Why Gunicorn is serving Flask app fine on its own but throws error when invoked by systemd?

Question

Thank you in advance for any pointers.

I've got a Flask app wired with Gunicorn and Nginx. Gunicorn is serving the app OK after running gunicorn --bind 0.0.0.0:5000 wsgi:app and I can see the app loaded in the browser.

But when invoked by systemd using project.service I get:

May 02 10:46:20 project gunicorn[1307]: Traceback (most recent call last):
May 02 10:46:20 project gunicorn[1307]:   File "/home/mark/project/staging/lib/python3.8/site-packages/gunicorn/arbiter.py", line 589, in s>
May 02 10:46:20 project gunicorn[1307]:     worker.init_process()
May 02 10:46:20 project gunicorn[1307]:   File "/home/mark/project/staging/lib/python3.8/site-packages/gunicorn/workers/base.py", line 134,>
May 02 10:46:20 project gunicorn[1307]:     self.load_wsgi()
May 02 10:46:20 project gunicorn[1307]:   File "/home/mark/project/staging/lib/python3.8/site-packages/gunicorn/workers/base.py", line 146,>
May 02 10:46:20 project gunicorn[1307]:     self.wsgi = self.app.wsgi()
May 02 10:46:20 project gunicorn[1307]:   File "/home/mark/project/staging/lib/python3.8/site-packages/gunicorn/app/base.py", line 67, in w>
May 02 10:46:20 project gunicorn[1307]:     self.callable = self.load()
May 02 10:46:20 project gunicorn[1307]:   File "/home/mark/project/staging/lib/python3.8/site-packages/gunicorn/app/wsgiapp.py", line 58, i>
May 02 10:46:20 project gunicorn[1307]:     return self.load_wsgiapp()
May 02 10:46:20 project gunicorn[1307]:   File "/home/mark/project/staging/lib/python3.8/site-packages/gunicorn/app/wsgiapp.py", line 48, i>
May 02 10:46:20 project gunicorn[1307]:     return util.import_app(self.app_uri)
May 02 10:46:20 project gunicorn[1307]:   File "/home/mark/project/staging/lib/python3.8/site-packages/gunicorn/util.py", line 359, in impo>
May 02 10:46:20 project gunicorn[1307]:     mod = importlib.import_module(module)
May 02 10:46:20 project gunicorn[1307]:   File "/usr/lib/python3.8/importlib/__init__.py", line 127, in import_module
May 02 10:46:20 project gunicorn[1307]:     return _bootstrap._gcd_import(name[level:], package, level)
May 02 10:46:20 project gunicorn[1307]:   File "<frozen importlib._bootstrap>", line 1014, in _gcd_import
May 02 10:46:20 project gunicorn[1307]:   File "<frozen importlib._bootstrap>", line 991, in _find_and_load
May 02 10:46:20 project gunicorn[1307]:   File "<frozen importlib._bootstrap>", line 975, in _find_and_load_unlocked
May 02 10:46:20 project gunicorn[1307]:   File "<frozen importlib._bootstrap>", line 671, in _load_unlocked
May 02 10:46:20 project gunicorn[1307]:   File "<frozen importlib._bootstrap_external>", line 783, in exec_module
May 02 10:46:20 project gunicorn[1307]:   File "<frozen importlib._bootstrap>", line 219, in _call_with_frames_removed
May 02 10:46:20 project gunicorn[1307]:   File "/home/mark/project/wsgi.py", line 1, in <module>
May 02 10:46:20 project gunicorn[1307]:     from project import app
May 02 10:46:20 project gunicorn[1307]:   File "/home/mark/project/project/__init__.py", line 107, in <module>
May 02 10:46:20 project gunicorn[1307]:     app = create_app()
May 02 10:46:20 project gunicorn[1307]:   File "/home/mark/project/project/__init__.py", line 82, in create_app
May 02 10:46:20 project gunicorn[1307]:     db.init_app(app)
May 02 10:46:20 project gunicorn[1307]: UnboundLocalError: local variable 'app' referenced before assignment
May 02 10:46:20 project gunicorn[1307]: [2021-05-02 10:46:20 +0000] [1307] [INFO] Worker exiting (pid: 1307)
May 02 10:46:20 project gunicorn[1294]: Traceback (most recent call last):
May 02 10:46:20 project gunicorn[1294]:   File "/home/mark/project/staging/lib/python3.8/site-packages/gunicorn/arbiter.py", line 209, in r>
May 02 10:46:20 project gunicorn[1294]:     self.sleep()
May 02 10:46:20 project gunicorn[1294]:   File "/home/mark/project/staging/lib/python3.8/site-packages/gunicorn/arbiter.py", line 357, in s>
May 02 10:46:20 project gunicorn[1294]:     ready = select.select([self.PIPE[0]], [], [], 1.0)
May 02 10:46:20 project gunicorn[1294]:   File "/home/mark/project/staging/lib/python3.8/site-packages/gunicorn/arbiter.py", line 242, in h>
May 02 10:46:20 project gunicorn[1294]:     self.reap_workers()
May 02 10:46:20 project gunicorn[1294]:   File "/home/mark/project/staging/lib/python3.8/site-packages/gunicorn/arbiter.py", line 525, in r>
May 02 10:46:20 project gunicorn[1294]:     raise HaltServer(reason, self.WORKER_BOOT_ERROR)
May 02 10:46:20 project gunicorn[1294]: gunicorn.errors.HaltServer: <HaltServer 'Worker failed to boot.' 3>
May 02 10:46:20 project gunicorn[1294]: During handling of the above exception, another exception occurred:
May 02 10:46:20 project gunicorn[1294]: Traceback (most recent call last):
May 02 10:46:20 project gunicorn[1294]:   File "/home/mark/project/staging/bin/gunicorn", line 8, in <module>
May 02 10:46:20 project gunicorn[1294]:     sys.exit(run())
May 02 10:46:20 project gunicorn[1294]:   File "/home/mark/project/staging/lib/python3.8/site-packages/gunicorn/app/wsgiapp.py", line 67, i>
May 02 10:46:20 project gunicorn[1294]:     WSGIApplication("%(prog)s [OPTIONS] [APP_MODULE]").run()
May 02 10:46:20 project gunicorn[1294]:   File "/home/mark/project/staging/lib/python3.8/site-packages/gunicorn/app/base.py", line 231, in >
May 02 10:46:20 project gunicorn[1294]:     super().run()
May 02 10:46:20 project gunicorn[1294]:   File "/home/mark/project/staging/lib/python3.8/site-packages/gunicorn/app/base.py", line 72, in r>
May 02 10:46:20 project gunicorn[1294]:     Arbiter(self).run()
May 02 10:46:20 project gunicorn[1294]:   File "/home/mark/project/staging/lib/python3.8/site-packages/gunicorn/arbiter.py", line 229, in r>
May 02 10:46:20 project gunicorn[1294]:     self.halt(reason=inst.reason, exit_status=inst.exit_status)
May 02 10:46:20 project gunicorn[1294]:   File "/home/mark/project/staging/lib/python3.8/site-packages/gunicorn/arbiter.py", line 342, in h>
May 02 10:46:20 project gunicorn[1294]:     self.stop()
May 02 10:46:20 project gunicorn[1294]:   File "/home/mark/project/staging/lib/python3.8/site-packages/gunicorn/arbiter.py", line 393, in s>
May 02 10:46:20 project gunicorn[1294]:     time.sleep(0.1)
May 02 10:46:20 project gunicorn[1294]:   File "/home/mark/project/staging/lib/python3.8/site-packages/gunicorn/arbiter.py", line 242, in h>
May 02 10:46:20 project gunicorn[1294]:     self.reap_workers()
May 02 10:46:20 project gunicorn[1294]:   File "/home/mark/project/staging/lib/python3.8/site-packages/gunicorn/arbiter.py", line 525, in r>
May 02 10:46:20 project gunicorn[1294]:     raise HaltServer(reason, self.WORKER_BOOT_ERROR)
May 02 10:46:20 project gunicorn[1294]: gunicorn.errors.HaltServer: <HaltServer 'Worker failed to boot.' 3>
May 02 10:46:20 project systemd[1]: project.service: Main process exited, code=exited, status=1/FAILURE
May 02 10:46:20 project systemd[1]: project.service: Failed with result 'exit-code'.
May 02 10:46:28 project sudo[1310]:     mark : TTY=pts/0 ; PWD=/home/mark/project ; USER=root ; COMMAND=/usr/bin/systemctl daemon-reload
May 02 10:46:28 project sudo[1310]: pam_unix(sudo:session): session opened for user root by mark(uid=0)
May 02 10:46:28 project systemd[1]: Reloading.
May 02 10:46:28 project sudo[1310]: pam_unix(sudo:session): session closed for user root
May 02 10:46:36 project sudo[1342]:     mark : TTY=pts/0 ; PWD=/home/mark/project ; USER=root ; COMMAND=/usr/bin/systemctl status offenderb>
May 02 10:46:36 project sudo[1342]: pam_unix(sudo:session): session opened for user root by mark(uid=0)
May 02 10:46:42 project sshd[1345]: Invalid user pi from 81.165.210.66 port 45190
May 02 10:46:42 project sshd[1346]: Invalid user pi from 81.165.210.66 port 45194
May 02 10:46:42 project sshd[1345]: Connection closed by invalid user pi 81.165.210.66 port 45190 [preauth]
May 02 10:46:42 project sshd[1346]: Connection closed by invalid user pi 81.165.210.66 port 45194 [preauth]
May 02 10:46:46 project sudo[1342]: pam_unix(sudo:session): session closed for user root

