///

```Python hl_lines="10"
{!> ../../docs_src/header_param_models/tutorial002.py!}
```

////

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": [
        {

        "profiler",
        defaultProfiler,
        display = ParameterDisplay.PROMPT,
        allowEmpty = false,
        description = "Command line option for the performance test task to enable profiling. For example `async-profiler`, `async-profiler-heap`, `async-profiler-all` or `jfr`. Use `none` for benchmarking only."
    )
}

object AdHocPerformanceScenarioLinux : AdHocPerformanceScenario(Os.LINUX)

    }

    @BeforeEach
    void createFileConfig() {
        final Map<String, Object> requestBody = new HashMap<>();
        requestBody.put("name", "test_fileconfig");
        requestBody.put("paths", "file:///example/path/");
        requestBody.put("num_of_thread", 5);
        requestBody.put("interval_time", 1000);
        requestBody.put("boost", 100.0);
        requestBody.put("available", true);

      dummy += cache.getUnchecked(nextRandomKey());
    }
    requests.addAndGet(reps);
    return dummy;
  }

  private int nextRandomKey() {
    int a = random.nextInt(max);

    /*
     * For example, if concentration=2.0, the following takes the square root of
     * the uniformly-distributed random integer, then truncates any fractional
     * part, so higher integers would appear (in this case linearly) more often

 * One Google-authored templating system available for external use is <a
 * href="https://developers.google.com/closure/templates/">Closure Templates</a>.
 *
 * <p>HTML escaping is particularly tricky: For example, <a
 * href="https://www.w3.org/TR/html4/types.html#h-6.2">some elements' text contents must not be HTML
 * escaped</a>. As a result, it is impossible to escape an HTML document correctly without

set -e

SCRIPTPATH=$( cd "$(dirname "$0")" && pwd -P )
ROOTDIR=$SCRIPTPATH/..
cd "$ROOTDIR" || exit

# rely on go build cache
ISTIOCTL=bin/istioctl
go build -o $ISTIOCTL ./istioctl/cmd/istioctl

for f in samples/**/*.yaml; do
  if grep -q -e "{{" "$f" ; then
    echo "Skipping check for helm template $f"
    continue
  else
    echo "Validating $f..."
  $ISTIOCTL validate -x \
    -f "$f"
  fi

It might also help avoid confusion for new developers that see an unused parameter in your code and could think it's unnecessary.

///

/// info

In this example we use invented custom headers `X-Key` and `X-Token`.

  }

  private fun logWithTime(message: String) {
    val startNs = startNs
    val timeMs =
      if (startNs == null) {
        // Event occurred before start, for an example an early cancel.
        0L
      } else {
        TimeUnit.NANOSECONDS.toMillis(System.nanoTime() - startNs)
      }

    logger.invoke("[$timeMs ms] $message")
  }

{* ../../docs_src/advanced_middleware/tutorial002.py hl[2,6:8] *}

Os seguintes argumentos são suportados:

* `allowed_hosts` - Uma lista de nomes de domínio que são permitidos como nomes de host. Domínios com coringa, como `*.example.com`, são suportados para corresponder a subdomínios. Para permitir qualquer nome de host, use `allowed_hosts=["*"]` ou omita o middleware.

Se uma requisição recebida não for validada corretamente, uma resposta `400` será enviada.

	runtime.ReadMemStats(&memstats)

	gcStats := debug.GCStats{
		// If stats.PauseQuantiles is non-empty, ReadGCStats fills
		// it with quantiles summarizing the distribution of pause time.
		// For example, if len(stats.PauseQuantiles) is 5, it will be
		// filled with the minimum, 25%, 50%, 75%, and maximum pause times.
		PauseQuantiles: make([]time.Duration, 5),
	}
	debug.ReadGCStats(&gcStats)