Blake Miner's Blog

This blog post will cover the varying levels of data caching and data persistence provided by various operating systems and database systems. Cache  - A device placed in front of another storage device that is used for temporary storage of data.  The use of a hardware cache is often transparent to the end user and is generally smaller, faster, and less persistent than the backed storage device.  Rather than reading/writing from/to a slower storage device (i.e. a hard disk), we read/write from/to the cache (i.e. RAM, NVRAM, etc.). Reading from a cache is simple.  If the datum we requested is in the cache, we simply read it from the cache.  If not, we need to retrieve the datum from the storage device and place it into the cache (often a much slower operation). There are different policies when we write to the cache, though... Write-Through Cache Policy  - When using this policy, writing over the cache also writes over the data on the backed storage device... synchronously and si

The purpose of this blog post is for me to ramble about Meteor, a new open-source platform for building JavaScript web applications in Node.js. Likes: JavaScript (Node.js) - If you know me, you know that I love JavaScript! Live Binding / Live Page Updates - IMHO, this is the best feature in Meteor.  View templates update automatically when data in your model changes.  Very cool! Data Synchronization - I like that the client and server communicate and synchronize data, but having database APIs on the client might not be the way to go... Latency Compensation - Cool Hot Code Pushes - A shiny new toy.  It's cool, but I'm not quite sure how useful this will be to most developers. Dislikes: Database APIs on the client - Okay, yes... having access to your database from any web browser can be nice for programming, but it makes it that much easier for a malicious person to compromise sensitive data.  If someone gains unauthorized access to your system (i.e. someone's

As a web developer, generally speaking, you should consider supporting the following browsers (at the time of this writing): Chrome (latest) - the browser that sets the bar for the others; you should be using it and supporting it Internet Explorer 9+ - the browser that finally caught up with the times a bit; basically, a Chrome wannabe.  I still say that IE sucks... even if it really doesn't anymore.  Yes... I'm sour about IE8 and below. Internet Explorer 8 - the old, sad browser that we sadly still have to support for a while.  CSS 3 is not well-supported here, so we use projects like CSS3 PIE or whatever.  By the way... IE8 sucks.  I can't wait until this comes off of the list. Firefox (latest) - the browser that was once awesome and has sadly suffered recently because it's slower than Chrome... but hey, lots of people still use it. Safari (latest) - Watch out for Safari as more iPhones, iPads, Macs, and more overly-priced Apple products flood the market a

Two nights ago, a leap second was added to system clocks running Linux, causing much-undesired havoc. On July 1st at 12:00 AM UTC, both of my Amazon EC2 instances fired an alarm indicating high CPU usage. I investigated to find that it was MySQL that was eating all of the CPU. I logged in and ran SHOW PROCESSLIST to find that no queries were running (these servers don't get hit much after business hours). I stopped MySQL, CPU utilization dropped back down to 1-3% (as normal). I restarted MySQL, and it started eating a lot of CPU again. Then, I restarted the server (shutdown -r now), and the problem went away. Both servers had the exact same problem (running Ubuntu 12.04 LTS). In my particular case, MySQL began eating CPU, even after being restarted.  It was a livelock. The only relevant item I saw in the syslog was: Jun 30 23:59:59 hostname kernel: [14152976.187987] Clock: inserting leap second 23:59:60 UTC Oh yeah... leap seconds.  Those are super important.

One thing I never really liked about JavaScript was the way it treats null , undefined , and false .  It's just, well... weird. Another example of this that I discovered today... null is greater than or equal to zero, but it's not greater than 0, nor is it equal to zero.  WTF? null > 0 false null >= 0 true null == 0 false

Carla and I are planning on getting married sometime in October next year.  We need to pick a date, and that decision may  involve some science and mathematics.  :) For example, we want the weather to be nice.  To be more precise, we'd like the high temperature for the wedding day to be between 60 and 80 degrees Fahrenheit.  Obviously, we have both lived in Ohio our entire lives, and we have a pretty good idea of what the weather will be like.  We both hypothesised that October was a "hit or miss" sort of month; it could be cold, or it could be nice. But, for me, a simple hypothesis was not enough; I really wanted to know the probabilities of decent weather based on historical weather data.  Many websites on the Internet (i.e. almanac.com) charge you to review historical weather data, but Carla and I discovered a cool page on cleveland.com that provided exactly what we wanted.  I loaded the historical temperature data from 1903 to 2011 for two particular dates of int

http://xkcd.com/844/

Email sucks, and it's incredibly broken! I mean.... sending an email in Gmail is obviously quite trivial.  But working with SMTP and email servers... not so much. Most people take email for granted.  It was invented way before I was born... way before Windows 95, Windows 3.1, or even DOS!  What?!?! Yeah... so not surprisingly, email sucks.  Remember... DOS sucked and Windows 95 sucked (not at that time, of course).  In fact, email sucks so much, it makes me sad that we still use it.  It's almost embarrassing... almost as embarrassing as Internet Explorer. Don't believe me?  Just go to the Postfix mail server documentation page.  Their website is straight out of the late-80's.  I think there might be one  image on the entire website?  After all, we can't have those 4.8K modems downloading images... it will take too long, tie up your phone line, and waste too much bandwidth.  :) So, why am I complaining about email?  Yeah... so all I wanted to do was send ma

I'm pretty sure that if I've played 100 games and won exactly 1 of them, my winning percentage should be 1%. I might be wrong, though.  There is no rounding error when you do 1/100 * 100%.  Single-precision floating point number rounding error?  For some reason, I doubt it... Weird... and stupid... EDIT:  Wrote a C program to make sure that Microsoft's Minesweeper has a bug. $ cat main.c #include <stdio.h> int main() {         float x = 1.0 / 100 * 100;         printf("%f\n", x);         return 0; } $ gcc main.c; ./a.out 1.000000 ... Yep... sure does.

I recently asked  this question on StackOverflow  about how to join to a derived table using an index.  I found out that even if your derived table is generated with tables that use all of the proper indexes, and you try to join that derived table to a base table in your outer query, no indexes are used.  Ever... So, let's start with a contrived example (as we often do)... SELECT * FROM t1 JOIN (SELECT * FROM t2) AS derived_t2 ON t1.f1=derived_t2.f1; OK... so let me get this straight... even if t1.f1 and  t2.f1  are indexed, the join will still be a full table scan?  You betcha! Let me say that again...  whenever you write a subquery and try to join the derived table to your outer query tables, no indexes are ever used .  It's a full table scan. So, I think to myself... "Wow... so that's really stupid, actually... because I have tables that only have a few thousand rows in them, and the query performance is shit.  Like... over 2 seconds... terrible and u

If you're like me, then you are probably building web applications using Node.JS and MySQL (and maybe Redis, too).  If so, you're probably going to need transactions, and you've probably already noticed that the current version of node-mysql doesn't support transactions yet.  :( But that's OK because I have a solution for you.  Check out node-mysql-queues on github .  This project provides pretty good support for MySQL transactions with a fairly simple API.  There are a couple of things to remember, though.  For one, Node.JS is very "callback-centric," so when executing a series of queries, you would normally chain the queries together with a series of callbacks.  node-mysql sort of changes this model, by allowing you to place queries on a queue to be executed in order.  If you only care about doing something when all of your queries are done, you can simply put your callback in the final query.  node-mysql-queues allows you to do the same sort of thing