Serving API via Flask / Gunicorn / Nginx: Connection refused - nginx

I'm having trouble getting gunicorn and Nginx to work together and allow me to offer a simple API via flask:
Locally, running gunicorn and getting responses from the server works fine:
gunicorn wsgi:app (start server)
[2019-06-11 23:12:48 +0000] [14615] [INFO] Starting gunicorn 19.9.0
[2019-06-11 23:12:48 +0000] [14615] [INFO] Listening at: http://127.0.0.1:8000 (14615)
[2019-06-11 23:12:48 +0000] [14615] [INFO] Using worker: sync
[2019-06-11 23:12:48 +0000] [14619] [INFO] Booting worker with pid: 14619
curl http://127.0.0.1:8000/predict (client call server for prediction)
output: "SERVER WORKS"
The problem arises when I try to use Nginx as well.
/etc/systemd/system/app.service
[Unit]
Description=Gunicorn instance to serve app
After=network.target
[Service]
User=root
Group=www-data
WorkingDirectory=/root/server
ExecStart=/usr/local/bin/gunicorn --bind unix:app.sock -m 007 wsgi:app
[Install]
WantedBy=multi-user.target
/etc/nginx/sites-available/app
server {
listen 80;
server_name [SERVER_IP_ADDRESS];
location / {
include proxy_params;
proxy_pass http://unix:/root/server/app.sock;
}
}
The status of my systemd looks fine:
systemctl status app
● app.service - Gunicorn instance to serve app
Loaded: loaded (/etc/systemd/system/app.service; enabled; vendor preset: enabled)
Active: active (running) since Tue 2019-06-11 23:24:07 UTC; 1s ago
Main PID: 14664 (gunicorn)
Tasks: 2 (limit: 4915)
CGroup: /system.slice/app.service
├─14664 /usr/bin/python /usr/local/bin/gunicorn --bind unix:app.sock -m 007 wsgi:app
└─14681 /usr/bin/python /usr/local/bin/gunicorn --bind unix:app.sock -m 007 wsgi:app
systemd[1]: Started Gunicorn instance to serve app.
gunicorn[14664]: [2019-06-11 23:24:07 +0000] [14664] [INFO] Starting gunicorn 19.9.0
gunicorn[14664]: [2019-06-11 23:24:07 +0000] [14664] [INFO] Listening at: unix:app.sock (14664)
gunicorn[14664]: [2019-06-11 23:24:07 +0000] [14664] [INFO] Using worker: sync
gunicorn[14664]: [2019-06-11 23:24:07 +0000] [14681] [INFO] Booting worker with pid: 14681
When I make a request to the server, I have trouble connecting:
curl http://[SERVER_IP_ADDRESS]:80/predict
<html>
<head><title>502 Bad Gateway</title></head>
<body bgcolor="white">
<center><h1>502 Bad Gateway</h1></center>
<hr><center>nginx/1.14.0 (Ubuntu)</center>
</body>
</html>
EDIT:
I tried removing server_name [SERVER_IP_ADDRESS]; from /etc/nginx/sites-available/app. I now receive 'Welcome to nginx!' at http://SERVER_IP_ADDRESS, and '404 Not Found' at http://SERVER_IP_ADDRESS/predict
FYI, my flask app only has one route, which is '/predict'

It looks like you don't have Port 80 open, so here's a quick iptables command to do so:
sudo iptables -A INPUT -p tcp --dport 80 -j ACCEPT

Related

Running nginx on gcp with docker-compose

I would like to run (to test if it works) nginx on my gcp vm instance with docker-compose.
My docker-compose.yml looks like:
version: '3'
services:
nginx:
image: nginx:latest
container_name: webserver
restart: unless-stopped
ports:
- 8080:8080
On my gcp I allow for http and https trafics.
When I start docker-compose I get:
Starting webserver ... done
Attaching to webserver
webserver | /docker-entrypoint.sh: /docker-entrypoint.d/ is not empty, will attempt to perform configuration
webserver | /docker-entrypoint.sh: Looking for shell scripts in /docker-entrypoint.d/
webserver | /docker-entrypoint.sh: Launching /docker-entrypoint.d/10-listen-on-ipv6-by-default.sh
webserver | 10-listen-on-ipv6-by-default.sh: info: IPv6 listen already enabled
webserver | /docker-entrypoint.sh: Launching /docker-entrypoint.d/20-envsubst-on-templates.sh
webserver | /docker-entrypoint.sh: Launching /docker-entrypoint.d/30-tune-worker-processes.sh
webserver | /docker-entrypoint.sh: Configuration complete; ready for start up
webserver | 2022/04/24 11:48:14 [notice] 1#1: using the "epoll" event method
webserver | 2022/04/24 11:48:14 [notice] 1#1: nginx/1.21.6
webserver | 2022/04/24 11:48:14 [notice] 1#1: built by gcc 10.2.1 20210110 (Debian 10.2.1-6)
webserver | 2022/04/24 11:48:14 [notice] 1#1: OS: Linux 4.19.0-20-cloud-amd64
webserver | 2022/04/24 11:48:14 [notice] 1#1: getrlimit(RLIMIT_NOFILE): 1048576:1048576
webserver | 2022/04/24 11:48:14 [notice] 1#1: start worker processes
webserver | 2022/04/24 11:48:14 [notice] 1#1: start worker process 26
And when I visit my vm's external ip: EXTERNAL_IP:8080 in web browser I don't get any information about nginx installed. What else do I need to make sure nginx works properly?
EDIT: Problem solved. From weird reson, nginx wasn't starting on 8080 port but on 49154

