nginx configuration for mapping two node.js servers to same address on same machine - node.js

Question

I am running two instances of node.js servers serving same code on two different port numbers on same machine. For example, one node.js process is running on port 8080 and other on port 1337.
I need to put nginx proxy in front of both these servers and route any request coming to to these servers.
The reason I want to do this is because lets say I have only one server. I need to change the code and restart the server and it takes nearly 1 minute for the server to restart. During this time, any requests coming to the server will return 502 Bad Gateway Error. I want to avoid this situation by running a replica of the same server.
Now I want to setup nginx in such a way that whenever either one of them is down (restarting while doing git pull), requests should be routed to the other one.
How can I accomplish this setting and where should I start reading about this ?

Answer 1

Requirement: suppose you have 2 application both running on different port at same machine.You have purchased only one domain and want to use it for multiple application.suppose below is the requirement.
purchased domain: example.com
app1_name/app1_port: app1/8081
app2_name/app2_port: app2/8082
You have two option here, you can choose any one you like
1st way: http://example.com/app1, http://example.com/app2
2nd way: http://app1.example.com, http://app2.example.com
Below are final configuration for both type
1st type using url resource indicator and multiple location
server{
listen 80;
server_name example.com;
location /app1{
proxy_pass http://localhost:8081;
}
location /app2{
proxy_pass http://localhost:8082;
}
}
2nd type using subdomain and multiple server block
server{
listen 80;
server_name example.com;
}
server{
server_name app1.example.com;
location /{
proxy_pass http://localhost:8081;
}
}
server{
server_name app2.example.com;
location /{
proxy_pass http://localhost:8082;
}
}
Note: Ideally nginx should run on port 80 and should mapped to main domain. So that you dont have to type port in browser as 80 is default port for http request. You might have to add additional configuration parameter, above is just for demo purpose.