I have the API Gateway that calls Lamdba function 1 and that invokes lambda function 2 in Go. I want to see these 2 functions joined in the service map.
The only way i have been able to do this so far is to create a custom segment eg called "parent" and the create a subsegment from this context eg called "child". Then using client.InvokeWithContext to invoke the function 2 passing the "child" segment context.
sess := session.Must(session.NewSession())
client := lambda.New(sess, &aws.Config{Region: aws.String(region)})
xray.Configure(xray.Config{LogLevel: "trace"})
xray.AWS(client.Client)
ctx, seg := xray.BeginSegment(context.Background(), "Parent")
ctx, subseg := xray.BeginSubsegment(ctx, "Child")
result, _ := client.InvokeWithContext(ctx,
lambda.InvokeInput{FunctionName: aws.String(functionName), Payload: nil})
subseg.Close(nil)
seg.Close(nil)
Problem is that this creates trace parent -> child in sevice map but also has function 1 too.
What is the best way to join these 2 functions on the service map please ? Note. I have more than 2 that i want to see linked up on the service map to show me my whole flow through lambdas.
Please help.
Thanks Rick
This Go and Lambda boilerplate app demonstrates Lambda to Lambda traces on the X-Ray service map:
https://github.com/nzoschke/gofaas/blob/master/worker.go
WorkCreateFunction (function 1) is an API Gateway handler function. It calls WorkerFunction (function 2) via a Lambda.InvokeWithContext call.
The trick is to instrument the Lambda API client with xray before making Lambda API calls:
// Lambda is an xray instrumented Lambda client
func Lambda() *lambda.Lambda {
c := lambda.New(sess)
xray.AWS(c.Client)
return c
}
out, err := Lambda().InvokeWithContext(ctx, &lambda.InvokeInput{
FunctionName: aws.String(os.Getenv("WORKER_FUNCTION_NAME")),
InvocationType: aws.String("Event"), // async
})
if err != nil {
return responseEmpty, errors.WithStack(err)
}
The aws-xray-sdk-go copies the X-Amzn-Trace-Id header from function 1 into the Lambda API request for function 2:
https://github.com/aws/aws-xray-sdk-go/blob/master/xray/aws.go#L56
If this is not working, try updating to the latest aws-xray-sdk-go.
You don't need to add a subsegment for the "child" call unless you want to add annotation/metadata.
The API gateway adds a trace ID called X-Amzn-Trace-Id to the header of incoming requests, which X-ray picks up. If you forward that trace ID in your call from lambda 1 to lambda 2, then X-ray will visually represent the calls with an arrow from lambda 1 to lambda 2 in the overview and include the trace details of lambda 2 when viewing the trace details of lambda 1.
As long as you forward the top trace ID through the call chain, X-ray will correctly visualize the call chain from service to service with nodes and arrows.
From https://aws.amazon.com/xray/faqs/:
Q: What is a trace?
An X-Ray trace is a set of data points that share the same trace ID. For example, when a client makes a request to your application, it is assigned a unique trace ID. As the request makes its way through services in your application, the services relay information regarding the request back to X-Ray using this unique trace ID. The piece of information relayed by each service in your application to X-Ray is a segment, and a trace is a collection of segments.
https://docs.aws.amazon.com/xray/latest/devguide/xray-concepts.html#xray-concepts-tracingheader
https://docs.aws.amazon.com/xray/latest/devguide/xray-services-apigateway.html