> ## Documentation Index
> Fetch the complete documentation index at: https://docs.sqd.dev/llms.txt
> Use this file to discover all available pages before exploring further.

# Dev runner

> Run multiple pipes in one process during development

`devRunner` runs multiple pipes concurrently inside a single Node.js process, with per-pipe restart retries, a shared metrics server, and per-pipe scoped loggers.

```ts theme={"system"}
import { PipeContext, devRunner } from '@subsquid/pipes/runtime/node'
```

<Warning>
  The dev runner is for local development only. All pipes share one JS thread, so a CPU-intensive pipe starves its neighbours, and an OS-level kill takes every pipe down together. For production, run each pipe as a separate process or container.
</Warning>

## Usage

Declare each pipe as `{ id, params, handler }` and hand the list to `devRunner`:

```ts theme={"system"}
const run = devRunner<Params>(pipes, { metrics: { port: 9090 } })
await run.start()
```

Each handler receives a `PipeContext` with the pipe's `id`, its `params`, the shared `metrics` server, and a `logger` scoped to the pipe ID. Pass those into the source so all pipes report to one metrics endpoint:

```ts expandable theme={"system"}
import { commonAbis, evmEventDecoder, evmPortalStream } from '@subsquid/pipes/evm'
import { PipeContext, devRunner } from '@subsquid/pipes/runtime/node'

export type Params = { dataset: string }

async function transfers({ id, params, metrics, logger }: PipeContext<Params>) {
  const stream = evmPortalStream({
    id,
    portal: `https://portal.sqd.dev/datasets/${params.dataset}`,
    metrics,
    logger,
    outputs: evmEventDecoder({
      range: { from: '0' },
      events: {
        transfers: commonAbis.erc20.events.Transfer,
      },
    }),
  })

  for await (const { ctx, data } of stream) {
    ctx.logger.debug(`fetched ${data.transfers.length} transfers`)
  }
}

async function main() {
  const run = devRunner<Params>(
    [
      { id: 'arb', params: { dataset: 'arbitrum-one' }, handler: transfers },
      { id: 'ethereum', params: { dataset: 'ethereum-mainnet' }, handler: transfers },
    ],
    { metrics: { port: 9090 } },
  )

  await run.start()
}

main()
```

## Configuration

```ts theme={"system"}
devRunner(pipes, config?)
```

| Option    | Default | Description                                                                                                                                                                                                           |
| --------- | ------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| `retry`   | `5`     | Maximum number of restart attempts per pipe before the runner gives up and re-throws the error. Failures are retried per pipe; one pipe crashing does not restart the others.                                         |
| `metrics` |         | [`metricsServer()`](../../reference/utility-components/metrics-server) options (`{ port?, enabled?, logger? }`). When provided, a single Prometheus server is shared by all pipes. When omitted, metrics are a no-op. |

Each pipe declared in the runner shows up separately in [Pipes UI](./pipes-ui), keyed by its `id`.

Full runnable example: [`12.runner.example.ts`](https://github.com/subsquid-labs/pipes-sdk/blob/main/docs/examples/evm/12.runner.example.ts).