什么是负载均衡

                            
                              worker_processes  1;        #nginx worker 数量
error_log logs/error.log;   #指定错误日志文件路径
events {
    worker_connections 1024;
}

http {
    log_format main '$remote_addr [$time_local] $status $request_time $upstream_status $upstream_addr $upstream_response_time';
    access_log logs/access.log main buffer=16384 flush=3;            #access_log 文件配置

    lua_package_path  "$prefix/deps/share/lua/5.1/?.lua;$prefix/deps/share/lua/5.1/?/init.lua;$prefix/?.lua;$prefix/?/init.lua;;./?.lua;/usr/local/openresty/luajit/share/luajit-2.1.0-beta3/?.lua;/usr/local/share/lua/5.1/?.lua;/usr/local/share/lua/5.1/?/init.lua;/usr/local/openresty/luajit/share/lua/5.1/?.lua;/usr/local/openresty/luajit/share/lua/5.1/?/init.lua;";
    lua_package_cpath "$prefix/deps/lib64/lua/5.1/?.so;$prefix/deps/lib/lua/5.1/?.so;;./?.so;/usr/local/lib/lua/5.1/?.so;/usr/local/openresty/luajit/lib/lua/5.1/?.so;/usr/local/lib/lua/5.1/loadall.so;";
    # 开启 lua code 缓存
    lua_code_cache on;  

    upstream nature_upstream {
        server 127.0.0.1:6699; #upstream 配置为 hello world 服务

        # 一样的balancer
        balancer_by_lua_block {
            local balancer = require "ngx.balancer"
            local upstream = ngx.ctx.api_ctx.upstream
            local ok, err = balancer.set_current_peer(upstream.host, upstream.port)
            if not ok then
                ngx.log(ngx.ERR, "failed to set the current peer: ", err)
                return ngx.exit(ngx.ERROR)
            end
        }
    }

    init_by_lua_block {

        -- 初始化 lb
        local roundrobin = require("resty.roundrobin") 
        local nodes = {k1 = {host = '127.0.0.1', port = 6698}, k2 = {host = '127.0.0.1', port = 6699}}
        local ns = {}
        for k, v in pairs(nodes) do
            -- 初始化 weight 
            ns[k] = 1
        end
        local picker = roundrobin:new(ns)

        -- 初始化路由
        local radix = require("resty.radixtree")
        local r = radix.new({
            {paths = {'/aa/d'}, metadata = picker},
        })

        -- 匹配路由
        router_match = function()
            local p, err = r:match(ngx.var.uri, {})
            if err then
                log.error(err)
            end

            -- 执行 roundrobin lb 选择
            local k, err = p:find()
            if not k then
                return nil, err
            end
            return nodes[k]
        end
    }

    server {
		#监听端口，若你的8699端口已经被占用，则需要修改
        listen 8699 reuseport;

        location / {

            # 在access阶段匹配路由
            access_by_lua_block {
                local upstream = router_match()
                if upstream then
                    ngx.ctx.api_ctx = { upstream = upstream }
                else
                    ngx.exit(404)
                end
            }

            proxy_http_version                  1.1;
            proxy_pass http://nature_upstream; #转发到 upstream
        }
    }


    #为了大家方便理解和测试，我们引入一个hello world 服务
    server {
		#监听端口，若你的6699端口已经被占用，则需要修改
        listen 6699;
        location / {
            default_type text/html;

            content_by_lua_block {
                ngx.say("HelloWorld")
            }
        }
    }
}