// GNU Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program.  If not, see <http://www.gnu.org/licenses/>.

package target

import (
	"sync"
	"sync/atomic"
)

// Inspired from Golang sync.Once but it is only marked
// initialized when the provided function returns nil.

type lazyInit struct {
	done uint32

/// info | Información

Para usar `EmailStr`, primero instala <a href="https://github.com/JoshData/python-email-validator" class="external-link" target="_blank">`email-validator`</a>.

Asegúrate de crear un [entorno virtual](../virtual-environments.md){.internal-link target=_blank}, activarlo, y luego instalarlo, por ejemplo:

```console
$ pip install email-validator
```

o con:

```console

/// note | Hinweis

Weitere Informationen finden Sie in Starlettes Dokumentation zum <a href="https://www.starlette.dev/testclient/#testing-websocket-sessions" class="external-link" target="_blank">Testen von WebSockets</a>.

Copy the example in a file `main.py`:

{* ../../docs_src/security/tutorial001_an_py39.py *}

## Run it { #run-it }

/// info

The <a href="https://github.com/Kludex/python-multipart" class="external-link" target="_blank">`python-multipart`</a> package is automatically installed with **FastAPI** when you run the `pip install "fastapi[standard]"` command.

	// transfer rate for small uploads
	XferRateSml *XferStats `json:"smallTransferRate" msg:"st"`
	// Endpoint is the replication target endpoint
	Endpoint string `json:"-"`
	// Secure is true if the replication target endpoint is secure
	Secure bool `json:"-"`
}

func (sr *SRStats) update(st replStat, dID string) {
	sr.lock.Lock()
	defer sr.lock.Unlock()
	srs, ok := sr.M[dID]

    * You can also add [`Security` dependencies with `scopes`](../advanced/security/oauth2-scopes.md){.internal-link target=_blank}.

/// tip

     | ...
     |
     | NOTE: If you just wanted to inject this configuration whenever someone set 'target-env' to
     |       anything, you could just leave off the <value/> inside the activation-property.
     |
    <profile>
      <id>env-dev</id>

      <activation>
        <property>
          <name>target-env</name>
          <value>dev</value>
        </property>
      </activation>

            return false;
        }

        return false;
    }

    /**
     * Checks if a model version is greater than or equal to a target version.
     *
     * @param modelVersion the model version to check
     * @param targetVersion the target version to compare against
     * @return true if modelVersion >= targetVersion
     */

///

### 尝试带有依赖项的 WebSockets

如果您的文件名为 `main.py`，请使用以下命令运行应用程序：

```console
$ uvicorn main:app --reload

<span style="color: green;">INFO</span>:     Uvicorn running on http://127.0.0.1:8000 (Press CTRL+C to quit)
```

在浏览器中打开 <a href="http://127.0.0.1:8000" class="external-link" target="_blank">http://127.0.0.1:8000</a>。

更多细节查看 <a href="https://www.starlette.dev/background/" class="external-link" target="_blank">Starlette's official docs for Background Tasks</a>.

## 告诫

如果您需要执行繁重的后台计算，并且不一定需要由同一进程运行（例如，您不需要共享内存、变量等），那么使用其他更大的工具（如 <a href="https://docs.celeryq.dev" class="external-link" target="_blank">Celery</a>）可能更好。

它们往往需要更复杂的配置，即消息/作业队列管理器，如RabbitMQ或Redis，但它们允许您在多个进程中运行后台任务，甚至是在多个服务器中。