# Profiling

> https://docs.errora.org/en/products/profiling

Profiling samples your process's call stacks while it works, so you can see where the time
actually goes — inside the transaction that tracing already told you was slow.

Errora accepts both profile shapes:

- **Transaction profiles** (v1) — bounded by one transaction.
- **Continuous profiling chunks** (v2) — a rolling stream, not tied to a transaction.

## Setup

Profiling rides on tracing, so `traces_sample_rate` must be non-zero.

```python
sentry_sdk.init(
    dsn="…",
    traces_sample_rate=0.2,
    profiles_sample_rate=1.0,   # fraction *of sampled transactions*
)
```

```javascript
// Node.js
import { nodeProfilingIntegration } from "@sentry/profiling-node";

Sentry.init({
  dsn: "…",
  tracesSampleRate: 0.2,
  profilesSampleRate: 1.0,
  integrations: [nodeProfilingIntegration()],
});
```

```php
# Laravel .env
SENTRY_TRACES_SAMPLE_RATE=0.2
SENTRY_PROFILES_SAMPLE_RATE=1.0
```

`profiles_sample_rate` multiplies with `traces_sample_rate`: `0.2 × 1.0` means 20% of
requests are traced and all of those are profiled.

## Reading a profile

**Profiling** lists profiles with their transaction, duration, sample count, environment and
release. Open one for:

- **The flamegraph** — width is *time*, not sample count. Each sample is weighted by the gap
  to the next sample **on the same thread**, so a thread that happens to be sampled twice as
  often does not look twice as slow. Gaps are clamped, so a paused profiler can't dominate
  the graph.
- **Self time per function** — the time spent in the function itself, excluding callees.
- **Threads** — switch between them.

**Slowest functions** for the whole project is its own view. That ranking is computed at
ingest and stored per function, so it is an indexed query rather than a
decompress-everything scan.

## API

```text
GET /api/v1/projects/{project_id}/profiles?stats_period=24h&limit=&offset=
GET /api/v1/projects/{project_id}/profiles/overview
GET /api/v1/projects/{project_id}/profiles/functions
GET /api/v1/projects/{project_id}/profiles/{profile_id}
GET /api/v1/projects/{project_id}/profiles/{profile_id}/flamegraph
```

## Cost

Profiles are metered as the **Profiling** service, per profile. They are also the bulkiest
payload the SDK sends, so keep `profiles_sample_rate` low in production once you have found
your hot paths — or turn it up temporarily during an investigation.

## Troubleshooting

| Symptom | Cause / fix |
| --- | --- |
| No profiles at all | `traces_sample_rate` is `0`, the profiling package isn't installed (Node needs `@sentry/profiling-node`), or the platform has no profiler |
| Profiles but empty flamegraph | The transaction was too short to collect samples — profile a heavier endpoint |
| Everything is `<unknown>` | Native frames without symbols; ship a build with symbols, or profile the interpreted layer |
| Costs climbing | Lower `profiles_sample_rate`; it multiplies with the trace sample rate |