Proxy error reported when accessing redmine

A redmine was previously set up for project management. Previously it was used normally and has not been logged on for nearly a week. When I tried to log on today, an error was reported:

Proxy Error

The proxy server has ed an invalid response from an upstream server.
The proxy server cocould not handle the requestGET/redmine/login.

Reason:Error reading from remote server

View Apache error_log and find the following content:

(OS 10061) unable to connect because the target computer is actively rejected. : Proxy: http: attempt to connect to 127.0.0.1: 3002 (127.0.0.1) failed
[Mon Sep 10 15:40:44 2012] [Error] ap_proxy_connect_backend disabling worker for (127.0.0.1)
[Mon Sep 10 15:40:46 2012] [Error] [client 192.168.1.205] (OS 10054) the remote host forces an existing connection to be closed. : Proxy: Error reading status line from remote server 127.0.0.1: 3003
[Mon Sep 10 15:40:46 2012] [Error] [client 192.168.1.205] Proxy: Error reading from remote server returned by/redmine
[Mon Sep 10 15:43:21 2012] [Error] [client 192.168.1.204] (20023) the given path was abve the root path: cannot map get/HTTP/1.1 To File

Port and 2 in log are occupied by mongrel. It is because a proxy is set up when redmine is set up. When we access Apache, Apache will access mongrel, but mongrel will not be able to access it, so an error occurs.

But why can't I access it suddenly ??

Google has been trying for a long time and has not solved this problem. Then I started to think back, when was the last time I was able to access and what was I doing after that?

I remembered that a week ago I wanted to install the roadmap plug-in to demonstrate milestones. I followed the instructions, but only to download the file back to the redmine/vendor/Plugins directory. I did not complete the operation, so I took the last step, to the redmine root directory, rake
DB: migrate: plugins

The result indicates that roadmap requires redmine1.4 or later. My redmine version is too low, so rake aborted.

In fact, I think there should be a folder in the plug-in that won't make redmine inaccessible, but since this plug-in cannot be installed, delete it.

So I deleted the files that were previously put in the redmine/vendor/Plugins directory.

Then, redmine can be accessed normally !!! My God.