# `AshScylla.Telemetry`
[🔗](https://github.com/ohhi-vn/ash_scylla/blob/main/lib/ash_scylla/telemetry.ex#L15)

Telemetry integration for AshScylla.

Emits standard `:telemetry` events for query execution, enabling
integration with LiveDashboard, Datadog, OpenTelemetry, and other
observability tools.

## Events

- `[:ash_scylla, :query, :start]` - Emitted when a query begins execution.
  Measurements: `%{system_time: integer()}`
  Metadata: `%{resource: module(), operation: atom(), query: String.t()}`

- `[:ash_scylla, :query, :stop]` - Emitted when a query finishes.
  Measurements: `%{duration: integer()}`
  Metadata: `%{resource: module(), operation: atom(), query: String.t()}`

- `[:ash_scylla, :query, :exception]` - Emitted when a query raises.
  Measurements: `%{duration: integer()}`
  Metadata: `%{resource: module(), operation: atom(), query: String.t(), kind: atom(), reason: term()}`

- `[:ash_scylla, :batch, :start]` - Emitted when a batch operation begins.
  Measurements: `%{system_time: integer()}`
  Metadata: `%{resource: module(), operation: atom(), batch_size: integer()}`

- `[:ash_scylla, :batch, :stop]` - Emitted when a batch operation finishes.
  Measurements: `%{duration: integer()}`
  Metadata: `%{resource: module(), operation: atom(), batch_size: integer()}`

## Attaching a Handler

    :telemetry.attach(
      "ash_scylla-logger",
      [:ash_scylla, :query, :stop],
      &MyApp.Telemetry.handle_event/4,
      nil
    )

# `batch_span`

```elixir
@spec batch_span(module(), atom(), integer(), (-> result)) :: result when result: var
```

Executes a batch operation within a telemetry span.

Emits `[:ash_scylla, :batch, :start]` before execution and
`[:ash_scylla, :batch, :stop]` after.

# `format_duration`

```elixir
@spec format_duration(integer()) :: String.t()
```

Formats a duration in nanoseconds to a human-readable string.

# `span`

```elixir
@spec span(module(), atom(), String.t(), (-> result)) :: result when result: var
```

Executes a function within a telemetry span.

Emits `[:ash_scylla, :query, :start]` before execution and
`[:ash_scylla, :query, :stop]` after. If the function raises,
`[:ash_scylla, :query, :exception]` is emitted.

Returns the function's return value.

---

*Consult [api-reference.md](api-reference.md) for complete listing*