cluster tasks for java (CT4j)

Features

Cluster aware

Each task runs at exactly one node at the time. Retries can run at the same or different node. Tasks on failed node will be run by different node.

Single node and in-memory support

For testing or smaller services running on single node or with in-memory data store are also supported.

Retrying and error handling

Task can declare retry behavior or implement logic to decide whether to retry or fail.

Task workflows

Task can spawn next task in workflow on failure or success.

Recurring tasks

Tasks can be configured to run periodically (e.g. every 10 seconds) with guaranteed execution on single cluster node only.

Spring boot support

Uses JPA for database access and cluster support

Tasks can be beans and can participate in dependency injection (with @Autowired)

Designed for millions of tasks

This library can process very short or long lived tasks

Resource based scheduling

Task can declare required resources, such as CPU and memory usage and scheduler will take this into account. This enables running long resource intensive tasks together with very short tasks without having to worry about situation where all resource intensive tasks are started at the same node.

Priority support

Tasks are by specified priority, making sure important tasks such as notifications are run before long-running processing tasks.

Ready to run

Includes liquibase database migration and docker commands to get you started quickly. See samples.

Example task

@ClusterTask(name = "example task", maxRetries = 5, retryDelay = 1000, retryBackoffFactor = 1.5f)
public class ExampleTask extends Task<String> {
    private static Logger log = LoggerFactory.getLogger(ExampleTask.class);

    @Override
    public void run(String input, TaskExecutionContext taskExecutionContext) throws Exception {
        log.info("Task {} called with input {}", taskExecutionContext.getTaskId(), input);
    }
}

Running example task

    final String taskId = taskManager.queueTask(ExampleTask.class, "example input");

Spring boot task

public class AutowiredTask extends Task<String> {
    private static Logger log = LoggerFactory.getLogger(AutowiredTask.class);

    private final DummyAutowiredClass autowiredObject;

    @Autowired
    public AutowiredTask(DummyAutowiredClass autowiredObject) {
        this.autowiredObject = autowiredObject;
    }

    @Override
    public void run(String input, TaskExecutionContext taskExecutionContext) throws Exception {
        log.info("Input was {} and autowired was {}", input, autowiredObject);
    }

    public DummyAutowiredClass getAutowiredObject() {
        return autowiredObject;
    }
}

Configuration

Property	Description	Default	Options
ct4j.task-factory	Task creation factory	spring	spring - spring boot factory with @Autowired support constructor - default constructor factory
ct4j.persistence	Task persistence mode	memory	memory - in-memory database jpa - JPA based persistence
ct4j.time-provider	Time provider	local	local - uses local date provider

Samples

List of samples