I've observed this line UnboundLocalError: local variable 'app' referenced before assignment which isn't showing up when Gunicorn runs on its own.

wsgi.py:

from project import app

if __name__ == '__main__':
    app.run(host='0.0.0.0')

project/init.py:

db = SQLAlchemy()


def create_app(script_info=None):

    if os.environ.get('FLASK_ENV') == 'production':
        app = Flask(__name__, ...)
        app.config.from_object(current_config)
        
    elif os.environ.get('FLASK_ENV') == 'staging':
        app = Flask(__name__, ...)
        app.config.from_object(current_config)
        
    elif os.environ.get('FLASK_ENV') == 'development':
        app = Flask(__name__, ...)
        app.config.from_object(current_config)
        toolbar.init_app(app)
        

    db.init_app(app)
    bcrypt.init_app(app)
    login_mgr.init_app(app)
    login_mgr.session_protection = "strong"
    ...
    ...  

    return app


app = create_app()

There's env variable set export FLASK_ENV=staging

If you need more details please ask.

using Python 3.8.5 system-wide.

Edit:

after adding pi user error output is now:

May 02 18:33:08 project gunicorn[2029]:     from project import app
May 02 18:33:08 project gunicorn[2029]:   File "/home/mark/project/project/__init__.py", line 107, in <module>
May 02 18:33:08 project gunicorn[2029]:     app = create_app()
May 02 18:33:08 project gunicorn[2029]:   File "/home/mark/project/project/__init__.py", line 82, in create_app
May 02 18:33:08 project gunicorn[2029]:     db.init_app(app)
May 02 18:33:08 project gunicorn[2029]: UnboundLocalError: local variable 'app' referenced before assignment
May 02 18:33:08 project gunicorn[2029]: [2021-05-02 18:33:08 +0000] [2029] [INFO] Worker exiting (pid: 2029)
May 02 18:33:08 project gunicorn[2017]: Traceback (most recent call last):
May 02 18:33:08 project gunicorn[2017]:   File "/home/mark/project/staging/lib/python3.8/site-packages/gunicorn/arbiter.py", line 209, in r>
May 02 18:33:08 project gunicorn[2017]:     self.sleep()
May 02 18:33:08 project gunicorn[2017]:   File "/home/mark/project/staging/lib/python3.8/site-packages/gunicorn/arbiter.py", line 357, in s>
May 02 18:33:08 project gunicorn[2017]:     ready = select.select([self.PIPE[0]], [], [], 1.0)
May 02 18:33:08 project gunicorn[2017]:   File "/home/mark/project/staging/lib/python3.8/site-packages/gunicorn/arbiter.py", line 242, in h>
May 02 18:33:08 project gunicorn[2017]:     self.reap_workers()
May 02 18:33:08 project gunicorn[2017]:   File "/home/mark/project/staging/lib/python3.8/site-packages/gunicorn/arbiter.py", line 525, in r>
May 02 18:33:08 project gunicorn[2017]:     raise HaltServer(reason, self.WORKER_BOOT_ERROR)
May 02 18:33:08 project gunicorn[2017]: gunicorn.errors.HaltServer: <HaltServer 'Worker failed to boot.' 3>
May 02 18:33:08 project gunicorn[2017]: During handling of the above exception, another exception occurred:
