How to understand Elasticsearch single-machine two-node cluster deployment

In this article, we still do some basic learning on how to perform CRUD in Elasticsearch.

Elasticsearch stand-alone dual-node cluster deployment

环境：CentOS 7.2       JDK 1.8.0_74

##1. Install the first ElasticSearch (master node)

1. Create an es user. You cannot use the root user to start es.

useradd es
passwd es

The root user enters the /home/es directory.

2. Obtain the ElasticSearch installation package.

wget https://artifacts.elastic.co/downloads/elasticsearch/elasticsearch-6.1.2.tar.gz

3. Unzip and rename (to facilitate the differentiation of another ES when clustering)

tar xf elasticsearch-6.1.2.tar.gzmv elasticsearch-6.1.2.tar.gz elasticsearch-node2

4. Modify the configuration file

vi elasticsearch-node2/config/elasticsearch.yml

The modification content is as follows:

cluster.name: my-application      
  各节点此名称必须一致node.name: node-2           
        节点名称，不能与其他节点相同        
         network.host: ***.***.***.***   
        自己的服务器IPhttp.port: ****         
           访问端口transport.tcp.port: ****  
    集群各节点间的通讯端口 discovery.zen.ping.unicast.hosts: ["主节点IP：通讯端口"，"辅节点IP：通讯端口"]

Add the following content to the end of the file , so that the connection head displays the health value (note that there should be no spaces before each line of code)

http.cors.enabled: truehttp.cors.allow-origin: "*"

5. Startup

sh elasticsearch-node2/bin/elasticsearch

[2018-01-24T15:36:41,990][INFO ][o.e.n.Node               ] [KMyyO-3] started
[2018-01-24T15:36:41,997][INFO ][o.e.g.GatewayService     ] [KMyyO-3] recovered [0] indices into cluster_state

Start successfully, enter

IP:access port## in the browser #The webpage displays the following content, indicating that the deployment is successful

{
  "name" : "node-2",
  "cluster_name" : "my-application",
  "cluster_uuid" : "j2aJ7CsRSuSo0G8Bgky2Ww",    
  "version" : {
    "number" : "6.1.2",
    "build_hash" : "5b1fea5",
    "build_date" : "2018-01-10T02:35:59.208Z",
    "build_snapshot" : false,
    "lucene_version" : "7.1.0",
    "minimum_wire_compatibility_version" : "5.6.0",
    "minimum_index_compatibility_version" : "5.0.0"
  },
  "tagline" : "You Know, for Search"}

6, error reporting and its handling

[Type 1]

Caused by: java.lang.RuntimeException: can not run elasticsearch as root

This problem is because running es cannot be used root user, so switch to es user and start again

chown -R es:es elasticsearch-node2/su - es
sh elasticsearch-node2/bin/elasticsearch

[Type 2]

max file descriptors [4096] for elasticsearch process is too low, increase to at least [65536]

Solution, change back to root user and modify the configuration file

vi /etc/security/limits.conf#在最后面追加下面内容es hard nofile 65536es soft nofile 65536

[Type 3]

max virtual memory areas vm.max_map_count [65530] is too low, increase to at least [262144]

Solution, change back to the root user and modify the configuration file

vi /etc/sysctl.conf 
#在最后面追加下面内容vm.max_map_count=655360#执行命令：sysctl -p

2. Install the second ElasticSearch (secondary node)

The installation method is the same as the first The two are consistent, pay attention to modifying the configuration fileroot user enters the /home/es directory

1. Unzip and change the name

tar xf elasticsearch-6.1.2.tar.gzmv elasticsearch-6.1.2.tar.gz elasticsearch-node3

2. Modify the configuration file

vi elasticsearch-node3/config/elasticsearch.yml

Modify The content is as follows:

cluster.name: my-application      
  各节点此名称必须一致node.name: node-3      
               节点名称，不能与其他节点相同network.host: ***.***.***.***   
                   自己的服务器IPhttp.port: ****          
                              访问端口（注意不要与第一个端口重复）                              transport.tcp.port: ****            集群各节点间的通讯端口（注意不要与第一个端口重复）discovery.zen.ping.unicast.hosts: ["主节点IP：通讯端口"，"辅节点IP：通讯端口"]

Also append the following code at the end of the file

http.cors.enabled: truehttp.cors.allow-origin: "*"

3. Start the

sh elasticsearch-node3/bin/elasticsearch

browser and enter

IP:access port

in the browser The webpage displays the following content, indicating that the second deployment is successful

{
  "name" : "node-3",
  "cluster_name" : "my-application",
  "cluster_uuid" : "j2aJ7CsRSuSo0G8Bgky2Ww",
  "version" : {
    "number" : "6.1.2",
    "build_hash" : "5b1fea5",
    "build_date" : "2018-01-10T02:35:59.208Z",
    "build_snapshot" : false,
    "lucene_version" : "7.1.0",
    "minimum_wire_compatibility_version" : "5.6.0",
    "minimum_index_compatibility_version" : "5.0.0"
  },
  "tagline" : "You Know, for Search"}

3. Install the Elasticsearch-head plug-in

1. You need to install node.js before installing the head plug-in

curl -sL https://rpm.nodesource.com/setup_8.x | bash -
yum install -y nodejs

After the installation is complete, execute the command to view the node and npm versions

[root@host]# node -vv8.12.0[root@host]# npm -v6.4.1

2. Get the head plug-in from git

wget https://github.com/mobz/elasticsearch-head/archive/master.zip

3. Unzip the installation package (you can rename it for easy operation)

unzip master.zip
mv elasticsearch-head-master/ head

4. Modify the configuration file

vi head/Gruntfile.js

Change the head port number

connect: {          server: {
                   options: {
                              port: ****,    改为head访问端口
                              base: '.',
                              keepalive: true                             }
                    }
          }

vi head/_site/app.js

Change the head link address

init: function(parent) {
                        this._super();                        this.prefs = services.Preferences.instance();                        this.base_uri = this.config.base_uri || this.prefs.get("app-base_uri") || "http://主节点IP:访问端口";

5. Start the head

nohup npm run start > ../head.log 2>&1 &

6. Browser login head

URL input server IP: head access port

Link address input such as the access address of the master node

7. Common errors in installing head
[Type 1] Started successfully, but the webpage cannot be accessed
Solution
Turn off the server firewall

service iptables stop

[Type 2]The cluster health value is not connected

Append the following code to elasticsearch.yml ( Note that there should be no spaces in front of the code)

http.cors.enabled: truehttp.cors.allow-origin: "*"

Q: Why do es nodes use node2 and node3?

Answer: Because we used node1 to build a set of unclustered ES before, we used 2 and 3 for the subsequent clusters

Related recommendations:

How to use Yii2-elasticsearch ah?

CRUD in Elasticsearch

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