The Creek: Flood Event Web Page

In the previous post I talked about scanning through the Elkhorn Creek MySql database and finding flood events.  This is a very IO intensive task and as such is slower than crap.  It takes something like 20 seconds on the Raspberry Pi and as such is not very ideal for an interactive application.  So to make this better, I will create code that runs once per minute and then creates the “floods.html” with all a table of all of the floods and links to the charts.  It will also recreate the chart for any flood event that is in the database but doesn’t have a chart.

After the “ProcessEvents” run method has done its thing, there is a table in the database called “floodevents” that will have columns for the start,end and maxdepth of all of the floods.   To make things easy I would like a directory full of PNG files with the charts of the floods.  Each PNG file will contain one flood event and be named by the date of the flood.  To do this I create a function called “createCharts” that will:

• [Line 71] Iterate through the list of events
• [Lines ] Create a string that represents the filename
• [lines] If that filename doesn’t exist (for some reason it was never created or it was deleted) or the flood isn’t over (and the chart needs to be redrawn) then:
• [Lines 77-88] Create the chart of the flood

After this function has been run, there will be a directory full of charts.  I can then copy this directory to the Tomcat web apps directory

As long as you know all of the floods, and you have created PNGs of the flood events you might as well also create and cache the HTML of the flood events.  This is simply done in the ProcessEvents object with the method “createHtml”.  This method take a filename  that will be the name of the HTML table file, then creates an HTML table, iterates through each of the events printing one row per flood event.

 

As always you can get of all this code on the IOT Expert github site.