使用 Cloud Functions 触发 DAG

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本页面介绍了如何使用 Cloud Run 函数 响应事件的 Cloud Composer DAG。

Apache Airflow 设计为定期运行 DAG，但您也可以触发 DAG 来响应事件。一种方法是使用 要触发的 Cloud Run 函数 发生指定事件时的 Cloud Composer DAG。

在本指南的示例中，每当 Cloud Storage 存储分区发生更改时，系统都会运行一个 DAG。对存储桶中的任何对象所做的任何更改都会触发一个函数。此函数向您的 Cloud Composer 环境的 Airflow REST API 发出请求。Airflow 会处理此请求并运行一个 DAG。DAG 会输出更改的相关信息。

准备工作

检查环境的网络配置

此解决方案不适用于专用 IP 和 VPC Service Controls 配置 因为无法通过 Cloud Run 函数配置连接 Airflow Web 服务器。

在 Cloud Composer 2 中，您可以使用另一种方法：使用 Cloud Run 函数和 Pub/Sub 消息触发 DAG

为您的项目启用 API

控制台

Enable the Cloud Composer and Cloud Run functions APIs.

Enable the APIs

gcloud

Enable the Cloud Composer and Cloud Run functions APIs: 

gcloud services enable cloudfunctions.googleapis.com composer.googleapis.com

启用 Airflow REST API

对于 Airflow 2，稳定的 REST API 默认处于启用状态。如果您的环境停用了稳定的 API，则启用稳定的 REST API。

允许使用 Web 服务器访问权限控制机制对 Airflow REST API 进行 API 调用

Cloud Run 函数可以使用 IPv4 连接到 Airflow REST API 或 IPv6 地址。

如果您不确定调用 IP 地址范围，请在网站服务器访问控制中使用默认配置选项 All IP addresses have access (default)，以免意外屏蔽您的 Cloud Run 函数。

创建 Cloud Storage 存储桶

此示例会在 Cloud Storage 存储桶中发生更改时触发 DAG。请创建一个新存储桶以用于此示例。

获取 Airflow 网络服务器网址

此示例向 Airflow 网络服务器端点发出 REST API 请求。您可以在 Cloud Functions 函数代码中使用 Airflow 网络服务器的网址。

控制台

  1. 在 Google Cloud 控制台中，前往环境页面。

    转到“环境”

  2. 点击您的环境的名称。

  3. 在环境详情页面上，前往环境配置标签页。

  4. Airflow 网页界面项中列出了 Airflow 网络服务器的网址。

gcloud

运行以下命令：

gcloud composer environments describe ENVIRONMENT_NAME \
    --location LOCATION \
    --format='value(config.airflowUri)'

替换：

  • ENVIRONMENT_NAME 替换为环境的名称。
  • LOCATION 替换为环境所在的区域。

将 DAG 上传到您的环境

将 DAG 上传到您的环境。以下示例 DAG 输出收到的 DAG 运行配置。您将通过本指南稍后创建的函数触发此 DAG。

import datetime

import airflow
from airflow.operators.bash import BashOperator


with airflow.DAG(
    "composer_sample_trigger_response_dag",
    start_date=datetime.datetime(2021, 1, 1),
    # Not scheduled, trigger only
    schedule_interval=None,
) as dag:
    # Print the dag_run's configuration, which includes information about the
    # Cloud Storage object change.
    print_gcs_info = BashOperator(
        task_id="print_gcs_info", bash_command="echo {{ dag_run.conf }}"
    )

部署触发 DAG 的 Cloud Functions 函数

您可以使用 Google Cloud 支持的首选语言部署 Cloud Functions 函数， Cloud Run 函数或 Cloud Run。本教程演示了 使用 Python 和 Java。

