Setup Sentry Tracing

Configure Sentry's performance monitoring to track transactions and spans.

Invoke This Skill When

• User asks to "enable tracing" or "add performance monitoring"
• User wants to track API response times, page loads, or latency
• User asks about tracesSampleRate or custom spans

Important: The SDK versions, API names, and code samples below are examples. Always verify against docs.sentry.io before implementing, as APIs and minimum versions may have changed.

Quick Reference

JavaScript Setup

Enable tracing

Sentry.init({
  dsn: "YOUR_DSN",
  tracesSampleRate: 1.0,  // 1.0 = 100%, lower for production
  integrations: [Sentry.browserTracingIntegration()],  // Browser/React only
  tracePropagationTargets: ["localhost", /^https:\/\/api\./],
});

Custom spans

// Async operation
const result = await Sentry.startSpan(
  { name: "fetch-user", op: "http.client" },
  async () => {
    return await fetch("/api/user").then(r => r.json());
  }
);

// Nested spans
await Sentry.startSpan({ name: "checkout", op: "transaction" }, async () => {
  await Sentry.startSpan({ name: "validate", op: "validation" }, validateCart);
  await Sentry.startSpan({ name: "payment", op: "payment" }, processPayment);
});

Dynamic sampling

tracesSampler: ({ name, inheritOrSampleWith }) => {
  if (name.includes("healthcheck")) return 0;
  if (name.includes("checkout")) return 1.0;
  return inheritOrSampleWith(0.1);  // Respects parent sampling decision, falls back to 0.1
},

Python Setup

Enable tracing

sentry_sdk.init(
    dsn="YOUR_DSN",
    traces_sample_rate=1.0,
)

Custom spans

# Decorator
@sentry_sdk.trace
def expensive_function():
    return do_work()

# Context manager
with sentry_sdk.start_span(name="process-order", op="task") as span:
    span.set_data("order.id", order_id)
    process(order_id)

Dynamic sampling

from sentry_sdk.types import SamplingContext

def traces_sampler(sampling_context: SamplingContext) -> float:
    name = sampling_context.get("transaction_context", {}).get("name", "")
    parent_sampled = sampling_context.get("parent_sampled")
    if "healthcheck" in name: return 0
    if "checkout" in name: return 1.0
    if parent_sampled is not None: return float(parent_sampled)  # Respect parent decision
    return 0.1

sentry_sdk.init(dsn="YOUR_DSN", traces_sampler=traces_sampler)

Ruby Setup

Sentry.init do |config|
  config.dsn = "YOUR_DSN"
  config.traces_sample_rate = 1.0
end

Common Operation Types

Sampling Recommendations

Distributed Tracing

Configure tracePropagationTargets to send trace headers to your APIs:

tracePropagationTargets: ["localhost", "https://api.yourapp.com"],

For Next.js 14 App Router, add to root layout (not needed in Next.js 15+):

export function generateMetadata(): Metadata {
  return { other: { ...Sentry.getTraceData() } };
}

Verification

After enabling tracing, trigger a traced operation (e.g., an HTTP request) and check the Sentry Performance dashboard for transactions. Custom spans should appear nested under the parent transaction.

Troubleshooting