May 02 18:33:08 project gunicorn[2017]: Traceback (most recent call last):
May 02 18:33:08 project gunicorn[2017]:   File "/home/mark/project/staging/bin/gunicorn", line 8, in <module>
May 02 18:33:08 project gunicorn[2017]:     sys.exit(run())
May 02 18:33:08 project gunicorn[2017]:   File "/home/mark/project/staging/lib/python3.8/site-packages/gunicorn/app/wsgiapp.py", line 67, i>
May 02 18:33:08 project gunicorn[2017]:     WSGIApplication("%(prog)s [OPTIONS] [APP_MODULE]").run()
May 02 18:33:08 project gunicorn[2017]:   File "/home/mark/project/staging/lib/python3.8/site-packages/gunicorn/app/base.py", line 231, in >
May 02 18:33:08 project gunicorn[2017]:     super().run()
May 02 18:33:08 project gunicorn[2017]:   File "/home/mark/project/staging/lib/python3.8/site-packages/gunicorn/app/base.py", line 72, in r>
May 02 18:33:08 project gunicorn[2017]:     Arbiter(self).run()
May 02 18:33:08 project gunicorn[2017]:   File "/home/mark/project/staging/lib/python3.8/site-packages/gunicorn/arbiter.py", line 229, in r>
May 02 18:33:08 project gunicorn[2017]:     self.halt(reason=inst.reason, exit_status=inst.exit_status)
May 02 18:33:08 project gunicorn[2017]:   File "/home/mark/project/staging/lib/python3.8/site-packages/gunicorn/arbiter.py", line 342, in h>
May 02 18:33:08 project gunicorn[2017]:     self.stop()
May 02 18:33:08 project gunicorn[2017]:   File "/home/mark/project/staging/lib/python3.8/site-packages/gunicorn/arbiter.py", line 393, in s>
May 02 18:33:08 project gunicorn[2017]:     time.sleep(0.1)
May 02 18:33:08 project gunicorn[2017]:   File "/home/mark/project/staging/lib/python3.8/site-packages/gunicorn/arbiter.py", line 242, in h>
May 02 18:33:08 project gunicorn[2017]:     self.reap_workers()
May 02 18:33:08 project gunicorn[2017]:   File "/home/mark/project/staging/lib/python3.8/site-packages/gunicorn/arbiter.py", line 525, in r>
May 02 18:33:08 project gunicorn[2017]:     raise HaltServer(reason, self.WORKER_BOOT_ERROR)
May 02 18:33:08 project gunicorn[2017]: gunicorn.errors.HaltServer: <HaltServer 'Worker failed to boot.' 3>
May 02 18:33:08 project systemd[1]: project.service: Main process exited, code=exited, status=1/FAILURE
May 02 18:33:08 project systemd[1]: project.service: Failed with result 'exit-code'.
May 02 18:33:23 project sudo[2032]:     mark : TTY=pts/0 ; PWD=/home/mark ; USER=root ; COMMAND=/usr/bin/systemctl status project
May 02 18:33:23 project sudo[2032]: pam_unix(sudo:session): session opened for user root by mark(uid=0)
May 02 18:33:29 project sudo[2032]: pam_unix(sudo:session): session closed for user root
May 02 18:33:42 project sudo[2035]:     mark : TTY=pts/0 ; PWD=/home/mark ; USER=root ; COMMAND=/usr/bin/systemctl daemon-reload
May 02 18:33:42 project sudo[2035]: pam_unix(sudo:session): session opened for user root by mark(uid=0)
May 02 18:33:42 project systemd[1]: Reloading.
May 02 18:33:42 project sudo[2035]: pam_unix(sudo:session): session closed for user root
mark@project:~$

