Examkin

Question

Difficulty: MediumInstrumenting Distributed Tracing with AWS X-Ray

A developer is troubleshooting a serverless application where an AWS Lambda function written in C# (.NET) processes order events. The Lambda function is invoked by an Amazon API Gateway REST API. The function makes downstream HTTP calls to a third-party payment gateway and performs read/write operations on an Amazon DynamoDB table. Active tracing is enabled on both the API Gateway stage and the Lambda function. However, when inspecting the AWS X-Ray console, the developer observes that while the API Gateway and Lambda function segments appear, the HTTP calls to the payment gateway and the DynamoDB operations are missing from the trace.

Which of the following actions should the developer take to record the downstream calls in the X-Ray traces?

  1. A
    Extract the X-Amzn-Trace-Id header from the API Gateway event inside the Lambda handler and manually assign it to the environment variables of the Lambda execution environment before invoking downstream services.
  2. Use the AWS X-Ray SDK for .NET to call AWSSDKHandler.RegisterXRayForAllServices() at application startup, and initialize HttpClient using the HttpClientXRayTracingHandler class.Answer
  3. C
    Hardcode an IAM user access key and secret key with the AWSXrayWriteOnlyAccess policy when initializing the DynamoDB client and HTTP clients to authenticate directly with the X-Ray daemon.
  4. D
    Increase the Lambda function's timeout configuration to allow enough time for the X-Ray daemon to flush segment data and implement client-side connection pooling to handle execution context reuse.

Answer

Use the AWS X-Ray SDK for .NET to call AWSSDKHandler.RegisterXRayForAllServices() at application startup, and initialize HttpClient using the HttpClientXRayTracingHandler class.
To trace AWS SDK operations and standard HTTP calls in a .NET application, the developer must instrument them using the AWS X-Ray SDK for .NET. Calling AWSSDKHandler.RegisterXRayForAllServices() registers the tracing handler globally for all AWS service clients, and initializing HttpClient with HttpClientXRayTracingHandler ensures that outbound HTTP calls to the payment gateway are intercepted and traced as subsegments.

Step-by-Step Solution

1
Identify the missing components in the X-Ray trace.
The DynamoDB operations (AWS SDK calls) and the third-party payment gateway calls (HTTP requests) are missing.
By default, enabling active tracing on Lambda only creates the Lambda service segment, but downstream network libraries and AWS SDKs must be instrumented explicitly in code.
2
Instrument the AWS SDK calls.
Call AWSSDKHandler.RegisterXRayForAllServices() during application initialization.
This automatically registers a request pipeline handler with the AWS SDK to trace calls to all AWS services, including DynamoDB.
3
Instrument downstream HTTP calls.
Pass an instance of HttpClientXRayTracingHandler when creating the HttpClient.
This handler intercepts outgoing HTTP calls and injects the trace header while generating subsegments for downstream external API calls.

Key Concept

Instrumenting AWS SDK and HTTP clients in C# (.NET) with AWS X-Ray SDK.
Estimated Time:1m 30s
Rate this question

Topics

Instrumenting Distributed Tracing with AWS X-Ray

More questions from this topic