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track()

Attribute API costs to specific features in your app. This lets you see “my chat feature costs $8/day” instead of just “OpenAI costs $8/day”.

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Usage

import { track } from '@burn0/burn0'

// Wrap any async function that makes API calls
await track('chat', { userId: 'user123' }, async () => {
  const response = await openai.chat.completions.create({
    model: 'gpt-4o-mini',
    messages: [{ role: 'user', content: 'Hello' }],
  })
  return response
})
All API calls made inside the track() callback are tagged with the feature name and metadata.

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Parameters

track(feature: string, metadata: Record<string, string | number | boolean>, fn: () => Promise<void>): Promise<void>
ParameterTypeDescription
featurestringFeature name (e.g., 'chat', 'summarize', 'search')
metadataobjectKey-value pairs (e.g., { userId: 'u123', tier: 'pro' })
fnasync functionThe function that makes API calls

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Alternative: startSpan

For cases where a callback wrapper doesn’t fit, use startSpan: 
import { startSpan } from '@burn0/burn0'

const span = startSpan('chat', { userId: 'user123' })

// ... make API calls ...

span.end()
Always call span.end() when done. Forgetting to end a span means subsequent API calls may be attributed to the wrong feature.

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Examples

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Per-user cost tracking

app.post('/api/chat', async (req, res) => {
  const { userId, message } = req.body

  await track('chat', { userId }, async () => {
    const response = await openai.chat.completions.create({
      model: 'gpt-4o-mini',
      messages: [{ role: 'user', content: message }],
    })
    res.json({ response: response.choices[0].message.content })
  })
})

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Per-feature breakdown

// Summarize feature
await track('summarize', { documentId: doc.id }, async () => {
  await anthropic.messages.create({ ... })
})

// Search feature
await track('search', { query: q }, async () => {
  await openai.embeddings.create({ ... })
  await pinecone.query({ ... })
})

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Viewing tracked data

Feature and metadata are stored with each event and visible in:
  • The dashboard event detail view
  • burn0 report (coming soon: per-feature breakdown)