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Difficulty: MediumInstrumenting Distributed Tracing with AWS X-Ray

An AWS Lambda function written in Node.js queries an Amazon DynamoDB table using the AWS SDK for JavaScript (v3). The function's configuration has active tracing enabled. However, when viewing traces in the AWS X-Ray console, only the Lambda service and function segments are displayed, while the downstream queries to DynamoDB are completely missing. What action must be taken to ensure that these DynamoDB queries are recorded as part of the traces?

  1. A
    Rely on the active tracing setting of the Lambda function to automatically intercept and trace all downstream AWS SDK calls without changing the application code
  2. Wrap the DynamoDB client instance in the Lambda function code using the captureAWSv3Client function from the AWS X-Ray SDKAnswer
  3. C
    Initialize the DynamoDB client by passing hardcoded IAM credentials into the client constructor to authorize tracing requests to the X-Ray daemon
  4. D
    Increase the Lambda function's timeout configuration to allow the execution context to remain active longer, giving the background processes more time to flush traces

Answer

Wrap the DynamoDB client instance in the Lambda function code using the captureAWSv3Client function from the AWS X-Ray SDK.
The correct action is to wrap the DynamoDB client using captureAWSv3Client from the AWS X-Ray SDK. Active tracing on AWS Lambda provides tracing for the environment and runtime execution but does not automatically capture downstream requests made by client libraries. To record queries made with the AWS SDK for JavaScript (v3), the client instance must be wrapped explicitly.

Step-by-Step Solution

1
Identify the cause of the missing downstream DynamoDB traces.
The AWS SDK client is not instrumented to forward context to AWS X-Ray.
Although active tracing is enabled on the Lambda function itself, this only covers the environment and the function execution. It does not automatically hook into internal SDK clients.
2
Select the correct SDK instrumentation method for AWS SDK for JavaScript (v3).
Use the captureAWSv3Client utility from the AWS X-Ray SDK.
In SDK v3, tracing requires wrapping the specific client instances (like the DynamoDB client) with the X-Ray library to construct downstream subsegments.

Key Concept

Instrumenting AWS SDK clients with AWS X-Ray SDK in AWS Lambda
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Topics

Instrumenting Distributed Tracing with AWS X-Ray

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