1、received plaintext http traffic on an https channel, closing connection Netty4HttpChannel

received plaintext http traffic on an https channel, closing connection Netty4HttpChannel
{localAddress=/[0:0:0:0:0:0:0:1]:9200, remoteAddress=/[0:0:0:0:0:0:0:1]:55367}

解决

是因为开启了 ssl 认证。
在 ES/config/elasticsearch.yml 文件中把 xpack.security.http.ssl:enabled 设置成 false 即可

# Enable encryption for HTTP API client connections, such as Kibana, Logstash, and Agents
xpack.security.http.ssl:
  enabled: false
  keystore.path: certs/http.p12

2、elasticsearch 账号密码

        windows 下直接启动 ElasticSearch ，见到 started 为成功启动，访问 htttp://localhost:9200 需要输入密码，是因为开启了密码验证模式。
找了一轮没看到有账号密码，干脆就设置免密登录就好。

解决

找到 elasticsearch.yml 文件， 把 xpack.security.enabled 属性设置为 false 即可。

# Enable security features
xpack.security.enabled: false

3. 设置内存大小

ES 的内存是自己调节的。在 config/jvm.options 文件中直接设置就好(追加):

-Xms512m
-Xmx2048m