概述

为了提高服务的访问速度，减轻geoserver服务的压力，同时避免服务节点出现问题而影响服务访问的稳定性，我们通常会通过部署多个geoserver来解决，但是部署了多个geoserver后，我们需要一个统一的接口提供出来供使用，nginx很好地可以这样的需求，本文讲讲如何通过nginx实现多geoserver服务的负载均衡。

实现效果

实现

1. 多geoserver部署

为了保持geoserver的服务一致，我们先配置好一个geoserver服务，配置好之后将部署的Tomcat复制，克隆多个出来，本文为演示复制了两个（共三个geoserver），修改Tomcat的端口，使三个端口不冲突，复制好之后分别启动三个Tomcat。

2. nginx配置

修改nginx.conf文件，配置信息如下：


#user  nobody;
worker_processes  1;

#error_log  logs/error.log;
#error_log  logs/error.log  notice;
#error_log  logs/error.log  info;

#pid        logs/nginx.pid;


events {
    worker_connections  1024;
}


http {
    include       mime.types;
    default_type  application/octet-stream;

    #log_format  main  '$remote_addr - $remote_user [$time_local] "$request" '
    #                  '$status $body_bytes_sent "$http_referer" '
    #                  '"$http_user_agent" "$http_x_forwarded_for"';

    #access_log  logs/access.log  main;

    sendfile        on;
    #tcp_nopush     on;

    #keepalive_timeout  0;
    keepalive_timeout  65;

    #gzip  on;
	
	# 反向代理配置
	upstream server_list{
	   # 这个是tomcat的访问路径
	   server localhost:8081;
	   server localhost:8082;
	   server localhost:8083;
	}
    server {
		listen       80;
	    server_name  localhost;
	 
		location / {
			add_header 'Access-Control-Allow-Origin' $http_origin;
			add_header 'Access-Control-Allow-Credentials' 'true';
			add_header 'Access-Control-Allow-Methods' 'GET, POST, OPTIONS';
			add_header 'Access-Control-Allow-Headers' 'DNT,web-token,app-token,Authorization,Accept,Origin,Keep-Alive,User-Agent,X-Mx-ReqToken,X-Data-Type,X-Auth-Token,X-Requested-With,If-Modified-Since,Cache-Control,Content-Type,Range';
			add_header 'Access-Control-Expose-Headers' 'Content-Length,Content-Range';
			if ($request_method = 'OPTIONS') {
				add_header 'Access-Control-Max-Age' 1728000;
				add_header 'Content-Type' 'text/plain; charset=utf-8';
				add_header 'Content-Length' 0;
				return 204;
			}
			root   html;
			proxy_pass http://server_list;
	        index  index.html index.htm;
		}
		
		error_page   500 502 503 504  /50x.html;
		location = /50x.html {
			root   html;
		}
	}
}

配置好nginx后，启动nginx。

3. 前端调用

根据上述的配置，nginx的端口为80，因此geoserver的地址为http://localhost/geoserver,在ol中的调用代码如下：

<!doctype html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>OpenLayers map preview</title>
  <link rel="stylesheet" href="lib/ol/ol.css" type="text/css">
  <link rel="stylesheet" href="css/common.css">
  <script src="../ol5/ol.js" type="text/javascript"></script>
</head>
<body>
<div id="map" class="map"></div>
<script>
  const options = {
    center: [52102781.07568731, 4456849.777083951],
    zoom: 3,
    minZoom: 0,
    maxZoom: 18
  }

  const base = new ol.layer.Tile({
    visible: true,
    source: new ol.source.OSM()
  });
  const wms = new ol.layer.Tile({
    source: new ol.source.TileWMS({
      url: 'http://localhost/geoserver/mapbox/wms',
      params: {'LAYERS': 'mapbox:city', 'TILED': true},
      serverType: 'geoserver',
      transition: 0
    })
  })

  window.map = new ol.Map({
    controls: ol.control.defaults({
      attribution: false
    }).extend([new ol.control.ScaleLine()]),
    target: 'map',
    layers: [base, wms],
    view: new ol.View({
      center: options.center,
      zoom: options.zoom,
      minZoom: options.minZoom,
      maxZoom: options.maxZoom
    })
  });
</script>
</body>
</html>