部署：consul

解压consul_1.4.4_linux_amd64.zip文件
unzip consul_1.4.4_linux_amd64.zip
单机开发模式启动
consul agent -dev

nginx配置

[root@k8smaster01 conf]# more nginx.conf
worker_processes  2;
events {
    worker_connections  1024;
}
http {
    include       mime.types;
     log_format main '$remote_addr - $remote_user [$time_local] "$request" ' '$status $body_bytes_sent "$http_referer" ' '"$http_user_agent" "$http_x_for
warded_for" "$upstream_addr"  "$request_body"';
    sendfile        on;
    keepalive_timeout  65;

    upstream test {
        sticky name=test_1 path=/;
#        upsync 127.0.0.1:2379/v2/keys/upstreams/test upsync_timeout=6m upsync_interval=500ms upsync_type=etcd strong_dependency=off;
#        upsync 192.168.23.1:8000/encode/etcd/upstreams/test upsync_timeout=6m upsync_interval=500ms upsync_type=etcd strong_dependency=off;
         upsync 127.0.0.1:8500/v1/kv/upstreams/test upsync_timeout=6m upsync_interval=500ms upsync_type=consul strong_dependency=off;
        upsync_dump_path /data/soft/openresty-1.13.6.1/nginx/conf/servers_test.conf;
        include /data/soft/openresty-1.13.6.1/nginx/conf/servers_test.conf;

        check interval=1000 rise=2 fall=2 timeout=3000 type=http default_down=false;
        check_http_send "HEAD / HTTP/1.0\r\n\r\n";
        check_http_expect_alive http_2xx http_3xx;
    }
    server {
        listen       8888;
        location /test {
             proxy_pass http://test;
        }
        location /upstream_show {
            upstream_show;
        }
        location /upstream_status {
            check_status;
            access_log off;
        }

        location / {
            default_type 'text/html';
            content_by_lua 'ngx.say("hello world")';
        }
        error_page   500 502 503 504  /50x.html;
        location = /50x.html {
            root   html;
        }
    }
}

验证

1、往consul写入数据

 [root@k8smaster01 logs]#  curl -X PUT -d '' http://127.0.0.1:8500/v1/kv/upstreams/test/192.168.23.101:80
true
[root@k8smaster01 logs]#
[root@k8smaster01 logs]#  curl -X PUT -d '' http://127.0.0.1:8500/v1/kv/upstreams/test/192.168.23.102:80
true
[root@k8smaster01 logs]#

2、浏览器查看upstream是否动态更新

 抓包查看底层原理

 1、手工写入数据

PUT /v1/kv/upstreams/test/192.168.23.101:80 HTTP/1.1
User-Agent: curl/7.29.0
Host: 127.0.0.1:8500
Accept: */*
Content-Length: 0
Content-Type: application/x-www-form-urlencoded

HTTP/1.1 200 OK
Content-Type: application/json
Vary: Accept-Encoding
Date: Fri, 29 Jul 2022 16:07:39 GMT
Content-Length: 5
true

2、openresty监听consul的变化，变化后拉取数据到本地内存

GET /v1/kv/upstreams/test?recurse&index=0 HTTP/1.0
Host: 127.0.0.1
Accept: */*

HTTP/1.0 200 OK
Content-Type: application/json
Vary: Accept-Encoding
X-Consul-Index: 16
X-Consul-Knownleader: true
X-Consul-Lastcontact: 0
Date: Fri, 29 Jul 2022 16:07:39 GMT
Content-Length: 187

[
    {
        "LockIndex": 0,
        "Key": "upstreams/test/192.168.23.101:80",
        "Flags": 0,
        "Value": null,
        "CreateIndex": 16,
        "ModifyIndex": 16
    }
]

3、总结：nginx启动后，一直监听consul上的upstream节点的变化，如果节点发送变化，监听直接返回全量信息，更新nginx对应的upstream的值到内存中。