ShedLock

ShedLock does one and only one thing. It makes sure your scheduled tasks are executed at most once at the same time. If a task is being executed on one node, it acquires a lock which prevents execution of the same task from another node (or thread). Please note, that if one task is already being executed on one node, execution on other nodes does not wait, it is simply skipped.

Currently, Spring scheduled tasks coordinated through Mongo, JDBC database, Redis, Hazelcast or ZooKeeper are supported. More scheduling and coordination mechanisms and expected in the future.

Feedback and pull-requests welcome!

ShedLock is not a distributed scheduler

Please note that ShedLock is not and will never be full-fledged scheduler, it's just a lock. If you need a distributed scheduler, please use another project. ShedLock is designed to be used in situations where you have scheduled tasks that are not ready to be executed in parallel, but can be safely executed repeatedly. For example if the task is fetching records from a database, processing them and marking them as processed at the end without using any transaction. In such case ShedLock may be right for you.

Usage

Requirements and dependencies

Java 8
slf4j-api
Spring Framework (optional)

Import project

<dependency>
    <groupId>net.javacrumbs.shedlock</groupId>
    <artifactId>shedlock-spring</artifactId>
    <version>0.18.2</version>
</dependency>

Annotate your scheduled tasks

import net.javacrumbs.shedlock.core.SchedulerLock;

...

@Scheduled(...)
@SchedulerLock(name = "scheduledTaskName")
public void scheduledTask() {
   // do something
}

The @SchedulerLock annotation has several purposes. First of all, only annotated methods are locked, the library ignores all other scheduled tasks. You also have to specify the name for the lock. Only one tasks with the same name can be executed at the same time.

You can also set lockAtMostFor attribute which specifies how long the lock should be kept in case the executing node dies. This is just a fallback, under normal circumstances the lock is released as soon the tasks finishes.

Lastly, you can set lockAtLeastFor attribute which specifies minimum amount of time for which the lock should be kept. Its main purpose is to prevent execution from multiple nodes in case of really short tasks and clock difference between the nodes.

Example

Let's say you have a task which you execute every 15 minutes and which usually takes few minutes to run. Moreover, you want to execute it at most once per 15 minutes. In such case, you can configure it like this

import net.javacrumbs.shedlock.core.SchedulerLock;

...
private static final int FOURTEEN_MIN = 14 * 60 * 1000;
...

@Scheduled(cron = "0 */15 * * * *")
@SchedulerLock(name = "scheduledTaskName", lockAtMostFor = FOURTEEN_MIN, lockAtLeastFor = FOURTEEN_MIN)
public void scheduledTask() {
   // do something
}

By setting lockAtMostFor we make sure that the lock is released even if the node dies and by setting lockAtLeastFor we make sure it's not executed more than once in fifteen minutes. Please note that if the task takes longer than 15 minutes, it will be executed again.

Configure the task scheduler

Now we need to integrate the library into Spring. It's done by wrapping standard Spring task scheduler.

import net.javacrumbs.shedlock.spring.SpringLockableTaskSchedulerFactory;

...
@Bean
public ScheduledLockConfiguration taskScheduler(LockProvider lockProvider) {
    return ScheduledLockConfigurationBuilder
        .withLockProvider(lockProvider)
        .withPoolSize(10)
        .withDefaultLockAtMostFor(Duration.ofMinutes(10))
        .build();
}

Or if you already have an instance of ScheduledExecutorService

@Bean
public TaskScheduler taskScheduler(ScheduledExecutorService executorService, LockProvider lockProvider) {
    return ScheduledLockConfigurationBuilder
        .withLockProvider(lockProvider)
        .withExecutorService(executorService)
        .withDefaultLockAtMostFor(Duration.ofMinutes(10))
        .build();
}

Configure LockProvider

Mongo

Import the project

<dependency>
    <groupId>net.javacrumbs.shedlock</groupId>
    <artifactId>shedlock-provider-mongo</artifactId>
    <version>0.18.2</version>
</dependency>

Configure:

import net.javacrumbs.shedlock.provider.mongo.MongoLockProvider;

...

