How to use nginx to simulate blue-green deployment

This article introduces blue-green deployment and how to use nginx to simulate blue-green deployment in the simplest way.

Blue-Green Deployment

The key points of blue-green deployment are as follows

• 1. Blue version and green version exist at the same time
• 2. The actual operating environment is blue or green, only one of them, controlled by the switch

Advantages and disadvantages analysis: The advantages are its speed and rollback. The disadvantages are also obvious. The reason why rollback is possible quickly is because there are two sets of environments at the same time, so the complexity and required resources will increase because there are two sets of environments.
In addition, although the speed has been improved, in the implementation process, the control of the switch, no matter how fast the switching speed is, cannot achieve completely seamless switching without combining other technologies.

Simulating blue-green deployment

Next, we use nginx's upstream to simply simulate the blue-green deployment scenario. The specific scenario is as follows: the blue version is currently active. By adjusting the nginx settings, the green version is set as the current active version.

Preparation

Two services are started on ports 7001/7002 respectively to display different information. For the convenience of demonstration, a mirror is made using tornado. Different parameters are passed when the docker container is started to display the differences in services.

docker run -d -p 7001:8080 liumiaocn/tornado:latest python /usr/local/bin/daemon.py "Hello blue/green service： v1 in 7001"
docker run -d -p 7002:8080 liumiaocn/tornado:latest python /usr/local/bin/daemon.py "Hello blue/green service： v2 in 7002"

Execution log

[root@kong ~]# docker run -d -p 7001:8080 liumiaocn/tornado:latest python /usr/local/bin/daemon.py "Hello blue/green service： v1 in 7001"
70c74dc8e43d5635983f7240deb63a3fc0599d5474454c3bc5197aa5c0017348
[root@kong ~]# docker run -d -p 7002:8080 liumiaocn/tornado:latest python /usr/local/bin/daemon.py "Hello blue/green service： v2 in 7002"
6c5c2ea322d4ac17b90feefb96e3194ec8adecedaa4c944419316a2e4bf07117
[root@kong ~]# curl http://192.168.163.117:7001
Hello, Service :Hello blue/green service： v1 in 7001
[root@kong ~]# curl http://192.168.163.117:7002
Hello, Service :Hello blue/green service: v2 in 7002
[root@kong ~]#

Start nginx

[root@kong ~]# docker run -p 9080:80 --name nginx-blue-green -d nginx
d3b7098c44890c15918dc47616b67e5e0eb0da7a443eac266dbf26d55049216a
[root@kong ~]# docker ps |grep nginx-blue-green
d3b7098c4489 nginx "nginx -g 'daemon ..." 10 seconds ago Up 9 seconds 0.0.0.0:9080->80/tcp nginx-blue-green
[root@kong ~]#

nginx code snippet

Prepare the following nginx code snippet and add it to /etc/nginx/conf.d/default.conf of nginx. The simulation method is very simple. Down is used to indicate that the traffic is zero (weight cannot be set to zero in nginx). At the beginning, 100% of the traffic is sent to the blue version.

http {
upstream nginx_blug_green {
  server 192.168.163.117:7001 weight=100;
  server 192.168.163.117:7002 down;
}
server {
  listen 80;
  server_name www.liumiao.cn 192.168.163.117;
  location / {
    proxy_pass http://nginx_blug_green;
  }
}

How to modify default.conf

This can be achieved by installing vim in the container, modifying it locally and then passing it in via docker cp, or modifying it directly with sed. If you install vim in the container, use the following method

[root@kong ~]# docker exec -it nginx-lb sh
# apt-get update
...omit #apt-get install vim
...omitted

Before modification

# cat default.conf
server {
  listen 80;
  server_name localhost;
  #charset koi8-r;
  #access_log /var/log/nginx/host.access.log main;
  location / {
    root /usr/share/nginx/html;
    index index.html index.htm;
  }
  #error_page 404 /404.html;
  # redirect server error pages to the static page /50x.html
  #
  error_page 500 502 503 504 /50x.html;
  location = /50x.html {
    root /usr/share/nginx/html;
  }
  # proxy the PHP scripts to Apache listening on 127.0.0.1:80
  #
  #location ~ \.php$ {
  # proxy_pass http://127.0.0.1;
  #}
  # pass the PHP scripts to FastCGI server listening on 127.0.0.1:9000
  #
  #location ~ \.php$ {
  #root html;
  # fastcgi_pass 127.0.0.1:9000;
  # fastcgi_index index.php;
  # fastcgi_param SCRIPT_FILENAME /scripts$fastcgi_script_name;
  #include fastcgi_params;
  #}
  # deny access to .htaccess files, if Apache's document root
  # concurs with nginx's one
  #
  #location ~ /\.ht {
  # deny all;
  #}
}
#

