Writing Logs

Writing Logs Locally

Users can specify a logs folder in airflow.cfg using the base_log_folder setting. By default, it is in the AIRFLOW_HOME directory.

In addition, users can supply a remote location for storing logs and log backups in cloud storage.

In the Airflow Web UI, local logs take precedance over remote logs. If local logs can not be found or accessed, the remote logs will be displayed. Note that logs are only sent to remote storage once a task completes (including failure). In other words, remote logs for running tasks are unavailable. Logs are stored in the log folder as {dag_id}/{task_id}/{execution_date}/{try_number}.log.

Writing Logs to Amazon S3

Before you begin

Remote logging uses an existing Airflow connection to read/write logs. If you don’t have a connection properly setup, this will fail.

Enabling remote logging

To enable this feature, airflow.cfg must be configured as in this example:

[core]
# Airflow can store logs remotely in AWS S3. Users must supply a remote
# location URL (starting with either 's3://...') and an Airflow connection
# id that provides access to the storage location.
remote_base_log_folder = s3://my-bucket/path/to/logs
remote_log_conn_id = MyS3Conn
# Use server-side encryption for logs stored in S3
encrypt_s3_logs = False

In the above example, Airflow will try to use S3Hook('MyS3Conn').

Writing Logs to Azure Blob Storage

Airflow can be configured to read and write task logs in Azure Blob Storage. Follow the steps below to enable Azure Blob Storage logging.

  1. Airflow’s logging system requires a custom .py file to be located in the PYTHONPATH, so that it’s importable from Airflow. Start by creating a directory to store the config file. $AIRFLOW_HOME/config is recommended.

  2. Create empty files called $AIRFLOW_HOME/config/log_config.py and $AIRFLOW_HOME/config/__init__.py.

  3. Copy the contents of airflow/config_templates/airflow_local_settings.py into the log_config.py file that was just created in the step above.

  4. Customize the following portions of the template:

    # wasb buckets should start with "wasb" just to help Airflow select correct handler
REMOTE_BASE_LOG_FOLDER = 'wasb-<whatever you want here>'

# Rename DEFAULT_LOGGING_CONFIG to LOGGING CONFIG
LOGGING_CONFIG = ...

  5. Make sure a Azure Blob Storage (Wasb) connection hook has been defined in Airflow. The hook should have read and write access to the Azure Blob Storage bucket defined above in REMOTE_BASE_LOG_FOLDER.

  6. Update $AIRFLOW_HOME/airflow.cfg to contain:

    remote_logging = True
logging_config_class = log_config.LOGGING_CONFIG
remote_log_conn_id = <name of the Azure Blob Storage connection>

  7. Restart the Airflow webserver and scheduler, and trigger (or wait for) a new task execution.

  8. Verify that logs are showing up for newly executed tasks in the bucket you’ve defined.

Writing Logs to Google Cloud Storage

Follow the steps below to enable Google Cloud Storage logging.

To enable this feature, airflow.cfg must be configured as in this example:

[core]
# Airflow can store logs remotely in AWS S3, Google Cloud Storage or Elastic Search.
# Users must supply an Airflow connection id that provides access to the storage
# location. If remote_logging is set to true, see UPDATING.md for additional
# configuration requirements.
remote_logging = True
remote_base_log_folder = gs://my-bucket/path/to/logs
remote_log_conn_id = MyGCSConn

  1. Install the gcp_api package first, like so: pip install apache-airflow[gcp_api].

  2. Make sure a Google Cloud Platform connection hook has been defined in Airflow. The hook should have read and write access to the Google Cloud Storage bucket defined above in remote_base_log_folder.

  3. Restart the Airflow webserver and scheduler, and trigger (or wait for) a new task execution.

  4. Verify that logs are showing up for newly executed tasks in the bucket you’ve defined.

  5. Verify that the Google Cloud Storage viewer is working in the UI. Pull up a newly executed task, and verify that you see something like:

    *** Reading remote log from gs://<bucket where logs should be persisted>/example_bash_operator/run_this_last/2017-10-03T00:00:00/16.log.
[2017-10-03 21:57:50,056] {cli.py:377} INFO - Running on host chrisr-00532
[2017-10-03 21:57:50,093] {base_task_runner.py:115} INFO - Running: ['bash', '-c', u'airflow run example_bash_operator run_this_last 2017-10-03T00:00:00 --job_id 47 --raw -sd DAGS_FOLDER/example_dags/example_bash_operator.py']
[2017-10-03 21:57:51,264] {base_task_runner.py:98} INFO - Subtask: [2017-10-03 21:57:51,263] {__init__.py:45} INFO - Using executor SequentialExecutor
[2017-10-03 21:57:51,306] {base_task_runner.py:98} INFO - Subtask: [2017-10-03 21:57:51,306] {models.py:186} INFO - Filling up the DagBag from /airflow/dags/example_dags/example_bash_operator.py

Note the top line that says it’s reading from the remote log file.