index.md

layout	title
default	Fault tolerance and resilience patterns for the JVM

{: .callout } For Golang projects, Failsafe-go has been released! See the project website for more info.

Overview

Failsafe is a lightweight, zero-dependency library for handling failures in Java 8+. It has a concise API for handling everyday use cases and the flexibility to handle everything else. Failsafe works by wrapping executable logic with one or more resilience [policies], which can be combined and [composed][policy-composition] as needed.

Setup

Add the latest [Failsafe dependency][maven] to your project.

Getting Started

To see how Failsafe works, we'll create a [retry policy][retry] that defines which failures to handle and when retries should be performed:

RetryPolicy<Object> retryPolicy = RetryPolicy.builder()
  .handle(ConnectException.class)
  .withDelay(Duration.ofSeconds(1))
  .withMaxRetries(3)
  .build();

We can then execute a Runnable or Supplier with retries:

// Run with retries
Failsafe.with(retryPolicy).run(() -> connect());

// Get with retries
Connection connection = Failsafe.with(retryPolicy).get(() -> connect());

Asynchronous Execution

Executing a Runnable or Supplier [asynchronously][async-execution] with a policy is simple:

// Run with retries asynchronously
CompletableFuture<Void> future = Failsafe.with(retryPolicy).runAsync(() -> connect());

// Get with retries asynchronously
CompletableFuture<Connection> future = Failsafe.with(retryPolicy).getAsync(() -> connect());

Composing Policies

Multiple [policies] can be arbitrarily composed to add additional layers of resilience or to handle different failures in different ways:

var fallback = Fallback.of(this::connectToBackup);
var circuitBreaker = CircuitBreaker.ofDefaults();
var timeout = Timeout.of(Duration.ofSeconds(10));

// Get with fallback, retries, circuit breaker, and timeout
Failsafe.with(fallback, retryPolicy, circuitBreaker, timeout).get(this::connect);

Order does matter when composing policies. See the [policy composition][policy-composition] overview for more details.

Failsafe Executor

Policy compositions can also be saved for later use via a [FailsafeExecutor]:

FailsafeExecutor<Object> executor = Failsafe.with(retryPolicy).compose(circuitBreaker);
executor.run(this::connect);

Further Reading

Read more about [policies] and how they're used, then explore some of Failsafe's other features in the site menu.

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