Polly is a robust and versatile .NET library designed to enhance the resilience and fault-handling capabilities of applications. It provides a fluent, thread-safe way for developers to implement various resilience strategies, enabling them to build more robust and reliable systems. The library targets .NET Standard 1.1 and 2.0+, ensuring broad compatibility across different .NET environments.
The core function of Polly is to allow developers to define and apply policies that manage transient faults and improve the overall stability of their applications. It achieves this through a set of pre-built resilience strategies, which can be combined and configured to address specific failure scenarios. These strategies are categorized into reactive and proactive approaches. Reactive strategies respond to errors that occur during operation, while proactive strategies take preventative measures to avoid errors.
Polly's main features revolve around its ability to implement key resilience patterns. These include: Retry, which automatically re-attempts failed operations; Circuit Breaker, which prevents cascading failures by temporarily halting calls to a failing service; Timeout, which limits the execution time of an operation; Fallback, which provides alternative actions or values when an operation fails; Hedging, which executes multiple operations in parallel to improve response times; and Rate Limiter, which controls the rate at which operations are executed.
The library offers a fluent API, making it easy to define and configure these strategies. Developers can chain together different strategies to create complex resilience pipelines tailored to their specific needs. The use of builders simplifies the integration of these strategies into the application's execution flow. Polly also supports dependency injection, allowing for seamless integration with modern .NET application architectures.
Polly's purpose is to empower developers to build resilient applications that can gracefully handle failures and maintain a high level of availability. By providing a set of pre-built, configurable resilience strategies, Polly reduces the complexity of implementing fault-handling logic, allowing developers to focus on their core business logic. The library helps to prevent cascading failures, improve the user experience, and increase the overall reliability of .NET applications.
The library is actively maintained and supported by the .NET Foundation, ensuring its continued development and relevance. The documentation, available at thepollyproject.org, provides comprehensive guides and examples for each strategy, making it easy for developers to learn and implement Polly in their projects. The project also includes NuGet packages for core functionality, extensions, testing, and rate limiting, providing a modular and flexible approach to resilience implementation. The library also provides support for telemetry and dependency injection, making it easy to integrate with existing application frameworks. The library also provides support for testing, allowing developers to verify the behavior of their resilience policies.
