redmine export long csv file failed: 502 proxy error

After modified the file \apps\redmine\conf\httpd-vhosts.conf：

<VirtualHost *:8080>
ServerName redmine.example.com
ServerAlias www.redmine.example.com
DocumentRoot "D:\App\Bitnami\redmine-3.3.0-0/apps/redmine/htdocs/public"
<Directory "D:\App\Bitnami\redmine-3.3.0-0/apps/redmine/htdocs/public">
Options -MultiViews
allow from all
</Directory>

Timeout 1200 # wuyan add, invalid

RewriteEngine On
RewriteRule ^/(.*)$ balancer://redminecluster%{REQUEST_URI} [P,QSA,L]
<Proxy balancer://redminecluster>
BalancerMember http://127.0.0.1:3001 timeout=1200 # wuyan modify,invalid
BalancerMember http://127.0.0.1:3002 timeout=1200 # wuyan modify,invalid
</Proxy>

Include "D:\App\Bitnami\redmine-3.3.0-0/apps/redmine/conf/httpd-app.conf"
</VirtualHost>

Now everything seems ok! 

Continue:

When the records is larger than 1500, it failed again! google and google again, i found the new info:

1)  as this page showed, i tried the access from port 3001(127.0.0.1:3001/), it was ok!

2)  as this page showed, the default timeout of thin server is 30 seconds, we can set it with: thin -t 60.

3)  as this page showed, the default timeout of apache is 300 seconds. and the default value of ProxyTimeout is the same.

4)  when i export csv with port 8080(the virtual host port), it will return the 502 proxy error after about 60 seconds.

5) the access path is: apache, the proxy balancer, port 3001 server(thinserver1). 

6) Maybe the timeout is from the proxy, but i change the timeout as this page showed, it failed!

7) change the timeout of thin server: open redmine-3.3.0-0\apps\redmine\scripts\serviceinstall.bat， add -t 300。

8) as this page showed, we can set KeepAlive=On in the ProxyPass option. i didn't try.

9) the final resolution is as this page, add "ProxyTimeout 400" line to Bitnami\redmine-3.3.0-0\apps\redmine\conf\httpd-prefix.conf. The default value of ProxyTimeout is Timeout, the default Timeout is 60 , change the value to 400 seconds. the config file:

ProxyPass / balancer://redminecluster
ProxyPassReverse / balancer
RewriteEngine On
RewriteRule ^/(.*)$ balancer://redminecluster%{REQUEST_URI} [P,QSA,L]

ProxyTimeout 400

<Proxy balancer://redminecluster>
BalancerMember http://127.0.0.1:3001
BalancerMember http://127.0.0.1:3002
</Proxy>

Include "D:\App\Bitnami\redmine-3.3.0-0/apps/redmine/conf/httpd-app.conf"