# 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**.

This module enables [Zstandard (zstd)][1] response compression in addition to Gzip, as long as
the `Accept-Encoding` header is not otherwise set. Web servers must be configured to return zstd
responses.

Note that zstd is not used for sending requests.

```java
OkHttpClient client = new OkHttpClient.Builder()
  .addInterceptor(CompressionInterceptor(Zstd, Gzip))
  .build();
```

```kotlin
implementation("com.squareup.okhttp3:okhttp-zstd:5.3.0")

3. If the daemon is not able to run the request, for example it is already running a request or is shutting down, it rejects the request. The client starts again.
4. The daemon runs the request, sending back data such as logging output or tooling API events and intermediate models while doing so.

## Reporting a Vulnerability

If you think you found a vulnerability, and even if you are not sure about it, please report it right away by sending an email to: ******@****.***. Please try to be as explicit as possible, describing all the steps and example code to reproduce the security issue.

{* ../../docs_src/dependencies/tutorial013_an_py310.py ln[19:21] *}

...would be run after the response finishes sending the slow data:

{* ../../docs_src/dependencies/tutorial013_an_py310.py ln[30:38] hl[31:33] *}

But as `generate_stream()` doesn't use the database session, it is not really necessary to keep the session open while sending the response.

     * @return true if registration exists
     */
    public boolean hasRegistration(String registrationId) {
        return registrations.containsKey(registrationId);
    }

    /**
     * Simulate sending a witness notification
     *
     * @param eventType the event type
     * @param resourceName the resource name
     */
    public void sendNotification(WitnessEventType eventType, String resourceName) {

    @Override public Response intercept(Chain chain) throws IOException {
      long t1 = System.nanoTime();
      Request request = chain.request();
      logger.info(String.format("Sending request %s on %s%n%s",
          request.url(), chain.connection(), request.headers()));
      Response response = chain.proceed(request);

      long t2 = System.nanoTime();

     * @param <T> the response type
     * @param request the request to send
     * @param params optional request parameters
     * @return response message
     * @throws CIFSException if an error occurs sending the request
     */
    <T extends CommonServerMessageBlockResponse> T send(Request<T> request, RequestParam... params) throws CIFSException;

          .build(),
      )
    call1.execute().use { response -> response.body.string() }

    listener.shouldClose = true
    // Large headers are a likely reason the servers would cut off the connection before it completes sending
    // request headers.
    // 431 "Request Header Fields Too Large"
    val largeHeaders =
      Headers
        .Builder()
        .apply {
          repeat(32) {

Consider an application streaming a video over http/2. Perhaps the user pauses the video and the application stops reading bytes from this stream. The buffer will fill up, and flow control prevents the server from sending more data on this stream. When the user unpauses her video the buffer drains, the read is acknowledged, and the server proceeds to stream data.

#### Shared reader thread