[Centos7]安装elasticsearch集群

https://www.elastic.co/cn/downloads/

准备三台ES服务器：

192.168.140.197
192.168.140.198
192.168.140.199

1、系统设置

Elasticsearch不能在 root 用户下启动，我们需要在三台机器上分别创建一个普通用户：

# 创建elk用户
useradd elk
# 设置用户密码
passwd elk
# 切换到elk用户
su elk

分别在三台机器上的 /data/ 目录下创建elasticsearch文件夹，然后在elasticsearch文件夹下分别创建data、logs文件夹：

cd /data
mkdir elasticsearch
cd elasticsearch
if

在生产环境下我们要把Elasticsearch生成的索引文件数据存放到自定义的目录下
data：存储Elasticsearch索引文件数据
logs：存储日志文件

2、配置Elasticsearch

我们只需要简单的配置一下Elasticsearch就可以使用了

wget https://artifacts.elastic.co/downloads/elasticsearch/elasticsearch-7.12.0-linux-x86_64.tar.gz
tar -zxvf elasticsearch-7.12.0-linux-x86_64.tar.gz -C /usr/local
ln -sf /usr/local/elasticsearch-7.12.0 /usr/local/elasticsearch

修改配置：

vim /usr/local/elasticsearch/config/elasticsearch.yml

修改结果如下：

# ======================== Elasticsearch Configuration =========================
#
# NOTE: Elasticsearch comes with reasonable defaults for most settings.
#       Before you set out to tweak and tune the configuration, make sure you
#       understand what are you trying to accomplish and the consequences.
#
# The primary way of configuring a node is via this file. This template lists
# the most important settings you may want to configure for a production cluster.
#
# Please consult the documentation for further information on configuration options:
# https://www.elastic.co/guide/en/elasticsearch/reference/index.html
#
# ---------------------------------- Cluster -----------------------------------
#
# Use a descriptive name for your cluster:
#
cluster.name: vodjk
#
# ------------------------------------ Node ------------------------------------
#
# Use a descriptive name for the node:
#
node.name: node-1
#
# Add custom attributes to the node:
#
#node.attr.rack: r1
#
# ----------------------------------- Paths ------------------------------------
#
# Path to directory where to store the data (separate multiple locations by comma):
#
path.data: /data/elasticsearch/data
#
# Path to log files:
#
path.logs: /data/elasticsearch/logs
#
# ----------------------------------- Memory -----------------------------------
#
# Lock the memory on startup:
#
#bootstrap.memory_lock: true
#
# Make sure that the heap size is set to about half the memory available
# on the system and that the owner of the process is allowed to use this
# limit.
#
# Elasticsearch performs poorly when the system is swapping the memory.
#
# ---------------------------------- Network -----------------------------------
#
# By default Elasticsearch is only accessible on localhost. Set a different
# address here to expose this node on the network:
#
#
network.host: 192.168.140.197
#
# By default Elasticsearch listens for HTTP traffic on the first free port it
# finds starting at 9200. Set a specific HTTP port here:
#
http.port: 9200
#
# For more information, consult the network module documentation.
#
# --------------------------------- Discovery ----------------------------------
#
# Pass an initial list of hosts to perform discovery when this node is started:
# The default list of hosts is ["127.0.0.1", "[::1]"]
#
discovery.seed_hosts: ["es-1", "es-2", "es-3"]
#
# Bootstrap the cluster using an initial set of master-eligible nodes:
#
cluster.initial_master_nodes: ["node-1", "node-2", "node-3"]
#
# For more information, consult the discovery and cluster formation module documentation.
#
# ---------------------------------- Various -----------------------------------
#
# Require explicit names when deleting indices:
#
action.destructive_requires_name: true