@Bean
public LockProvider lockProvider(MongoClient mongo) {
    return new MongoLockProvider(mongo, "databaseName");
}

Please note that MongoDB integration requires Mongo >= 2.4 and mongo-java-driver >= 3.4.0

JdbcTemplate

Create the table

CREATE TABLE shedlock(
    name VARCHAR(64), 
    lock_until TIMESTAMP(3) NULL, 
    locked_at TIMESTAMP(3) NULL, 
    locked_by  VARCHAR(255), 
    PRIMARY KEY (name)
)

script for MS SQL is here

Add dependency

<dependency>
    <groupId>net.javacrumbs.shedlock</groupId>
    <artifactId>shedlock-provider-jdbc-template</artifactId>
    <version>0.18.2</version>
</dependency>

Configure:

import net.javacrumbs.shedlock.provider.jdbctemplate.JdbcTemplateLockProvider;

...

@Bean
public LockProvider lockProvider(DataSource dataSource) {
    return new JdbcTemplateLockProvider(dataSource);
}

Tested with MySql, Postgres and HSQLDB

Plain JDBC

For those who do not want to use jdbc-template, there is plain JDBC lock provider. Just import

<dependency>
    <groupId>net.javacrumbs.shedlock</groupId>
    <artifactId>shedlock-provider-jdbc</artifactId>
    <version>0.18.2</version>
</dependency>

and configure

import net.javacrumbs.shedlock.provider.jdbc.JdbcLockProvider;

...

@Bean
public LockProvider lockProvider(DataSource dataSource) {
    return new JdbcLockProvider(dataSource);
}

the rest is the same as with JdbcTemplate lock provider.

Warning

Do not manually delete lock row or document from DB table or Mongo collection. ShedLock has an in-memory cache of existing locks so the row will NOT be automatically recreated until application restart. If you need to, you can edit the row/document, risking only that multiple locks will be held. Since 0.18.2 you can clean the cache by calling clearCache() on LockProvider.

ZooKeeper (using Curator)

Import

<dependency>
    <groupId>net.javacrumbs.shedlock</groupId>
    <artifactId>shedlock-provider-zookeeper-curator</artifactId>
    <version>0.18.2</version>
</dependency>

and configure

import net.javacrumbs.shedlock.provider.zookeeper.curator.ZookeeperCuratorLockProvider;

...

@Bean
public LockProvider lockProvider(org.apache.curator.framework.CuratorFramework client) {
    return new ZookeeperCuratorLockProvider(client);
}

By default, ephemeral nodes for locks will be created under /shedlock node.

Redis (using Spring RedisConnectionFactory)

Import

<dependency>
    <groupId>net.javacrumbs.shedlock</groupId>
    <artifactId>shedlock-provider-redis-spring</artifactId>
    <version>0.18.2</version>
</dependency>

and configure

import net.javacrumbs.shedlock.provider.redis.spring.RedisLockProvider;

...

@Bean
public LockProvider lockProvider(JedisPool jedisPool) {
    return new RedisLockProvider(connectionFactory, ENV);
}

Redis (using Jedis)

Import

<dependency>
    <groupId>net.javacrumbs.shedlock</groupId>
    <artifactId>shedlock-provider-redis-jedis</artifactId>
    <version>0.18.0</version>
</dependency>

and configure

import net.javacrumbs.shedlock.provider.redis.jedis.JedisLockProvider;

...

@Bean
public LockProvider lockProvider(JedisPool jedisPool) {
    return new JedisLockProvider(jedisPool, ENV);
}

Hazelcast

Import the project

<dependency>
    <groupId>net.javacrumbs.shedlock</groupId>
    <artifactId>shedlock-provider-hazelcast</artifactId>
    <version>0.18.0</version>
</dependency>

Configure:

import net.javacrumbs.shedlock.provider.hazelcast.HazelcastLockProvider;

...

