Scheduled Tasks

Finally, an application also has to send email notifications and do other kind of scheduled tasks. In Frappe, if you have setup the bench, the task / scheduler is setup via RQ using Redis Queue.

To add a new task handler, go to hooks.py and add a new handler. Default handlers are all, daily, weekly, monthly, cron. The all handler is called every 4 minutes by default.

# Scheduled Tasks
# ---------------

scheduler_events = {
    "daily": [
        "library_management.tasks.daily"
    ],
    "cron": {
        "0/10 * * * *": [
            "library_management.task.run_every_ten_mins"
        ],
        "15 18 * * *": [
            "library_management.task.every_day_at_18_15"
        ]
    }

}

Here we can point to a Python function and that function will be executed every day. Let us look what this function looks like:

# Copyright (c) 2013, Frappe
# For license information, please see license.txt

from __future__ import unicode_literals
import frappe
from frappe.utils import datediff, nowdate, format_date, add_days

def every_ten_minutes():
    # stuff to do every 10 minutes
    pass

def every_day_at_18_15():
    # stuff to do every day at 6:15pm
    pass

def daily():
    loan_period = frappe.db.get_value("Library Management Settings",
        None, "loan_period")

    overdue = get_overdue(loan_period)

    for member, items in overdue.iteritems():
        content = """<h2>Following Items are Overdue</h2>
        <p>Please return them as soon as possible</p><ol>"""

        for i in items:
            content += "<li>{0} ({1}) due on {2}</li>".format(i.article_name,
                i.article,
                format_date(add_days(i.transaction_date, loan_period)))

        content += "</ol>"

        recipient = frappe.db.get_value("Library Member", member, "email_id")
        frappe.sendmail(recipients=[recipient],
            sender="test@example.com",
            subject="Library Articles Overdue", content=content, bulk=True)

def get_overdue(loan_period):
    # check for overdue articles
    today = nowdate()

    overdue_by_member = {}
    articles_transacted = []

    for d in frappe.db.sql("""select name, article, article_name,
        library_member, member_name
        from `tabLibrary Transaction`
        order by transaction_date desc, modified desc""", as_dict=1):

        if d.article in articles_transacted:
            continue

        if d.transaction_type=="Issue" and \
            datediff(today, d.transaction_date) > loan_period:
            overdue_by_member.setdefault(d.library_member, [])
            overdue_by_member[d.library_member].append(d)

        articles_transacted.append(d.article)

We can place the above code in any accessible Python module. The route is defined in hooks.py, so for our purposes we would place this code in library_management/tasks.py.

Note:

1. We get the loan period from Library Management Settings by using frappe.db.get_value.
2. We run a query in the database with frappe.db.sql
3. Email is sent via frappe.sendmail

Next: Conclusion