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PSQL

Magic words:

psql -U postgres
sudo -u postgres psql

Some interesting flags (to see all, use -h or --help depending on your psql version):

• -E: will describe the underlaying queries of the \ commands (cool for learning!)

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# views
# https://django.readthedocs.io/en/2.1.x/topics/class-based-views/index.html
# https://django.readthedocs.io/en/2.1.x/ref/class-based-views/index.html
  
  #urls.py
from django.urls import include,path, re_path
from django.views.generic import TemplateView
from . import views

urlpatterns = [

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https://docs.python.org/3/howto/pyporting.html

https://docs.python.org/3/whatsnew/index.html

https://stackoverflow.com/questions/43957004/upgrade-python-3-4-3-to-python-3-6-1-in-ubuntu-15-0464-bit

https://docs.python.org/3/library/venv.html

https://stackoverflow.com/questions/6587507/how-to-install-pip-with-python-3

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; Create default config file -- solves the unix server error
; credits: https://stackoverflow.com/questions/20067116/supervisorctl-error-unix-var-run-supervisord-sock-refused-connection
echo_supervisord_conf > /etc/supervisord.conf
sudo supervisord -c /etc/supervisord.conf
sudo supervisorctl status

; Missing '/var/run/supervisor.sock' file?
touch var/run/supervisor.sock
chmod 777 var/run/supervisor.sock
service supervisor restart

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from django_cron import CronJobBase, Schedule

class FetchData(CronJobBase):
    #RUN_EVERY_MINS = 1 
    #RUN_EVERY_SECONDS = 30 :: non-existent feature
    # maybe we should just write a simple django-mgt comd then daemonize it
    RUN_AT_TIMES = trading_hours #list of hours

    schedule = Schedule(run_every_mins=RUN_EVERY_MINS, run_at_times=RUN_AT_TIMES)
    code = 'my_app.my_cron_job'    # a unique code

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# Toy solution :: not production-ready but food for thought
# https://jeffknupp.com/blog/2014/02/11/a-celerylike-python-task-queue-in-55-lines-of-code/

# This article shows how to daemonize a job using supervisord
# https://adamj.eu/tech/2014/08/16/time-to-move-on-from-cron/

# Below is the github repo link
# https://github.com/dbader/schedule

# --------------------------------------- #

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# execute a python script in virtualenn using cron
# web links to solutions

# http://www.adminschoice.com/crontab-quick-reference
# https://www.unix.com/man-page/linux/5/crontab/

PATH="" # RUN 'echo PATH' as root

MAILTO=mwaigaryan@gmail.com
# setup e-mail first :: https://www.nixtutor.com/linux/send-mail-with-gmail-and-ssmtp/

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# -------------------------------- #
# the main advanatages of celery : #
# -------------------------------- #
# queueing, 
# 0. http://python-rq.org/
# queueing is for invoking a function asynchronously

# retries (the most important feature)::
#  0. https://pypi.org/project/backoff/ :: perfect solution

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def my_wrapper(func):
  try:
      return func
  except MyException as e:
      return "My traceback"
      
 def my_task(*args,**kwargs):
    yada = x + 1

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# create this in etc/supervisor/conf.d/task_manager.conf

[program:task_manager]
command=bash -c "echo starting main.huey && sleep $(( $RANDOM / 2500 + 4)) && exec huey_consumer.py main.huey"
environment=PYTHONPATH=%(here)s/..
numprocs=1
process_name=%(program_name)s-%(process_num)d
stopwaitsecs=5
stdout_logfile=%(here)s/huey.log