Flask + Gunicorn + Nginx: Group www-data not installed

I am new to web services especially when it comes to deployment options.
I made a Flask application webserver, and now I would like to deploy it on production mode. I went for Gunicorn + Nginx options and followed this tutorial on Medium.
I installed nginx with:
~ >>> sudo pacman -S nginx
~ >>> sudo systemctl start nginx
~ >>> sudo systemctl enable nginx
Everything worked well, but when I created my systemd service webserver.service, the Group=www-data made the service exited, with status=216/GROUP.
Here is the webserver.service file:
[Unit]
Description=Gunicorn instance to serve the test server webserver
After=network.target
[Service]
User=user
Group=www-data
WorkingDirectory=/home/user/webserver/
Environment="PATH=/home/user/webserver/.env/bin"
ExecStart=/home/user/webserver/.env/bin/gunicorn --workers 3 --bind unix:app.sock -m 007 wsgi:app
[Install]
WantedBy=multi-user.target
Here is the full log:
~ >>> sudo systemctl start webserver
~ >>> sudo systemctl enable webserver
~ >>> sudo systemctl status webserver
● webserver.service - Gunicorn instance to serve the test server webserver
Loaded: loaded (/etc/systemd/system/webserver.service; enabled; vendor preset: disabled)
Active: failed (Result: exit-code) since Sun 2020-07-05 14:50:02 CEST; 20min ago
Main PID: 5464 (code=exited, status=216/GROUP)
juil. 05 14:50:02 user systemd[1]: Started Gunicorn instance to serve the test server webserver.
juil. 05 14:50:02 user systemd[5464]: webserver.service: Failed to determine group credentials: No such process
juil. 05 14:50:02 user systemd[5464]: webserver.service: Failed at step GROUP spawning /home/user/webserver/.env/bin/gunicorn: No such process
juil. 05 14:50:02 user systemd[1]: webserver.service: Main process exited, code=exited, status=216/GROUP
juil. 05 14:50:02 user systemd[1]: webserver.service: Failed with result 'exit-code'.
In fact, when I list all the groups, the www-data required by Nginx is missing:
~ >>> groups
sys network power docker lp wheel user
So obviously the above code won't work with www-data group.
What I tried
1. A different group
I tried to change the group option to Group=root, and it worked. I then finished the tutorial without any errors.
I thought it fixed my issue, but I couldn't access my server on my browser at http://www.my_domain_webserver.com, so I guess the www-data is mandatory to work with Nginx and GUnicorn.
My nginx location block:
server {
listen 80;
server_name my_domain_webserver.com www.my_domain_webserver.com;
location / {
include proxy_params;
proxy_pass http://unix:/home/user/webserver/app.sock;
}
}
2. Reloading Daemon
I also tried to re-execute daemon with systemctl daemon-reexec, but it didn't solved my issue.
My project tree is:
webserver
├── app.py
├── app.sock
└── wsgi.py
Why is the group www-data missing ?
Do I need to add special nginx.conf files ? I didn't modify any of them.
Thanks for your help !
You could try to add the folder to the "www-data" group:
sudo chown www-data /home/user/webserver
That helped for me...

Is there a way to resolve an issue with nginx status Active: inactive (dead) problem in CENTOS

