# Configuring Blackfire Continuous Profiler for Node.js

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[configuring continuous profiling](https://www.youtube-nocookie.com/embed/1q_E6fk2Q1Q?rel=0&showinfo=0&modestbranding=1&autoplay=0)

The Node.js continuous profiling is currently made across 2 dimensions:

- **wall-time**: elapsed time per function call
- **heap**: memory allocation and reserved space over time

## Requirements

- Node.js >= 16.0.0
- [Blackfire Agent](../../up-and-running/configuration/agent) >= 2.13.0

## Installation

Get the [Blackfire Continuous Profiler Node.js library](https://github.com/blackfireio/node-continuous-profiling):

```bash
npm install @blackfireio/node-tracing
```

### Node.js continuous profiler API

The Node.js continuous profiler API has two functions:

```js
function start(config) {}
function stop() {}
```

#### `function start(config) {}`

The `start` function starts the continuous profiler probe. It collects profiling information in the background and periodically uploads it to the Blackfire Agent until the `stop` function is called.

```js
const Blackfire = require('@blackfireio/node-tracing');

Blackfire.start({
    appName: 'my-app'
});

// your application...
// If needed, you can stop profiling before cpuDuration
// Blackfire.stop();
```

The `Start` function accepts an object as a parameter with the following keys:

- `appName`: name of the application
- `durationMillis`: time in milliseconds for which to collect profile (default: 45\_000)
- `cpuProfileRate`: average sampling frequency in Hz. (default: 100)
- `labels`: Labels to add to the profile. (default: {})
- `uploadTimeoutMillis`: Timeout in milliseconds for the upload request (default: 10000)

#### `function stop() {}`

Stops the continuous profiling probe.

### A simple example application

#### 1/ Get the Blackfire Continuous Profiler Node.js library:

```bash
npm install express @blackfireio/node-tracing
```

#### 2/ Create `index.js` with the following code:

```js
const Blackfire = require('@blackfireio/node-tracing');
const express = require('express')
const crypto = require("crypto");
const app = express()
const port = 3000

app.get('/', (req, res) => {
    const salt = crypto.randomBytes(128).toString("base64");
    const hash = crypto.pbkdf2Sync("this is my password", salt, 10000, 512, "sha512");

    res.send('Hello World!');
})


app.listen(port, () => {
    console.log(`Example app listening on port ${port}`)
    Blackfire.start({appName: 'blackfire-example'});
})
```

#### 3/ Run the Node.js server:

```
node index.js
```