How to Setup NGINX as Reverse Proxy Using Docker

A reverse proxy server is a server that typically position itself behind the firewall in a private network and retrieves resources on behalf of a client from one or more servers. A reverse proxy provides an additional level of abstraction like SSL termination, load balancing, request routing, caching, compression etc. It also provides control to ensure smooth flow of traffic between clients and servers. In this tutorial we will setup a reverse proxy in NGINX that will serve two upstream servers, all inside a docker.

The setup

Our setup includes three containers, two containers for two upstream servers and one container for a reverse proxy. The client request will be intercepted by proxy and forwards the same to the upstream.

nginx reverse proxy inside docker

Inside container, ports and IP's are private and cannot be accessed externally unless they are bound to the host. So only one container can bind to port 80 of the docker host. So how can you access multiple web applications running on multiple container through port 80 of docker host ? The answer is through reverse proxy and we will use nginx reverse proxy inside a container which will bind its port 80 to the docker host's port 80 and forwards request to web application running across multiple containers.

Setup web services

Since we will setup two containers for two web services therefore each of them will have its own docker-composer.yml, one for site1 and another for site2. Remember these web services will not bind to any external ports, the communication with outside world will be done through reverse proxy. For this tutorial these web services will return a simple HTML using nginx, although it can be PHP/JSP/Python apps as well. Also we will connect these two web services using the name site1.test and site2.test

Let us create folders and files for webservice1 i.e for site1

site1
├── docker-compose.yml
└── index.html

[email protected]:~# cd ~
[email protected]:~# mkdir site1
[email protected]:~# cd site1
[email protected]:~/site1# vi docker-compose.yml

version: '2'
services:
app:
image: nginx:1.9
volumes:
- .:/usr/share/nginx/html/
expose:
- "80"

Create a index file for web service 1

[email protected]:~/site1# vi index.html

<!DOCTYPE html>
<html>
<head>
<title>Site 1</title>
</head>
<body>
<h1>This is a sample "site1" response</h1>
</body>
</html>

The docker-compose.yml is pretty straight forward. This web service is a "app" service and will pull nginx version 1.9 . The root of site1 from docker host is mounted to /usr/share/nginx/html/ and exposed the port 80. Build the web service 1 with the following command.

[email protected]:~/site1# docker-compose build

Now start the container for services.

[email protected]:~/site1# docker-compose up -d

List the container

[email protected]:~# docker ps -a

Similarly create second container i.e web service 2

site2
├── docker-compose.yml
└── index.html

[email protected]:~# cd ~
[email protected]:~# mkdir site2
[email protected]:~# cd site2
[email protected]:~/site2# vi docker-compose.yml

version: '2'
services:
app:
image: nginx:1.9
volumes:
- .:/usr/share/nginx/html/
expose:
- "80"

Create an index file for web service 2

[email protected]:~/site2# vi index.html

<!DOCTYPE html>
<html>
<head>
<title>Site 2</title>
</head>
<body>
<h1>This is a sample "site2" response</h1>
</body>
</html>

Build the web service 2 with the following command.

[email protected]:~/site2# docker-compose build

Now start the container for services.

[email protected]:~/site2# docker-compose up -d

List the container

[email protected]:~# docker ps -a

Setup Proxy

Now that two web services are up and running inside container, we proceed to configuring reverse proxy inside a container. We will start by creating folders and files for proxy.

proxy/
├── backend-not-found.html
├── default.conf
├── docker-compose.yml
├── Dockerfile
├── includes
│ ├── proxy.conf
│ └── ssl.conf
└── ssl
├── site1.crt
├── site1.key
├── site2.crt
└── site2.key

[email protected]:~# mkdir proxy
[email protected]:~# cd proxy/
[email protected]:~/proxy# touch Dockerfile
[email protected]:~/proxy# touch backend-not-found.html
[email protected]:~/proxy# touch default.conf
[email protected]:~/proxy# touch docker-compose.yml
[email protected]:~/proxy# mkdir includes
[email protected]:~/proxy# mkdir ssl
[email protected]:~/proxy# cd ../includes
[email protected]:~/proxy/includes# touch proxy.conf
[email protected]:~/proxy/includes# touch ssl.conf

