Airflow web interface

Apache Airflow includes a web interface that you can use to manage workflows (DAGs), manage the Airflow environment, and perform administrative actions. For example, you can use the web interface to review the progress of a DAG, set up a new data connection, or review logs from previous DAG runs.

Airflow web server

Each Cloud Composer environment has a web server that runs the Airflow web interface. The web server is separate from your environment's GKE cluster and runs on an App Engine instance with a fixed machine type.

The web server parses the DAG definition files in the dags/ folder and must be able to access a DAG's data and resources to load the DAG and serve HTTP requests.

The web server refreshes the DAGs every 60 seconds, which is the default worker_refresh_interval in Cloud Composer. A web server error can occur if the web server cannot parse all the DAGs within the refresh interval.

Exceeding 60 seconds to load DAGs can occur if there are a large number of DAG files or there is a non-trivial workload to load the DAG files. To ensure that web server remains accessible regardless of DAG load time, you can configure asynchronous DAG loading to parse and load DAGs in the background at a pre-configured interval (available in composer-1.7.1-airflow-1.10.2 and later versions). This configuration can also reduce DAG refresh time.

Other than exceeding the worker refresh interval, the web server can gracefully handle DAG loading failures in most cases. DAGs that cause the web server to crash or exit might cause errors to be returned in the browser. For information, see Troubleshooting DAGs.

If you continue to experience web server issues due to DAG parsing, we recommend that you use asynchronous DAG loading.

Before you begin

  • The following permission is required to access the Airflow web server in the Cloud Composer environment: composer.environments.get. For more information, see Cloud Composer Access Control.

  • During environment creation, Cloud Composer configures the URL for the web server that runs the Airflow web interface. The URL is non-customizable.

  • For Cloud Composer environments running Airflow 1.10, the Roles Based Access Control (RBAC) feature for the Airflow web interface is not supported.

Accessing the web interface

The Airflow web server service is deployed to the appspot.com domain and provides access to the Airflow web interface. Cloud Identity-Aware Proxy protects the interface, guarding access based on user identities.

After creating a new Cloud Composer environment, it takes up to 25 minutes for the web interface to finish hosting and become accessible.

Accessing the web interface via the Google Cloud Platform Console

To access the Airflow web interface from the Google Cloud Platform Console:

  1. To view your existing Cloud Composer environments, open the Environments page.

    Open the Environments page

  2. In the Airflow webserver column, click the new window icon for the environment whose Airflow web interface you want to view.
  3. Log in with the Google account that has the appropriate permissions.

Retrieving the web interface URL via the gcloud command-line tool

You can access the Airflow web interface from any web browser. To get the URL for the web interface, enter the following gcloud command:

gcloud composer environments describe ENVIRONMENT_NAME \
--location LOCATION

where:

  • ENVIRONMENT_NAME is the name of the environment.
  • LOCATION is the Compute Engine region where the environment is located.

The gcloud command shows the properties of a Cloud Composer environment, including the URL for the web interface. The URL is listed as airflowUri.

airflowUri: https://uexamplebcd3fff-tp.appspot.com/
  dagGcsPrefix: gs://us-central1-example-environment-00a47695-bucket/dags
  gkeCluster: projects/example-project/zones/us-central1-a/clusters/us-central1-example-environment-00a47695-gke
  nodeConfig:
    diskSizeGb: 100
    location: projects/example-project/zones/us-central1-a
    machineType: projects/example-project/zones/us-central1-a/machineTypes/n1-standard-1
    network: projects/example-project/global/networks/default
    oauthScopes:
    - https://www.googleapis.com/auth/cloud-platform
    serviceAccount: N13597NNN465-compute@developer.gserviceaccount.com
  nodeCount: 3
  softwareConfig:
    imageVersion: composer-0.5.1-airflow-1.9.0
createTime: '2018-05-19T02:13:36.749Z'
name: projects/example-project/locations/us-central1/environments/example-environment
state: RUNNING
updateTime: '2018-05-19T02:30:21.387Z'
uuid: 66bd6a28-5b48-4da3-a0aa-898199b569da

Configuring asynchronous DAG loading

With asynchronous DAG loading (webserver-async_dagbag_loader), the web server creates a new process. The process loads DAGs in the background, sends newly loaded DAGs (dagbag_sync_interval), and then sleeps.

The process wakes up periodically to reload DAGs (collect_dags_interval). Requires composer-1.7.1-airflow-1.10.2 or later.

To configure asynchronous DAG loading, override the following Airflow configurations:

Section and Configuration Notes
webserver-async_dagbag_loader = True The default is False.
webserver-collect_dags_interval = 30 The default is 30. Use a smaller value for faster refreshes.
webserver-dagbag_sync_interval = 10 The default is 10.
webserver-worker_refresh_interval = 3600 The default is 60. With asynchronous DAG loading, you can use a larger refresh interval.
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