Simple Scheduler

A simple to use, lightweight clustered scheduler for Java/Scala. It can be used for job processing also, but it is recommended that the operations are restricted to light-weight processing only.

Note: For recurring jobs make sure that execution time is less than recurring jobs otherwise the job results in misfire for for that frequency and effective frequency = max(next execution time based on cron, current job execution time).

Features

• Clustered: When a Lock is used, guarantees execution by a single scheduler instance
• Requirements: A single relational database table.
• Impact on database: Does not require pessimistic locking. With the possibility to process updates in batches, reduces the write load on the database. The task fetches adapt to the pending work-load

Getting Started

1. Include the jar as a maven dependency
2. Create the database table.
3. Create a DataSource reference. eg:

dataSource.setDriverClassName("com.mysql.jdbc.Driver");
dataSource.setUsername(mySqlProfile.user);
dataSource.setPassword(mySqlProfile.password);
dataSource.setUrl("jdbc:mysql://hostname:3306/my_db_schema");

4. Create a JobResolverFactory or use the default job resolver that creates a new instance of the executor class on each invocation

JobResolverFactory jobResolverFactory = new ConstructionBasedFactory();

5. (Not required in a single instance mode) Create a Lock or use the default Redis based Lock

Lock lock = new RedisBasedLock(String namespace, JedisPool jedisPool)

6. Create the Scheduler instance and start it

WorkConfig workConfig = new WorkConfig("host_name_1").logFailures(false);
SchedulerConfig schedulerConfig = new SchedulerConfig(dataSource, workConfig).withLock(lock);
Scheduler scheduler = new Scheduler(schedulerConfig, jobResolverFactory);
scheduler.start()

7. Register a few tasks (one time) irrespective of JVM restarts

scheduler.schedulerRegistry().register(new RepeatableTask("Fizz_Namespace", "PollJob-9", Duration.apply(30, TimeUnit.SECONDS), "com.foo.bar.poll.ReadJob").withParameters("Xing"));
scheduler.schedulerRegistry().register(new CronTask("Buzz_Namespace", "SR-192", "0/33 * * * * ?", "com.foo.bar.poll.SpecificReadsJob"));

8. Stop the Scheduler

scheduler.stop()

Configurations

• WorkConfig
• SchedulerConfig

Workflow

Using in a Java project

Maven Dependencies - Click to expand

  <dependency>
      <groupId>org.scala-lang</groupId>
      <artifactId>scala-library</artifactId>
      <version>2.11.12</version>
  </dependency>
  <dependency>
      <groupId>com.cronutils</groupId>
      <artifactId>cron-utils</artifactId>
      <version>5.0.5</version>
  </dependency>
  <dependency>
      <groupId>mysql</groupId>
      <artifactId>mysql-connector-java</artifactId>
      <version>8.0.23</version>
  </dependency>
  <dependency>
      <groupId>org.slf4j</groupId>
      <artifactId>slf4j-api</artifactId>
      <version>1.7.5</version>
  </dependency>
  <dependency>
      <groupId>org.slf4j</groupId>
      <artifactId>slf4j-simple</artifactId>
      <version>1.7.5</version>
  </dependency>
  <dependency>
      <groupId>org.apache.commons</groupId>
      <artifactId>commons-dbcp2</artifactId>
      <version>2.8.0</version>
  </dependency>
  
  
  <dependency>
      <groupId>com.hevodata</groupId>
      <artifactId>simple-scheduler_2.11</artifactId>
      <version>0.1.6</version>
  </dependency>