All posts tagged with bond

Mailing mortgage bond prices using Azure Functions, PuppeteerSharp MSSQL, and SendGrid

July 05, 2019 - Søren Alsbjerg Hørup

The mortgage interest rate in Denmark is approaching all-time low this summer. The current 30 year bond has a interest of 1% and it seems the interest rate will stay the same or decline even more this year.

I myself have a 3% mortgage loan on my house, therefore it makes perfect sense to convert from my 3% loan to the 1% load currently being offered. Bond prices, and thus the interest rate, goes up and down each day - therefore it makes perfect sense to follow the prices and take the loan when the interest rate is at its lowest.

To follow the bond price, and thus interest rate, I implemented an Azure Function which uses PuppeteerSharp, an high-level C# API to control Chromium over the DevTools protocol, to connect to my mortgage provider to fetch and email the daily price of my target mortgage using SendGrid.

Azure Functions’ do not allow GDI applications to run, due to the restricted sandbox nature, and will therefore not allow Chromium to run. Therefore, I have Chromium running on a seperate low-powered Windows VM in the cloud which my Azure Function connects to using PuppeteerSharp.

After connecting, the Azure Functions spawns a new page on the remote Chromium, redirects the page to the mortgage provider and uses jQuery to fetch the price of the bond. This price is saved in an SQL database, such that a comparison can be made to determine if the price has changed and by how much.

When a price change is detected, the new price + change is emailed to me using SendGrid, an easy to use Email Service. This allows me to easily monitor the bond price each day, since I am actively checking my email all day, without having to visit the mortgage provider.

Getting an email with the necessary information really helps monitoring the trend of the bond and when to act, since it automatically is pushed to me (my mailbox) and all unnecessary clutter is removed, such as the prices of the other bonds.

My next step is to find some other domain where I can apply these principles, or perhaps feature creep and make graph and/or prediction support to my bond monitor :-)