Another Edit:

I've added the pi user (even though I'm not on RPi) and added app = None. I also used Python debugger to get a better picture of what's happening. Python debugger revealed what I expected. Regular Flask app object is passed into db.init_app(app). Nothing suspicious.

Yet when I start off gunicorn by running gunicorn --preload --bind 0.0.0.0:5000 wsgi:app I get:

Traceback (most recent call last):
  File "/home/mark/project/staging/bin/gunicorn", line 8, in <module>
    sys.exit(run())
  File "/home/mark/project/staging/lib/python3.8/site-packages/gunicorn/app/wsgiapp.py", line 67, in run
    WSGIApplication("%(prog)s [OPTIONS] [APP_MODULE]").run()
  File "/home/mark/project/staging/lib/python3.8/site-packages/gunicorn/app/base.py", line 231, in run
    super().run()
  File "/home/mark/project/staging/lib/python3.8/site-packages/gunicorn/app/base.py", line 72, in run
    Arbiter(self).run()
  File "/home/mark/project/staging/lib/python3.8/site-packages/gunicorn/arbiter.py", line 58, in __init__
    self.setup(app)
  File "/home/mark/project/staging/lib/python3.8/site-packages/gunicorn/arbiter.py", line 118, in setup
    self.app.wsgi()
  File "/home/mark/project/staging/lib/python3.8/site-packages/gunicorn/app/base.py", line 67, in wsgi
    self.callable = self.load()
  File "/home/mark/project/staging/lib/python3.8/site-packages/gunicorn/app/wsgiapp.py", line 58, in load
    return self.load_wsgiapp()
  File "/home/mark/project/staging/lib/python3.8/site-packages/gunicorn/app/wsgiapp.py", line 48, in load_wsgiapp
    return util.import_app(self.app_uri)
  File "/home/mark/project/staging/lib/python3.8/site-packages/gunicorn/util.py", line 359, in import_app
    mod = importlib.import_module(module)
  File "/usr/lib/python3.8/importlib/__init__.py", line 127, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
  File "<frozen importlib._bootstrap>", line 1014, in _gcd_import
  File "<frozen importlib._bootstrap>", line 991, in _find_and_load
  File "<frozen importlib._bootstrap>", line 975, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 671, in _load_unlocked
  File "<frozen importlib._bootstrap_external>", line 783, in exec_module
  File "<frozen importlib._bootstrap>", line 219, in _call_with_frames_removed
  File "/home/mark/project/wsgi.py", line 1, in <module>
    from project import app
ImportError: cannot import name 'app' from 'project' (/home/mark/project/project/__init__.py)

my wsgi.py file now looks like this:

from project import app

if __name__ == '__main__':
    app.run()

and __init__.py:

db = SQLAlchemy()


def create_app(script_info=None):
    app = None  # added
    if os.environ.get('FLASK_ENV') == 'production':
        app = Flask(__name__, ...)
        app.config.from_object(current_config)

    elif os.environ.get('FLASK_ENV') == 'staging':
        app = Flask(__name__, ...)
        app.config.from_object(current_config)

    elif os.environ.get('FLASK_ENV') == 'development':
        app = Flask(__name__, ...)
        app.config.from_object(current_config)
        toolbar.init_app(app)


    db.init_app(app)
    bcrypt.init_app(app)
    login_mgr.init_app(app)
    login_mgr.session_protection = "strong"
    ...
    ...  

