Logging AWS Lambda API calls using AWS CloudTrail

AWS Lambda is integrated with AWS CloudTrail, a service that provides a record of actions taken by a user, role, or an AWS service. CloudTrail captures API calls for Lambda as events. The calls captured include calls from the Lambda console and code calls to the Lambda API operations. Using the information collected by CloudTrail, you can determine the request that was made to Lambda, the IP address from which the request was made, when it was made, and additional details.

Every event or log entry contains information about who generated the request. The identity information helps you determine the following:

CloudTrail is active in your AWS account when you create the account and you automatically have access to the CloudTrail Event history. The CloudTrail Event history provides a viewable, searchable, downloadable, and immutable record of the past 90 days of recorded management events in an AWS Region. For more information, see Working with CloudTrail Event history in the AWS CloudTrail User Guide. There are no CloudTrail charges for viewing the Event history.

For an ongoing record of events in your AWS account past 90 days, create a trail or a CloudTrail Lake event data store.

Lambda data events in CloudTrail

Data events provide information about the resource operations performed on or in a resource (for example, reading or writing to an Amazon S3 object). These are also known as data plane operations. Data events are often high-volume activities. By default, CloudTrail doesn’t log most data events, and the CloudTrail Event history doesn't record them.

One CloudTrail data event that is logged by default for supported services is LambdaESMDisabled. To learn more about using this event to help troubleshoot issues with Lambda event source mappings, see Using CloudTrail to troubleshoot disabled Lambda event sources.

Additional charges apply for data events. For more information about CloudTrail pricing, see AWS CloudTrail Pricing.

You can log data events for the AWS::Lambda::Function resource type by using the CloudTrail console, AWS CLI, or CloudTrail API operations. For more information about how to log data events, see Logging data events with the AWS Management Console and Logging data events with the AWS Command Line Interface in the AWS CloudTrail User Guide.

The following table lists the Lambda resource type for which you can log data events. The Data event type (console) column shows the value to choose from the Data event type list on the CloudTrail console. The resources.type value column shows the resources.type value, which you would specify when configuring advanced event selectors using the AWS CLI or CloudTrail APIs. The Data APIs logged to CloudTrail column shows the API calls logged to CloudTrail for the resource type.

You can configure advanced event selectors to filter on the eventName, readOnly, and resources.ARN fields to log only those events that are important to you. The following example is the JSON view of a data event configuration that logs events for a specific function only. For more information about these fields, see AdvancedFieldSelector in the AWS CloudTrail API Reference.

[
  {
    "name": "function-invokes",
    "fieldSelectors": [
      {
        "field": "eventCategory",
        "equals": [
          "Data"
        ]
      },
      {
        "field": "resources.type",
        "equals": [
          "AWS::Lambda::Function"
        ]
      },
      {
        "field": "resources.ARN",
        "equals": [
          "arn:aws:lambda:us-east-1:111122223333:function:hello-world"
        ]
      }
    ]
  }
]

Lambda management events in CloudTrail

Management events provide information about management operations that are performed on resources in your AWS account. These are also known as control plane operations. By default, CloudTrail logs management events.

Lambda supports logging the following actions as management events in CloudTrail log files.

Using CloudTrail to troubleshoot disabled Lambda event sources

When you change the state of an event source mapping using the UpdateEventSourceMapping API action, the API call is logged as a management event in CloudTrail. Event source mappings can also transition directly to the Disabled state due to errors.

For the following services, Lambda publishes the LambdaESMDisabled data event to CloudTrail when your event source transitions to the Disabled state:

Lambda doesn't support this event for any other event source mapping types.

To receive alerts when event source mappings for supported services transition to the Disabled state, set up an alarm in Amazon CloudWatch using the LambdaESMDisabled CloudTrail event. To learn more about setting up a CloudWatch alarm, see Creating CloudWatch alarms for CloudTrail events: examples.

The serviceEventDetails entity in the LambdaESMDisabled event message contains one of the following error codes.

Lambda event examples

An event represents a single request from any source and includes information about the requested API operation, the date and time of the operation, request parameters, and so on. CloudTrail log files aren't an ordered stack trace of the public API calls, so events don't appear in any specific order.

The following example shows CloudTrail log entries for the GetFunction and DeleteFunction actions.

{
  "Records": [
    {
      "eventVersion": "1.03",
      "userIdentity": {
        "type": "IAMUser",
        "principalId": "A1B2C3D4E5F6G7EXAMPLE",
        "arn": "arn:aws:iam::111122223333:user/myUserName",
        "accountId": "111122223333",
        "accessKeyId": "AKIAIOSFODNN7EXAMPLE",
        "userName": "myUserName"
      },
      "eventTime": "2015-03-18T19:03:36Z",
      "eventSource": "lambda.amazonaws.com",
      "eventName": "GetFunction",
      "awsRegion": "us-east-1",
      "sourceIPAddress": "127.0.0.1",
      "userAgent": "Python-httplib2/0.8 (gzip)",
      "errorCode": "AccessDenied",
      "errorMessage": "User: arn:aws:iam::111122223333:user/myUserName is not authorized to perform: lambda:GetFunction on resource: arn:aws:lambda:us-west-2:111122223333:function:other-acct-function",
      "requestParameters": null,
      "responseElements": null,
      "requestID": "7aebcd0f-cda1-11e4-aaa2-e356da31e4ff",
      "eventID": "e92a3e85-8ecd-4d23-8074-843aabfe89bf",
      "eventType": "AwsApiCall",
      "recipientAccountId": "111122223333"
    },
    {
      "eventVersion": "1.03",
      "userIdentity": {
        "type": "IAMUser",
        "principalId": "A1B2C3D4E5F6G7EXAMPLE",
        "arn": "arn:aws:iam::111122223333:user/myUserName",
        "accountId": "111122223333",
        "accessKeyId": "AKIAIOSFODNN7EXAMPLE",
        "userName": "myUserName"
      },
      "eventTime": "2015-03-18T19:04:42Z",
      "eventSource": "lambda.amazonaws.com",
      "eventName": "DeleteFunction20150331",
      "awsRegion": "us-east-1",
      "sourceIPAddress": "127.0.0.1",
      "userAgent": "Python-httplib2/0.8 (gzip)",
      "requestParameters": {
        "functionName": "basic-node-task"
      },
      "responseElements": null,
      "requestID": "a2198ecc-cda1-11e4-aaa2-e356da31e4ff",
      "eventID": "20b84ce5-730f-482e-b2b2-e8fcc87ceb22",
      "eventType": "AwsApiCall",
      "recipientAccountId": "111122223333"
    }
  ]
}

For information about CloudTrail record contents, see CloudTrail record contents in the AWS CloudTrail User Guide.