Elasticsearch升级后出现SSL routines::wrong version number错误

我刚部署了一套全新的ELK环境，一开始搞错了版本要求装了v7.x，后来通过修改Elastic官方PPA的源地址，直接用apt原地升级到了8.x版本，整个升级过程没出现任何报错。

但升级完成后遇到了SSL routines::wrong version number错误，排查后发现是Elasticsearch的SSL配置项在7.x和8.x版本间有变化，需要调整elasticsearch.yml里的相关设置：

ELK 7.x 原配置 #

xpack.security.http.ssl.enabled: 'true'
xpack.security.http.ssl.verification_mode: 'none'
xpack.security.http.ssl.certificate_authorities: /etc/elasticsearch/certs/ca/ca.crt
xpack.security.http.ssl.key: /etc/elasticsearch/certs/netflow/netflow.key
xpack.security.http.ssl.certificate: /etc/elasticsearch/certs/netflow/netflow.crt

ELK 8.x 修改后的配置 #

xpack.security.transport.ssl.enabled: 'true'
xpack.security.transport.ssl.verification_mode: 'none'
xpack.security.transport.ssl.certificate_authorities: /etc/elasticsearch/certs/ca/ca.crt
xpack.security.transport.ssl.key: /etc/elasticsearch/certs/netflow/netflow.key
xpack.security.transport.ssl.certificate: /etc/elasticsearch/certs/netflow/netflow.crt

核心就是把配置项里的http替换成transport，调整后重启Elasticsearch，这个SSL版本错误就解决了。

备注：内容来源于stack exchange，提问作者ericx