In Apache Airflow, an executor is a component responsible for executing tasks within a workflow. When you define a workflow in Airflow, you specify a set of tasks and the dependencies between them. Executors are responsible for executing these tasks according to their specified dependencies.
Local and Remote Executors
Apache Airflow has two types of executors: local and remote.
Local Executors
Local executors run tasks on the same machine as the Airflow scheduler and webserver. Local executors are suitable for small to medium-sized workflows that can be run on a single machine. A couple of key local executors are:
The LocalExecutor runs tasks in parallel on the local machine. It is suitable for workflows that can be parallelized and run on a single machine.
The SequentialExecutor runs tasks sequentially in the same process. It is suitable for small to medium-sized workflows and is the default executor in Airflow. Airflow comes configured with the SequentialExecutor by default.
Remote Executors
Remote executors run tasks on a separate group of worker machines. Remote executors are suitable for larger workflows that require more resources or need to scale horizontally across multiple machines. Some of the key remote executors are:
The CeleryExecutor distributes tasks across a group of worker nodes using a message queue (e.g., RabbitMQ). It allows workflows to scale horizontally across a cluster of machines.
The CeleryKubernetes Executor is a combination of the CeleryExecutor and the KubernetesExecutor in Apache Airflow. It allows you to scale your workflows horizontally across a cluster of worker nodes using a message queue (e.g., RabbitMQ) and run the tasks on a Kubernetes cluster
The KubernetesExecutor runs tasks on a Kubernetes cluster. It is suitable for running workflows on a scalable, containerized platform.
The choice of executor can have a significant impact on the performance, scalability & resource utilization of your workflow. It is important to choose the executor that is best suits your use case and environment.
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