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Posted to commits@airflow.apache.org by GitBox <gi...@apache.org> on 2020/08/21 20:23:23 UTC
[GitHub] [airflow] rgrizzell edited a comment on issue #10024: Writing Logs to Elasticsearch: asctime field in JSON log output set to null
rgrizzell edited a comment on issue #10024:
URL: https://github.com/apache/airflow/issues/10024#issuecomment-678469071
A further deep dive into this issue, I believe this is the result of default behavior in the Python logging module.
When utilizing the [PercentStyle Formatter](https://github.com/python/cpython/blob/3.8/Lib/logging/__init__.py#L413) (as the [JSONFormatter](https://github.com/apache/airflow/blob/master/airflow/utils/log/json_formatter.py#L29) does by default with `style='%'`), if `fmt` is `None` when the class is instantiated, the PercentStyle Formatter uses `"%(levelname)s:%(name)s:%(message)s"` as its default logging format.
This is important because if `%(asctime)s` is not included in the logging format, [the function responsible for generating the `asctime` field is never called](https://github.com/python/cpython/blob/3.8/Lib/logging/__init__.py#L665).
_But wait, if the `asctime` field doesn't exists why does it show up in the log messages as `null`?_ Well, in the case because `asctime` exists in the `json_fields` object, the `JSONFormatter.format()` merges the `json_fields` object with the LogRecord object and `asctime` is set to `None`.
### Workaround
The following patch is a workaround for this issue that demonstrates the behavior of the standard logging library.
```
Index: airflow/utils/log/json_formatter.py
IDEA additional info:
Subsystem: com.intellij.openapi.diff.impl.patch.CharsetEP
<+>UTF-8
===================================================================
--- airflow/utils/log/json_formatter.py (revision c35a01037ad4bb03d39a0319d37bc36b08ccf766)
+++ airflow/utils/log/json_formatter.py (date 1598039818218)
@@ -25,6 +25,7 @@
from airflow.utils.helpers import merge_dicts
+JSON_FMT = "%(asctime)s:%(levelname)s:%(name)s:%(message)s"
class JSONFormatter(logging.Formatter):
"""
@@ -32,6 +33,8 @@
"""
# pylint: disable=too-many-arguments
def __init__(self, fmt=None, datefmt=None, style='%', json_fields=None, extras=None):
+ if fmt is None:
+ fmt = JSON_FMT
super().__init__(fmt, datefmt, style)
if extras is None:
extras = {}
```
This patch generates the following log message:
```
{"asctime": "2020-08-21 18:42:33,625", "filename": "bash.py", "lineno": 162, "levelname": "INFO", "message": "Command exited with return code 0", "dag_id": "example_bash_operator", "task_id": "run_after_loop", "execution_date": "2020_08_20T00_00_00_000000", "try_number": "1"}
```
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