Artem Russakovskii's programming and technology blog

Updated: July 29th, 2021

Introduction

Screen is awesome. Once you become comfortable navigating around it, you start using it ALL the time. No more dropped sessions, no having 10 Putty windows open at the same time, no more nohup.

However, with default screen settings I've always felt a bit lost and out of place, mostly because there was no "taskbar" with a bird's eye view of all windows. Pressing ctrl-a, " really does get annoying fast (that's the command that brings up the window selector – screenshot below).

So instead I modded my screen to have a "taskbar" which sits at the bottom of screen and adds:

• the name of each window
• a clear marking of window states, such as
  • the currently active window

…

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Updated: July 30th, 2021

The Problem

I am throwing up a quick post about a relatively cryptic error that Solr started throwing the other day here at Plaxo. After happily running for a few days, I suddenly started getting pages about failed Solr indexing.

Upon closer examination, I saw the following repeatedly in the log file:

catalina.2009-09-18.log:SEVERE: java.io.IOException: directory 'DATADIR/index'
exists and is a directory, but cannot be listed: list() returned null

I tried to see if sending an OPTIMIZE command would help but the server returned the same response.

Digging Deeper

The reason was these errors was quite simple – Solr was running …

Updated: July 30th, 2021

In the past few weeks I've been implementing advanced search at Plaxo, working quite closely with Solr enterprise search server. Today, I saw this relatively detailed comparison between Solr and its main competitor Sphinx (full credit goes to StackOverflow user mausch who had been using Solr for the past 2 years). For those still confused, Solr and Sphinx are similar to MySQL FULLTEXT search, or for those even more confused, think Google (yeah, this is a bit of a stretch, I know).

Similarities

• Both Solr and Sphinx satisfy all of your requirements. They're fast and designed to index and search large bodies of data efficiently.
• Both have a long list of high-traffic sites using them (Solr, Sphinx

…

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Updated: September 16th, 2012

Introduction

StackOverflow is an amazing site for coding questions. It was created by Joel Spolsky of joelonsoftware.com, Jeff Atwood of codinghorror.com, and some other incredibly smart guys who truly care about user experience. I have been a total fan of SO since it went mainstream and it's now a borderline addiction (you can see my StackOverflow badge on the right sidebar).

The Story

Update 6/21/09: This server is currently under very heavy load (10-200), even with caching plugins enabled. Please bear with me as I try to resolve the situation.

Feel free to bookmark this page and return to it later when the fires have been put out.

Update 06/21/09: I think I've got the situation …

Updated: October 6th, 2009

Introduction

Every time I have to deal with svn:externals in SVN, I forget the command line syntax. Every single damn time. Normally, I use SVN GUI clients, such as SmartSVN, which make it very simple to add an svn:externals property. But for command line, it always takes looking at 25 different sites on google, which are all incredibly unhelpful for this question for some reason. Trying "svn help propset" on the command line was bloated and equally useless.

So this time I needed to write it down and make sure everyone who needed help with svn:externals would find exactly what they need here. I hope this page will soon come up on top of all the unhelpful results on …

Updated: June 10th, 2009

* Lightning Fast is a blatant exaggeration. Got you to look though, didn't it?

Introduction

Whether you are a web developer or a self-hosting business owner, the only excuse for not activating compression capabilities of your web server can be that you didn't know about it. And now that you are reading this, there is no excuse left at all.

Here is how big a single page of this blog was before compression was enabled on CSS and Javascript files (computed by YSlow):

And here it is after compression:

As you see, the difference is quite substantial – almost 30% savings.

Compressing your HTML, XML, Javascript, CSS, etc pages will mean less data transferred between the server and the …

The Problem

I use a lot of extensions. A LOT. They slow down my Firefox while giving something useful in return. Most of them are harmless and do not affect the speed too much but there are select few that are just CPU, memory, and performance hogs.

Until Firefox gets an extension manager that can show what the impact from each extension on time/CPU/memory is, one can resort to guessing, disabling, testing, and looking for clues to find these conniving little bastards.

Anyway, so where was I? Recently, my Firefox became increasingly unresponsive, especially when switching tabs. After some time, it was a pain to switch tabs altogether, so I had to resort to restarting the browser, only to …

Introduction

A question I recently saw on Stack Overflow titled Faster way to delete matching [database] rows? prompted me to organize my thoughts and observations on the subject and quickly jot them down here.

