The Creek: Creek Server 1.2

In the previous post, I talked about two problems that I had discovered in my system.  I addressed first one,  a serious bug in the data collection, last time.  In this post Ill address the slow performance of the website.  A common way to solve a performance problem is with a cache.  Instead of running the web page charts in real time, I will create them automatically every couple of minutes, then serve up a cached version.   In some ways this kind of sucks.  If I had known that I was going to go this way then there would have been 0 need of Tomcat and the Java Server Pages.  Oh well.

I start this process by copying the CreekHistory java object into the “getCreek” part of my project.  I then modify the main batch Java program, called “CreekServer” to understand the CreekHistory object.

Then I add a new function “createHtml” to the CreekHistory object.  This function creates the webpage with the current information on it.  Basically

1. A table of the last three hours [line 221-235]
2. Link to the current chart [line 237]
3. Link to the floods charts [line 237/238]

I then add the “Current” command to the “runi2c” batch program.

This program is run every 2 minutes by the crontab on the Raspberry Pi.  I picked 2 minutes because that is a good bit longer than each job takes to run in total.   Notice that I check to see if the jobs are already running and quit the “runi2c” job if the chart creation process is already going on.

At this point I have (at least) several things which are ugly

1. I don’t have a good back up system
2. I duplicate the “CreekHistory” object in the JSP as well as the “getCreek”
3. I duplicate the “readProperties” method into a bunch of different objects
4. I have 5Vs (I think) on the I2C pins of the Raspberry Pi, which I don’t understand why this isn’t a problem
5. I need to get the PSoC4 Bootloader Host going on the Raspberry Pi