support signal SIGHUB reload modules config

[kwanhur]

_{Sent from PPHub}

[liu-song]

说一下我的理解，如果存在理解上的错误，请指正。目前这个想法是想通过 SIGHUB来重新加载 bfe/conf/.../ ....data 这样的配置文件吗，目前的重载实现的方式是通过conf-agent里面for循环sleep 一定的时间来发送http 请求来对比是否配置文件已经被更新了，如果更新了还是通过http 请求发送给bfe 来重新加载对应配置。目前在bfe 上面还没有对配置文件的监控，如果使用sighub 的话，当有一个配置修改了，无法定位到是那个配置修改，需要对比全部的配置文件来定位，或者直接对所有对应的配置文件都重新加载一遍？所以我想这里是不是可以采取这样的方式，https://github.com/spf13/viper 通过viper 来在每个配置文件初次加载的时候，使用viper 来监控对应的配置文件，当配置文件有所改动的时候，可以直接监控到变化，直接就更新了对应的配置文件。如果viper 的配置动态更新机制适合这边的场景，我这边可以在bfe的基础上来尝试实现一版。

[kwanhur]

Thx for response :-)

This idea comes from Nginx, when BFE deploy as a raw process service on host, after configuration's files modified, always command systemctl reload bfe or kill -HUB $(pidof bfe) to trigger bfe update inner configurations gracefully.

Support conf/bfe.conf and conf/mod_*/* files will be the best.

[liu-song]

#887 (comment)

Some Results of discussion:

1 : bfe more suitable for using http trigger reload update configurations , in conf-agent provided temporary conf File which prepare check the conf file will more security。

2 : conf -agent pull conf from api-server , which is easy to implement than api-server push to conf-agent.

3: Configuration center will make the bfe more complex to build，the current approach is simpler.

[liu-song]

My ppt of discussion：

[kwanhur]

Config center solution like etcd consul nacos sounds the better between conf-agent and bfe.

When bfe just run locally, then it needs to focus on configuration files.

From viper's description, it has these abilities. viper maybe a candidate solution.