Wednesday, September 12, 2007

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/'. 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/'.

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.

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