protected static final int SLOW_FUNC_VALID_INPUT_DATA = 3;
  private static final String RESULT_DATA = "SUCCESS";

  private SettableFuture<String> outputFuture;
  // Signals that the function is waiting to complete
  private CountDownLatch funcIsWaitingLatch;
  // Signals the function so it will complete
  private CountDownLatch funcCompletionLatch;

  @Override

      <a class="announce-link" href="https://fastapicloud.com" target="_blank">
        <span class="twemoji">
          {% include ".icons/material/cloud-arrow-up.svg" %}
        </span> Join the <strong>FastAPI Cloud</strong> waiting list 🚀
      </a>
    </div>
    <div class="item">
      <a class="announce-link" href="https://x.com/fastapi" target="_blank">
        <span class="twemoji">

# 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:

}

// DetectLeak - Creates a snapshot of runtime stack and compares it with the initial stack snapshot.
func (initialSnapShot LeakDetect) DetectLeak(t TestErrHandler) {
	if t.Failed() {
		return
	}
	// Loop, waiting for goroutines to shut down.
	// Wait up to 5 seconds, but finish as quickly as possible.
	deadline := UTCNow().Add(leakDetectDeadline * time.Second)
	for {
		// get sack snapshot of relevant go routines.

				}
			}

			if task.respCh != nil {
				task.respCh <- healResult{result: res, err: err}
				continue
			}

			// when respCh is not set caller is not waiting but we
			// update the relevant metrics for them
			if bgSeq != nil {
				if err == nil {
					bgSeq.countHealed(res.Type)
				} else {
					bgSeq.countFailed(res.Type)
				}
			}

/// info

Added in FastAPI 0.134.0.

///

## What is a Stream? { #what-is-a-stream }

"**Streaming**" data means that your app will start sending data items to the client without waiting for the entire sequence of items to be ready.

So, it will send the first item, the client will receive and start processing it, and you might still be producing the next item.

```mermaid
sequenceDiagram

### Deploy your app (optional) { #deploy-your-app-optional }

You can optionally deploy your FastAPI app to [FastAPI Cloud](https://fastapicloud.com), go and join the waiting list if you haven't. 🚀

If you already have a **FastAPI Cloud** account (we invited you from the waiting list 😉), you can deploy your application with one command.

<div class="termy">

```console
$ fastapi deploy

Deploying to FastAPI Cloud...

              });
      thread.start();
      // we want to wait until each thread is WAITING - one thread waiting inside CacheLoader.load
      // (in startSignal.await()), and the others waiting for that thread's result.
      while (thread.isAlive() && thread.getState() != Thread.State.WAITING) {
        Thread.yield();
      }
    }
    gettersStartedSignal.countDown();
    gettersComplete.await();

	if len(args.Resources) > maxDeleteList {
		return false, fmt.Errorf("internal error: localLocker.Lock called with more than %d resources", maxDeleteList)
	}

	// If we have too many waiting, reject this at once.
	if l.waitMutex.Load() > lockMutexWaitLimit {
		l.locksOverloaded.Add(1)
		return false, nil
	}
	// Wait for mutex
	defer l.getMutex()()
	if ctx.Err() != nil {

  fun connectionCount(): Int = connectionCount.get()

  fun shutdown() {
    serverSocket!!.close()
    executor.shutdown()
    if (!executor.awaitTermination(5, TimeUnit.SECONDS)) {
      throw IOException("Gave up waiting for executor to shut down")
    }
  }

  private fun service(from: Socket) {
    val name = "SocksProxy ${from.remoteSocketAddress}"
    threadName(name) {
      try {