| .. 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. |
| |
| Autoscaling with KEDA |
| --------------------- |
| |
| *This feature is still experimental.* |
| |
| KEDA stands for Kubernetes Event Driven Autoscaling. |
| `KEDA <https://github.com/kedacore/keda>`__ is a custom controller that |
| allows users to create custom bindings to the Kubernetes `Horizontal Pod |
| Autoscaler <https://kubernetes.io/docs/tasks/run-application/horizontal-pod-autoscale/>`__. |
| The autoscaler will adjust the number of active celery workers based on the number |
| of tasks in ``queued`` or ``running`` state. |
| |
| .. code-block:: bash |
| |
| helm repo add kedacore https://kedacore.github.io/charts |
| |
| helm repo update |
| |
| kubectl create namespace keda |
| |
| helm install keda kedacore/keda \ |
| --namespace keda \ |
| --version "v2.0.0" |
| |
| Enable for the airflow instance by setting ``workers.keda.enabled=true`` in your |
| helm command or in the ``values.yaml``. |
| |
| .. code-block:: bash |
| |
| kubectl create namespace airflow |
| helm repo add apache-airflow https://airflow.apache.org |
| helm install airflow apache-airflow/airflow \ |
| --namespace airflow \ |
| --set executor=CeleryExecutor \ |
| --set workers.keda.enabled=true \ |
| |
| A ``ScaledObject`` and an ``hpa`` will be created in the airflow namespace. |
| |
| KEDA will derive the desired number of celery workers by querying |
| Airflow metadata database: |
| |
| .. code-block:: none |
| |
| SELECT |
| ceil(COUNT(*)::decimal / {{ .Values.config.celery.worker_concurrency }}) |
| FROM task_instance |
| WHERE state='running' OR state='queued' |
| |
| .. note:: |
| |
| Set celery worker concurrency through the helm value |
| ``config.celery.worker_concurrency`` (i.e. instead of airflow.cfg or |
| environment variables) so that the KEDA trigger will be consistent with |
| the worker concurrency setting. |