durable

A lightweight library for real-time, consistent and scalable coordination of events.

Durable Rules

Durable Rules is a polyglot micro-framework for real-time, consistent and scalable coordination of events. With Durable Rules you can track and analyze information about things that happen (events) by combining data from multiple sources to infer more complicated circumstances.

A full forward chaining implementation (A.K.A. Rete) is used to evaluate facts and massive streams of events in real time. A simple, yet powerful meta-liguistic abstraction lets you define simple and complex rulesets, such as flowcharts, statecharts, nested statecharts, paralel and time driven flows.

The Durable Rules core engine is implemented in C, which enables ultra fast rule evaluation and inference as well as muti-language support. Durable Rules relies on state of the art technologies:

  • Node.js, Werkzeug, Sinatra are used to host rulesets written in JavaScript, Python and Ruby respectively.
  • Inference state is cached using Redis, which lets scaling out without giving up performance.
  • A web client based on D3.js provides powerful data visualization and test tools.

###Example #1

Let’s consider a couple of fictitious fraud rules used in bank account management.
Note: I'm paraphrasing the example presented in this article.

  1. If there are two debit requests greater than 200% the average monthly withdrawal amount in a span of 2 minutes, flag the account as medium risk.
  2. If there are three consecutive increasing debit requests, withdrawing more than 70% the average monthly balance in a span of three minutes, flag the account as high risk.

####Ruby

require "durable"
 
Durable.ruleset :fraud_detection do
  # compute monthly averages 
  when_all span(86400), (m.== "debit_cleared") | (m.== "credit_cleared") do
    debit_total = 0
    credit_total = 0
    for tx in m do
      if tx.== "debit_cleared"
        debit_total += tx.amount
      else
        credit_total += tx.amount
      end
    end
 
    s.balance = s.balance - debit_total + credit_total
    s.avg_balance = (s.avg_balance * 29 + s.balance) / 30
    s.avg_withdraw = (s.avg_withdraw * 29 + debit_total) / 30
  end
 
  # medium risk rule 
  when_all c.first = (m.== "debit_request") & 
                     (m.amount > s.avg_withdraw * 2),
           c.second = (m.== "debit_request") & 
                      (m.amount > s.avg_withdraw * 2) & 
                      (m.stamp > first.stamp) &
                      (m.stamp < first.stamp + 120) do
    puts "Medium risk #{first.amount}#{second.amount}"
  end
 
  # high risk rule 
  when_all c.first = m.== "debit_request",
           c.second = (m.== "debit_request") &
                      (m.amount > first.amount) & 
                      (m.stamp < first.stamp + 180),
           c.third = (m.== "debit_request") & 
                     (m.amount > second.amount) & 
                     (m.stamp < first.stamp + 180),
           s.avg_balance < (first.amount + second.amount + third.amount) / 0.7 do
    puts "High risk #{first.amount}#{second.amount}#{third.amount}"
  end
end
 
Durable.run_all

####Python

from durable.lang import *
import time
 
with ruleset('fraud_detection'):
    # compute monthly averages 
    @when_all(span(86400)(m.t == 'debit_cleared') | (m.t == 'credit_cleared'))
    def handle_balance(c):
        debit_total = 0
        credit_total = 0
        for tx in c.m:
            if tx.t == 'debit_cleared':
                debit_total += tx.amount
            else:
                credit_total += tx.amount
 
        c.s.balance = c.s.balance - debit_total + credit_total
        c.s.avg_balance = (c.s.avg_balance * 29 + c.s.balance) / 30
        c.s.avg_withdraw = (c.s.avg_withdraw * 29 + debit_total) / 30
    
    # medium risk rule 
    @when_all(c.first << (m.t == 'debit_request') & 
                         (m.amount > c.s.avg_withdraw * 2),
              c.second << (m.t == 'debit_request') & 
                          (m.amount > c.s.avg_withdraw * 2) & 
                          (m.stamp > c.first.stamp) &
                          (m.stamp < c.first.stamp + 120))
    def first_rule(c):
        print('Medium Risk {0}{1}'.format(c.first.amountc.second.amount))
 
    # high risk rule 
    @when_all(c.first << m.t == 'debit_request',
              c.second << (m.t == 'debit_request') &
                          (m.amount > c.first.amount) & 
                          (m.stamp < c.first.stamp + 180),
              c.third << (m.t == 'debit_request') & 
                         (m.amount > c.second.amount) & 
                         (m.stamp < c.first.stamp + 180),
              s.avg_balance < (c.first.amount + c.second.amount + c.third.amount) / 0.7)
    def second_rule(c):
        print('High Risk {0}{1}{2}'.format(c.first.amountc.second.amountc.third.amount))
 
run_all()

####JavaScript

var d = require('durable');
 
with (d.ruleset('fraudDetection')) {
    // compute monthly averages 
    whenAll(span(86400), or(m.t.eq('debitCleared'), m.t.eq('creditCleared')), 
    function(c) {
        var debitTotal = 0;
        var creditTotal = 0;
        for (var i = 0; i < c.m.length; ++i) {
            if (c.m[i].=== 'debitCleared') {
                debitTotal += c.m[i].amount;
            } else {
                creditTotal += c.m[i].amount;
            }
        }
 
        c.s.balance = c.s.balance - debitTotal + creditTotal;
        c.s.avgBalance = (c.s.avgBalance * 29 + c.s.balance) / 30;
        c.s.avgWithdraw = (c.s.avgWithdraw * 29 + debitTotal) / 30;
    });
 
    // medium risk rule 
    whenAll(c.first = and(m.t.eq('debitRequest'), 
                          m.amount.gt(c.s.avgWithdraw.mul(2))),
            c.second = and(m.t.eq('debitRequest'),
                           m.amount.gt(c.s.avgWithdraw.mul(2)),
                           m.stamp.gt(c.first.stamp),
                           m.stamp.lt(c.first.stamp.add(120))),
    function(c) {
        console.log('Medium risk ' + c.first.amount + ' ,' + c.second.amount);
    });
 
    // high risk rule  
    whenAll(c.first = m.t.eq('debitRequest'),
            c.second = and(m.t.eq('debitRequest'),
                           m.amount.gt(c.first.amount),
                           m.stamp.lt(c.first.stamp.add(180))),
            c.third = and(m.t.eq('debitRequest'),
                          m.amount.gt(c.second.amount),
                          m.stamp.lt(c.first.stamp.add(180))),
            s.avgBalance.lt(add(c.first.amount, c.second.amount, c.third.amount).div(0.7)),
    function(c) {
        console.log('High risk ' + c.first.amount + ' ,' + c.second.amount + ' ,' + c.third.amount);
    });
}
 
d.runAll();

#####Resources to learn more:
Reference Manual
Blog post: