ORACLE OHS 12 Timeout : HTTP/1.1 503 Service Temporarily Unavailable

Error found in Weblogic Log

HTTP/1.1 503 Service Temporarily Unavailable 
Date: Mon, 07 Sep 2015 08:47:13 GMT 
Server: Oracle-HTTP-Server-11g 
Content-Length: 250 
Connection: close 
Content-Type: text/html 
Content-Language: en 
. 

Failure 

of Web Server bridge:

---

No backend server available for connection:

timed out after 10 seconds or idempotent set to OFF or method not 
idempotent.

---

----------------- 
This means,  <"Any ERROR">  is caused by connection timeout, the OHS(Oracle Http Server) will reset the connection if it doesn't receive the response from Weblogic server in certain time (By default, 5 minute). 
Many debug log enabled in your system seems to affect this problem. 

To avoid this problem, you can increase the connection timeout for OHS. 
Solution

Set OHS timeout default it is 5 min change it to 30 min by 

Timeout  1800  in below file

///instances/instance1/config/OHS/ohs1/httpd.conf