django – error code=H10 desc=”App crashed” method=GET I Have Installed Gunicorn But Its Showing Error

django – error code=H10 desc=”App crashed” method=GET I Have Installed Gunicorn But Its Showing Error – Stack Overflow

mongodb – pymongo + flask + gunicorn: “Authentication failed” before first operation when “connect=False”

I’m using MongoDB Atlas. I’m have this URL for connecting: mongodb+srv://<LOGIN>:<PASSWORD>@<URL>/<DB>?retryWrites=true&w=majority&authSource=admin.

I’m using this stack: flask, gunicorn, pymongo, mongoengine (i don’t think that it is related, because mongoengine actually uses pymongo).

gunicorn config:

  • sync workers,
  • threads = 1,
  • workers count = 8

When connecting, i’m using connect=False because pymongo itself is not fork-safe. With connect=False it will connect to the DB before first operation. It need to be set to False, because gunicorn uses pre-fork model.

But I am faced with the following situation:

  1. On first request (endpoint makes some DB operations) i’m getting this error: pymongo.errors.OperationFailure: Authentication failed., full error: {'ok': 0, 'errmsg': 'Authentication failed.', 'code': 8000, 'codeName': 'AtlasError'}
  2. On second request everything is fine (i.e., DB operations were successfully completed).
  3. If you press many times on F5, then sometimes you will occur a “Authentication failed” error, and sometimes everything will be fine.

If i’m set connect=True, everything will be fine. I’m never seen this “Authentication failed” error.

But then i’m getting this warning message: UserWarning: MongoClient opened before fork. Create MongoClient only after forking. See PyMongo's documentation for details: https://pymongo.readthedocs.io/en/stable/faq.html#is-pymongo-fork-safe.

So, obviously, connect need to be set to False.

I’m tested with two workers. Looks like this situation occurs:

  1. Let’s say i have two gunicorn sync workers with following pid’s: 22429 and 22430.
  2. I’m getting request. Worker 22429 handles it. Everything is fine, because it is first worker and looks like it successfully made a DB connection.
  3. I’m pressing F5, worker 22429 again handles it and everything is fine.
  4. I’m pressing F5 again, and now worker 22430 handles it. It throws an error “Authentication failed.”
  5. I’m pressing F5 again, worker 22430 handles it. Now everything is fine, because that worker has made a connection.
  6. Now, all my workers (i have only two) were connected to the DB. Doesn’t matter how many times i’m press on F5, every request will be successfully completed.

But why it happens on first reques? From pymongo: “if connect=False, then connect on the first operation.”. If i’m understanding it right, pymongo should connect before actual first operation, successfully completed the connection, and only then perform that operation.

Then why my first DB operation fails for each worker? How i should handle this?

web development – Why does a Django web server need Gunicorn and Nginx?

I recently had a question about trying to understand the importance of Nginx and Gunicorn, and was given a helpful answer from one of the users (link here).

It makes a decent amount of sense now as far as I can tell, but as it stands I have two confusions.

  1. Why is Nginx necessary if I already have a web server I’m using, DigitalOcean?
  2. What does a WSGI server do, exactly?

Please keep in mind I am almost entirely uninitiated in the field of web design/development so please don’t scare me with too many jargonated words!

What is the appropriate usage of SCRIPT_NAME in gunicorn + flask?

I want to add url prefix to every route in my flask application.

PREFIX = "/api"

@app.route(PREFIX + "/")
def index():
  return "Hello world!"

@app.route(PREFIX + "/users")
def users():
  return ()

I’m looking for way to do this without using PREFIX const.

Is there something like below?

gunicorn -w 4 --bind 0.0.0.0:80 run:app --script_name /api

server – Understanding the importance of Gunicorn and Nginx for Django web development

When author says that Django can’t handle real workloads, they most likely refer specifically to Django’s built-in webserver.

When you run Django in development environment, you can use it to test things out, but a proper webserver is a fairly complex piece of software and requires very specific competences to build. Moreover, there is no real reason for the people behind Django to also spend time making a fully fleshed-out webserver: it is much easier to build an interface for an existing one.

Nginx is a professionally made workhorse of a server. It is feature-rich and is built to handle production workloads. Most apps use a server like that on the front to handle niche responsibilities like caching, redirection, forming headers, compression etc.