After

# cat default.conf
upstream nginx_blug_green {
  server 192.168.163.117:7001 weight=100;
  server 192.168.163.117:7002 down;
}
server {
  listen 80;
  server_name www.liumiao.cn 192.168.163.117;
  #charset koi8-r;
  #access_log /var/log/nginx/host.access.log main;
  location / {
    #root /usr/share/nginx/html;
    #index index.html index.htm;
    proxy_pass http://nginx_blug_green;
  }
  #error_page 404 /404.html;
  # redirect server error pages to the static page /50x.html
  #
  error_page 500 502 503 504 /50x.html;
  location = /50x.html {
    root /usr/share/nginx/html;
  }
  # proxy the PHP scripts to Apache listening on 127.0.0.1:80
  #
  #location ~ \.php$ {
  # proxy_pass http://127.0.0.1;
  #}
  # pass the PHP scripts to FastCGI server listening on 127.0.0.1:9000
  #
  #location ~ \.php$ {
  #root html;
  # fastcgi_pass 127.0.0.1:9000;
  # fastcgi_index index.php;
  # fastcgi_param SCRIPT_FILENAME /scripts$fastcgi_script_name;
  #include fastcgi_params;
  #}
  # deny access to .htaccess files, if Apache's document root
  # concurs with nginx's one
  #
  #location ~ /\.ht {
  # deny all;
  #}
}
#

Reload nginx settings

# nginx -s reload
2018/05/28 04:39:47 [notice] 321#321: signal process started
#

Confirm the result

All 10 calls output v1 in 7001

[root@kong ~]# cnt=0; while [ $cnt -lt 10 ]
> do
> curl http://localhost:9080
> let cnt++
> done
Hello, Service :Hello blue/green service： v1 in 7001
Hello, Service :Hello blue/green service： v1 in 7001
Hello, Service :Hello blue/green service： v1 in 7001
Hello, Service :Hello blue/green service： v1 in 7001
Hello, Service :Hello blue/green service： v1 in 7001
Hello, Service :Hello blue/green service： v1 in 7001
Hello, Service :Hello blue/green service： v1 in 7001
Hello, Service :Hello blue/green service： v1 in 7001
Hello, Service :Hello blue/green service： v1 in 7001
Hello, Service :Hello blue/green service： v1 in 7001
[root@kong ~]#

Blue-Green Deployment: Switching to the Green Version

By adjusting the weight of default.conf and then executing nginx -s reload, you can dynamically switch to the green version without stopping the nginx service. The goal is to output all traffic to v2 in 7002

How to modify default.conf

You only need to adjust the weight of the server in the upstream as follows:

upstream nginx_blug_green {
  server 192.168.163.117:7001 down;
  server 192.168.163.117:7002 weight=100;
}

Reload nginx settings

# nginx -s reload
2018/05/28 05:01:28 [notice] 330#330: signal process started
#

Confirm the result

[root@kong ~]# cnt=0; while [ $cnt -lt 10 ]; do curl http://localhost:9080; let cnt++; done
Hello, Service :Hello blue/green service: v2 in 7002
Hello, Service :Hello blue/green service: v2 in 7002
Hello, Service :Hello blue/green service: v2 in 7002
Hello, Service :Hello blue/green service: v2 in 7002
Hello, Service :Hello blue/green service: v2 in 7002
Hello, Service :Hello blue/green service: v2 in 7002
Hello, Service :Hello blue/green service: v2 in 7002
Hello, Service :Hello blue/green service: v2 in 7002
Hello, Service :Hello blue/green service: v2 in 7002
Hello, Service :Hello blue/green service: v2 in 7002
[root@kong ~]#

Summarize

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