README.md

BEL - Minimalistic Java EE executor library with back-off

This library provides a CDI injectable resilient executor with a configurable back-off. The executor simplifies calling potentially fragile services without overloading them, as it will retry code execution based on a back-off strategy.

This library implements an Executor as a simple wrapper around the Java EE ManagedScheduledExecutorService. The Executor is a dependent CDI bean and will thus be instantiated in the same scope as the bean it is injected into.

The resilient executor will automatically start a new transaction when executing code using ManagedScheduledExecutorService, further simplifying creating resilient asynchronous code.

Status

Module is considered beta quality.

Usage

Add the following Maven dependency to your project:

<dependency>
    <groupId>dk.nykredit.resilience</groupId>
    <artifactId>bel</artifactId>
    <version>0.9.2</version>
</dependency>

The resilient executor implements the Executor interface and using the executor is thus similar to using Java EE ManagedScheduledExecutorService:

@Inject
@Resilient(strategy = PolynomialBackoffStrategy.class)
@PolynomialBackoffStrategyConfig(delay = 1, maxDelay = 1800, retries = 100, timeUnit = TimeUnit.SECONDS)
private ResilientExecutor executor;

executor.execute(() -> {
        Customer customer = repository.get(id);
        StatusRepresentation status = statusConnector.get(customer.getId());
        customer.setStatus(status.getStatus());
    }, e -> {
        LOGGER.error("Error calling service...", e);
        Customer customer = repository.get(id);
        customer.setStatus(Status.UNKNOWN);
    });
}