[GitHub] [airflow] hterik commented on a diff in pull request #26004: [Loki log handler] - Integration with Grafana Loki

[GitBox <gi...@apache.org>]

hterik commented on code in PR #26004:
URL: https://github.com/apache/airflow/pull/26004#discussion_r960681889


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airflow/providers/grafana/log/loki_task_handler.py:
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@@ -0,0 +1,242 @@
+#
+# Licensed to the Apache Software Foundation (ASF) under one
+# or more contributor license agreements.  See the NOTICE file
+# distributed with this work for additional information
+# regarding copyright ownership.  The ASF licenses this file
+# to you under the Apache License, Version 2.0 (the
+# "License"); you may not use this file except in compliance
+# with the License.  You may obtain a copy of the License at
+#
+#   http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing,
+# software distributed under the License is distributed on an
+# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+# KIND, either express or implied.  See the License for the
+# specific language governing permissions and limitations
+# under the License.
+
+"""Loki logging handler for tasks"""
+import time
+from typing import Dict, Optional, Tuple, Union
+
+import logging_loki
+import requests
+from cached_property import cached_property
+
+from airflow.hooks.base_hook import BaseHook
+from airflow.models import TaskInstance
+from airflow.utils.log.file_task_handler import FileTaskHandler
+from airflow.utils.log.logging_mixin import LoggingMixin
+
+DEFAULT_LOGGER_NAME = "airflow"
+
+
+class LokiTaskHandler(FileTaskHandler, LoggingMixin):
+    """
+    LokiTaskHandler that directly makes Loki logging API calls while reading and writing logs.
+    This is a Python standard ``logging`` handler using that can be used to route Python standard
+    logging messages directly to the Loki Logging API. It can also be used to save logs for
+    executing tasks. To do this, you should set as a handler with the name "tasks". In this case,
+    it will also be used to read the log for display in Web UI.
+    :param base_log_folder: Base log folder to place logs (incase Loki is down).
+    :type base_log_folder: str
+    :param filename_template: template filename string (incase Loki is down)
+    :type filename_template: str
+    :param loki_conn_id: Connection ID that will be used for authorization to the Loki Platform.
+    :type loki_conn_id: str
+    :param name: the name of the custom log in Loki Logging. Defaults to 'airflow'.
+    :type name: str
+    :param labels: (Optional) Mapping of labels for the entry.
+    :type labels: dict
+    """
+
+    # pylint: disable=too-many-arguments
+    def __init__(
+        self,
+        base_log_folder: str,
+        filename_template: str,
+        loki_conn_id: str,
+        name: str = DEFAULT_LOGGER_NAME,
+        labels: Optional[Dict[str, str]] = None,
+    ):
+        super().__init__(base_log_folder, filename_template)
+        self.loki_conn_id = loki_conn_id
+        self.name: str = name
+        self.timestamp_pattern = "%Y-%m-%dT%H:%M:%S"
+        self.labels = labels
+        self._session: Optional[requests.Session] = None
+
+    @cached_property
+    def get_conn(self):
+        """Loki connection for client"""
+        return BaseHook.get_connection(self.loki_conn_id)
+
+    @property
+    def session(self) -> requests.Session:
+        """Create HTTP session"""
+        if self._session is None:
+            self._session = requests.Session()
+            self._session.auth = (self.get_conn.login, self.get_conn.password) or None
+        return self._session
+
+    def is_loki_alive(self):
+        """Checks whether Loki is ready for pushing/pulling logs"""
+        try:
+            status = self.session.get(
+                f"{self.get_conn.host}/ready",
+            )
+            return status.status_code
+        except ConnectionError as error_msg:
+            self.log.exception(error_msg)
+            return None
+
+    @staticmethod
+    def _task_label(task_instance: TaskInstance) -> Dict[str, str]:
+        """
+        Returns task instance labels for Loki which will use while reading
+        and writing logs from loki.
+        :param task_instance: task instance object
+        :type: task_instance: TaskInstance
+        """
+        # Not adding execution date since it violates Loki label standards
+        # https://grafana.com/blog/2020/08/27/the-concise-guide-to-labels-in-loki/
+
+        return {
+            "airflow_dag_id": task_instance.dag_id,
+            "airflow_task_id": task_instance.task_id,
+            "airflow_try_number": str(task_instance.try_number),

Review Comment:
   Should run_id be included here? For dags where multiple runs go in parallel. 
   Note though, that dynamic labels such as run_id are discouraged according to https://grafana.com/docs/loki/latest/best-practices/ 
   It's a little odd that try_number is included and run_id is not. If you want to flatten it into single stream i would argue try_number should not be included either.
   
   We use Loki for airflow tasks today (but ship the logs via Promtail) What we have done is to use dag_id and task_id as labels, then "[pack](https://grafana.com/docs/loki/latest/clients/promtail/stages/pack/)" the run_id into the stream. Since the task start+end date limits the stream length it becomes a short search.  Anecdotally It's working fine for us, but our volumes are not very big either.



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