# Background Tasks { #background-tasks }

You can define background tasks to be run *after* returning a response.

This is useful for operations that need to happen after a request, but that the client doesn't really have to be waiting for the operation to complete before receiving the response.

This includes, for example:

* Email notifications sent after performing an action:

      Request
        .Builder()
        .url("http://httpbin.org/delay/2") // This URL is served with a 2 second delay.
        .build()

    client.newCall(request).execute().use { response ->
      println("Response completed: $response")
    }
  }
}

fun main() {
  ConfigureTimeouts().run()

    Note over client,operation: Response is already sent, can't change it anymore
    opt Tasks
        operation -->> tasks: Send background tasks
    end
    opt Raise other exception
        tasks -->> tasks: Handle exceptions in the background task code
    end
```

/// info

Only **one response** will be sent to the client. It might be one of the error responses or it will be the response from the *path operation*.

import org.codelibs.fess.suggest.request.Response;

/**
 * Represents the response for popular words request.
 */
public class PopularWordsResponse implements Response {

    /**
     * The index associated with the response.
     */
    protected final String index;

    /**
     * The time taken to generate the response in milliseconds.
     */
    protected final long tookMs;

      @Override public void onFailure(Call call, IOException e) {
      }

      @Override public void onResponse(Call call, Response response) throws IOException {
        try (ResponseBody body = response.body()) {
          // Consume and discard the response body.
          body.source().readByteString();
        }
      }
    });

    Request newYorkTimesRequest = new Request.Builder()

## API Response

XML response for this API is similar to [AWS STS AssumeRoleWithWebIdentity](https://docs.aws.amazon.com/STS/latest/APIReference/API_AssumeRoleWithWebIdentity.html#API_AssumeRoleWithWebIdentity_ResponseElements)

## Example request and response

Sample request with `curl`:

```sh

import org.codelibs.fess.util.RenderDataUtil;
import org.dbflute.optional.OptionalEntity;
import org.dbflute.optional.OptionalThing;
import org.lastaflute.web.Execute;
import org.lastaflute.web.response.HtmlResponse;
import org.lastaflute.web.response.render.RenderData;
import org.lastaflute.web.ruts.process.ActionRuntime;

import jakarta.annotation.Resource;

/**
 * Admin action for Web Config management.
 *
 */

        @Test
        @DisplayName("Should create correct response type")
        void testCreateResponse() {
            Smb2EchoResponse response = echoRequest.createResponse(mockContext, echoRequest);

            assertNotNull(response);
            assertInstanceOf(Smb2EchoResponse.class, response);
        }

        @Test
        @DisplayName("Should create response with correct configuration")

   *
   * ### Duplex Transmission
   *
   * With regular HTTP calls the request always completes sending before the response may begin
   * receiving. With duplex the request and response may be interleaved! That is, request body bytes
   * may be sent after response headers or body bytes have been received.
   *
   * Though any call may be initiated as a duplex call, only web servers that are specially

        "404": {
            "description": "Additional Response",
            "content": {
                "application/json": {
                    "schema": {
                        "$ref": "#/components/schemas/Message"
                    }
                }
            }
        },
        "200": {
            "description": "Successful Response",
            "content": {
                "application/json": {