What is Resilience4clj?

Resilience4clj is a lightweight fault tolerance set of libraries built on top of GitHub's Resilience4j and inspired by Netflix Hystrix. It was designed for Clojure and functional programming with composability in mind.

The three core benefits of Resilience4clj are:

1. The libraries have very few dependencies making them extremely lightweight.
2. You don’t have to go all-in; you can pick what features you need (See All modules for a list of what you can cherry pick from).
3. Functional and highly composable interfaces by default. You can mix and match as you see fit.

Motivation

Resiliency is the ability to recover from failures and continue to function. It is not about avoiding failures but accepting the fact that failures will happen and responding to them in a way that avoids downtime or data loss. The goal of resiliency is to return the application to a fully functioning state after a failure.

Building resilient systems requires inculcating a strong sense of acceptance of failures to the team since the very first day of a project. The team will need to create solutions to make sure that the system either recovers from failures or that it still functions despite ongoing failures.

Some of these potential failures may involve lost computing or data nodes, inaccessible clusters, network losses, among many other. Sometimes there are ripple effects due to natural latency of the involved dependencies.

Most complex systems have several (sometimes hundreds) points of access to remote systems, services, APIs, and 3rd party libraries. Any one (or many) of these may fail or be slow to respond. In order to reach a level of acceptable resilience it is important to isolate these issues and stop cascading them through the bigger system.

Resilience4clj enables resilience in complex distributed systems where failure is inevitable.

All Modules

• resilience4clj-circuitbreaker - lets you protect an external call with a safety mechanism to interrupt the propagation of failures.
• resilience4clj-timelimiter - lets you decorate an external call with a specified time limit.
• resilience4clj-cache - lets you create distributed memoized copies of your exchanged payloads in order to reduce failure and latency impacts.
• resilience4clj-retry - lets you estabilish rules for retrying failed calls.