Apache2代理Tomcat负载均衡子路径失效：无有效协议处理器

问题现象 #

根URL https://www.myexample.com 可正常访问，但图片、JS/CSS等静态资源无法加载，例如：

• https://www.myexample.com/images/logo.jpg
• https://www.myexample.com/css/main.css

Apache错误日志输出：

AH01144: No protocol handler was valid for the URL /images/logo.jpg (scheme 'balancer'). If you are using a DSO version of mod_proxy, make sure the proxy submodules are included in the configuration using LoadModule., referer: https://www.myexample.com:443/

当前使用的VirtualHost配置：

<VirtualHost *:443>    
        ServerName www.myexample.com      
        ProxyPreserveHost On

        SSLProxyEngine On
        SSLProxyCheckPeerCN on
        SSLProxyCheckPeerExpire on

        <Proxy "balancer://mycluster">
                BalancerMember "https://localhost:8443" route=node1
        </Proxy>

        ProxyPass        "/" "balancer://mycluster" stickysession=JSESSIONID|jsessionid scolonpathdelim=On
        ProxyPassReverse "/" "balancer://mycluster"

        ...
</VirtualHost>

已加载的Apache模块（执行sudo apachectl -M结果）：

Loaded Modules:
 core_module (static)
 so_module (static)
 watchdog_module (static)
 http_module (static)
 log_config_module (static)
 logio_module (static)
 version_module (static)
 unixd_module (static)
 access_compat_module (shared)
 alias_module (shared)
 auth_basic_module (shared)
 authn_core_module (shared)
 authn_file_module (shared)
 authz_core_module (shared)
 authz_host_module (shared)
 authz_user_module (shared)
 autoindex_module (shared)
 deflate_module (shared)
 dir_module (shared)
 env_module (shared)
 filter_module (shared)
 lbmethod_byrequests_module (shared)
 mime_module (shared)
 mpm_event_module (shared)
 negotiation_module (shared)
 proxy_module (shared)
 proxy_balancer_module (shared)
 proxy_http_module (shared)
 reqtimeout_module (shared)
 setenvif_module (shared)
 slotmem_shm_module (shared)
 socache_shmcb_module (shared)
 ssl_module (shared)
 status_module (shared)

Apache版本信息：

Server version: Apache/2.4.41 (Ubuntu)
Server built:   2022-06-14T13:30:55

问题分析与解决方案 #

你已经加载了proxy_module、proxy_balancer_module、proxy_http_module等核心代理模块，但缺少proxy_ssl_module——这是导致问题的关键。

因为你的BalancerMember使用的是https://协议，Apache需要proxy_ssl_module来处理负载均衡器到后端HTTPS服务器的SSL通信，没有这个模块，Apache无法正确转发HTTPS请求，从而触发"无有效协议处理器"的错误。

修复步骤 #

1. 启用proxy_ssl_module模块：

   sudo a2enmod proxy_ssl
   

2. 重启Apache服务使配置生效：

   sudo systemctl restart apache2
   

完成上述操作后，静态资源的请求应该能被正确转发到Tomcat后端，解决加载失败的问题。

内容的提问来源于stack exchange，提问作者eastwater