Flash boot, more cron, and caching.

I learned an interesting thing today. Depending on the bios of your system, you can boot your box from a flash drive (memory stick). The flash drive needs to be in the usb port when you start your box up though, otherwise the bios won't know that's it's available.

I learned one more thing about cron today. To get cron to run once daily, don't do this: '* 0 *** /opt/myscript.sh'. What will happen is cron will wait until midnight to run, and then it'll run every minute because you've used a '*' instead of a '0' in the minutes space. The correct format is '0 0 *** /opt/myscript.sh'.

I've pretty much finished up my little project with FusionCharts. However, I've noticed there a bit of an issue with caching. It's actually not very consistent. I can have 5 charts displaying 5 different data sets on one page, and 4 of them will update with new data, one of them will absolutely refuse to until I shut down the browser and open a new one. (I'm working with Firefox, by the way).

Firefox seems to really be in love with pages it's seen before. I haven't just seen this issue with FusionCharts. Some time ago we ran into a situation at work where clients were actually having to log in twice because the first login seemed to be ignored. What was happening was Firefox was overwriting the cookie for the login page with the favicon cookie. We had to examine every packet for each request to figure that one out. We used an obscure setting in the ajp connector in tomcat's server.xml file to resolve that one. 'emptySession=true' or something like that - I can't remember it off the top of my head right now - it was a couple of months ago.

Random assimilations and Business ideas

Today I learned that you can pass in parameters to .sql scripts that are destined to be run with sqlplus. It looks like this: 'sqlplus -s dbuser/dbpasswd@dbname @scriptname.sql param1 param2' and then in the sql file you output the params using &1 and &2. I was finding though that for the replacement sqlplus was being verbose and telling me about every replacement it made. I didn't like that so much, but couldn't figure out how to turn it off. I've already got 'set headers off' and 'set feedback off' set at the beginning of the script. I tried 'set logging off' but it didn't like that (because logging is set to off as a default I believe). Anyhow, the replacements were working.

With Oracle SQL, if you want to select back by a time interval, do something like this: 'select count(*) from my_log_table where logdatetime > current_date - interval '15' minute;' or you can use '- interval '6' hour' ... or '- interval '2' day' etc. Single quotes around the number!

Back to cron: to set cron to run every minute go '*/1 * * * * /scriptToBeRun.sh' Every 3 minutes: '*/3 * * * * /script2BRun.sh'

One problem I've run into with FusionCharts is the limitation of the Flash plugin to handle a big data dump. Put more than a few graphs with, say, 50 datapoints each on a page, and the browser hangs and the plugin throws our of memory errors.

Interesting IT Business Ideas:
- Reusing software development tools for other industries/applications. For example: other than the obvious issue with binary file types, why don't architects and lawyers use a repository like SVN, or Monotone? ( I left out the ones you have to pay for :-) We've tossed this idea around wondering if anybody has tried to market repositories this way....
- Becoming a freeware software consultant for small businesses. You can get everything from a good OS to all the 'openOffice' applications for free, not to mention what Google and others are putting on line (word processors and spreadsheets, etc), and universally accessible too! Seems to me if you're good at training, you can really help small businesses save a buck on software by showing them how to use all the free stuff out there. It wouldn't surprise me if people are doing this one already.
- write a GOOD, scalable, secure, extensible front end framework for web applications. There's a tonne of them out there now, but it seems like every one of them (Ruby, JSF, Struts, Facelets, Tapestry, SpringMVC, etc) has a downside. I've had conversations with a number of knowledgeable architect types and they agree that there is no good front end web solution out there right now. So, one could code a good freeware framework, consult using it, and then sell it to Red Hat (like the JBoss consultants did).

Got Something done today!

...or at least, it felt like it. After doing housekeeping with our production application yesterday at work, today was a 'sit down and code' day. Boy did it feel good. I had told myself that I had to get this charting solution finished today or it would turn into a waste of time. It turns out that FusionCharts are super easy to implement, and boy, do they look sharp.

In my 'solution', I'm using Nagios to provide the data, with its 'service-perfdata' process. That file gets big quickly. I just enabled it in the Nagios configuration on Friday last week, and I already had 12 Megs of data. Going through the Nagios documentation and forums, there doesn't appear to be any mechanism to 'roll' this file or archive it or buffer it.... It had me stumped for a while. Then I realized I could just do a simple 'tail -1000 service-perfdata.out > service-perfdata.out' in a shell script with a cron job, and presto - a simple fix.

So, mental note to self.... whenever you're coding a shell script (or any kind of script) that gets run by cron, make all the file paths in the script(s) absolute. I keep on running into this problem. Cron is ignorant about everybody's profile and position.

I just started coding with Perl this summer on this project, and I really like it. Working with arrays is tricky and not very intuitive. Otherwise, though, Perl is fantastic for whipping up something quick. Today I found out that you can use && and || in conditional 'if' statements. That was good. Also, something I've noticed in the past and ran into again today - the 'chop' and 'chomp' functions in perl don't seem to work like the documentation says they should. I ended up having to something like this to get rid of spaces '$var =~ s| ||g' - basically using sed (or the like) to get rid of spaces I didn't want. Perl's localtime() function to convert unix to to something readable worked slick for me today. Another thing I ran into not too long ago - the proper way to concatenate strings in Perl is with '.'

Rode my bike into work today. Just had the pedal axle fixed, and wow, what a difference. The aphids are all over the place right now. After a ride they are just plastered all over me. It's hard to not breathe them in while one rides.

Assumptions and Critical Thinking

A couple of weeks ago I programmed a DB load process that ran off a cron job. It ftp-ed data files from a public box to a local one, and then loaded the data based on .dat files that were extracted from the download, and .CTL files already on hand. I assumed this process worked correctly because every time I ran it manually it worked, and when I started it using cron, it 'looked' like it workded. It turned out that when it ran off the cron, it didn't do everything I wanted it to do. I set about debugging this today, and it turned out that my problem was very similar to my PLSQL problem from earlier this week.

Part of the Load process used a java program to created create the .dat files. The java worked fine when I ran it manually because the user I was running it with had JAVA_HOME set in it's profile. Cron runs differently. Even though my cron job su's to the proper user, doing the same thing manually and then checking with a 'who am i' command (which, by the way, gets different results than a 'whoami' command) returns a surprise. It's not my su'ed user. Adding JAVA_HOME into the script that gets run solved the problem.

Been looking at graphing solutions for a little thing I'm working on. GDchart seems usable. I might do some more work with it on Tuesday next week. FusionCharts seems very interesting as well. I've worked with Cewolf and JFreeCharts in the past, but I need something quicker right now.

Picked up a book called Th!nk off the discount shelf at Cole's today. I'm liking it so far. It's something of a rebuttal to another book called Blink!.