# OpenAPI Webhooks { #openapi-webhooks }

There are cases where you want to tell your API **users** that your app could call *their* app (sending a request) with some data, normally to **notify** of some type of **event**.

This means that instead of the normal process of your users sending requests to your API, it's **your API** (or your app) that could **send requests to their system** (to their API, their app).

This is normally called a **webhook**.

    successorIterator = graph.successors(node).iterator();
    return true;
  }

  /**
   * If the graph is directed, each ordered [source, target] pair will be visited once if there is
   * an edge connecting them.
   */
  private static final class Directed<N> extends EndpointPairIterator<N> {
    private Directed(BaseGraph<N> graph) {
      super(graph);
    }

    @Override

This is normally the best way to contribute to the project.

## External Contributions

External contributions are very welcome and appreciated, including answering questions, submitting PRs, etc. 🙇‍♂️

We are not using `scopes` in this example, but the functionality is there if you need it.

///

Now, get the user data from the (fake) database, using the `username` from the form field.

If there is no such user, we return an error saying "Incorrect username or password".

For the error, we use the exception `HTTPException`:

	"slices"
	"strings"

	"github.com/prometheus/client_golang/prometheus"
	"github.com/prometheus/client_golang/prometheus/collectors"
)

// Collector paths.
//
// These are paths under the top-level /minio/metrics/v3 metrics endpoint. Each
// of these paths returns a set of V3 metrics.
//
// Per-bucket metrics endpoints always start with /bucket and the bucket name is

{* ../../docs_src/dependencies/tutorial006_an_py39.py hl[19] *}

These dependencies will be executed/solved the same way as normal dependencies. But their value (if they return any) won't be passed to your *path operation function*.

/// tip

Some editors check for unused function parameters, and show them as errors.

{* ../../docs_src/dependencies/tutorial011_an_py39.py hl[22] *}

/// tip

All this might seem contrived. And it might not be very clear how is it useful yet.

These examples are intentionally simple, but show how it all works.

In the chapters about security, there are utility functions that are implemented in this same way.

If you understood all this, you already know how those utility tools for security work underneath.

        this.wordCount = buffer[bufferIndex];
        bufferIndex++;

        if (this.wordCount != 0) {
            /*
             * these fields are common to all andx commands
             * so let's populate them here
             */

            this.andxCommand = buffer[bufferIndex];
            this.andxOffset = SMBUtil.readInt2(buffer, bufferIndex + 2);

    ```kotlin
    if (credential == response.request.header("Authorization")) {
      return null // If we already failed with these credentials, don't retry.
     }
    ```

## Additional Features { #additional-features }

There are some extra features to handle security apart from the ones covered in the [Tutorial - User Guide: Security](../../tutorial/security/index.md){.internal-link target=_blank}.

/// tip

The next sections are **not necessarily "advanced"**.

And it's possible that for your use case, the solution is in one of them.

///

## Read the Tutorial first { #read-the-tutorial-first }