    return app


if __name__ == '__main__':
    app = create_app()
    app.run(host='0.0.0.0')

running flask shell takes me into shell with Flask app context. the below is as expected which is telling that the app object is being returned OK:

Python 3.8.5 (default, Jan 27 2021, 15:41:15) 
[GCC 9.3.0] on linux
App: project [staging]
Instance: /home/mark/project/instance
>>> app
<Flask 'project'>
>>> dir(app)
['__call__', '__class__', '__delattr__', '__dict__', '__dir__', '__doc__', '__eq__', '__format__', '__ge__', '__getattribute__', '__gt__', '__hash__', '__init__', '__init_subclass__', '__le__', '__lt__', '__module__', '__ne__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__setattr__', '__sizeof__', '__str__', '__subclasshook__', '__weakref__', '_before_request_lock', '_blueprint_order', '_find_error_handler', '_get_exc_class_and_code', '_got_first_request', '_register_error_handler', '_static_folder', '_static_url_path', 'add_template_filter', 'add_template_global', 'add_template_test', 'add_url_rule', 'after_request', 'after_request_funcs', 'app_context', 'app_ctx_globals_class', 'auto_find_instance_path', 'before_first_request', 'before_first_request_funcs', 'before_request', 'before_request_funcs', 'blueprints', 'cli', 'config', 'config_class', 'context_processor', 'create_global_jinja_loader', 'create_jinja_environment', 'create_url_adapter', 'debug', 'default_config', 'dispatch_request', 'do_teardown_appcontext', 'do_teardown_request', 'endpoint', 'env', 'error_handler_spec', 'errorhandler', 'extensions', 'finalize_request', 'full_dispatch_request', 'get_send_file_max_age', 'got_first_request', 'handle_exception', 'handle_http_exception', 'handle_url_build_error', 'handle_user_exception', 'has_static_folder', 'import_name', 'inject_url_defaults', 'instance_path', 'iter_blueprints', 'jinja_env', 'jinja_environment', 'jinja_loader', 'jinja_options', 'json_decoder', 'json_encoder', 'log_exception', 'logger', 'login_manager', 'make_config', 'make_default_options_response', 'make_null_session', 'make_response', 'make_shell_context', 'name', 'open_instance_resource', 'open_resource', 'open_session', 'permanent_session_lifetime', 'preprocess_request', 'preserve_context_on_exception', 'process_response', 'propagate_exceptions', 'raise_routing_exception', 'register_blueprint', 'register_error_handler', 'request_class', 'request_context', 'response_class', 'root_path', 'route', 'run', 'save_session', 'secret_key', 'select_jinja_autoescape', 'send_file_max_age_default', 'send_static_file', 'session_cookie_name', 'session_interface', 'shell_context_processor', 'shell_context_processors', 'should_ignore_error', 'static_folder', 'static_url_path', 'subdomain_matching', 'teardown_appcontext', 'teardown_appcontext_funcs', 'teardown_request', 'teardown_request_funcs', 'template_context_processors', 'template_filter', 'template_folder', 'template_global', 'template_test', 'templates_auto_reload', 'test_cli_runner', 'test_cli_runner_class', 'test_client', 'test_client_class', 'test_request_context', 'testing', 'trap_http_exception', 'try_trigger_before_first_request_functions', 'update_template_context', 'url_build_error_handlers', 'url_default_functions', 'url_defaults', 'url_map', 'url_map_class', 'url_rule_class', 'url_value_preprocessor', 'url_value_preprocessors', 'use_x_sendfile', 'view_functions', 'wsgi_app']

looks like the user "pi" doesn't have the correct permissions to run that via systremd — Dean Van Greunen, May 02 '21 at 11:52
I was confused about seeing it to be honest. I didn't even created the `pi` user. The machine is a virtual machine running on Google Cloud Platform. — itsallgood, May 02 '21 at 12:09
I ran `sudo chown pi staging/bin/gunicorn` but got `chown: invalid user: ‘pi’` — itsallgood, May 02 '21 at 12:11
then run this `sudo usermod -aG sudo pi` this will elevate your pi user to have sudo access — Dean Van Greunen, May 02 '21 at 16:38

