Hazelcast – 第一个应用程序

Hazelcast 可以单独运行（单节点），也可以运行多个节点组成集群。让我们首先尝试启动单个实例。

单实例

例子

现在，让我们尝试创建和使用 Hazelcast 集群的单个实例。为此，我们将创建 SingleInstanceHazelcastExample.java 文件。

package com.example.demo;

import java.util.Map;
import com.hazelcast.core.Hazelcast;
import com.hazelcast.core.HazelcastInstance;

public class SingleInstanceHazelcastExample {
   public static void main(String... args){
      //initialize hazelcast server/instance
      HazelcastInstance hazelcast = Hazelcast.newHazelcastInstance();
      System.out.println(“Hello world”);
        
      // perform a graceful shutdown
      hazelcast.shutdown();
   }
}

现在让我们编译代码并执行它 –

mvn clean install
java -cp target/demo-0.0.1-SNAPSHOT.jar
com.example.demo.SingleInstanceHazelcastExample

输出

如果您执行上面的代码，输出将是 –

Hello World

然而，更重要的是，您还会注意到 Hazelcast 的日志行，这表示 Hazelcast 已启动。由于我们只运行此代码一次，即单个 JVM，因此我们的集群中将只有一个成员。

Jan 30, 2021 10:26:51 AM com.hazelcast.config.XmlConfigLocator
INFO: Loading 'hazelcast-default.xml' from classpath.
Jan 30, 2021 10:26:51 AM com.hazelcast.instance.AddressPicker
INFO: [LOCAL] [dev] [3.12.12] Prefer IPv4 stack is true.
Jan 30, 2021 10:26:52 AM com.hazelcast.instance.AddressPicker
INFO: [LOCAL] [dev] [3.12.12] Picked [localhost]:5701, using socket
ServerSocket[addr=/0:0:0:0:0:0:0:0,localport=5701], bind any local is true
Jan 30, 2021 10:26:52 AM com.hazelcast.system
...

Members {size:1, ver:1} [
   Member [localhost]:5701 - 9b764311-9f74-40e5-8a0a-85193bce227b this
]

Jan 30, 2021 10:26:56 AM com.hazelcast.core.LifecycleService
INFO: [localhost]:5701 [dev] [3.12.12] [localhost]:5701 is STARTED
...

You will also notice log lines from Hazelcast at the end which signifies
Hazelcast was shutdown:
INFO: [localhost]:5701 [dev] [3.12.12] Hazelcast Shutdown is completed in 784 ms.
Jan 30, 2021 10:26:57 AM com.hazelcast.core.LifecycleService
INFO: [localhost]:5701 [dev] [3.12.12] [localhost]:5701 is SHUTDOWN

集群：多实例

现在，让我们创建用于多实例集群的 MultiInstanceHazelcastExample.java 文件（如下所示）。

package com.example.demo;

import com.hazelcast.core.Hazelcast;
import com.hazelcast.core.HazelcastInstance;

public class MultiInstanceHazelcastExample {
   public static void main(String... args) throws InterruptedException{
      //initialize hazelcast server/instance
      HazelcastInstance hazelcast = Hazelcast.newHazelcastInstance();
        
      //print the socket address of this member and also the size of the cluster
      System.out.println(String.format("[%s]: No. of hazelcast members: %s",
         hazelcast.getCluster().getLocalMember().getSocketAddress(),
         hazelcast.getCluster().getMembers().size()));
        
      // wait for the member to join
      Thread.sleep(30000);
        
      //perform a graceful shutdown
      hazelcast.shutdown();
   }
}

让我们在两个不同的 shell上执行以下命令–

java -cp .\target\demo-0.0.1-SNAPSHOT.jar
com.example.demo.MultiInstanceHazelcastExample

您会在第一个 shell 上注意到 Hazelcast 实例已启动并已分配成员。请注意输出的最后一行，它表示有一个成员使用端口 5701。

Jan 30, 2021 12:20:21 PM com.hazelcast.internal.cluster.ClusterService
INFO: [localhost]:5701 [dev] [3.12.12]
Members {size:1, ver:1} [
   Member [localhost]:5701 - b0d5607b-47ab-47a2-b0eb-6c17c031fc2f this
]
Jan 30, 2021 12:20:21 PM com.hazelcast.core.LifecycleService
INFO: [localhost]:5701 [dev] [3.12.12] [localhost]:5701 is STARTED
[/localhost:5701]: No. of hazelcast members: 1

您会在第2 个 shell 上注意到 Hazelcast 实例已加入第一个实例。请注意输出的最后一行，它表示现在有两个成员使用端口 5702。

INFO: [localhost]:5702 [dev] [3.12.12]
Members {size:2, ver:2} [
   Member [localhost]:5701 - b0d5607b-47ab-47a2-b0eb-6c17c031fc2f
   Member [localhost]:5702 - 037b5fd9-1a1e-46f2-ae59-14c7b9724ec6 this
]
Jan 30, 2021 12:20:46 PM com.hazelcast.core.LifecycleService
INFO: [localhost]:5702 [dev] [3.12.12] [localhost]:5702 is STARTED
[/localhost:5702]: No. of hazelcast members: 2