This is what it brings when you check nginx status
[root#ttproxyapp conf.d]# service nginx status
Redirecting to /bin/systemctl status nginx.service
● nginx.service - nginx - high performance web server
Loaded: loaded (/usr/lib/systemd/system/nginx.service; disabled; vendor preset: disabled)
Active: inactive (dead)
sudo systemctl stop apache2
sudo systemctl start nginx
should work since looks like the port is in use (with apache probably)
It realy looks like your NGINX ins't running. nginx -s reload is just working if there is a running instance and therfore a PID-file.
Please check the result of the following command.
[root#localhost conf.d]# sudo ps -elf | grep nginx
Should be something like
1 S root 88262 1 0 80 0 - 13143 sigsus 23:47 ? 00:00:00 nginx: master process /usr/sbin/nginx -c /etc/nginx/nginx.conf
5 S nginx 88263 88262 0 80 0 - 13257 ep_pol 23:47 ? 00:00:00 nginx: worker process
0 R root 88265 69227 0 80 0 - 28178 - 23:47 pts/1 00:00:00 grep --color=auto nginx
You need at least! the master process and the worker process! If there is no process start your instance by typing
sudo /bin/systemctl start nginx.service OR sudo service nginx start
Check your processlist after running the command.
After you have started the NGINX service there should be PID-file located at
/var/run/nginx.pid and sudo systemctl status nginx.service should printout something like
[root#localhost conf.d]# systemctl status nginx.service
● nginx.service - NGINX Plus - high performance web server
Loaded: loaded (/usr/lib/systemd/system/nginx.service; enabled; vendor preset: disabled)
Active: active (running) since Sat 2020-03-14 23:47:13 EDT; 5min ago
Docs: https://www.nginx.com/resources/
Process: 88232 ExecStop=/bin/kill -s TERM $MAINPID (code=exited, status=0/SUCCESS)
Process: 88260 ExecStart=/usr/sbin/nginx -c /etc/nginx/nginx.conf (code=exited, status=0/SUCCESS)
Process: 88251 ExecStartPre=/usr/libexec/nginx-plus/check-subscription (code=exited, status=0/SUCCESS)
Main PID: 88262 (nginx)
Tasks: 2
Memory: 1.7M
CGroup: /system.slice/nginx.service
├─88262 nginx: master process /usr/sbin/nginx -c /etc/nginx/nginx.conf
└─88263 nginx: worker process
Mar 14 23:47:13 localhost.localdomain systemd[1]: Starting NGINX Plus - high performance web server...
Mar 14 23:47:13 localhost.localdomain systemd[1]: Can't open PID file /var/run/nginx.pid (yet?) after start: No such file or directory
Mar 14 23:47:13 localhost.localdomain systemd[1]: Started NGINX Plus - high performance web server.
I am running NGINX Plus but it doesn't matter in this case.
there is maybe an apache server running. you must stop that apache server order run the Nginx server.
sudo systemctl stop apache2
sudo systemctl start nginx

Nginx is not proxying Gunicorn

I'm trying to deploy my Flask project using Gunicorn and Nginx but I'm still struggling.
/etc/systemd/system/gunicorn3.service
[Unit] Description=Gunicorn service After=network.target
[Service]
User=www-data
Group=adm
WorkingDirectory=/home/project/
Environment="PATH=/home/project/env/bin"
ExecStart=/home/project/env/bin/gunicorn --workers 3 --bind unix:cima.sock -m 007 run:app
[Install] WantedBy=multi-user.target
Then I check if there's any problem, everything seems OK
>>sudo systemctl status gunicorn3
gunicorn3.service - Gunicorn service
Loaded: loaded (/etc/systemd/system/gunicorn3.service; enabled; vendor preset: enabled)
Active: active (running) since Fri 2020-01-17 20:25:01 UTC; 18min ago
Main PID: 18451 (gunicorn)
Tasks: 4 (limit: 4915)
CGroup: /system.slice/gunicorn3.service
├─18451 /home/acelerathon_cima_grupo_3/chatbot-grupo-3/chatbot-cima/chatbot-cima-back/cimaenv/bin/python3 /home/acelerathon_cima_grupo_3/chatbo
├─18453 /home/acelerathon_cima_grupo_3/chatbot-grupo-3/chatbot-cima/chatbot-cima-back/cimaenv/bin/python3 /home/acelerathon_cima_grupo_3/chatbo
├─18454 /home/acelerathon_cima_grupo_3/chatbot-grupo-3/chatbot-cima/chatbot-cima-back/cimaenv/bin/python3 /home/acelerathon_cima_grupo_3/chatbo
└─18456 /home/acelerathon_cima_grupo_3/chatbot-grupo-3/chatbot-cima/chatbot-cima-back/cimaenv/bin/python3 /home/acelerathon_cima_grupo_3/chatbo
Jan 17 20:25:01 acelerathon-cima-grupo-3 systemd[1]: Started Gunicorn service.
Jan 17 20:25:01 acelerathon-cima-grupo-3 gunicorn[18451]: [2020-01-17 20:25:01 +0000] [18451] [INFO] Starting gunicorn 19.9.0
Jan 17 20:25:01 acelerathon-cima-grupo-3 gunicorn[18451]: [2020-01-17 20:25:01 +0000] [18451] [INFO] Listening at: unix:cima.sock (18451)
Jan 17 20:25:01 acelerathon-cima-grupo-3 gunicorn[18451]: [2020-01-17 20:25:01 +0000] [18451] [INFO] Using worker: sync
Jan 17 20:25:01 acelerathon-cima-grupo-3 gunicorn[18451]: [2020-01-17 20:25:01 +0000] [18453] [INFO] Booting worker with pid: 18453
Jan 17 20:25:01 acelerathon-cima-grupo-3 gunicorn[18451]: [2020-01-17 20:25:01 +0000] [18454] [INFO] Booting worker with pid: 18454
Jan 17 20:25:01 acelerathon-cima-grupo-3 gunicorn[18451]: [2020-01-17 20:25:01 +0000] [18456] [INFO] Booting worker with pid: 18456
/etc/nginx/sites-enabled/project
server {
listen 80;
server_name 127.0.0.1;
location / {
include proxy_params;
proxy_pass http://unix:/home/acelerathon_cima_grupo_3/chatbot-grupo-3/chatbot-cima/chatbot-cima-back/cima.sock;
}
}
And then I checked for errors.
sudo nginx -t
nginx: the configuration file /etc/nginx/nginx.conf syntax is ok
nginx: configuration file /etc/nginx/nginx.conf test is successful
So both services are OK, now when I access to http://localhost I see the Nginx Home Page, not my Flask app home page
I'm not sure why is not proxying
Add localhost to server_name directive in Nginx. Nginx use this directive to match server block for each request and in your case localhost doesn't match 127.0.0.1 so it's server by default server.
May be this example will help to understand:
server {
listen 127.0.0.1:80;
server_name 127.0.0.1;
return 200 "At 127.0.0.1\n";
}
server {
listen 127.0.0.1:80;
server_name localhost;
return 200 "At localhost\n";
}
> curl -4 127.0.0.1:80
At 127.0.0.1
> curl -4 localhost:80
At localhost

