I have an installed free account on Heroku to get started.
A python code that accepts web requests is starting a shell subprocess, does starting this subprocess count and need a dyno?
I am seeing this specific code not do its intended purpose, but when run through the shell on Heroku it does what it is supposed too.
Related
I have a web app that I deployed to a machine that has ubuntu 20 installed
to be able to run the app I should open ssh to the ubuntu machine and then run this command
cd mywebapp
python3 app.py
it works successfully, but once I close the ssh console or reboot the machine or anything happens, it stopped and I have to repeat these commands
I tried to add it as a corn job to be run after machine reboot but it does not work
I post a question in the following link : run python app after server restart does not work using crontab
nothing work with me, and I have to make sure that this web app will always be running because it should be working to send push notification to mobile devices
can anyone please advice, I have been searching and trying for so many time
I'm not expert in it, but two solutions come in my mind:
1- Using systemd:
systemd can be responsible to keep services up.
You can write a custom unit for your app, and config it as a way to be up always.
This tutorial may be useful: writing unit
2- Using Docker:
When you have containerized app, you config it as to come up, on failure or anything like that.
Read about it here
What if you have the calling piece of Python script within a bash script and run that as a daemon:
Your bash script could like below (test.sh):
#!/bin/sh
cd desired/directory
python3 app.py
and you can run the bashscript like this by using nohup:
nohup ./test.sh 0<&- &>/dev/null &
You could refer this, if you want to store the outputs of nohup.
I am executing my Robot Framework Selenium tests in a remote machine (it's a Docker container, but I need it to be working using Podman, too... so I guess using docker commands wouldn't help me) and in this remote machine, there is an automatic process running on the background, which is producing terminal logs.
I can read this cmd output when I execute docker logs <container_id> in my terminal, but I need to get them using python and extract some info from these logs to show them in the Robot Framework test log file.
Any ideas how to do it?
I have found several ways how to execute a command in the remote machine and get the output, but here I am not executing any command, I just need to read what's being produced automatically.
Thank you for your advice
I am looking to run commands I typically would run through Heroku CLI via a python script, namely:
heroku pg:backups:capture
Historically, for running Heroku commands in Python I have used Heroku3.py, which works for me for things like restarting dynos. I am having difficulty finding a way to execute commands for addons, such as the one listed above.
Is there a way to call CLI commands through python?
I have developed a Python web server using Flask, and some of the endpoints make use of the subprocess module to call different executables. On development, using the Flask debug server, everything works fine. However, when running the server along with nginx+WSGI (on the exact same machine), some subprocess calls fail.
For example, one of the tools I'm using is Microsoft's dotnet, which I installed from my user as sudo apt-get install -y aspnetcore-runtime-5.0 and is then called from Python with the subprocess module. When I run the server with python3 server.py, it works like a charm. However, when using nginx and WSGI, the subprocess call fails with an exception that says: /bin/sh: 1: dotnet: not found.
I suspect this is due to the command not being accessible to the user and group running the server. I have used this guide as a reference to deploy the app, and on the wsgi .ini file, I have set uid = javierd and gid = www-data, while on the systemd .service file I have User=javierd, Group=www-data.
I have tried to add the executables' paths to /etc/profile, but it didn't work, and I don't know any other way to fix it. I find also very surprising that this happens to some executables, but not to all, and that it happes to dotnet, for example, which is located at /usr/bin/dotnet and therefore should be accessible to every user. Any idea on how to solve this problem? Furthermore, if somebody could explain me why this is happening, I would really appreciate the effort.
Thanks a lot!
Ok, finally after having a big headache, I noticed the error, and it was really simple.
On the tutorial I linked, when creating the system service file, the following line was included: Environment="PATH=/home/myuser/myfolder/enviroment/bin".
Of course, as this was overriding the path, there was no way of executing the commands. Once I notices it I just removed that line, restarted the service, and it was fixed.
I am looking for help deploying my flash app. I've already written the app and it works well. I'm currently using the following command in the directory of my flask code:
sudo uwsgi --socket 0.0.0.0:70 --protocol=http -w AppName:app --buffer-size=32768
This is on my Amazon Lightsail instance. I have the instance linked to a static public IP, and if I navigate to the website, it works great. However, to get the command to continuously run in the background even after logging out of the Lightsail, I first start a screen command, execute the above line of code, and then detach the screen using ctrl-a-d.
The problem is, if the app crashes (which is understandable since it is very large and under development), or if the command is left running for too long, the process is killed, and it is no longer being served.
I am looking for a better method of deploying a flask app on Amazon Lightsail so that it will redeploy the app in the event of a crash without any interaction from myself.
Generally you would write your own unit file for systemd to keep your application running, auto restart when it crashes and start when you boot your instances.
There are many tutorials out there showing how to write such a unit file. Some examples:
Systemd: Service File Examples
Creating a Linux service with systemd
How to write startup script for Systemd?
You can use pm2
Starting an application with PM2 is straightforward. It will auto
discover the interpreter to run your application depending on the
script extension. This can be configurable via the Ecosystem config
file, as I will show you later on this article.
All you need to install pm2 and then
pm2 start appy.py
Great, this application will now run forever, meaning that if the process exit or throw an exception it will get automatically restarted. If you exit the console and connect again you will still be able to check the application state.
To list application managed by PM2 run:
pm2 ls
You can also check logs
pm2 logs
Keeping Processes Alive at Server Reboot
If you want to keep your application online across unexpected (or expected) server restart, you will want to setup init script to tell your system to boot PM2 and your applications.
It’s really simple with PM2, just run this command (without sudo):
pm2 startup
Pm2 Manage-Python-Processes