1 Recap: Automatically Instrument Your Go Source Code with Orchestrion mercari.go #24 - GopherCon 2023 Recap Shunta Komatsu

2 About me ● Shunta Komatsu ● Backend Engineer at Merpay ○ Developing the payment platform ● Joined Merpay in April 2022

3 What kind of presentation? https://www.gophercon.com/agenda/session/1160499

4 What kind of presentation? Introduction of a tool “Orchestrion” developed by Datadog ● The tool generates Datadog APM traces in Go code ● More of code instrumentation rather than code generation ● https://github.com/DataDog/orchestrion

5 What is traces? ● Traces show the flow of data within and between the components ● A trace has one or more span(s) ● Span is a section of interesting activity in your program ○ receiving an HTTP request, calling in database, etc. https://www.datadoghq.com/product/apm/

6 ● Just adding some code How to gather data?

7 ● You need to set up all traces ● You have to make sure you properly close your traces and spans When you add handlers

8 Motivations behind orchestrion ● Go doesn’t do magic ○ Java provides “annotation” ○ Python provides “decorator” ● Instead, Go is simple and easy to parse the AST ● Orchestrion generates code to add traces and spans https://docs.datadoghq.com/tracing/trace_collection/custom_instrumentation/python/ https://docs.datadoghq.com/tracing/trace_collection/custom_instrumentation/java/

9 Demo of Orchestrion 1. Prepare the initial code 2. Run orchestrion -w .

10 What does generated code do? ● Launch the tracer ● Stop the tracer as defer ● Embed metadata package: github.com/orchestrion/instrument

11 What does generated code do? package: github.com/orchestrion/instrument package: gopkg.in/DataDog/dd-trace-go.v1/contrib/net/http package: gopkg.in/DataDog/dd-trace-go.v1/ddtrace/tracer

12 (Appendix) What Is dd-trace-go.v1/contrib package? ● https://github.com/DataDog/dd-trace-go/tree/main/contrib ● A package to make tracer easier to use in various web frameworks, SQL frameworks, etc. ○ gin-gonic/gin ○ go-chi/chi ○ labstack/echo ○ net/http ○ …

13 Flexible usage ● Orchestrion provides the –rm option ○ You can revert to what it was before Orchestrion adde code ● Any span tags can be set with dd:span magic comment

14 How it works ● Orchestrion scans each source code with the dave/dst package to get AST ○ The standard go/ast package doesn’t attach comments to nodes

15 Impressions of this session ● Orchestrion is easy to use and reversible to change, and you’ll be able to try it out in no time ● However, it still lacks functionality and would be especially difficult to apply to large repositories and microservices ○ Ignore is not supported ○ OpenTelemetry is not supported ● The gopkg.in/DataDog/dd-trace-go.v1 package already has orchestrionConfig in the tracer.config struct, so the feature will be enhanced in the future

16 Summary ● Orchestrion installs the trace with just one line of command ○ You don’t have to worry about forgetting to add spans ● However, it may be better not to use it until more flexibility is brought to the functionality

17 The Go gopher was designed by Renee French Thanks for your attention!