Airflow won't write logs to s3

Question

I tried different ways to configure Airflow 1.9 to write logs to s3 however it just ignores it. I found a lot of people having problems reading the Logs after doing so, however my problem is that the Logs remain local. I can read them without problem but they are not in the specified s3 bucket.

What I tried was first to write into the airflow.cfg file

# Airflow can store logs remotely in AWS S3 or Google Cloud Storage. Users
# must supply an Airflow connection id that provides access to the storage
# location.
remote_base_log_folder = s3://bucketname/logs
remote_log_conn_id = aws
encrypt_s3_logs = False

Then I tried to set environment variables

AIRFLOW__CORE__REMOTE_BASE_LOG_FOLDER=s3://bucketname/logs
AIRFLOW__CORE__REMOTE_LOG_CONN_ID=aws
AIRFLOW__CORE__ENCRYPT_S3_LOGS=False

However it gets ignored and the log files remain local.

I run airflow from a container, I adapted https://github.com/puckel/docker-airflow to my case but it won't write logs to s3. I use the aws connection to write to buckets in dags and this works but the Logs just remain local, no matter if I run it on an EC2 or locally on my machine.

Answer 1

I finally found an answer using https://stackoverflow.com/a/48969421/3808066 which is most of the work I then had to ad one more step. I reproduce this answer here and adapt it a bit the way I did:

Some things to check:

1. Make sure you have the log_config.py file and it is in the correct dir: ./config/log_config.py.
2. Make sure you didn't forget the __init__.py file in that dir.
3. Make sure you defined the s3.task handler and set its formatter to airflow.task
4. Make sure you set airflow.task and airflow.task_runner handlers to s3.task
5. Set task_log_reader = s3.task in airflow.cfg
6. Pass the S3_LOG_FOLDER to log_config. I did that using a variable and retrieving it as in the following log_config.py.

Here is a log_config.py that work:

import os

from airflow import configuration as conf


LOG_LEVEL = conf.get('core', 'LOGGING_LEVEL').upper()
LOG_FORMAT = conf.get('core', 'log_format')

BASE_LOG_FOLDER = conf.get('core', 'BASE_LOG_FOLDER')
PROCESSOR_LOG_FOLDER = conf.get('scheduler', 'child_process_log_directory')

FILENAME_TEMPLATE = '{{ ti.dag_id }}/{{ ti.task_id }}/{{ ts }}/{{ try_number }}.log'
PROCESSOR_FILENAME_TEMPLATE = '{{ filename }}.log'

S3_LOG_FOLDER = conf.get('core', 'S3_LOG_FOLDER')

LOGGING_CONFIG = {
    'version': 1,
    'disable_existing_loggers': False,
    'formatters': {
        'airflow.task': {
            'format': LOG_FORMAT,
        },
        'airflow.processor': {
            'format': LOG_FORMAT,
        },
    },
    'handlers': {
        'console': {
            'class': 'logging.StreamHandler',
            'formatter': 'airflow.task',
            'stream': 'ext://sys.stdout'
        },
        'file.task': {
            'class': 'airflow.utils.log.file_task_handler.FileTaskHandler',
            'formatter': 'airflow.task',
            'base_log_folder': os.path.expanduser(BASE_LOG_FOLDER),
            'filename_template': FILENAME_TEMPLATE,
        },
        'file.processor': {
            'class': 'airflow.utils.log.file_processor_handler.FileProcessorHandler',
            'formatter': 'airflow.processor',
            'base_log_folder': os.path.expanduser(PROCESSOR_LOG_FOLDER),
            'filename_template': PROCESSOR_FILENAME_TEMPLATE,
        },
       's3.task': {
            'class': 'airflow.utils.log.s3_task_handler.S3TaskHandler',
            'formatter': 'airflow.task',
            'base_log_folder': os.path.expanduser(BASE_LOG_FOLDER),
            's3_log_folder': S3_LOG_FOLDER,
            'filename_template': FILENAME_TEMPLATE,
        },
    },
    'loggers': {
        '': {
            'handlers': ['console'],
            'level': LOG_LEVEL
        },
        'airflow': {
            'handlers': ['console'],
            'level': LOG_LEVEL,
            'propagate': False,
        },
        'airflow.processor': {
            'handlers': ['file.processor'],
            'level': LOG_LEVEL,
            'propagate': True,
        },
        'airflow.task': {
            'handlers': ['s3.task'],
            'level': LOG_LEVEL,
            'propagate': False,
        },
        'airflow.task_runner': {
            'handlers': ['s3.task'],
            'level': LOG_LEVEL,
            'propagate': True,
        },
    }
}

Note that this way S3_LOG_FOLDER can be specified in airflow.cfg or as environment the variable AIRFLOW__CORE__S3_LOG_FOLDER.