Lightweight Date-driven business rule configuration without database

Question

I'd like to be able to have a list of values available to a web service where the contents of that list can be preconfigured to change starting on a given date.

For example, let's say we had a new feature that was rolling out in the USA on a state by state basis.

Let's say that starting on 2018-09-01, the allowed states are: NJ, NY, PA.

Then, as the rollout continues, starting on 2018-10-01, the allowed states are: NJ, NY, PA, and MA and CT.

And later, starting on 2019-01-01, the allowed states are: NJ, NY, PA, MA, CT, and VT and ME.

Ideally, additional dates and state lists could be updated without stopping and starting the service (without any new build/deployment activity).

What's the best way to implement this?

So far I can think of how to do this using a separate SQL database (table with date column and list column, select row with newest date that doesn't exceed otday's date), but I'm hoping to avoid the complexity of standing up a database for this.

score 0 · Answer 1 · answered Sep 28 '18 at 18:31

Solution I'm using for now:

Describe rules in an external XML file
Make that XML file available to the service
Use Xpath expressions to "query" the XML to execute the rules against inputs to the service

For example:

<?xml version="1.0" encoding="UTF-8"?>
<ExampleRulesXML>
    <ApprovedStates>
        <State code="NY" approvedDate="2018-09-01"/>
        <State code="TX" approvedDate="2018-10-01"/>
        <State code="VT" approvedDate="2018-10-01"/>
        <State code="CA" approvedDate="2018-11-01"/>
    </ApprovedStates>
</ExampleRulesXML>

If the inputs are "2018-09-15" and "NY" (New York), I'd construct the following Xpath, which would evaluate to true, indicating the state is approved as of this date:

exists(/ExampleRulesXML/ApprovedStates/State[@code="NY"][@approvedDate <= "2018-09-15"])

If the inputs are "2018-09-15" and "TX" (Texas), I'd construct the following Xpath, which would evaluate to false, indicating the state is not yet approved as of this date:

exists(/ExampleRulesXML/ApprovedStates/State[@code="TX"][@approvedDate <= "2018-09-15"])

Lightweight Date-driven business rule configuration without database

1 Answers1