Edit the Dockerfile with the following contents

[email protected]:~/proxy# vi Dockerfile

FROM nginx:1.9

# default conf for proxy service
COPY ./default.conf /etc/nginx/conf.d/default.conf

# NOT FOUND response
COPY ./backend-not-found.html /var/www/html/backend-not-found.html

# Proxy and SSL configurations
COPY ./includes/ /etc/nginx/includes/

# Proxy SSL certificates
COPY ./ssl/ /etc/ssl/certs/nginx/

Edit backend-not-found.html

[email protected]:~/proxy# vi backend-not-found.html

<html>
<head><title>Proxy Backend Not Found</title></head>
<body >
<h2>Proxy Backend Not Found</h2>
</body>
</html>

Edit default.conf

[email protected]:~/proxy# vi default.conf

# web service1 config.
server {
listen 80;
listen 443 ssl http2;
server_name site1.test;

# Path for SSL config/key/certificate
ssl_certificate /etc/ssl/certs/nginx/site1.crt;
ssl_certificate_key /etc/ssl/certs/nginx/site1.key;
include /etc/nginx/includes/ssl.conf;

location / {
include /etc/nginx/includes/proxy.conf;
proxy_pass http://site1_app_1;
}

access_log off;
error_log /var/log/nginx/error.log error;
}

# web service2 config.
server {
listen 80;
listen 443 ssl http2;
server_name site2.test;

# Path for SSL config/key/certificate
ssl_certificate /etc/ssl/certs/nginx/site2.crt;
ssl_certificate_key /etc/ssl/certs/nginx/site2.key;
include /etc/nginx/includes/ssl.conf;

location / {
include /etc/nginx/includes/proxy.conf;
proxy_pass http://site2_app_1;
}

access_log off;
error_log /var/log/nginx/error.log error;
}

# Default
server {
listen 80 default_server;

server_name _;
root /var/www/html;

charset UTF-8;

error_page 404 /backend-not-found.html;
location = /backend-not-found.html {
allow all;
}
location / {
return 404;
}

access_log off;
log_not_found off;
error_log /var/log/nginx/error.log error;
}

In nginx configuration, each of the two web services have its own server block. This block instructs nginx to pass requests to the appropriate web services apps container and they are namely site1_app_1 and site2_app_1. Find this name in the output of docker ps -a under name column. The proxy_intercept_errors option is set to on so that nginx return error from the web apps container itself rather than the default nginx response. The path for SSL configuration/key/certificates instructs nginx from where to pick these files.

Edit docker-compose.yml

version: '2'
services:
proxy:
build: ./
networks:
- site1
- site2
ports:
- 80:80
- 443:443

networks:
site1:
external:
name: site1_default
site2:
external:
name: site2_default

The above docker-compose.yml will create a proxy service and that connects to two external network namely our two web services. This is due to fact that the proxy service need to connect to these external networks for proxy the request it receives from web services docker container. The binding of port no 80/443 of proxy service is done to the docker host's port 80/443. The name of the two external web services/containers are site1_default and site2_default.

Generate certificates and keys for both the web services inside ssl folder.

For Site1

[email protected]:~/proxy# cd ssl
[email protected]:~/proxy/ssl# sudo openssl req -x509 -nodes -days 365 -newkey rsa:2048 -keyout site1.key -out site1.crt
Generating a 2048 bit RSA private key
..........................+++
..............+++
writing new private key to 'site1.key'
-----

For Site2

[email protected]:~/proxy/ssl# sudo openssl req -x509 -nodes -days 365 -newkey rsa:2048 -keyout site2.key -out site2.crt
Generating a 2048 bit RSA private key
....................+++
..........................................+++
writing new private key to 'site2.key'
-----

Edit proxy.conf inside include directory.

[email protected]:~/proxy/includes# vi proxy.conf

proxy_set_header Host $host;
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
proxy_set_header X-Forwarded-Proto $scheme;
proxy_buffering off;
proxy_request_buffering off;
proxy_http_version 1.1;
proxy_intercept_errors on;

Edit SSL configuration inside include folder

[email protected]:~/proxy/includes# vi ssl.conf

ssl_session_timeout 1d;
ssl_session_cache shared:SSL:50m;
ssl_session_tickets off;

ssl_protocols TLSv1 TLSv1.1 TLSv1.2;
ssl_ciphers 'ECDHE-ECDSA-CHACHA20-POLY1305:ECDHE-RSA-CHACHA20-POLY1305:ECDHE-
ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES256-GCM-
SHA384:ECDHE-RSA-AES256-GCM-SHA384:DHE-RSA-AES128-GCM-SHA256:DHE-RSA-AES256-
GCM-SHA384:ECDHE-ECDSA-AES128-SHA256:ECDHE-RSA-AES128-SHA256:ECDHE-ECDSA-
AES128-SHAECDHE-RSA-AES256-SHA384:ECDHE-RSA-AES128-SHA:ECDHE-ECDSA-AES256-
SHA384:ECDHE-ECDSA-AES256-SHA:ECDHE-RSA-AES256-SHA:DHE-RSA-AES128-SHA256:
DHE-RSA-AES128-SHA:DHE-RSA-AES256-SHA256:DHE-RSA-AES256-SHA:ECDHE-ECDSA-
DES-CBC3-SHA:ECDHE-RSA-DES-CBC3-SHA:EDH-RSA-DES-CBC3-SHA:AES128-GCM-SHA256:
AES256-GCM-SHA384:AES128-SHA256:AES256-SHA256:AES128-SHA:AES256-SHA:DES-
CBC3-SHA:!DSS';
ssl_prefer_server_ciphers on;

For name resolution for two web services, add the following two lines in /etc/hosts

[email protected]:~/proxy# vi /etc/hosts

172.31.30.78 site1.test
172.31.30.78 site2.test

The above IP address is the private IP of docker-host. Remember, the request from client will arrive at port 80 of dockerhost which will be mapped to port 80 of nginx container.

Build the proxy container

[email protected]:~/proxy# docker-compose build
Building proxy
Step 1 : FROM nginx:1.9
---> c8c29d842c09
Step 2 : COPY ./default.conf /etc/nginx/conf.d/default.conf
---> Using cache
---> 4c459326c3a2
Step 3 : COPY ./backend-not-found.html /var/www/html/backend-not-found.html
---> Using cache
---> e3d817f5fb8e
Step 4 : COPY ./includes/ /etc/nginx/includes/
---> Using cache
---> 0c5ca9eb16d8
Step 5 : COPY ./ssl/ /etc/ssl/certs/nginx/
---> Using cache
---> 92007e83d405
Successfully built 92007e83d405

Run the proxy container

[email protected]:~/proxy# docker-compose up -d
Building proxy
Step 1 : FROM nginx:1.9
---> c8c29d842c09
Step 2 : COPY ./default.conf /etc/nginx/conf.d/default.conf
---> 4c459326c3a2
Removing intermediate container 86c1ea72022e
Step 3 : COPY ./backend-not-found.html /var/www/html/backend-not-found.html
---> e3d817f5fb8e
Removing intermediate container 51b12caded59
Step 4 : COPY ./includes/ /etc/nginx/includes/
---> 0c5ca9eb16d8
Removing intermediate container 66f2c8dd0d56
Step 5 : COPY ./ssl/ /etc/ssl/certs/nginx/
---> 92007e83d405
Removing intermediate container 29bca9e3ba0a
Successfully built 92007e83d405
Creating proxy_proxy_1

Now list all the running containers.

[email protected]:~/# docker ps -a

The above command will list all the three containers.

Show running containers

To verify that, we have set up reverse proxy correctly, use curl to get a response from two web services from docker host.

[email protected]:~/proxy# curl site1.test
<!DOCTYPE html>
<html>
<head>
<title>Site1</title>
</head>
<body>
<h1>This is a sample "Site1" response</h1>
</body>
</html>
[email protected]:~/proxy# curl site2.test
<!DOCTYPE html>
<html>
<head>
<title>Site2</title>
</head>
<body>
<h1>This is a sample "Site2" response</h1>
</body>
</html>

Conclusion

Since we have containerized reverse proxy, you can add more web services when you need. But this method needs to start and stop container each time you add services. This can be automated using the Docker APIs and some basic template. This leads to painless deployments as well as improve availability.

