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Difficulty: MediumInstrumenting Distributed Tracing with AWS X-Ray

A developer has deployed a Node.js Express application on AWS Elastic Beanstalk. The application has the AWS X-Ray daemon enabled via a configuration file in the .ebextensions directory. The application handles incoming client requests and uses the AWS SDK for JavaScript (v3) to read and write items in an Amazon DynamoDB table. While the X-Ray service map shows the incoming HTTP requests to the Express application, the downstream calls to DynamoDB are completely missing from the traces. Which action should the developer take to ensure the DynamoDB calls are traced and associated with the incoming requests?

  1. Wrap the DynamoDB client instance using the captureAWSv3Client function from the AWS X-Ray SDK for Node.js.Answer
  2. B
    Initialize the DynamoDB client with hardcoded AWS access keys in the application code to allow the SDK to authenticate with the X-Ray daemon.
  3. C
    Increase the Amazon SQS visibility timeout configuration to ensure messages are not reprocessed before the DynamoDB client completes.
  4. D
    Set up API Gateway to use a Lambda proxy integration and return the tracing headers in the JSON response payload.

Answer

Wrap the DynamoDB client instance using the captureAWSv3Client function from the AWS X-Ray SDK for Node.js.
The correct answer is correct because AWS SDK v3 for JavaScript requires explicit wrapping of service client instances using the captureAWSv3Client function from the AWS X-Ray SDK. Once wrapped, the client automatically records metadata and subsegments for every downstream call, associating them with the active trace context in the environment.

Step-by-Step Solution

1
Identify the missing tracing data source.
The incoming HTTP requests to Elastic Beanstalk are traced, but downstream calls to DynamoDB are missing.
This indicates that context propagation from the incoming HTTP request wrapper to the downstream client is not occurring because the SDK client itself is not instrumented.
2
Apply the appropriate instrumentation method for AWS SDK for JavaScript (v3).
Import the captureAWSv3Client function from 'aws-xray-sdk-core' and wrap the DynamoDB client during initialization.
In SDK v3, unlike SDK v2 which supported patching the entire AWS module, individual client instances must be wrapped explicitly using captureAWSv3Client.

Key Concept

AWS X-Ray SDK Client Instrumentation for JavaScript (v3)
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Topics

Instrumenting Distributed Tracing with AWS X-Ray

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