python - Gunicorn async workers (gevent) not working with Django-Oscar: 500 Internal server error -

brief

django-oscar web application running in production , staging environment, hosted in virtual environment, running systemd daemon using gunicorn.

nginx used proxy, gunicorn working left default "worker-class" "sync", not suitable our case, need change async, "gevent", done adding following parameters execstart

--worker-class gevent --worker-connections 768 

but workers did not start , got following error

[2017-08-15 08:42:35 +0000] [25425] [info] starting gunicorn 19.7.1 [2017-08-15 08:42:35 +0000] [25425] [debug] arbiter booted [2017-08-15 08:42:35 +0000] [25425] [info] listening at: unix:/tmp/myapp.sock (25425) [2017-08-15 08:42:35 +0000] [25425] [info] using worker: gevent [2017-08-15 08:42:35 +0000] [25430] [info] booting worker pid: 25430 [2017-08-15 08:42:35 +0000] [25425] [debug] 1 workers [2017-08-15 11:42:37 +0000] [25430] [error] exception in worker process traceback (most recent call last):   file "/home/ubuntu/.virtualenv/myapp-env/local/lib/python2.7/site-packages/gunicorn/arbiter.py", line 578, in spawn_worker     worker.init_process()   file "/home/ubuntu/.virtualenv/myapp-env/local/lib/python2.7/site-packages/gunicorn/workers/ggevent.py", line 190, in init_process     super(geventworker, self).init_process()   file "/home/ubuntu/.virtualenv/myapp-env/local/lib/python2.7/site-packages/gunicorn/workers/base.py", line 126, in init_process     self.load_wsgi()   file "/home/ubuntu/.virtualenv/myapp-env/local/lib/python2.7/site-packages/gunicorn/workers/base.py", line 135, in load_wsgi     self.wsgi = self.app.wsgi()   file "/home/ubuntu/.virtualenv/myapp-env/local/lib/python2.7/site-packages/gunicorn/app/base.py", line 67, in wsgi     self.callable = self.load()   file "/home/ubuntu/.virtualenv/myapp-env/local/lib/python2.7/site-packages/gunicorn/app/wsgiapp.py", line 65, in load     return self.load_wsgiapp()   file "/home/ubuntu/.virtualenv/myapp-env/local/lib/python2.7/site-packages/gunicorn/app/wsgiapp.py", line 52, in load_wsgiapp     return util.import_app(self.app_uri)   file "/home/ubuntu/.virtualenv/myapp-env/local/lib/python2.7/site-packages/gunicorn/util.py", line 352, in import_app     __import__(module)   file "/home/ubuntu/.virtualenv/myapp-env/local/lib/python2.7/site-packages/gevent/builtins.py", line 93, in __import__     result = _import(*args, **kwargs)   file "/home/ubuntu/myapp/myapp/wsgi.py", line 16, in <module>     application = get_wsgi_application()   file "/home/ubuntu/.virtualenv/myapp-env/local/lib/python2.7/site-packages/django/core/wsgi.py", line 14, in get_wsgi_application     django.setup()   file "/home/ubuntu/.virtualenv/myapp-env/local/lib/python2.7/site-packages/django/__init__.py", line 18, in setup     apps.populate(settings.installed_apps)   file "/home/ubuntu/.virtualenv/myapp-env/local/lib/python2.7/site-packages/django/apps/registry.py", line 108, in populate     app_config.import_models(all_models)   file "/home/ubuntu/.virtualenv/myapp-env/local/lib/python2.7/site-packages/django/apps/config.py", line 198, in import_models     self.models_module = import_module(models_module_name)   file "/usr/lib/python2.7/importlib/__init__.py", line 37, in import_module     __import__(name)   file "/home/ubuntu/.virtualenv/myapp-env/local/lib/python2.7/site-packages/gevent/builtins.py", line 93, in __import__     result = _import(*args, **kwargs)   file "/home/ubuntu/myapp/main/checkout/models.py", line 5, in <module>     main.shipping.models import shippingperiod   file "/home/ubuntu/.virtualenv/myapp-env/local/lib/python2.7/site-packages/gevent/builtins.py", line 93, in __import__     result = _import(*args, **kwargs)   file "/home/ubuntu/myapp/main/shipping/models.py", line 57, in <module>     oscar.apps.shipping.models import *  # noqa   file "/home/ubuntu/.virtualenv/myapp-env/local/lib/python2.7/site-packages/gevent/builtins.py", line 93, in __import__     result = _import(*args, **kwargs)   file "/home/ubuntu/.virtualenv/myapp-env/local/lib/python2.7/site-packages/oscar/apps/shipping/models.py", line 1, in <module>     oscar.apps.shipping import abstract_models   file "/home/ubuntu/.virtualenv/myapp-env/local/lib/python2.7/site-packages/gevent/builtins.py", line 93, in __import__     result = _import(*args, **kwargs)   file "/home/ubuntu/.virtualenv/myapp-env/local/lib/python2.7/site-packages/oscar/apps/shipping/abstract_models.py", line 12, in <module>     scale = loading.get_class('shipping.scales', 'scale')   file "/home/ubuntu/.virtualenv/myapp-env/local/lib/python2.7/site-packages/oscar/core/loading.py", line 29, in get_class     return get_classes(module_label, [classname], module_prefix)[0]   file "/home/ubuntu/.virtualenv/myapp-env/local/lib/python2.7/site-packages/oscar/core/loading.py", line 100, in get_classes     local_module = _import_module(local_module_label, classnames)   file "/home/ubuntu/.virtualenv/myapp-env/local/lib/python2.7/site-packages/oscar/core/loading.py", line 121, in _import_module     return __import__(module_label, fromlist=classnames)   file "/home/ubuntu/.virtualenv/myapp-env/local/lib/python2.7/site-packages/gevent/builtins.py", line 93, in __import__     result = _import(*args, **kwargs) importerror: no module named scales [2017-08-15 11:42:37 +0000] [25430] [info] worker exiting (pid: 25430) [2017-08-15 08:42:37 +0000] [25425] [info] shutting down: master [2017-08-15 08:42:37 +0000] [25425] [info] reason: worker failed boot. 

after reading , trying many solutions, tried --preload in mix, , got workers up, unfortunately reason causing application return internal server error (500)

[2017-08-15 14:44:51 +0000] [26323] [debug] / [2017-08-15 14:44:51 +0000] [26323] [error] error handling request / traceback (most recent call last):   file "/home/ubuntu/.virtualenv/myapp-env/local/lib/python2.7/site-packages/gunicorn/workers/async.py", line 56, in handle     self.handle_request(listener_name, req, client, addr)   file "/home/ubuntu/.virtualenv/myapp-env/local/lib/python2.7/site-packages/gunicorn/workers/ggevent.py", line 152, in handle_request     super(geventworker, self).handle_request(*args)   file "/home/ubuntu/.virtualenv/myapp-env/local/lib/python2.7/site-packages/gunicorn/workers/async.py", line 107, in handle_request     respiter = self.wsgi(environ, resp.start_response)   file "/home/ubuntu/.virtualenv/myapp-env/local/lib/python2.7/site-packages/django/core/handlers/wsgi.py", line 170, in __call__     self.load_middleware()   file "/home/ubuntu/.virtualenv/myapp-env/local/lib/python2.7/site-packages/django/core/handlers/base.py", line 50, in load_middleware     mw_class = import_string(middleware_path)   file "/home/ubuntu/.virtualenv/myapp-env/local/lib/python2.7/site-packages/django/utils/module_loading.py", line 26, in import_string     module = import_module(module_path)   file "/usr/lib/python2.7/importlib/__init__.py", line 37, in import_module     __import__(name)   file "/home/ubuntu/.virtualenv/myapp-env/local/lib/python2.7/site-packages/gevent/builtins.py", line 93, in __import__     result = _import(*args, **kwargs)   file "/home/ubuntu/myapp/oscarapi/middleware.py", line 16, in <module>     oscarapi.basket.operations import (   file "/home/ubuntu/.virtualenv/myapp-env/local/lib/python2.7/site-packages/gevent/builtins.py", line 93, in __import__     result = _import(*args, **kwargs)   file "/home/ubuntu/myapp/oscarapi/basket/operations.py", line 22, in <module>     applicator = get_class('offer.applicator', 'applicator')   file "/home/ubuntu/.virtualenv/myapp-env/local/lib/python2.7/site-packages/oscar/core/loading.py", line 29, in get_class     return get_classes(module_label, [classname], module_prefix)[0]   file "/home/ubuntu/.virtualenv/myapp-env/local/lib/python2.7/site-packages/oscar/core/loading.py", line 100, in get_classes     local_module = _import_module(local_module_label, classnames)   file "/home/ubuntu/.virtualenv/myapp-env/local/lib/python2.7/site-packages/oscar/core/loading.py", line 121, in _import_module     return __import__(module_label, fromlist=classnames)   file "/home/ubuntu/.virtualenv/myapp-env/local/lib/python2.7/site-packages/gevent/builtins.py", line 93, in __import__     result = _import(*args, **kwargs) importerror: no module named applicator  ==> /var/log/nginx/access.log <== 10.0.52.154 - - [15/aug/2017:11:44:51 +0000] "get / http/1.1" 500 141 "-" "mozilla/5.0 (x11; linux x86_64) applewebkit/537.36 (khtml, gecko) chrome/56.0.2924.87 safari/537.36" 