Dean Van Greunen · Answer 1 · 2021-05-03T14:59:35.863

0

Steps

run sudo adduser pi
run sudo usermod -aG sudo pi
change your code to this for project/init.py:

db = SQLAlchemy()


def create_app(script_info=None):
    app = None # You need a top level variable called app...
    if os.environ.get('FLASK_ENV') == 'production':
        app = Flask(__name__, ...) # as this creates a variable in local scope of the elif statement
        app.config.from_object(current_config)
        
    elif os.environ.get('FLASK_ENV') == 'staging':
        app = Flask(__name__, ...) # as this creates a variable in local scope of the elif statement
        app.config.from_object(current_config)
        
    elif os.environ.get('FLASK_ENV') == 'development':
        app = Flask(__name__, ...) # as this creates a variable in local scope of the elif statement
        app.config.from_object(current_config)
        toolbar.init_app(app)
        

    db.init_app(app)
    bcrypt.init_app(app)
    login_mgr.init_app(app)
    login_mgr.session_protection = "strong"
    ...
    ...  

    return app


app = create_app()

Edit 1:

change wsgi.py: to this:

import app

if __name__ == '__main__':
    app.run()

edited May 03 '21 at 14:59

answered May 03 '21 at 11:23

Dean Van Greunen

5,060
2
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I've added another edit to reflect your answer. – itsallgood May 03 '21 at 12:48
No, sorry. Your answer made no difference on my end. – itsallgood May 03 '21 at 14:59
@itsallgood make sure that the wsgi file is in the same directory as your `__init__.py` file is – Dean Van Greunen May 03 '21 at 15:01
also read [this](http://web.cs.iastate.edu/~smkautz/cs127f16/notes/chapter07/?source=post_page---------------------------) – Dean Van Greunen May 03 '21 at 15:01
also read these [Flask with Gunicorn](https://www.digitalocean.com/community/tutorials/how-to-serve-flask-applications-with-gunicorn-and-nginx-on-ubuntu-18-04) and [docs](https://docs.gunicorn.org/en/stable/run.html) – Dean Van Greunen May 03 '21 at 15:02
1

^ that's exactly what I've been following. Funny hm ? And it worked locally but can't seem get it to work on linux running on GCP. – itsallgood May 03 '21 at 15:19
@itsallgood you need to allow the port on your GCP Instance. `gunicorn --bind 0.0.0.0:5000 wsgi:app` go into your network settings / firewall and allow inbound connections on port 5000. – Dean Van Greunen May 03 '21 at 19:50
also you will also need to allow the port via the `ufw` command – Dean Van Greunen May 03 '21 at 19:50
follow [this tutorial](https://stackoverflow.com/a/55933943/6651840) – Dean Van Greunen May 03 '21 at 19:51

score 0 · Answer 2 · answered May 04 '21 at 07:30

Gunicorn started working for me in production after changing my __init__.py:

from flask import Flask, render_template
from flask_sqlalchemy import SQLAlchemy
from flask_login import LoginManager
from flask_bcrypt import Bcrypt
from project.config import StagingConfig


login_mgr = LoginManager()
bcrypt = Bcrypt()
db = SQLAlchemy()


def create_app(script_info=None):

    app = Flask(__name__, ...)
    app.config.from_object(StagingConfig)
    
    db.init_app(app)
    ...
    ...
    
    return app

and changing wsgi.py file to:

from project import create_app

app = create_app()

Notice I dropped if __name__ == '__main__' statements and hardcoded passing config attributes. I've got different branches for different environments anyway so it's not as much of an issue.

Why Gunicorn is serving Flask app fine on its own but throws error when invoked by systemd?

2 Answers2

Steps

Edit 1: