HazelcastExecutor IScheduledExecutorService Arayüzü

Giriş

Şu satırı dahil ederiz

import com.hazelcast.scheduledexecutor.IScheduledExecutorService;

1. XML için IScheduledExecutorService Ayarları yazısına bakabilirsiniz.

2. Açıklaması şöyle. Yani cron tarzı yapıları desteklemez

IScheduledExecutorService is not a full cron scheduler 

3. retry ve failure recovery için herhangi bir şey sağlamaz.

schedule metodu

İmzası şöyle. Belirtilen delay değerinden sonra tek seferlik (one shot) bir işi rastgele bir cluster üyesinde çalıştırır.

<V> IScheduledFuture<V> schedule(Runnable command, long delay, TimeUnit unit);
<V> IScheduledFuture<V> schedule(Callable<V> command, long delay, TimeUnit unit);

Örnek

Şöyle yaparız

HazelcastInstance instance = ...;
 IScheduledExecutorService scheduler = instance
  .getScheduledExecutorService("distributed-scheduler");
 scheduler.schedule(new MyRunnableTask(), 10, TimeUnit.SECONDS);

Örnek

Şöyle yaparız

@Scheduled(fixedDelay = 10000, initialDelay = 60000)
void startJob() {
  String leaderAddress = getOldestMember().getSocketAddress().toString();
  String currentAddress = instance.getCluster().getLocalMember().getSocketAddress()
    .toString();

  //Run the task only on leader node

  if (currentAddress.equals(leaderAddress)) {
    System.out.println("I am leader, use me to poll database, distribute task etc");
    IScheduledExecutorService scheduler = instance
      .getScheduledExecutorService("distributed-scheduler");
    scheduler.schedule(new MyScheduledTask(), 10, TimeUnit.SECONDS);
  }
}

private Member getOldestMember() {
  Cluster cluster = instance.getCluster();
  Member oldestMember = null;
  for (Member member : cluster.getMembers()) {
    if (oldestMember == null || member.getUuid().compareTo(oldestMember.getUuid()) < 0) {
      oldestMember = member;
    }
  }
return oldestMember;
}

static class MySchedulerJob implements Serializable, Runnable {
  ...
}

scheduleAtFixedRate metodu

İmzası şöyle

<V> IScheduledFuture<V> scheduleAtFixedRate(Runnable command,long initialDelay,
  long period,TimeUnit unit);

TaskUtils sınıfının named() metodu kullanılarak, aynı işin birden fazla kere teslim edilmesi engellenebilir. Açıklaması şöyle

The solution is to use com.hazelcast.scheduledexecutor.NamedTask or com.hazelcast.scheduledexecutor.TaskUtils#named(String, Runnable) helper method

Örnek - Çift (Duplicate) İşi Tespit Etmek

Şöyle yaparız

HazelcastInstance hz = Hazelcast.newHazelcastInstance();

IScheduledExecutorService myScheduler = hz.getScheduledExecutorService("myScheduler");
try {
  IScheduledFuture<Object> future = myScheduler.scheduleAtFixedRate(
    TaskUtils.named( "myTask",
      (RunnableEx) () -> System.out.println(System.currentTimeMillis() + " Hello World!")
     ),
     0, 5, SECONDS);
} catch (DuplicateTaskException e) {
  // expected on one of the members
}

Örnek

Şöyle yaparız

try {
  IScheduledExecutorService es = hz.getScheduledExecutorService("default");
  /*
  Having same task name in the cluster will restrict the multiple tasks
  in the cluster and execution will be single instance
  when 1st instance will execute below code the task will be created
  further instances will not be able to register same name tasks
  and the will have ‘DuplicateTaskException’ error
  */
  IScheduledFuture<?> future = es.scheduleAtFixedRate(
    TaskUtils.named("MyTask", new MyTask()),
    5, 30, TimeUnit.SECONDS);

} catch (DuplicateTaskException e) {
  System.out.println("Already scheduled task");
}

scheduleOnMember metodu

Eğer işin nerede çalıştığı önemliyse bu belirtilebilir. Açıklaması şöyle

Tasks can be scheduled to run on a specific member, all members, or a randomly selected member of the cluster.

İmzası şöyle

<V> IScheduledFuture<V> scheduleOnMember(Runnable command, Member member,
                                         long delay, TimeUnit unit);
<V> IScheduledFuture<V> scheduleOnMember(Callable<V> command, Member member,
                                         long delay, TimeUnit unit);