can kindly point me in right direction :) in advance everyone!

update tried eventlet since gevent not working, , this

[2017-08-16 07:19:30 +0000] [7481] [debug] current configuration: proxy_protocol: false   worker_connections: 768   statsd_host: none   max_requests_jitter: 0   post_fork: <function post_fork @ 0x7f1637e18938>   errorlog: /tmp/logging.log   enable_stdio_inheritance: false   worker_class: eventlet   ssl_version: 2   suppress_ragged_eofs: true   syslog: false   syslog_facility: user   when_ready: <function when_ready @ 0x7f1637e18668>   pre_fork: <function pre_fork @ 0x7f1637e187d0>   cert_reqs: 0   preload_app: false   keepalive: 2   accesslog: none   group: 1000   graceful_timeout: 30   do_handshake_on_connect: false   spew: false   workers: 3   proc_name: none   sendfile: none   pidfile: none   umask: 0   on_reload: <function on_reload @ 0x7f1637e18500>   pre_exec: <function pre_exec @ 0x7f1637e18ed8>   worker_tmp_dir: none   limit_request_fields: 100   pythonpath: none   on_exit: <function on_exit @ 0x7f1637e1e758>   config: none   logconfig: none   check_config: false   statsd_prefix:    secure_scheme_headers: {'x-forwarded-protocol': 'ssl', 'x-forwarded-proto': 'https', 'x-forwarded-ssl': 'on'}   reload_engine: auto   proxy_allow_ips: ['127.0.0.1']   pre_request: <function pre_request @ 0x7f1637e1e0c8>   post_request: <function post_request @ 0x7f1637e1e1b8>   forwarded_allow_ips: ['127.0.0.1']   worker_int: <function worker_int @ 0x7f1637e18c08>   raw_paste_global_conf: []   threads: 1   max_requests: 0   chdir: /home/ubuntu   daemon: false   user: 1000   limit_request_line: 4094   access_log_format: %(h)s %(l)s %(u)s %(t)s "%(r)s" %(s)s %(b)s "%(f)s" "%(a)s"   certfile: none   on_starting: <function on_starting @ 0x7f1637e18398>   post_worker_init: <function post_worker_init @ 0x7f1637e18aa0>   child_exit: <function child_exit @ 0x7f1637e1e320>   worker_exit: <function worker_exit @ 0x7f1637e1e488>   paste: none   default_proc_name: myapp.wsgi:application   syslog_addr: udp://localhost:514   syslog_prefix: none   ciphers: tlsv1   worker_abort: <function worker_abort @ 0x7f1637e18d70>   loglevel: debug   bind: ['unix:/tmp/myapp.sock']   raw_env: []   initgroups: false   capture_output: false   reload: false   limit_request_field_size: 8190   nworkers_changed: <function nworkers_changed @ 0x7f1637e1e5f0>   timeout: 30   keyfile: none   ca_certs: none   tmp_upload_dir: none   backlog: 2048   logger_class: gunicorn.glogging.logger [2017-08-16 07:19:30 +0000] [7481] [info] starting gunicorn 19.7.1 [2017-08-16 07:19:30 +0000] [7481] [debug] arbiter booted [2017-08-16 07:19:30 +0000] [7481] [info] listening at: unix:/tmp/myapp.sock (7481) [2017-08-16 07:19:30 +0000] [7481] [info] using worker: eventlet [2017-08-16 07:19:30 +0000] [7486] [info] booting worker pid: 7486 [2017-08-16 07:19:30 +0000] [7487] [info] booting worker pid: 7487 [2017-08-16 07:19:30 +0000] [7487] [error] exception in worker process traceback (most recent call last):   file "/home/ubuntu/.virtualenv/myapp-env/local/lib/python2.7/site-packages/gunicorn/arbiter.py", line 578, in spawn_worker     worker.init_process()   file "/home/ubuntu/.virtualenv/myapp-env/local/lib/python2.7/site-packages/gunicorn/workers/geventlet.py", line 102, in init_process     self.patch()   file "/home/ubuntu/.virtualenv/myapp-env/local/lib/python2.7/site-packages/gunicorn/workers/geventlet.py", line 91, in patch     hubs.use_hub()   file "/home/ubuntu/.virtualenv/myapp-env/local/lib/python2.7/site-packages/eventlet/hubs/__init__.py", line 70, in use_hub     mod = get_default_hub()   file "/home/ubuntu/.virtualenv/myapp-env/local/lib/python2.7/site-packages/eventlet/hubs/__init__.py", line 38, in get_default_hub     import eventlet.hubs.epolls   file "/home/ubuntu/.virtualenv/myapp-env/local/lib/python2.7/site-packages/eventlet/hubs/epolls.py", line 27, in <module>     eventlet.hubs.hub import basehub   file "/home/ubuntu/.virtualenv/myapp-env/local/lib/python2.7/site-packages/eventlet/hubs/hub.py", line 23, in <module>     eventlet.support import greenlets greenlet, clear_sys_exc_info, monotonic, 6   file "/home/ubuntu/.virtualenv/myapp-env/local/lib/python2.7/site-packages/eventlet/support/monotonic.py", line 167, in <module>     raise runtimeerror('no suitable implementation system') runtimeerror: no suitable implementation system [2017-08-16 07:19:30 +0000] [7486] [error] exception in worker process traceback (most recent call last):   file "/home/ubuntu/.virtualenv/myapp-env/local/lib/python2.7/site-packages/gunicorn/arbiter.py", line 578, in spawn_worker     worker.init_process()   file "/home/ubuntu/.virtualenv/myapp-env/local/lib/python2.7/site-packages/gunicorn/workers/geventlet.py", line 102, in init_process     self.patch()   file "/home/ubuntu/.virtualenv/myapp-env/local/lib/python2.7/site-packages/gunicorn/workers/geventlet.py", line 91, in patch     hubs.use_hub()   file "/home/ubuntu/.virtualenv/myapp-env/local/lib/python2.7/site-packages/eventlet/hubs/__init__.py", line 70, in use_hub     mod = get_default_hub()   file "/home/ubuntu/.virtualenv/myapp-env/local/lib/python2.7/site-packages/eventlet/hubs/__init__.py", line 38, in get_default_hub     import eventlet.hubs.epolls   file "/home/ubuntu/.virtualenv/myapp-env/local/lib/python2.7/site-packages/eventlet/hubs/epolls.py", line 27, in <module>     eventlet.hubs.hub import basehub   file "/home/ubuntu/.virtualenv/myapp-env/local/lib/python2.7/site-packages/eventlet/hubs/hub.py", line 23, in <module>     eventlet.support import greenlets greenlet, clear_sys_exc_info, monotonic, 6   file "/home/ubuntu/.virtualenv/myapp-env/local/lib/python2.7/site-packages/eventlet/support/monotonic.py", line 167, in <module>     raise runtimeerror('no suitable implementation system') runtimeerror: no suitable implementation system [2017-08-16 07:19:30 +0000] [7486] [info] worker exiting (pid: 7486) [2017-08-16 07:19:30 +0000] [7487] [info] worker exiting (pid: 7487) [2017-08-16 07:19:30 +0000] [7481] [info] shutting down: master [2017-08-16 07:19:30 +0000] [7481] [info] reason: worker failed boot.