When using containers, you would normally have some component **listening on the main port**. It could possibly be another container that is also a **TLS Termination Proxy** to handle **HTTPS** or some similar tool.

As this component would take the **load** of requests and distribute that among the workers in a (hopefully) **balanced** way, it is also commonly called a **Load Balancer**.

/// tip

@app.get("/items/{item_id}")
async def read_item(item_id: str):
    if item_id not in items:
        raise HTTPException(
            status_code=404,
            detail="Item not found",
            headers={"X-Error": "Some custom header"},
        )
    return {"item": items[item_id]}


@app.get("/http-no-body-statuscode-exception")
async def no_body_status_code_exception():
    raise HTTPException(status_code=204)

## Forbid Extra Query Parameters { #forbid-extra-query-parameters }

In some special use cases (probably not very common), you might want to **restrict** the query parameters that you want to receive.

You can use Pydantic's model configuration to `forbid` any `extra` fields:

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

    response = client.put(
        "/items/123",
        json={"name": "Foo", "price": 50.1, "description": "Some Foo", "tax": 0.3},
    )
    assert response.status_code == 200
    assert response.json() == {
        "item_id": 123,
        "name": "Foo",
        "price": 50.1,
        "description": "Some Foo",
        "tax": 0.3,
    }


def test_put_only_required(client: TestClient):
    response = client.put(

                }
            }
        }
    }
}
```

## Additional media types for the main response { #additional-media-types-for-the-main-response }

You can use this same `responses` parameter to add different media types for the same main response.

For example, you can add an additional media type of `image/png`, declaring that your *path operation* can return a JSON object (with media type `application/json`) or a PNG image:

	getLockers func() ([]dsync.NetLocker, string)

	// getEndpoints returns list of endpoint belonging this set.
	// some may be local and some remote.
	getEndpoints func() []Endpoint

	// getEndpoints returns list of endpoint strings belonging this set.
	// some may be local and some remote.
	getEndpointStrings func() []string

	// Locker mutex map.
	nsMutex *nsLockMap
}

   * opening the data stream.
   *
   * <p>The default implementation returns {@link Optional#absent}. Some sources, such as a file,
   * may return a non-absent value. Note that in such cases, it is <i>possible</i> that this method
   * will return a different number of bytes than would be returned by reading all of the bytes (for
   * example, some special files may return a size of 0 despite actually having content when read).
   *

```java
public void test() throws Exception {
  // Create a MockWebServer. These are lean enough that you can create a new
  // instance for every unit test.
  MockWebServer server = new MockWebServer();

  // Schedule some responses.
  server.enqueue(new MockResponse.Builder()
      .body("hello, world!")
      .build());
  server.enqueue(new MockResponse.Builder()
      .body("sup, bra?")
      .build());

     * is given by {@link #getSource()}.
     *
     * @return the one-based index of the line containing the problem or a non-positive value if unknown
     */
    int getLineNumber();

    /**
     * Gets the one-based index of the column containing the problem. The column number should refer to some text file
     * that is given by {@link #getSource()}.
     *

     * <syntax>project.distributionManagementArtifactRepository</syntax>
     * <origin><![CDATA[
     * <distributionManagement>
     * <repository>
     * <id>some-repo</id>
     * <url>scp://host/path</url>
     * </repository>
     * <snapshotRepository>
     * <id>some-snap-repo</id>
     * <url>scp://host/snapshot-path</url>
     * </snapshotRepository>
     * </distributionManagement>
     * ]]></origin>
     * <usage><![CDATA[