how to log response body via log plugins?

[gracekk]

Sometimes I want to save response body details into logs, such as http 400 occurs. Tried to modify http-logger plugins, but seems context of log_by_lua no appropriate. Any suggestions? Thank you.

[tokers]

How did you get the response body? You may have to add the body_filter hook to save the response body.

[syzygyyy]

Thanks for reply.
Tried add "body_filter_by_lua_file" partition in tpl.lua to edit ngnix.conf, got errors:

usr/local/openresty/luajit/bin/luajit ./apisix/cli/apisix.lua init_etcd
nginx: [emerg] "body_filter_by_lua_file" directive is duplicate in /usr/local/apisix/conf/nginx.conf:345
/usr/local/openresty/luajit/bin/luajit ./apisix/cli/apisix.lua init

seems conflict with
body_filter_by_lua_block {
apisix.http_body_filter_phase()
}

[tokers]

You don't add these directly, just implement the method (body_filter) in the plugin implementation.