Here is the brief description of the task: say, you have 2 MySQL tables a and b. The tables contain the same type of data, for example log entries. Now you want to delete all or a subset of the entries in table a that exist in table b.

Solutions Suggested By Others

DELETE FROM a WHERE EXISTS (SELECT b.id FROM b WHERE b.id = a.id);

DELETE a 

Updated: October 6th, 2009

No matter what programming language you use, there comes a time when you need to search for a file somewhere on the file system. Here, I want to talk about accomplishing this task in Perl. There are many ways of doing so, most of them boring, but I want to discuss the fun and elegant way – using File::Find::Rule.

Let me briefly discuss some of the other methods first.

Limited

Using glob() (or <>, TODO verify) you can find files in a single directory, using only the limited shell wildcard support. For example,

1

my @files = glob("tmp*");

…

Updated: June 24th, 2020

Introduction

If you, like me, are building or thinking of implementing a MySQL-powered application that has any need for prioritizing selecting certain data over other data, this article is for you.

Example

As a real world example, consider a queue-like video processing system. Your application receives new videos and processes them. The volume of incoming videos can at times be higher than the processing rate because the process is CPU bound, so occasionally a pretty long queue may form. You will try to process them as fast as you can but…

…

Updated: June 9th, 2009

Problem

While writing a 1093985th Perl script the other day I was facing the following dilemma:

• Let’s say there is a local library, called TheUberLib.pm. It is so uber that most of my scripts, located all over the machine, include it.
• Now, let’s also say that there’s an even more uberly important binary called run_me_now_or_you_will_die but the only way to find it is by using a relative path to the aforementioned TheUberLib.pm, for example ../bin (RELATIVE TO TheUberLib.pm).
• I don’t want to hardcode the path to run_me_now_or_you_will_die because it can be different on multiple machines and the code wouldn’t be robust enough – all I know is that the path is relative to an included library.

So …

Updated: July 1st, 2010

From time to time my, still curious, mind accumulates a variety of questions and concerns which it has to spill onto the pages of this blog. How random are these? Pretty damn random, and I need to see some answers, quick. Oh, and I’m deliberately not searching Google, as I want to facilitate discussion. What fun would it be if I just looked up all these?

Password Protected Garage Door Remotes

As a paranoid person and a recent homeowner, I started to wonder how safe I actually am in my house. Consider this likely scenario that nobody seems to be concerned with:

I park my car outside for one night and don’t take out my portable garage door remote, the

…

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Updated: September 16th, 2012

Today I had to swap 2 columns in one of my MySQL tables. The task, which seems easily accomplishable by a temp variable, proved to be a bit harder to complete. But only just a bit.

Here are my findings:

1. The

   UPDATE swap_test SET x=y, y=x;

   UPDATE swap_test SET x=y, y=x;

   approach doesn't work, as it'll just set both values to y.

   PostgreSQL seems to handle this query differently, as it apparently uses the old values throughout the whole query. [Reference]

2. Here's a method that uses a temporary variable. Thanks to Antony from the comments for the "IS NOT NULL" tweak. Without it, the query works unpredictably. See the table schema at the end of the post. This

…

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Updated: June 24th, 2020

Introduction

Clickjacking is a malicious technique of tricking web users into revealing confidential information or taking control of their computer while clicking on seemingly innocuous web pages. A vulnerability across a variety of browsers and platforms, a clickjacking takes the form of embedded code or script that can execute without the user's knowledge, such as clicking on a button that appears to perform another function (credit: Wikipedia).

Clickjacking is hard to combat. From a technical standpoint, the attack is executed using a combination of CSS and iFrames, which are both harmless web technologies, and relies mostly on tricking users by means of social engineering. Additionally, the only server side technique against clickjacking known to me is “frame breaking…

Updated: July 30th, 2021

During my day-to-day activities, I use the Bash shell a lot. My #1 policy is to optimize the most frequently used activities as much as possible, so I’ve compiled these handy bash shortcuts and hints (tested in SecureCRT on Windows and Konsole on Linux). The article only touches on the default bash mode – emacs, not vi. If you haven’t specifically assigned your shell mode to vi (set –o vi), you’re almost certainly using the emacs mode. Learn these and your shell productivity will skyrocket, I guarantee it.

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