Hazelcast - 初次應用

Hazelcast 可以獨立（單節點）執行，也可以執行多個節點以形成一個叢集。讓我們首先嚐試啟動單個例項。

單個例項

示例

現在，讓我們嘗試建立並使用單個 Hazelcast 叢集例項。為此，我們將建立 SingleInstanceHazelcastExample.java 檔案。

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();
   }
}

現在讓我們編譯程式碼並執行它 −

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

輸出

如果你執行上面的程式碼，輸出將是 −

Hello World

然而，更重要的是，你還會注意到 Hazelcast 的日誌行，它表示 Hazelcast 已啟動。由於我們只執行此程式碼一次，即一個 JVM，因此我們的叢集中只有一個成員。

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

叢集：多例項

現在，讓我們建立 MultiInstanceHazelcastExample.java 檔案（如下所示），用於多例項叢集。

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();
   }
}

讓我們在兩個不同的外殼上執行以下命令 −

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

你將在第一個外殼上注意到 Hazelcast 例項已啟動且成員已分配。注意輸出的最後一行指出使用埠 5701 的單個成員。

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

你將在第二個外殼上注意到 Hazelcast 例項已加入第一個例項。注意輸出的最後一行指出現在使用埠 5702 的有兩個成員。

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