go-tracing.md

Instrumenting Go Code in AWS Lambda

You can use the X-Ray SDK for Go with your Lambda function. If your handler includes AWS Lambda Context Object in Go as its first argument, that object can be passed to the X-Ray SDK. Lambda passes values through this context that the SDK can use to attach subsegments to the Lambda invoke service segment. Subsegments created with the SDK will appear as a part of your Lambda traces.

Installing the X-Ray SDK for Go

Use the following command to install the X-Ray SDK for Go. (The SDK's non-testing dependencies will be included).

go get -u github.com/aws/aws-xray-sdk-go/...

If you want to include the test dependencies, use the following command:

go get -u -t github.com/aws/aws-xray-sdk-go/...

You can also use Glide to manage dependencies.

glide install

Configuring the X-Ray SDK for Go

The following code sample illustrates how to configure the X-Ray SDK for Go in your Lambda function:

import (
  "github.com/aws/aws-xray-sdk-go/xray"
) 
func myHandlerFunction(ctx context.Context, sample string) {
  xray.Configure(xray.Config{    
    LogLevel:         "info",           // default
    ServiceVersion:   "1.2.3",
  })
   ... //remaining handler code
}

Create a subsegment

The following code illustrates how to start a subsegment:

// Start a subsegment
  ctx, subSeg := xray.BeginSubsegment(ctx, "subsegment-name")
  // ...
  // Add metadata or annotation here if necessary
  // ...
  subSeg.Close(nil)

Capture

The following code illustrates how to trace and capture a critical code path:

func criticalSection(ctx context.Context) {
  // This example traces a critical code path using a custom subsegment
  xray.Capture(ctx, "MyService.criticalSection", func(ctx1 context.Context) error {
    var err error

    section.Lock()
    result := someLockedResource.Go()
    section.Unlock()

    xray.AddMetadata(ctx1, "ResourceResult", result)
  })
}

Tracing HTTP Requests

You can also use the xray.Client() method if you want to trace an HTTP client, as shown below:

func myFunction (ctx context.Context) ([]byte, error) {
    resp, err := ctxhttp.Get(ctx, xray.Client(nil), "https://aws.amazon.com")
    if err != nil {
      return nil, err
    }
    return ioutil.ReadAll(resp.Body), nil
}