system-design-primer/solutions/object_oriented_design/call_center/call_center.ipynb
2017-03-03 18:52:50 -08:00

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"This notebook was prepared by [Donne Martin](https://github.com/donnemartin). Source and license info is on [GitHub](https://github.com/donnemartin/system-design-primer-primer)."
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"source": [
"# Design a call center"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"## Constraints and assumptions\n",
"\n",
"* What levels of employees are in the call center?\n",
" * Operator, supervisor, director\n",
"* Can we assume operators always get the initial calls?\n",
" * Yes\n",
"* If there is no free operators or the operator can't handle the call, does the call go to the supervisors?\n",
" * Yes\n",
"* If there is no free supervisors or the supervisor can't handle the call, does the call go to the directors?\n",
" * Yes\n",
"* Can we assume the directors can handle all calls?\n",
" * Yes\n",
"* What happens if nobody can answer the call?\n",
" * It gets queued\n",
"* Do we need to handle 'VIP' calls where we put someone to the front of the line?\n",
" * No\n",
"* Can we assume inputs are valid or do we have to validate them?\n",
" * Assume they're valid"
]
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"cell_type": "markdown",
"metadata": {},
"source": [
"## Solution"
]
},
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"text": [
"Overwriting call_center.py\n"
]
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"source": [
"%%writefile call_center.py\n",
"from abc import ABCMeta, abstractmethod\n",
"from collections import deque\n",
"from enum import Enum\n",
"\n",
"\n",
"class Rank(Enum):\n",
"\n",
" OPERATOR = 0\n",
" SUPERVISOR = 1\n",
" DIRECTOR = 2\n",
"\n",
"\n",
"class Employee(metaclass=ABCMeta):\n",
"\n",
" def __init__(self, employee_id, name, rank, call_center):\n",
" self.employee_id = employee_id\n",
" self.name = name\n",
" self.rank = rank\n",
" self.call = None\n",
" self.call_center = call_center\n",
"\n",
" def take_call(self, call):\n",
" \"\"\"Assume the employee will always successfully take the call.\"\"\"\n",
" self.call = call\n",
" self.call.employee = self\n",
" self.call.state = CallState.IN_PROGRESS\n",
"\n",
" def complete_call(self):\n",
" self.call.state = CallState.COMPLETE\n",
" self.call_center.notify_call_completed(self.call)\n",
"\n",
" @abstractmethod\n",
" def escalate_call(self):\n",
" pass\n",
"\n",
" def _escalate_call(self):\n",
" self.call.state = CallState.READY\n",
" call = self.call\n",
" self.call = None\n",
" self.call_center.notify_call_escalated(call)\n",
"\n",
"\n",
"class Operator(Employee):\n",
"\n",
" def __init__(self, employee_id, name):\n",
" super(Operator, self).__init__(employee_id, name, Rank.OPERATOR)\n",
"\n",
" def escalate_call(self):\n",
" self.call.level = Rank.SUPERVISOR\n",
" self._escalate_call()\n",
"\n",
"\n",
"class Supervisor(Employee):\n",
"\n",
" def __init__(self, employee_id, name):\n",
" super(Operator, self).__init__(employee_id, name, Rank.SUPERVISOR)\n",
"\n",
" def escalate_call(self):\n",
" self.call.level = Rank.DIRECTOR\n",
" self._escalate_call()\n",
"\n",
"\n",
"class Director(Employee):\n",
"\n",
" def __init__(self, employee_id, name):\n",
" super(Operator, self).__init__(employee_id, name, Rank.DIRECTOR)\n",
"\n",
" def escalate_call(self):\n",
" raise NotImplemented('Directors must be able to handle any call')\n",
"\n",
"\n",
"class CallState(Enum):\n",
"\n",
" READY = 0\n",
" IN_PROGRESS = 1\n",
" COMPLETE = 2\n",
"\n",
"\n",
"class Call(object):\n",
"\n",
" def __init__(self, rank):\n",
" self.state = CallState.READY\n",
" self.rank = rank\n",
" self.employee = None\n",
"\n",
"\n",
"class CallCenter(object):\n",
"\n",
" def __init__(self, operators, supervisors, directors):\n",
" self.operators = operators\n",
" self.supervisors = supervisors\n",
" self.directors = directors\n",
" self.queued_calls = deque()\n",
"\n",
" def dispatch_call(self, call):\n",
" if call.rank not in (Rank.OPERATOR, Rank.SUPERVISOR, Rank.DIRECTOR):\n",
" raise ValueError('Invalid call rank: {}'.format(call.rank))\n",
" employee = None\n",
" if call.rank == Rank.OPERATOR:\n",
" employee = self._dispatch_call(call, self.operators)\n",
" if call.rank == Rank.SUPERVISOR or employee is None:\n",
" employee = self._dispatch_call(call, self.supervisors)\n",
" if call.rank == Rank.DIRECTOR or employee is None:\n",
" employee = self._dispatch_call(call, self.directors)\n",
" if employee is None:\n",
" self.queued_calls.append(call)\n",
"\n",
" def _dispatch_call(self, call, employees):\n",
" for employee in employees:\n",
" if employee.call is None:\n",
" employee.take_call(call)\n",
" return employee\n",
" return None\n",
"\n",
" def notify_call_escalated(self, call): # ...\n",
" def notify_call_completed(self, call): # ...\n",
" def dispatch_queued_call_to_newly_freed_employee(self, call, employee): # ..."
]
}
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