airflow/utils/log/task_handler_with_custom_formatter.py

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# to you under the Apache License, Version 2.0 (the
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#   http://www.apache.org/licenses/LICENSE-2.0
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"""Custom logging formatter for Airflow"""

import logging
from logging import StreamHandler

from airflow.configuration import conf
from airflow.utils.helpers import parse_template_string


class TaskHandlerWithCustomFormatter(StreamHandler):
    """Custom implementation of StreamHandler, a class which writes logging records for Airflow"""

    def __init__(self, stream):
        super().__init__()
        self.prefix_jinja_template = None

    def set_context(self, ti):
        """
        Accept the run-time context (i.e. the current task) and configure the formatter accordingly.

        :param ti:
        :return:
        """
        if ti.raw:
            return
        prefix = conf.get('logging', 'task_log_prefix_template')

        rendered_prefix = ""
        if prefix:
            _, self.prefix_jinja_template = parse_template_string(prefix)
            rendered_prefix = self._render_prefix(ti)
        formatter = logging.Formatter(rendered_prefix + ":" + self.formatter._fmt)  # pylint: disable=W0212
        self.setFormatter(formatter)
        self.setLevel(self.level)

    def _render_prefix(self, ti):
        if self.prefix_jinja_template:
            jinja_context = ti.get_template_context()
            return self.prefix_jinja_template.render(**jinja_context)
        logging.warning("'task_log_prefix_template' is in invalid format, ignoring the variable value")
        return ""