style core_runtime stroke:#1abc9c,fill:#b1f4e7,stroke-width:2px,color:#000;

        core_configuration["core-configuration module"]
        style core_configuration stroke:#1abc9c,fill:#b1f4e7,stroke-width:2px,color:#000;

        core_execution["core-execution module"]
        style core_execution stroke:#1abc9c,fill:#b1f4e7,stroke-width:2px,color:#000;
    end
    style core fill:#c2e0f4,stroke:#3498db,stroke-width:2px,color:#000;

{!../../../docs_src/wsgi/tutorial001.py!}
```

## Check it

Now, every request under the path `/v1/` will be handled by the Flask application.

And the rest will be handled by **FastAPI**.

If you run it and go to <a href="http://localhost:8000/v1/" class="external-link" target="_blank">http://localhost:8000/v1/</a> you will see the response from Flask:

```txt
Hello, World from Flask!
```

    * This will be done by sending a POST request (from *your API*) to some *external API* provided by that external developer (this is the "callback").

## The normal **FastAPI** app

Let's first see how the normal API app would look like before adding the callback.

It will have a *path operation* that will receive an `Invoice` body, and a query parameter `callback_url` that will contain the URL for the callback.

      labelPods: false
      # deletePods will delete any broken pod. These will then be rescheduled, hopefully onto a node that is fully ready.
      # Note this gives the DaemonSet a relatively high privilege, as it can delete any Pod.
      deletePods: false
      # repairPods will dynamically repair any broken pod by setting up the pod networking configuration even after it has started.

## `fastapi dev`

When you run `fastapi dev`, it will run on development mode.

By default, it will have **auto-reload** enabled, so it will automatically reload the server when you make changes to your code. This is resource intensive and could be less stable than without it, you should only use it for development.

You will see a simple page like:

<img src="/img/tutorial/websockets/image01.png">

You can type messages in the input box, and send them:

<img src="/img/tutorial/websockets/image02.png">

And your **FastAPI** application with WebSockets will respond back:

<img src="/img/tutorial/websockets/image03.png">

type Options struct {
	// Directory defines the directory where log files will be written to.
	// If the directory does not exist, it will be created.
	Directory string

	// MaximumFileSize defines the maximum size of each log file in bytes.
	MaximumFileSize int64

	// FileNameFunc specifies the name a new file will take.
	// FileNameFunc must ensure collisions in filenames do not occur.

			gatherer := h.metricsData.mgGatherers[collectorPath]

			// For Bucket metrics we need to set the buckets argument inside the
			// metric group, so that it will affect collection. If no buckets
			// are provided, we will not return bucket metrics.
			if bmg, ok := h.metricsData.bucketMGMap[collectorPath]; ok {
				if len(buckets) == 0 {
					continue
				}
				unLocker := bmg.LockAndSetBuckets(buckets)

This is normally called a **webhook**.

## Webhooks steps

The process normally is that **you define** in your code what is the message that you will send, the **body of the request**.

You also define in some way at which **moments** your app will send those requests or events.

And **your users** define in some way (for example in a web dashboard somewhere) the **URL** where your app should send those requests.

	}

	return client, nil
}

// createHostsideProbeIpset creates an ipset. This is designed to be called from the host netns.
// Note that if the ipset already exist by name, Create will not return an error.
//
// We will unconditionally flush our set before use here, so it shouldn't matter.
func createHostsideProbeIpset(isV6 bool) (ipset.IPSet, error) {
	linDeps := ipset.RealNlDeps()