这里注意在/etc/hosts里解析es-1、es-2、es-3

主要修改如下几处配置：

1. cluster.name：集群的名称，集群中所有节点的 cluster.name 的值必须要相同。
2. node.name：集群中每个Elasticsearch的节点名称，不可以重复。
3. path.data：设置存放Elasticsearch索引文件数据的路径。
4. path.logs：设置存放日志文件的路径。
5. network.host：Elasticsearch绑定的IP，外界可以通过这个IP访问到当前Elasticsearch节点，一般配配置当前系统的IP，或者 0.0.0.0 （任何地址都能访问到）。
6. http.port：当前启动Elasticsearch的端口号，一般默认 9200 即可，当然你也可以修改
7. discovery.seed_hosts：配置所有Elasticsearch节点绑定的IP地址。
8. cluster.initial_master_nodes：配置那些节点可以有资格被选为主节点。
9. xpack.monitoring.collection.enabled：收集监控数据默认为false不收集监控数据。

我们已经配置好一台Elasticsearch节点了接下来我们只需要把这台配置好的Elasticsearch复制到另外两台机器中在做一些简单的修改就就可以了。

主要修改：

node.name: node-2
network.host: 192.168.140.198

3、启动Elasticsearch

从命令行运行Elasticsearch

Elasticsearch可以从命令行启动，如下所示：

./bin/elasticsearch

作为后台启动

要将Elasticsearch作为后台程序运行，请在命令中指定-d，然后使用-p将进程ID记录在文件中：

./bin/elasticsearch -d -p pid

PS：常见错误

1、设置虚拟内存

ERROR: [1] bootstrap checks failed
[1]: max virtual memory areas vm.max_map_count [65530] is too low, increase to at least [262144]

将虚拟内存设置大一些，否则在启动elasticsearch时会出错导致启动失败：

输入 vi /etc/sysctl.conf 命令在 sysctl.conf 中配置如下内容：

vm.max_map_count=655360
sysctl -p

2、设置最大文件描述符

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

错误说明：elasticsearch过程的最大文件描述符 [4096] 太低，增加到
最少 [65536]

输入 vi /etc/security/limits.conf 命令在 limits.conf 中配置如下内容：

* soft nofile 65536
* hard nofile 131072
* soft nproc 2048
* hard nproc 4096

3、设置最大线程数

[2]: max number of threads [1024] for user [elsearch] is too low, increase to at least[4096]

错误说明：线程[1024]用户[elsearch]的最大数量太低，增加至少[4096]

输入 vi /etc/security/limits.d/20-nproc.conf 命令在 20-nproc.conf 中配置如下内容：

* soft nproc 4096

4、SecComp

[3]: system call filters failed to install; check the logs and fix your configuration or disable system call filters at your own risk

错误说明：系统调用过滤器安装失败;检查日志和修复配置或禁用系统调用过滤器需要您自担风险
这是在因为 Centos7 不支持 SecComp ，而ES5.2.0之后默认 bootstrap.system_call_filter 为true进行检测，所以导致检测失败，失败后直接导致ES不能启动。

输入 vim config/elasticsearch.yml 命令，在 elasticsearch.yml 中配置如下内容：

# ----------------------------------- Memory -----------------------------------
#
# Lock the memory on startup:
#
#bootstrap.memory_lock: true
# 设置为false不进行检测
bootstrap.system_call_filter: false
#
# Make sure that the heap size is set to about half the memory available
# on the system and that the owner of the process is allowed to use this
# limit.
#
# Elasticsearch performs poorly when the system is swapping the memory.
#

检查集群

面我们已经搭建好了三个节点的集群，并且已经启动了。

接下来我们来检查一下集群是否已经形成，给三台服务器中的任意一台发送http请求：

http://192.168.140.197:9200/_cat/health?v

应该会反馈如下内容：

cluster：显示的是当前集群的名称
status：显示的是 green 表示当前集群是健康的状态
node.total：显示 3 表示当前集群有三个节点

最后我们的Elasticsearch集群已经搭建好了，本教程主要参考Elastic官方文档和https://segmentfault.com/a/1190000021589726。