 1 day is good as well.

Thank you.

[kishiel]

I spent some time trying to solve this myself, and I think I've chased it to the bottom. In order for this to work as currently implemented we'll need:

1. A new interface property autoDeleteObjectsLambdaLogRetention in bucket.ts that accepts aws-logs/RetentionDays.
2. Add a new property logRetention?: RetentionDays to CustomResourceProviderOptions in shared.ts
3. Add a new dimension LoggingConfig to the properties section of the CfnResource definition in custom-resource-provider-base
4. extend the functionality of the existing AWS::Lambda::Function LoggingConfig to incorporate the Log Duration as a dimension.

Related: aws-cloudformation/cloudformation-coverage-roadmap#147

There's a lot more complexity in this than I expected, to be honest. This is hard because we're not leveraging native CDK constructs to build the resource, but rather we're leveraging Cloudformation Templates.

I suspect we could get around this by implementing the autoDeleteObjects handler as a custom-resource. This seems like a better long-term solution, but I know it will present some headaches in the near-term.

Edit: #28737 was merged into the aws-cdk-lib release one hour after this post. This deprecates logRetention in favor of logGroup, which doesn't really change this post, but it will make the interface a bit weirder.

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[JavrelWork]

also having problems with this, just realised our log group count got over 10000 in our dev env due to this, would like a way to set the log retention

[mpiltz]

Also it would be really nice to have control over the log group itself. Since we are now able to set the LogGroup for a lambda function, custom_resource.Provider and AwsCustomResource explicitly, could we also have the same ability in this case.

[kishiel]

I've got a working prototype of a solution for this problem following the suggestion by @mpiltz. This solution creates the log group and then feeds it into the lambda by name.

  private enableAutoDeleteObjects(retention?: RetentionDays, removalPolicy?: RemovalPolicy) {

    const logGroup = new LogGroup(this, 'auto-deletion-log-group', {
      retention: retention ?? RetentionDays.THREE_MONTHS,
      removalPolicy: removalPolicy ?? RemovalPolicy.DESTROY,
    });

    const provider = AutoDeleteObjectsProvider.getOrCreateProvider(this, AUTO_DELETE_OBJECTS_RESOURCE_TYPE, {
      useCfnResponseWrapper: false,
      description: `Lambda function for auto-deleting objects in ${this.bucketName} S3 bucket.`,
      logGroupName: logGroup.logGroupName,
    });

This requires a new optional parameter:

export interface CustomResourceProviderOptions {
  [...]

  /**
   * The Cloudwatch Log Group name to use for the provider.
   * @default - A log group name is automatically generated
   */
  readonly logGroupName?: string;
}

An unexpected behavior was that the provider lambda was re-creating the log group after I got it to successfully delete itself on stack deletion, but the new log group came back with infinite duration (argh!). This is because the default role for the lambda has permission to create a log group (which was occurring when it issued a final log stream on delete). Fortunately policyStatements was already wired up so I just explicitly denied CreateLogGroup for the Lambda role.

  public constructor(scope: Construct, id: string, props?: CustomResourceProviderOptions) {
    super(scope, id, {
      ...props,
      "codeDirectory": path.join(__dirname, 'auto-delete-objects-handler'),
      "runtimeName": "nodejs18.x",
      policyStatements: [
        {
          Effect: 'Deny',
          Action: 'logs:CreateLogGroup',
          Resource: '*',
        }
      ],
    });
  }

The name of the log group is plumbed into the custom resource lambda via loggingConfig:

    let loggingConfig = {};
    if (props.logGroupName) {
      loggingConfig = { LogGroup: props.logGroupName };
    }

    const handler = new CfnResource(this, 'Handler', {
      type: 'AWS::Lambda::Function',
      properties: {
        Code: code,
        Timeout: timeout.toSeconds(),
        MemorySize: memory.toMebibytes(),
        Handler: codeHandler,
        LoggingConfig: loggingConfig ?? undefined,
        Role: this.roleArn,
        Runtime: props.runtimeName,
        Environment: this.renderEnvironmentVariables(props.environment),
        Description: props.description ?? undefined,
      },
    });

I need to write some tests for this and then go through at least three affected snapshot tests and then I'll open a PR.

[yerzhan7]

I think there is a similar problem with Bucket Notification Custom Resource Lambda:

https://github.com/aws/aws-cdk/blob/main/packages/aws-cdk-lib/aws-s3/lib/notifications-resource/notifications-resource-handler.ts

It currently creates log group without expiration. Example from integration test: /aws/lambda/aws-cdk-s3-notifications-BucketNotificationsHandle-suEzv62inRVo

[samson-keung]

Providing an update on my progress:

I had an PR up to add a autoDeleteObjectsLogGroup prop but it did not work out (see PR comment for reason).

I am now taking another approach where a new static method will be added to the Bucket class:

export class Bucket extends BucketBase {
  // ...
  public static setAutoDeleteObjectsLogGroup(scope: Construct, logGroup: logs.ILogGroup): void {
    // find the AutoDeleteObjectsProvider lambda and set the log group
  }
  // ...
}

When completed, users should be able to do the following:

class TestStack extends Stack {
  constructor(scope: Construct, id: string, props?: StackProps) {
    super(scope, id, props);

    const bucket = new s3.Bucket(this, 'Bucket', {
      removalPolicy: RemovalPolicy.DESTROY,
      autoDeleteObjects: true,
    });
    
    const myLogGroup = new logs.LogGroup(this, 'MyLogGroup', {
      logGroupName: 'MyLogGroup',
    });
    s3.Bucket.setAutoDeleteObjectsLogGroup(this, myLogGroup);
  }
}

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[GavinZZ]

A follow-up on this issue. The original PR that fixes this issue was reverted due to a number of issues. Note that this is a more general issue happening across all custom resources. Will going to keep this issue as closed and track this issue in a duplicate GitHub issue #23909.

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