Recording traces

The observability plugin provides two options for starting new spans:

• startSpan() ends the span automatically after the callback function completes, whether it returns normally or throws an error
• startManualSpan() ends the span when you call span.end()

To start a new span:

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// This span ends automatically after the callback completes
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LDObserve.startSpan('fetchData', (span) => {
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  // Your code here
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});

To learn more, read startSpan and startManualSpan.

The Node.js (server-side) SDK’s observability plugin uses the OpenTelemetry Tracing API to work with spans.

Additionally, it provides the following functions for working with spans:

• setAttributes() sets attributes on the active span
• startWithHeaders() starts a span with information from the request headers
• runWithHeaders() runs a callback with information from the request headers and returns the result

Here’s an example:

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app.get("/start-span-example", (req: Request, res: Response) => {
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  const {span} = LDObserve.startWithHeaders('example-span-a', req.headers);
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  LDObserve.setAttributes({
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    "example-attribute": "example-value",
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  });
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  res.send("Hello World");
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  span.end();
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});
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app.get("/run-span-example", async (req: Request, res: Response) => {
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  await LDObserve.runWithHeaders('example-span-b', req.headers, (span) => {
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    LDObserve.setAttributes({
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      "example-attribute": "example-value",
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    });
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    res.send("Hello World");
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  });
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});

To learn more, read Observe.