@Bean
public HazelcastLockProvider lockProvider(HazelcastInstance hazelcastInstance) {
    return new HazelcastLockProvider(hazelcastInstance);
}

Spring XML configuration

If you are using Spring XML config, use this configuration

<!-- lock provider of your choice (jdbc/zookeeper/mongo/whatever) -->
<bean id="lockProvider" class="net.javacrumbs.shedlock.provider.jdbctemplate.JdbcTemplateLockProvider">
    <constructor-arg ref="dataSource"/>
</bean>

<bean id="scheduler" class="net.javacrumbs.shedlock.spring.SpringLockableTaskSchedulerFactoryBean">
    <constructor-arg>
        <task:scheduler id="sch" pool-size="10"/>
    </constructor-arg>
    <constructor-arg ref="lockProvider"/>
    <constructor-arg name="defaultLockAtMostFor">
        <bean class="java.time.Duration" factory-method="ofMinutes">
            <constructor-arg value="10"/>
        </bean>
    </constructor-arg>
</bean>


<!-- Your task(s) without change (or annotated with @Scheduled)-->
<task:scheduled-tasks scheduler="scheduler">
    <task:scheduled ref="task" method="run" fixed-delay="1" fixed-rate="1"/>
</task:scheduled-tasks>

Annotate scheduler method(s)

@SchedulerLock(name = "taskName")
public void run() {

}

Running without Spring

It is possible to use ShedLock without Spring

LockingTaskExecutor executor = new DefaultLockingTaskExecutor(lockProvider);

...

Instant lockAtMostUntil = Instant.now().plusSeconds(600);
executor.executeWithLock(runnable, new LockConfiguration("lockName", lockAtMostUntil));

Change log

0.18.2

ablility to clean lock cache

0.18.1

shedlock-provider-redis-spring made compatible with spring-data-redis 1.x.x

0.18.0

Added shedlock-provider-redis-spring (thanks to @siposr)
shedlock-provider-jedis moved to shedlock-provider-redis-jedis

0.17.0

Support for SPEL in lock name annotation

0.16.1

Automatically closing TaskExecutor on Spring shutdown

0.16.0

Removed spring-test from shedlock-spring compile time dependencies
Added Automatic-Module-Names

0.15.1

Hazelcast works with remote cluster

0.15.0

Fixed ScheduledLockConfigurationBuilder interfaces #32
Hazelcast code refactoring

0.14.0

Support for Hazelcast (thanks to @peyo)

0.13.0

Jedis constructor made more generic (thanks to @mgrzeszczak)

0.12.0

Support for property placeholders in annotation lockAtMostForString/lockAtLeastForString
Support for composed annotations
ScheduledLockConfigurationBuilder introduced (deprecating SpringLockableTaskSchedulerFactory)

0.11.0

Support for Redis (thanks to @clamey)
Checking that lockAtMostFor is in the future
Checking that lockAtMostFor is larger than lockAtLeastFor

0.10.0

jdbc-template-provider does not participate in task transaction

0.9.0

Support for @SchedulerLock annotations on proxied classes

0.8.0

LockableTaskScheduler made AutoClosable so it's closed upon Spring shutdown

0.7.0

Support for lockAtLeastFor

0.6.0

Possible to configure defaultLockFor time so it does not have to be repeated in every annotation

0.5.0

ZooKeeper nodes created under /shedlock by default

0.4.1

JdbcLockProvider insert does not fail on DataIntegrityViolationException

0.4.0

Extracted LockingTaskExecutor
LockManager.executeIfNotLocked renamed to executeWithLock
Default table name in JDBC lock providers

0.3.0

@ShedlulerLock.name made obligatory
@ShedlulerLock.lockForMillis renamed to lockAtMostFor
Adding plain JDBC LockProvider
Adding ZooKeepr LockProvider

ShedLock

ShedLock is not a distributed scheduler

Usage

Requirements and dependencies

Import project

Annotate your scheduled tasks

Example

Configure the task scheduler

Configure LockProvider

Mongo

JdbcTemplate

Plain JDBC

Warning

ZooKeeper (using Curator)

Redis (using Spring RedisConnectionFactory)

Redis (using Jedis)

Hazelcast

Spring XML configuration

Running without Spring

Change log

0.18.2

0.18.1

0.18.0

0.17.0

0.16.1

0.16.0

0.15.1

0.15.0

0.14.0

0.13.0

0.12.0

0.11.0

0.10.0

0.9.0

0.8.0

0.7.0

0.6.0

0.5.0

0.4.1

0.4.0

0.3.0

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