# Overview

OpenTelemetry HTTP Instrumentation allows the user to automatically collect trace data and export them to the backend of choice (we can use Zipkin or Jaeger for this example), to give observability to distributed systems.

This is a simple example that demonstrates tracing HTTP request from client to server. The example
shows key aspects of tracing such as

- Root Span (on Client)
- Child Span (on Client)
- Child Span from a Remote Parent (on Server)
- SpanContext Propagation (from Client to Server)
- Span Events
- Span Attributes

## Installation

```sh
# from this directory
npm install
```

Setup [Zipkin Tracing](https://zipkin.io/pages/quickstart.html)
or
Setup [Jaeger Tracing](https://www.jaegertracing.io/docs/latest/getting-started/#all-in-one)

## Run the Application

### Zipkin

- Run the server

   ```sh
   # from this directory
   npm run zipkin:server
   ```

- Run the client

   ```sh
   # from this directory
   npm run zipkin:client
   ```

#### Zipkin UI

`zipkin:server` script should output the `traceid` in the terminal (e.g `traceid: 4815c3d576d930189725f1f1d1bdfcc6`).
Go to Zipkin with your browser <http://localhost:9411/zipkin/traces/(your-trace-id)> (e.g <http://localhost:9411/zipkin/traces/4815c3d576d930189725f1f1d1bdfcc6>)

<p align="center"><img alt="Zipkin UI showing a trace" src="./images/zipkin-ui.png?raw=true"/></p>

### Jaeger

- Run the server

   ```sh
   # from this directory
   npm run jaeger:server
   ```

- Run the client

   ```sh
   # from this directory
   npm run jaeger:client
   ```

#### Jaeger UI

`jaeger:server` script should output the `traceid` in the terminal (e.g `traceid: 4815c3d576d930189725f1f1d1bdfcc6`).
Go to Jaeger with your browser <http://localhost:16686/trace/(your-trace-id)> (e.g <http://localhost:16686/trace/4815c3d576d930189725f1f1d1bdfcc6>)

<p align="center"><img alt="Jaeger UI showing a trace"  src="images/jaeger-ui.png?raw=true"/></p>

## Useful links

- For more information on OpenTelemetry, visit: <https://opentelemetry.io/>
- For more information on OpenTelemetry for Node.js, visit: <https://github.com/open-telemetry/opentelemetry-js/tree/main/packages/opentelemetry-sdk-trace-node>

## LICENSE

Apache License 2.0