nginx proxy_pass does not take affect

I want to deploy an flask app and followed a tutorial to get this done using nginx.
As the tutorial states I do as follows:
sudo nano /etc/nginx/sites-available/app
this file contains:
server {
listen 80;
server_name server_domain_or_IP;
location / {
include proxy_params;
proxy_pass http://unix:/home/pi/Desktop/python_scripts/internetdisplay/app.sock;
}
}
A systemd Unit service was created and is succesfully running. This created the app.sock file in the 'internetdisplay' directory. Systemctl status app.service results:
● app.service - Gunicorn instance to serve myproject
Loaded: loaded (/etc/systemd/system/app.service; enabled; vendor preset: enabled)
Active: active (running) since Sun 2019-11-10 21:16:49 CET; 16h ago
Main PID: 438 (gunicorn)
Tasks: 4 (limit: 2200)
Memory: 46.4M
CGroup: /system.slice/app.service
├─438 /usr/bin/python2 /usr/bin/gunicorn --workers 3 --bind unix:app.sock -m 007 wsgi:app
├─679 /usr/bin/python2 /usr/bin/gunicorn --workers 3 --bind unix:app.sock -m 007 wsgi:app
├─681 /usr/bin/python2 /usr/bin/gunicorn --workers 3 --bind unix:app.sock -m 007 wsgi:app
└─682 /usr/bin/python2 /usr/bin/gunicorn --workers 3 --bind unix:app.sock -m 007 wsgi:app
Nov 10 21:16:49 raspberrypi systemd[1]: Started Gunicorn instance to serve myproject.
Nov 10 21:16:57 raspberrypi gunicorn[438]: [2019-11-10 21:16:57 +0000] [438] [INFO] Starting gunicorn 19.9.0
Nov 10 21:16:57 raspberrypi gunicorn[438]: [2019-11-10 21:16:57 +0000] [438] [INFO] Listening at: unix:app.sock (438)
Nov 10 21:16:57 raspberrypi gunicorn[438]: [2019-11-10 21:16:57 +0000] [438] [INFO] Using worker: sync
Nov 10 21:16:57 raspberrypi gunicorn[438]: [2019-11-10 21:16:57 +0000] [679] [INFO] Booting worker with pid: 679
Nov 10 21:16:57 raspberrypi gunicorn[438]: [2019-11-10 21:16:57 +0000] [681] [INFO] Booting worker with pid: 681
Nov 10 21:16:57 raspberrypi gunicorn[438]: [2019-11-10 21:16:57 +0000] [682] [INFO] Booting worker with pid: 682
Then I link to sites-enabled and restart nginx:
sudo ln -s /etc/nginx/sites-available/app /etc/nginx/sites-enabled
sudo systemctl restart nginx
But surfing to http://localhost leads to an "this site can't be reached" error
It sounds like your location block is not set up correctly to find your resourses.
I assume that this is not the location of your unix socket:
/home/tasnuva/work/deployment/src/app.sock
Check the following:
systemd unit file is creating a socket in the expected location
the daemon is indeed running and the socket file exists
your nginx config is pointing to the correct socket file.
If none of this tells you anything, please update your question with appropriate error log entries.

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