7 Comments

jpartain89 says:

January 23, 2017 at 4:13 am

Its NGINX

1. Bobbin Zachariah says:
  
  January 23, 2017 at 12:05 pm
  
  updated typo. Thanks
  
Lex says:

May 11, 2017 at 4:02 pm

I get the following error when attempting to start up... Any ideas on how to fix this? (p.s. Thanks for the article)

$ docker-compose up

Starting proxy_proxy_1
Attaching to proxy_proxy_1
proxy_1 | 2017/05/11 14:49:00 [emerg] 1#1: SSL_CTX_set_cipher_list("ECDHE-ECDSA-CHACHA20-POLY1305:ECDHE-RSA-CHACHA20-POLY1305:ECDHE-
proxy_1 | ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES256-GCM-
proxy_1 | SHA384:ECDHE-RSA-AES256-GCM-SHA384:DHE-RSA-AES128-GCM-SHA256:DHE-RSA-AES256-
proxy_1 | GCM-SHA384:ECDHE-ECDSA-AES128-SHA256:ECDHE-RSA-AES128-SHA256:ECDHE-ECDSA-
proxy_1 | AES128-SHAECDHE-RSA-AES256-SHA384:ECDHE-RSA-AES128-SHA:ECDHE-ECDSA-AES256-
proxy_1 | SHA384:ECDHE-ECDSA-AES256-SHA:ECDHE-RSA-AES256-SHA:DHE-RSA-AES128-SHA256:
proxy_1 | DHE-RSA-AES128-SHA:DHE-RSA-AES256-SHA256:DHE-RSA-AES256-SHA:ECDHE-ECDSA-
proxy_1 | DES-CBC3-SHA:ECDHE-RSA-DES-CBC3-SHA:EDH-RSA-DES-CBC3-SHA:AES128-GCM-SHA256:
proxy_1 | AES256-GCM-SHA384:AES128-SHA256:AES256-SHA256:AES128-SHA:AES256-SHA:DES-
proxy_1 | CBC3-SHA:!DSS") failed (SSL: error:140E6118:SSL routines:SSL_CIPHER_PROCESS_RULESTR:invalid command error:140E6118:SSL routines:SSL_CIPHER_PROCESS_RULESTR:invalid command)
proxy_1 | nginx: [emerg] SSL_CTX_set_cipher_list("ECDHE-ECDSA-CHACHA20-POLY1305:ECDHE-RSA-CHACHA20-POLY1305:ECDHE-
proxy_1 | ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES256-GCM-
proxy_1 | SHA384:ECDHE-RSA-AES256-GCM-SHA384:DHE-RSA-AES128-GCM-SHA256:DHE-RSA-AES256-
proxy_1 | GCM-SHA384:ECDHE-ECDSA-AES128-SHA256:ECDHE-RSA-AES128-SHA256:ECDHE-ECDSA-
proxy_1 | AES128-SHAECDHE-RSA-AES256-SHA384:ECDHE-RSA-AES128-SHA:ECDHE-ECDSA-AES256-
proxy_1 | SHA384:ECDHE-ECDSA-AES256-SHA:ECDHE-RSA-AES256-SHA:DHE-RSA-AES128-SHA256:
proxy_1 | DHE-RSA-AES128-SHA:DHE-RSA-AES256-SHA256:DHE-RSA-AES256-SHA:ECDHE-ECDSA-
proxy_1 | DES-CBC3-SHA:ECDHE-RSA-DES-CBC3-SHA:EDH-RSA-DES-CBC3-SHA:AES128-GCM-SHA256:
proxy_1 | AES256-GCM-SHA384:AES128-SHA256:AES256-SHA256:AES128-SHA:AES256-SHA:DES-
proxy_1 | CBC3-SHA:!DSS") failed (SSL: error:140E6118:SSL routines:SSL_CIPHER_PROCESS_RULESTR:invalid command error:140E6118:SSL routines:SSL_CIPHER_PROCESS_RULESTR:invalid command)
proxy_proxy_1 exited with code 1

Dwijadas Dey says:

May 13, 2017 at 3:27 pm

Hi
SSl ciphers value should be a string without any line break, inside a quotes '' like

SSl ciphers ''

You have 8 line breaks in the SSL ciphers value and because of this you are getting this error. Remove the breaks and make this value a single string.

Ahmad Magdy says:

May 16, 2017 at 12:47 pm

Hey,

Thanks for the article, it helped me get started :)

I've created a repo with the code in this article in case someone wants to save a little of time

https://github.com/a-magdy/nginx-reverse-proxy-docker

Div says:

June 19, 2017 at 9:13 pm

Hi,

Any tips on if you don't have root permissions to modify /etc/hosts?

Thanks!

Alberto says:

June 9, 2018 at 4:00 pm

I can not get SSL working, the certificates are generated and in the correct folder. Can you give me some help?