So, now, Gunicorn. Gunicorn is a WSGI server. Broadly speaking, it facilitates communication between a variety of webservers and a variety of frameworks through a standardized interface. Plus it handles additional tasks, like load-balancing and maintaining instances of your app alive, so you don’t have to.

server – Understanding the importance of Gunicorn and Nginx for Django web development

I’m entirely uninitiated to the world of web development, and only have a tentative grasp on Django and web development through the test server it works through.

From the guide I’m reading, the author turns to using Nginx once he starts working on site deployment, because Django is “not designed for real-life workloads.” What does that mean, and why doesn’t it? In terms of justification for using Gunicorn, the author remarks:

Do you know why the Django mascot is a pony? The story is that Django
comes with so many things you want: an ORM, all sorts of middleware,
the admin site…​ “What else do you want, a pony?” Well, Gunicorn
stands for “Green Unicorn”, which I guess is what you’d want next if
you already had a pony…​

Well and good, but I don’t really know what the two are doing for the server. I know for web developers this is like asking what multiplication is to a maths professor, so please excuse the naivety. In your please keep in mind I have almost no knowledge of web development other than what I’ve thus far learned from this guide, doing my best to understand as much as I can for the previously entirely uninitiated (I’m from a computational programming background).

amazon ec2 – Cannot access Django application using Gunicorn and NGINX on Ubuntu 18

I cannot access my django application on my public site. I am running Gunicorn with
gunicorn --workers 3 --bind unix:/webapps/pcfnet/paulcflynn/pcfnet/pcfnet.sock pcfnet.wsgi:application and my NGINX file looks like so:

server {
        listen 80;
        server_name paulcflynn.net;

    # to avoid any error while fetching fevicon
    location = /favicon.ico { access_log off; log_not_found off; }

    location /static/ {
        root /webapps/pcfnet/paulcflynn/pcfnet;
    }

    location / {
        include proxy_params;
        # communicate via socket file created by Gunicorn
        proxy_pass http://unix:/webapps/pcfnet/paulcflynn/pcfnet/pcfnet.sock;
    }
}

I am hosting an Ubuntu 18 instance on EC2 and cannot figure out why I am receiving this error. When I curl localhost I get a bad request error 400. Any idea what my configuration is missing?

python 3.x – profiling api with django, gunicorn and threadpool

I have an API to do the below operations. I am using python, Django framework and gunicorn/nginx for deployment.

API has deployed in AWS lightsail. Request will come in for every 2secs.

  1. receives data from the client.
  2. creates record in local SQLite database and sends response.
  3. runs task asynchronously in thread. (running in thread). Entire task takes about 1 sec on average.
    a. gets the updated record from step 2 with ID. (0 sec)
    b. posts data to another API using requests. (.5 secs)
    c. updates to database (AWS RDS) (.5 secs)

Setup:

  1. I have ThreadPoolExecutor max_workers=12.
  2. gunicorn has one worker as the instance has 1vCPU.
  3. The reason asyncio is used was that base update in Django is not supported with this. So I kept the post API in the threading itself.
  4. Each request will be unique. No same request.

Even If I keep max_worker to 1 in threadpool, it is bursting 10% mark in AWS 5$ instance. API only receive request for every 2secs.

I am not able to profile this situation where it is causing the CPU usage.

There are a couple of reason, I can think of.

  1. gunicorn master is constantly checking on the worker.
  2. OS is managing threads for context switching.

Any pointer will be helpful for profiling.

Gunicorn and openrc

I’m looking for a solution to run gunicorn as a daemon on openrc, specifically on gentoo.
I searched on google and found nothing related.
If anyone has been through this situation please help me.

google compute engine – ERROR: (gcloud.app.deploy) Error Response: [9] Application startup error! Code: APP_CONTAINER_CRASHED /bin/sh: 1: exec: gunicorn: not found

I am deploying my Django project on google cloud app engine with my virtual environment I get the error
ERROR: (gcloud.app.deploy) Error Response: (9)
Application startup error! Code: APP_CONTAINER_CRASHED
/bin/sh: 1: exec: gunicorn: not found
i already install gunicorn and my app.yaml

runtime: python
env: flex
  entrypoint: gunicorn -b :$PORT tiwari.wsgi
automatic_scaling:
  min_num_instances: 1
  max_num_instances: 2

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