# Tareas en Segundo Plano { #background-tasks }

Puedes definir tareas en segundo plano para que se ejecuten *después* de devolver un response.

Esto es útil para operaciones que necesitan ocurrir después de un request, pero para las que el cliente realmente no necesita esperar a que la operación termine antes de recibir el response.

Esto incluye, por ejemplo:

* Notificaciones por email enviadas después de realizar una acción:

import jcifs.internal.smb2.io.Smb2ReadResponse;
import jcifs.internal.smb2.io.Smb2WriteRequest;
import jcifs.internal.util.SMBUtil;
import jcifs.util.Hexdump;
import jcifs.util.transport.Response;

/**
 * SMB2 Negotiate Protocol response message.
 *
 * This response contains the server's protocol capabilities,
 * security mode, and negotiated dialect version.
 *
 * @author mbechler
 */

                    
                    Smb2ChangeNotifyResponse response = (Smb2ChangeNotifyResponse) 
                        handle.directoryFile.getTree().send(request);
                    
                    if (response.isSuccess()) {
                        processChangeNotification(handle, response);
                    }
                    
                } catch (Exception e) {

from datetime import datetime

from fastapi import FastAPI
from fastapi.encoders import jsonable_encoder
from fastapi.responses import JSONResponse
from pydantic import BaseModel


class Item(BaseModel):
    title: str
    timestamp: datetime
    description: str | None = None


app = FastAPI()


@app.put("/items/{id}")
def update_item(id: str, item: Item):
    json_compatible_item_data = jsonable_encoder(item)

    /**
     * Gets the next request in the chain.
     *
     * @return chained request
     */
    Request getNext();

    /**
     * Gets the response for this request.
     *
     * @return the response for this request
     */
    Response getResponse();

    val request =
      Request
        .Builder()
        .url(server.url("/"))
        .header("Accept", "text/plain")
        .build()
    val response = client.newCall(request).execute()
    assertThat(response.code).isEqualTo(200)
    assertThat(response.body.string()).isEqualTo("hello, OkHttp")

    val recorded = server.takeRequest()
    assertThat(recorded.headers["Accept"]).isEqualTo("text/plain")

from fastapi import FastAPI, Request
from fastapi.responses import HTMLResponse
from fastapi.staticfiles import StaticFiles
from fastapi.templating import Jinja2Templates

app = FastAPI()

app.mount("/static", StaticFiles(directory="static"), name="static")


templates = Jinja2Templates(directory="templates")


@app.get("/items/{id}", response_class=HTMLResponse)
async def read_item(request: Request, id: str):

public class CurlTest {
    private static final Logger logger = Logger.getLogger(CurlTest.class.getName());

    @Test
    public void test_Get() {
        Curl.get("https://www.codelibs.org/").execute(response -> {
            final String content = response.getContentAsString();
            logger.info(content);
            assertTrue(content.length() > 0);
        }, e -> {
            logger.log(Level.SEVERE, "error", e);
            fail();

{* ../../docs_src/header_param_models/tutorial002_an_py310.py hl[10] *}

If a client tries to send some **extra headers**, they will receive an **error** response.

For example, if the client tries to send a `tool` header with a value of `plumbus`, they will receive an **error** response telling them that the header parameter `tool` is not allowed:

```json
{
    "detail": [
        {
            "type": "extra_forbidden",

	// 		// connection. 5 minutes is sufficient time for any idle connection.
	// 		trhttp2.ReadIdleTimeout = 5 * time.Minute
	// 		// PingTimeout is the timeout after which the connection will be closed
	// 		// if a response to Ping is not received.
	// 		trhttp2.PingTimeout = dialTimeout
	// 		// DisableCompression, if true, prevents the Transport from
	// 		// requesting compression with an "Accept-Encoding: gzip"