aws 基于延迟策略配置dns故障切换

前提：由于国内访问首尔地区经常出现不稳定情况，现将请求从nginx(sz)转发到nginx(hk)再转发到首尔地区，在基于不改变nginx(seoul)的配置的前提下，引入aws的延迟策略，同时保证国内

解析出现问题时，迅速将解析切至首尔的nginx。

实现：基于aws route53 配置延迟故障切换策略

nginx(sz)配置:
server {
    listen       80;
    listen       443 ssl;
    server_name  test.imcati.com;
    if ( $server_port = 80 ) {
    return  301  https://$server_name$request_uri;}

    ssl_certificate      /etc/nginx/ssl/test.imcati.com.crt;
    ssl_certificate_key  /etc/nginx/ssl/test.imcati.com.key;
    ssl_session_timeout  5m;
    ssl_protocols TLSv1 TLSv1.1 TLSv1.2;
    ssl_prefer_server_ciphers   on;
    access_log  /var/log/nginx/access.log access_log_json;
    location / {
        proxy_set_header Host $http_host;
        proxy_set_header X-Forwarded-Server $host;
        proxy_set_header X-Real-IP      $remote_addr;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_pass https://xx.xx.xx.xx;  #nginx(hk) ip addr
    }
}

nginx(hk)配置:
server {
    listen       80;
    listen       443 ssl;
    server_name  test.imcati.com;
    location / {
        proxy_set_header Host  $http_host;
        proxy_set_header X-Forwarded-Server $host;
        proxy_set_header X-Real-IP      $remote_addr;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_pass https://xx.xx.xx.xx; nginx(seoul) ip addr
    }
}

nginx(seoul)配置:
server {
    listen       80;
    listen       443 ssl;
    server_name  test.imcati.com;
    if ( $server_port = 80 ) {
    return  301  https://$server_name$request_uri;}

    ssl_certificate      /etc/nginx/ssl/test.imcati.com.crt;
    ssl_certificate_key  /etc/nginx/ssl/test.imcati.com.key;
    ssl_session_timeout  5m;
    ssl_protocols TLSv1 TLSv1.1 TLSv1.2;
    ssl_prefer_server_ciphers   on;
    access_log  /var/log/nginx/access.log access_log_json;
    location / {
        proxy_set_header Host $http_host;
        proxy_set_header X-Forwarded-Server $host;
        proxy_set_header X-Real-IP      $remote_addr;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_pass https://xx.xx.xx.xx;  # backend server addr
    }
}

aws dns策略配置参考图：