健康检测

TCP心跳检查

upstream backend {
    server 192.168.61.1:9080 weight=1;
    server 192.168.61.1:9090 weight=2;
    check interval=3000 rise=1 fall=3 timeout=2000 type=tcp;
}

interval：检测间隔时间
fall：检测失败多少次后，后端服务器标识为不存活
rise：检测成功多少次后，后端服务器标识为存活
timeout：检测请求超时时间配置

HTTP心跳检测

upstream backend {
    server 192.168.61.1:9080 weight=1;
    server 192.168.61.1:9090 weight=2;

    check interval=3000 rise=1 fall=3 timeout=2000 type=http;
    check_http_send "HEAD /status HTTP/1.0\r\n\r\n";
    check_http_expect_alive http_2xx http_3xx;
}

check_http_send：检查时发的HTTP请求内容
check_http_expect_alive：后端服务器返回匹配响应状态码，则认为后端服务器存活