指定 Cloud Functions 函数配置参数

  • 触发器。在本示例中，请选择在存储桶中创建新对象或现有对象被覆盖时触发的触发器。

    • 触发器类型。Cloud Storage。

    • 事件类型。完成创建/创建。

    • 存储桶。选择必须触发此函数的存储桶。

    • 失败时重试。在本示例中，我们建议停用此选项。如果您在生产环境中使用自己的函数，请启用此选项以处理暂时性错误。

  • 运行时服务账号（位于 运行时、构建、连接和安全设置部分。根据您的偏好使用下列选项之一：

    • 选择 Compute Engine 默认服务账号。此账号使用默认 IAM 权限，可以运行访问 Cloud Composer 环境的函数。

    • 创建自定义服务账号，使其具有 Composer User 角色，并将其指定为此函数的运行时服务账号。此选项遵循最小权限原则。

  • 在代码步骤中运行时和入口点：

    • （Python）为此示例添加代码时，请选择 Python 3.7 或更高版本的运行时，并将 trigger_dag_gcf 指定为入口点。

    • （Java）为此示例添加代码时，请选择 Java 17 运行时，并将 com.example.Example 指定为入口点。

添加要求

Python

在 requirements.txt 文件中指定依赖项：

google-auth==2.19.1
requests==2.32.2

Java

将以下依赖项添加到 pom.xml 的 dependencies 部分 由 Google Cloud Functions 界面生成。

    <dependency>
      <groupId>com.google.apis</groupId>
      <artifactId>google-api-services-docs</artifactId>
      <version>v1-rev20210707-1.32.1</version>
    </dependency>
    <dependency>
      <groupId>com.google.api-client</groupId>
      <artifactId>google-api-client</artifactId>
      <version>1.32.1</version>
    </dependency>
    <dependency>
      <groupId>com.google.auth</groupId>
      <artifactId>google-auth-library-credentials</artifactId>
      <version>1.14.0</version>
    </dependency>
    <dependency>
      <groupId>com.google.auth</groupId>
      <artifactId>google-auth-library-oauth2-http</artifactId>
      <version>1.14.0</version>
    </dependency>

Python

添加使用 Airflow REST API 触发 DAG 的代码。创建一个名为 composer2_airflow_rest_api.py 的文件，并将进行 Airflow REST API 调用的代码放在此文件中。

请勿更改任何变量。Cloud Functions 函数会从 main.py 文件导入此文件。

from __future__ import annotations

from typing import Any

import google.auth
from google.auth.transport.requests import AuthorizedSession
import requests


# Following GCP best practices, these credentials should be
# constructed at start-up time and used throughout
# https://cloud.google.com/apis/docs/client-libraries-best-practices
AUTH_SCOPE = "https://www.googleapis.com/auth/cloud-platform"
CREDENTIALS, _ = google.auth.default(scopes=[AUTH_SCOPE])


def make_composer2_web_server_request(
    url: str, method: str = "GET", **kwargs: Any
) -> google.auth.transport.Response:
    """
    Make a request to Cloud Composer 2 environment's web server.
    Args:
      url: The URL to fetch.
      method: The request method to use ('GET', 'OPTIONS', 'HEAD', 'POST', 'PUT',
        'PATCH', 'DELETE')
      **kwargs: Any of the parameters defined for the request function:
                https://github.com/requests/requests/blob/master/requests/api.py
                  If no timeout is provided, it is set to 90 by default.
    """

    authed_session = AuthorizedSession(CREDENTIALS)

    # Set the default timeout, if missing
    if "timeout" not in kwargs:
        kwargs["timeout"] = 90

    return authed_session.request(method, url, **kwargs)


def trigger_dag(web_server_url: str, dag_id: str, data: dict) -> str:
    """
    Make a request to trigger a dag using the stable Airflow 2 REST API.
    https://airflow.apache.org/docs/apache-airflow/stable/stable-rest-api-ref.html

    Args:
      web_server_url: The URL of the Airflow 2 web server.
      dag_id: The DAG ID.
      data: Additional configuration parameters for the DAG run (json).
    """

    endpoint = f"api/v1/dags/{dag_id}/dagRuns"
    request_url = f"{web_server_url}/{endpoint}"
    json_data = {"conf": data}

    response = make_composer2_web_server_request(
        request_url, method="POST", json=json_data
    )

    if response.status_code == 403:
        raise requests.HTTPError(
            "You do not have a permission to perform this operation. "
            "Check Airflow RBAC roles for your account."
            f"{response.headers} / {response.text}"
        )
    elif response.status_code != 200:
        response.raise_for_status()
    else:
        return response.text

将以下代码放入 main.py 文件中。将 web_server_url 变量的值替换为您之前获得的 Airflow 网站服务器地址。

# Copyright 2021 Google LLC
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     https://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

"""
Trigger a DAG in a Cloud Composer 2 environment in response to an event,
using Cloud Functions.
"""

from typing import Any

import composer2_airflow_rest_api

def trigger_dag_gcf(data, context=None):
    """
    Trigger a DAG and pass event data.

    Args:
      data: A dictionary containing the data for the event. Its format depends
      on the event.
      context: The context object for the event.

    For more information about the arguments, see:
    https://cloud.google.com/functions/docs/writing/background#function_parameters
    """

    # TODO(developer): replace with your values
    # Replace web_server_url with the Airflow web server address. To obtain this
    # URL, run the following command for your environment:
    # gcloud composer environments describe example-environment \
    #  --location=your-composer-region \
    #  --format="value(config.airflowUri)"
    web_server_url = (
        "https://example-airflow-ui-url-dot-us-central1.composer.googleusercontent.com"
    )
    # Replace with the ID of the DAG that you want to run.
    dag_id = 'composer_sample_trigger_response_dag'

    composer2_airflow_rest_api.trigger_dag(web_server_url, dag_id, data)

