Load Balancing for root and different paths

nginx.conf

#credit to Subhra Paladhi

# This is for layer 7 (application layer) load balancer
http{
	
	# A http request is sent on port 80. A TCP connection is established between
	# the client(the one who sent the request) and loadbalancer on port 80 over http.
	# The load balancer further establishes TCP connections with one of the server 
 	# depending on the algorithm it is using and forwards the request from the
	# client to it. The server communicats with nginx.Hense nginx acts as a 
	# middle man between the client and server.
    
	# default loadbalancing algo is round robin
	
	# load balanances between app running on port 2222,3333,4444,5555
	upstream allbackend {
		server 127.0.0.1:2222;
		server 127.0.0.1:3333;
		server 127.0.0.1:4444;
		server 127.0.0.1:5555;
	}

	# load balanances between server running on port 2222,3333
	upstream app1backend{
	    server 127.0.0.1:2222;
	    server 127.0.0.1:3333;
	}

	# loadbalanances between server running on port 4444,5555
	upstream app2backend{
	    server 127.0.0.1:4444;
	    server 127.0.0.1:5555;
  	}

	# This block decides for which route which upstream will be used.
	server{
   		# This is the port over will nginx communicats with the client. 
   		# For HTTP it is 80.
		
		listen 80;
		
		# if someone requests "/" route then redirent to upstream allbackend
		location /{
			proxy_pass http://allbackend/;
		}
		
		# If someone requests "/app1" route then it should be loadbalanced 
		# between 2 ports. 
        	# Redirent to upstream app1backend.
		location /app1{
			proxy_pass http://app1backend/;
		}

		# If someone requests "/app2" route then it should be loadbalanced 
		# between 2 ports. 
        	# Redirent to upstream app2backend
		location /app2{
		    proxy_pass http://app2backend/;
		}	
		
		# Access to /admin is forbidden over port 80(public internet).
        	# Hense return status code 403 (forbidden) when /admin request 
		# is received.
		location /admin{
			return 403;
		}
	}
}

events { }