Capture Your First Distributed Tracing Error

Now that the sample apps are up and running on your local environment and integrated with the Sentry SDKs, you're ready to generate the first error. Please ensure you have BOTH apps running (on http://localhost:3000 and http://localhost:3001).

You should see the 'One-Stop Shop' site running on http://localhost:3000. When you click on any of the product buttons, this will trigger a call to the backend for product info. As long as your Express server is running, you should see titles, images and descriptions for each product.

1. Trigger an Error

To start using Sentry's error monitoring feature, you need some errors first. Let's add in an obvious error that will be easy to see in Sentry.

If you're using your own source code, skip this step. Instead, select your platform and follow its Verify step inside the Getting Started guide to introduce an error.

1. In the tracing-frontend repo, open src/App.js and update the onClick handler by replacing the string passed to the getProduct() function from nonfat-water to debug-sentry.

    <div className="btn-parent">
        <button className="btn" onClick={() => getProduct("clown-shoes")}>
            Clown Shoes
        </button>
    </div>
    <div className="btn-parent">
        <button className="btn" onClick={() => getProduct("debug-sentry")}>
        Nonfat Water
       </button>
    </div>

Take note that in the server.js file of the backend-tracing repo, there is a middleware function handling the /products/debug-sentry route, which throws a sample error:

app.get("/products/debug-sentry", (req, res) => {
    console.log('Sentry Error thrown!');
    throw new Error("My first Sentry error!");
  });

1. Save the file.

2. Go back to the browser window and try clicking on the Nonfat Water button again, you will no longer see the expected product information. Instead, you'll see text saying something went wrong. If you look at line 88 of the App.js file in the frontend-tracing repo, you'll see this is what the frontend displays when it's call to the backend doesn't return any data.

3. Open the terminal window that's running the backend-tracing server. Here, you'll see that a log letting you know that an error has occurred.

Sentry Error thrown!

2. View the Error in Sentry

Now that you've triggered an error, let's see what it looks like in Sentry.

1. Open the Traces page in Sentry.io. Make sure one (or both) of the projects you are using here is selected in the projects dropdown.

2. You should see a trace that shows both the React and Express icons, indicating that this trace traverses both projects. Click on the blue trace ID on the left to see the Trace View.

3. On the Trace View page, you can see every span that happened within this trace. You can see the error on the React app that directly triggered the error on the Express app.

UI Walkthrough

The interactive demo below walks through how to view a distributed trace in Sentry.

Next

At this point, you've verified that Sentry is providing distributed tracing across your projects. You can now dig in to issues to easily find the original source of the issue, so you can diagnose and fix it in less time.