SequentialExecutor vs LocalExecutor in Airflow: Key Differences and Usage

In Airflow, SequentialExecutor runs tasks one at a time, making it simple but slow, ideal for testing or small setups. LocalExecutor runs multiple tasks in parallel on the same machine, improving speed and suitable for moderate workloads.

Quick Comparison

This table summarizes the main differences between SequentialExecutor and LocalExecutor in Airflow.

Feature	SequentialExecutor	LocalExecutor
Task Execution	One task at a time (sequential)	Multiple tasks in parallel on local machine
Use Case	Testing, development, very small workloads	Production with moderate concurrency needs
Performance	Slow due to no parallelism	Faster with parallel task execution
Setup Complexity	Very simple, no extra configuration	Requires setting up a database and worker processes
Resource Usage	Minimal CPU and memory	Higher CPU and memory due to parallelism

Key Differences

SequentialExecutor is the simplest executor in Airflow. It runs only one task at a time, which means no parallelism. This makes it very easy to set up and use, but it limits throughput and speed. It is mainly used for testing or very small workflows where running tasks one by one is acceptable.

LocalExecutor, on the other hand, allows Airflow to run multiple tasks simultaneously on the same machine. It uses multiprocessing to spawn worker processes, enabling parallel task execution. This improves performance significantly for moderate workloads without needing a distributed setup.

While SequentialExecutor requires almost no configuration, LocalExecutor needs a backend database like PostgreSQL or MySQL to manage task states and worker coordination. It also uses more CPU and memory because of parallel task execution. Choosing between them depends on your workload size and performance needs.

Code Comparison

Here is how you configure Airflow to use SequentialExecutor in the airflow.cfg file.

ini

[core]
executor = SequentialExecutor

Output

Airflow runs tasks one at a time sequentially.

LocalExecutor Equivalent

To switch to LocalExecutor, update the airflow.cfg file as shown below. This enables parallel task execution on the local machine.

ini

[core]
executor = LocalExecutor

Output

Airflow runs multiple tasks in parallel on the local machine.

When to Use Which

Choose SequentialExecutor when you want the simplest setup for testing or very small workflows that do not need speed or parallelism. It is perfect for learning Airflow or running on resource-limited environments.

Choose LocalExecutor when you need better performance with parallel task execution but want to keep everything on a single machine without setting up a distributed cluster. It suits moderate production workloads where concurrency improves throughput.

Key Takeaways

SequentialExecutor runs tasks one by one, ideal for testing and small workloads.

LocalExecutor runs tasks in parallel on the same machine, improving performance.

SequentialExecutor requires minimal setup; LocalExecutor needs a database backend.

Use SequentialExecutor for simplicity and LocalExecutor for moderate concurrency.

LocalExecutor consumes more resources but speeds up workflow execution.