aws-lambda-api-call-recorder

Client for the recording of AWS API calls in Node-based Lambda functions, leveraging AWS Client Side Monitoring.

Why does this project exist?

Mainly curiosity. But also because AWS CloudTrail doesn't record all API calls, thus it's possible to gather more insights how your Lambda functions behave.

Also, it's possible to determine the latencies of the API calls of different AWS services.

Preconditions

To be able to use the client library, you need to have the backend installed in the AWS account you want to record the AWS SDK API calls. Please see the appropriate backend section in the README.

Installation

To install the client library, just do the following:

$ npm i --save aws-lambda-api-call-recorder

Usage

To use the client library, you can wrap you handler function with ApiCallRecorder:

const AWS = require('aws-sdk');
const ApiCallRecorder = require('aws-lambda-api-call-recorder');

const sts = new AWS.STS();

const handler = async (event, context) => {
  console.log(event);
  console.log(context);
  const callerIdentity = await sts.getCallerIdentity({}).promise();
  console.log(callerIdentity);
  return {
    statusCode: 200,
    headers: {
      'Content-Type': 'application/json'
    },
    body: JSON.stringify({
      ok: true
    })
  };
}

exports.handler = ApiCallRecorder(handler);

Also, you will have to set the following environment variables to enable the detailled AWS SDK API Call recording:

• AWS_CSM_ENABLED: This environment variable should be set to true
• Either NODE_ENV needs to be set to development, or, in case you want production, you can additionally set API_CALL_RECORDER_IS_ACTIVATED to true
• API_CALL_RECORDER_DELIVERY_STREAM_NAME needs to be set to the name of the Kinesis DeliveryStream. In case you use the Serverless framework and already installed the backend, you should be able to use the backed stack's output for this: ${cf:api-call-recorder-backend-${self:provider.stage}.ApiCallRecorderDeliveryStreamName}

Hints:

• Running production workloads with the APICallRecorder enabled is not advise, because it will add latency (and hence, costs)
• The APICallRecorder will NOT log the final upload of the recorded events to the Firehose DeliveryStream

How it works

The client will wrap the Node Lambda function handler, start a UDP server on localhost on port 31000, so that it can receive the published messages of the AWS Client Side Monitoring (CSM). Once the wrapped handler functions completes, the UDP server will be kept running another 25ms to make sure all API calls can be recorded. After it's shut down, the API calls will be pushed to a Kinesis Firehose DeliveryStream, which will batch the events to gzipped files in S3.

Those files in S3 are then made queryable in Athena by an appropriate Glue Table definition.