elasticsearch启动常见错误

原文链接：https://www.cnblogs.com/zhi-leaf/p/8484337.html

问题出现环境，OS版本：CentOS-7-x86_64；ES版本：elasticsearch-7.13

Q1：max file descriptors [4096] for elasticsearch process is too low, increase to at least [65536]

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

   每个进程最大同时打开文件数太小，可通过下面2个命令查看当前数量

   ulimit -Hn
   ulimit -Sn
   

   修改/etc/security/limits.conf文件，增加配置，用户退出后重新登录生效

   *               soft    nofile          65536
   *               hard    nofile          65536
   

Q2：max number of threads [3818] for user [es] is too low, increase to at least [4096]

2. max number of threads [3818] for user [es] is too low, increase to at least [4096]

   问题同上，最大线程个数太低。修改配置文件/etc/security/limits.conf（和问题1是一个文件），增加配置

   	*               soft    nproc           4096
   	*               hard    nproc           4096
   

   可通过命令查看

   	ulimit -Hu
   	ulimit -Su
   

   修改后的文件：

   *               soft    nofile          65536
   *               hard    nofile          65536
   *               soft    nproc           4096
   *               hard    nproc           4096
   

Q3：max virtual memory areas vm.max_map_count [65530] is too low, increase to at least [262144]

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

   修改/etc/sysctl.conf文件，增加配置vm.max_map_count=262144

   vi /etc/sysctl.conf
   sysctl -p
   

   执行命令sysctl -p生效

Q4：Exception in thread “main” java.nio.file.AccessDeniedException: /usr/local/elasticsearch/elasticsearch-7.13/config/jvm.options

4. Exception in thread “main” java.nio.file.AccessDeniedException: /usr/local/elasticsearch/elasticsearch-7.13/config/jvm.options

   elasticsearch用户没有该文件夹的权限，执行命令

   chown -R es:es /usr/local/elasticsearch/

Q5： the default discovery settings are unsuitable for production use; at least one of [discovery.seed_hosts, discovery.seed_providers, cluster.initial_master_nodes] must be configured

原文链接： https://blog.youkuaiyun.com/qq_43655835/article/details/104637625

在elasticsearch的config目录下，修改elasticsearch.yml配置文件，将下面的配置加入到该配置文件中：

ip替换host1等，多节点请添加多个ip地址，单节点可写按默认来
#配置以下三者，最少其一
#[discovery.seed_hosts, discovery.seed_providers, cluster.initial_master_nodes]
cluster.initial_master_nodes: ["node-1"] #这里的node-1为node-name配置的值

Q6：es集群启动完成后浏览器输入/_cat/nodes?pretty报master_not_discovered_exception

原文链接：https://yanglinwei.blog.youkuaiyun.com/article/details/105274464

es集群启动后，在浏览器输入：http://es ip地址:端口/_cat/nodes?pretty，会提示如下错误：
{ "error" : { "root_cause" : [ { "type" : "master_not_discovered_exception", "reason" : null } ], "type" : "master_not_discovered_exception", "reason" : null }, "status" : 503 }

解决方案：
在每个配置文件指定初始节点：

cluster.initial_master_nodes: node-1

重启ES集群，浏览器再次输入http://es ip地址:端口/_cat/nodes?pretty，就可以看到集群启动成功了：