# OpenAPI Callbacks

You could create an API with a *path operation* that could trigger a request to an *external API* created by someone else (probably the same developer that would be *using* your API).

Then, you try with the old programmer's friend, editor autocompletion.

You type the first parameter of the function, `first_name`, then a dot (`.`) and then hit `Ctrl+Space` to trigger the completion.

But, sadly, you get nothing useful:

<img src="/img/python-types/image01.png">

### Add types

Let's modify a single line from the previous version.

        connection.idleAtNs = now - keepAliveDurationNs
        return 0
      }
    }

    return references.size
  }

  /**
   * Adds or replaces the policy for [address].
   * This will trigger a background task to start creating connections as needed.
   */
  fun setPolicy(
    address: Address,
    policy: ConnectionPool.AddressPolicy,
  ) {

    }

    // Cause the rebuild action to fail.
    filesystem.setFaultyRename(
      cacheDir / DiskLruCache.JOURNAL_FILE_BACKUP,
      true,
    )
    taskFaker.runNextTask()

    // Trigger a job to trim the cache.
    cache.maxSize = 4
    taskFaker.runNextTask()
    assertAbsent("a")
    assertValue("b", "bb", "bb")
  }

  @ParameterizedTest

build:nonccl --define=no_nccl_support=true

# Modular TF build options
build:dynamic_kernels --define=dynamic_loaded_kernels=true
build:dynamic_kernels --copt=-DAUTOLOAD_DYNAMIC_KERNELS

# Don't trigger --config=<host platform> when cross-compiling.
build:android --noenable_platform_specific_config
build:ios --noenable_platform_specific_config

# Suppress all C++ compiler warnings, otherwise build logs become 10s of MBs.

- Ensure Job status updates are batched by 1s. This fixes an unlikely scenario when a sequence of immediately 
  completing pods could trigger a sequence of non-batched Job status updates. ([#118470](https://github.com/kubernetes/kubernetes/pull/118470), [@mimowo](https://github.com/mimowo)) [SIG Apps]

```Python hl_lines="1  3" title="app/routers/users.py"
{!../../../docs_src/bigger_applications/app/routers/users.py!}
```

### *➡ 🛠️* ⏮️ `APIRouter`

& ⤴️ 👆 ⚙️ ⚫️ 📣 👆 *➡ 🛠️*.

⚙️ ⚫️ 🎏 🌌 👆 🔜 ⚙️ `FastAPI` 🎓:

```Python hl_lines="6  11  16" title="app/routers/users.py"
{!../../../docs_src/bigger_applications/app/routers/users.py!}
```

👆 💪 💭 `APIRouter` "🐩 `FastAPI`" 🎓.

```Python hl_lines="1  3" title="app/routers/users.py"
{!../../../docs_src/bigger_applications/app/routers/users.py!}
```

### *Path operations* with `APIRouter`

And then you use it to declare your *path operations*.

Use it the same way you would use the `FastAPI` class:

```Python hl_lines="6  11  16" title="app/routers/users.py"
{!../../../docs_src/bigger_applications/app/routers/users.py!}
```

你可以导入它并通过与 `FastAPI` 类相同的方式创建一个「实例」：

```Python hl_lines="1  3" title="app/routers/users.py"
{!../../../docs_src/bigger_applications/app/routers/users.py!}
```

### 使用 `APIRouter` 的*路径操作*

然后你可以使用它来声明*路径操作*。

使用方式与 `FastAPI` 类相同：

```Python hl_lines="6  11  16" title="app/routers/users.py"
{!../../../docs_src/bigger_applications/app/routers/users.py!}
```

你可以将 `APIRouter` 视为一个「迷你 `FastAPI`」类。

所有相同的选项都得到支持。

- sidecar interception is enabled if:
    - "istio-init" container is not present in the pod.
    - istio-proxy container exists and
        - does not have DISABLE_ENVOY environment variable (which triggers proxyless mode)
        - has a istio-proxy container, with first 2 args "proxy" and "sidecar" - or less then 2 args, or first arg not proxy.
        - "sidecar.istio.io/inject" is not false