duct-tape :: index

Duct Tape

Duct Tape is a little Java 8 library providing fault tolerance support for code that calls external APIs and unreliable components, including those that may fail, time out, or return inconsistent results.


This library was formerly named circuitbreakers, but given the inclusion of more general purpose fault tolerance features, it was renamed.

Circle CI

View on Github



See here


This example combines several of the above features:

// Shared instances (e.g. fields on a singleton object)
circuitBreaker = BreakerBuilder.newBuilder().build();
rateLimiter = RateLimiterBuilder.newBuilder()
                                .withRate(20, TimeUnit.SECONDS)

// ...

// Try and get the result but trip a circuit breaker if the component is dead:
Result result = circuitBreaker.tryGet(() -> {
    // Retry the call for up to 2s if an exception is thrown
    return Unreliables.retryUntilSuccess(2, TimeUnit.SECONDS, () -> {
        // Limit calls to a max rate of 20 per second
        return rateLimiter.getWhenReady(() -> {
            // Limit each call to 100ms
            return Timeouts.getWithTimeout(100, TimeUnit.MILLISECONDS, () -> {
                // Actually call the external service/API/unreliable component
                return exampleService.getValue("Hello World");
}, () -> {
    // Report the first time a failure occurs (probably fire off a monitoring alert IRL)
    LOGGER.error("Circuit breaker was tripped");
}, () -> {
    // Provide a default value if the circuit breaker is tripped
    return DEFAULT_VALUE;

Why not Hystrix?

Hystrix is a leading Java fault tolerance library that is undoubtedly more mature, more battle-tested and probably more robust. However, it is fairly prescriptive, and imposes a structure that might not fit with existing codebases. Duct Tape is intended to be very easy to understand and easy to integrate, with least disruption: integration should not be much harder than wrapping integration points.

If you need the strength of Hystrix or pre JDK-1.8 support then absolutely go for Hystrix. Otherwise, please at least consider Duct Tape :)

Maven dependency






Copyright (c) 2014-2015 Richard North.

See AUTHORS for contributors.