One of the OpenTelemetry Project's many Special Interest Groups (SIG) is the [OpenTelemetry Community Demo SIG](https://github.com/open-telemetry/community/issues/1038) which gives support to a set of instrumented backend microservices and a web frontend app that are primarily used to showcase how to instrument a distributed system using OpenTelemetry.
The application's main focus is to demonstrate the implementation process to instrument an application no matter what programming language, platform, or operating system your team is using, as well as providing different approaching techniques (automatic and manual instrumentation, metrics, baggage). All of this while following the standards and conventions defined by the official OpenTelemetry Documentation. More about the specific requirements can be [found here](https://github.com/open-telemetry/opentelemetry-demo/tree/main/docs/requirements).
At Tracetest, we have always focused on becoming part of and embracing the OpenTelemetry community. One of our goals this summer was to get more involved with a core OpenTelemetry project where we could provide a meaningful contribution. The OTel demo became the best match for achieving that goal as it would not only help the community, but we at Tracetest needed a good example to test and showcase what can be done with our tool.
During the version 0.7 project cycle, we created two specific tickets to get us closer to the community and start looking for things to pick up:
1. [[Wildcard #2] OTEL Demo Contribution](https://github.com/kubeshop/tracetest/issues/917)
2. [[Wildcard #1] OTEL Demo Contribution](https://github.com/kubeshop/tracetest/issues/916)
The first thing we did was to get in contact with Carter Socha, the organizer of the OTel Demo SIG. Carter was really welcoming and helped us identify where our contributions could be the most impactful. We started looking at [the issue created by Austin Parker](https://github.com/open-telemetry/opentelemetry-demo/issues/39) referencing a complete front-end overhaul that would involve moving the application away from Go (SSR) to an architecture that included a browser-side client (CSR), as well as improving the overall style, theme, and user experience. A fun aspect of the work was the request to move the store from a ‘normal’ store to an astronomy store to match the OpenTelemetry project’s overall branding.
Once we got confirmation and the green light from the rest of the OTel Demo SIG team the Tracetest team started working on the different changes included as part of the application frontend architecture overhaul.
## OpenTelemetry Demo Application Description and Tech Stack
The demo app is an astronomy webstore that has the basic functionality to purchase online products such as a shopping cart, currency selector, product listing, and payment & checkout. It also includes features to display promotional items (ads) and related products depending on the context of the user.
The demo stack includes a set of multiple microservices built in different languages, one for each of the following programming languages:
Every microservice has a specific goal and can communicate with others by using a global GRPC definition. Persistent information is saved into a Postgres database and there are outbound services that connect with third-party services to trigger events (such as confirmation emails).
All of the microservices, including the front end, are connected to the same Open Telemetry collector instance, which uses Jaeger as one of the data stores for the traces and spans.
The front end was constituted by a Golang SSR application which sent the complete HTML to the browser client to be displayed. Each request and form call was redirecting the user back to the server so the new piece of information was shown.
## Web App Styling Improvements, Theme Updates, and User Experience Redesign
Before the Tracetest team got involved in the development process, the frontend application wasn’t matching the theme that OpenTelemetry had been using in terms of colors, products, and overall user experience. In addition, the demo lacked a real frontend (browser side) application as the current implementation was a Go SSR application.
The first task at hand was to bring the demo to the modern age by updating the design, color schemes, and user experience. Our UX designer Olly walked into the fray to help us achieve this by creating a [modernized version of the application](https://www.figma.com/file/6YjjnLhE7QExI2RY0LyCpU/OTEL-demo). It included an improved way to display the products landing page, an updated product details page, a mini cart, and a fully compatible mobile version of the application.
Now we had an application design that would match the rest of the OpenTelemetry themes and colors and look more like the OpenTelemetry.io website.
## Frontend Application Architecture Overhaul
The Tracetest team worked on an initial proposal that included the following bullet points:
- Framework and tooling (Scaffolding, I/O, styling, UI library)
- Code Architecture and structure (Directories, coding patterns)
- Deployment & Distribution
- Testing (E2E, unit test)
This proposal was presented to the OpenTelemetry Demo SIG during one of the weekly Monday meetings and we were given the green light to move ahead.
As part of the changes, we decided to use Next.js to not only work as the primary frontend application but also to work as an aggregation layer between the frontend and the GRPC backend services.
As you can see in the Diagram, the application has two major connectivity points, one coming from the browser side (REST) to connect to the Next.js aggregation layer and the other from the aggregation layer to the backend services (GRPC).
## OpenTelemetry Instrumentation
The next big thing we worked on was having a way to instrument both sides of the Next.js application. To accommodate this we had to connect the same application twice to the same open telemetry collector that was being used by all of the other microservices.
For the backend side, a simple solution was designed that involved using the [official GRPC exporter](https://www.npmjs.com/package/@opentelemetry/exporter-trace-otlp-grpc) in combination with the [Nodejs SDK](https://www.npmjs.com/package/@opentelemetry/sdk-node). You can find the full [implementation here](https://github.com/open-telemetry/opentelemetry-demo/blob/main/src/frontend/utils/telemetry/Instrumentation.js).
The basic instrumentation includes auto instrumentation for most of the commonly used [libraries and tools for Node.js](https://www.npmjs.com/package/@opentelemetry/auto-instrumentations-node). But as part of having a better example for users, a manual instrumentation piece was added in the form of a route middleware that would catch the incoming HTTP request and create a span based on it, including the context propagation. The [implementation can be found here](https://github.com/open-telemetry/opentelemetry-demo/blob/main/src/frontend/utils/telemetry/InstrumentationMiddleware.ts).
After adding validations to check for the browser side, we then can proceed to load the custom front-end tracing module which includes the creation of the [web tracer provider and the automatic web instrumentations](https://github.com/open-telemetry/opentelemetry-demo/blob/main/src/frontend/utils/telemetry/FrontendTracer.ts).
The automatic web instrumentations capture the most common user interactions such as click events, fetch requests, and page loads.
Another takeaway is that in order to allow the browser side to interact with the OTel collector there is a configuration change that needs to be done to enable incoming CORS requests from the web app. Having the collector receivers configuration looking similar to this:
Once the setup is complete, by loading the application from docker and interacting with the different features, we can start looking at the full traces that begin from the frontend user events all the way to the backend GRPC services.
## Bringing the OTel Demo to Tracetest
The latest version of Tracetest includes the complete setup to have an instance of the OTel demo running side by side with Tracetest.
You can start the demo by simply cloning the Tracetest repository and, from the root folder, execute the following command:
`docker compose -f ./examples/tracetest-otel-demo/docker-compose.yaml up`
This will trigger the dockerized version of the app plus all of the services required for the OTel demo microservices.
After going through the test creation process on Tracetest and running the initial transaction by using one of the provided examples, we can see the full trace coming back.
## Contributing to OpenTelemetry was Rewarding!
As a team focused on building an open source tool in the Observability space, the opportunity to help the overall OpenTelemetry community was important to us. In addition, having a complex microservice-based application that uses multiple different languages and technologies is directly useful for our team. It helps us when developing Tracetest and when showing the capabilities of Tracetest to the world.
P.S. Have any questions about Tracetest? You can [add issues on Github](https://github.com/kubeshop/tracetest/issues) or join us on our [Discord channel](https://discord.com/channels/884464549347074049/963470167327772703) to discuss the future of Trace-Based Testing with Tracetest.
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