Java

将以下代码放入 Example.java 文件中。将 webServerUrl 变量的值替换为您之前获得的 Airflow 网站服务器地址。


// Copyright 2022 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package com.example;

import com.example.Example.GcsEvent;
import com.google.api.client.http.GenericUrl;
import com.google.api.client.http.HttpContent;
import com.google.api.client.http.HttpRequest;
import com.google.api.client.http.HttpRequestFactory;
import com.google.api.client.http.HttpResponse;
import com.google.api.client.http.HttpResponseException;
import com.google.api.client.http.javanet.NetHttpTransport;
import com.google.api.client.http.json.JsonHttpContent;
import com.google.api.client.json.gson.GsonFactory;
import com.google.auth.http.HttpCredentialsAdapter;
import com.google.auth.oauth2.GoogleCredentials;
import com.google.cloud.functions.BackgroundFunction;
import com.google.cloud.functions.Context;
import java.util.HashMap;
import java.util.Map;
import java.util.logging.Logger;

/**
 * Cloud Function that triggers an Airflow DAG in response to an event (in
 * this case a Cloud Storage event).
 */
public class Example implements BackgroundFunction<GcsEvent> {
  private static final Logger logger = Logger.getLogger(Example.class.getName());

  // TODO(developer): replace with your values
  // Replace webServerUrl with the Airflow web server address. To obtain this
  // URL, run the following command for your environment:
  // gcloud composer environments describe example-environment \
  //  --location=your-composer-region \
  //  --format="value(config.airflowUri)"
  @Override
  public void accept(GcsEvent event, Context context) throws Exception {
    String webServerUrl = "https://example-airflow-ui-url-dot-us-central1.composer.googleusercontent.com";
    String dagName = "composer_sample_trigger_response_dag";
    String url = String.format("%s/api/v1/dags/%s/dagRuns", webServerUrl, dagName);

    logger.info(String.format("Triggering DAG %s as a result of an event on the object %s.",
      dagName, event.name));
    logger.info(String.format("Triggering DAG via the following URL: %s", url));

    GoogleCredentials googleCredentials = GoogleCredentials.getApplicationDefault()
        .createScoped("https://www.googleapis.com/auth/cloud-platform");
    HttpCredentialsAdapter credentialsAdapter = new HttpCredentialsAdapter(googleCredentials);
    HttpRequestFactory requestFactory =
      new NetHttpTransport().createRequestFactory(credentialsAdapter);

    Map<String, Map<String, String>> json = new HashMap<String, Map<String, String>>();
    Map<String, String> conf = new HashMap<String, String>();
    conf.put("bucket", event.bucket);
    conf.put("name", event.name);
    conf.put("generation", event.generation);
    conf.put("operation", context.eventType());
    json.put("conf", conf);
    HttpContent content = new JsonHttpContent(new GsonFactory(), json);
    HttpRequest request = requestFactory.buildPostRequest(new GenericUrl(url), content);
    request.getHeaders().setContentType("application/json");
    HttpResponse response;
    try {
      response = request.execute();
      int statusCode = response.getStatusCode();
      logger.info("Response code: " + statusCode);
      logger.info(response.parseAsString());
    } catch (HttpResponseException e) {
      // https://cloud.google.com/java/docs/reference/google-http-client/latest/com.google.api.client.http.HttpResponseException
      logger.info("Received HTTP exception");
      logger.info(e.getLocalizedMessage());
      logger.info("- 400 error: wrong arguments passed to Airflow API");
      logger.info("- 401 error: check if service account has Composer User role");
      logger.info("- 403 error: check Airflow RBAC roles assigned to service account");
      logger.info("- 404 error: check Web Server URL");
    } catch (Exception e) {
      logger.info("Received exception");
      logger.info(e.getLocalizedMessage());
    }
  }

  /** Details of the storage event. */
  public static class GcsEvent {
    /** Bucket name. */
    String bucket;
    /** Object name. */
    String name;
    /** Object version. */
    String generation;
  }
}

测试函数

要检查函数和 DAG 是否按预期工作，请执行以下操作：

  1. 等待您的函数完成部署。
  2. 向您的 Cloud Storage 存储分区上传一个文件。或者，您也可以手动触发函数，方法是在 Google Cloud 控制台中为该函数选择测试函数操作。
  3. 查看 Airflow 网页界面中的 DAG 页面。DAG 应具有一个处于活动状态或已完成的 DAG 运行。
  4. 在 Airflow 界面中，检查此运行的任务日志。您应该会看到 print_gcs_info 任务将从函数接收的数据输出到日志中：

Python

[2021-04-04 18:25:44,778] {bash_operator.py:154} INFO - Output:
[2021-04-04 18:25:44,781] {bash_operator.py:158} INFO - Triggered from GCF:
    {bucket: example-storage-for-gcf-triggers, contentType: text/plain,
    crc32c: dldNmg==, etag: COW+26Sb5e8CEAE=, generation: 1617560727904101,
    ... }
[2021-04-04 18:25:44,781] {bash_operator.py:162} INFO - Command exited with
    return code 0h

Java

[2023-02-08, 08:00:09 UTC] {subprocess.py:86} INFO - Output:
[2023-02-08, 08:00:09 UTC] {subprocess.py:93} INFO - {bucket: example-storage-for-gcf-triggers, generation: 1675843189006715, name: file.txt, operation: google.storage.object.create}
[2023-02-08, 08:00:09 UTC] {subprocess.py:97} INFO - Command exited with return code 0

后续步骤