Quixir/Supervision

Quixir/Supervision

File:Supervision Icon.png

Supervision Icon

Quixir provides a powerful mechanism for building fault-tolerant and resilient systems through its supervision functionality. Supervision allows developers to define a hierarchical structure of processes and monitor their behavior, ensuring that the system remains stable and can recover from failures.

Introduction

Supervision is a fundamental concept in Quixir that is inspired by the Erlang programming language. It enables automatic restarts of failed processes and the management of the life cycle of a system. By organizing processes into supervision trees, developers can apply different strategies for handling errors and failures, making the system robust and fault-tolerant.

Supervision Trees

In Quixir, supervision trees are defined using the `Supervisor` module. A supervision tree consists of a supervisor process and its child processes. Each child process can either be a worker or a supervisor itself, forming a hierarchical structure.

When a process fails, the supervisor is notified and can take predefined actions, such as restarting the failed process, terminating it, or performing a custom recovery strategy. By defining restart strategies and intensity levels, developers can control how failures propagate through the supervision tree and limit the impact on the overall system.

Restart Strategies

Quixir provides several restart strategies that determine how a failed process is restarted:

• `:one_for_one` - Only the failed process is restarted while leaving the other processes in the tree unaffected.
• `:one_for_all` - All processes in the subtree are restarted, starting with the failed process.
• `:rest_for_one` - Restarts all processes in the subtree that were started after the failed process.

These strategies allow developers to adapt the restart behavior based on the requirements of different parts of the system.

Supervision Strategies

Supervisors in Quixir can have different strategies for handling restarts:

• `:simple_one_for_one` - Allows a supervisor to dynamically create and manage workers of the same type.
• `:one_for_one` - Restarts child processes individually.
• `:one_for_all` - Restarts all child processes together.
• `:rest_for_one` - Restarts child processes in order, starting from the failed process.

Choosing the right supervision strategy depends on the specific requirements of the system and the desired fault-tolerance properties.

For more information about supervision strategies, please see the Supervision Strategies article.

Conclusion

Supervision is a core concept in Quixir that enables developers to build robust and fault-tolerant systems. By structuring processes into supervision trees and defining appropriate restart and intensity strategies, the system can automatically recover from failures. Quixir's supervision functionality greatly simplifies the task of building reliable and resilient applications.

For a comprehensive guide to using supervision in Quixir, please refer to the Supervision Guide.