Posted by Adam on April 21st, 2009 — Posted in General
I’ve been having problems with too much memory usage on the 256 slice I use to serve my web pages. I was using Apache and mod_php, and the Apache processes were growing large enough that I could only have 4 of them running at once, which killed any hope of decent concurrency. I decided to switch to using PHP with FastCGI and after some research decided to go with nginx. The switch has now been made and page generation is faster, the server can handle greater concurrency, and memory usage is under control.
I actually ended up using nginx, PHP, PHP-FPM, and xcache. I’m running 8 instances of PHP and 2 nginx worker processes. First, I got started by using the step-by-step instructions I found on someone’s blog. After the initial setup, there was still a lot of configuration to do, some of which was not trivial. Below are some notes from my experience:
1. When setting up FastCGI processes for PHP, make sure the firewall isn’t blocking access to the port the FastCGI servers are listening on. If your firewall is filtering packets to the port, you’ll get a “504 Gateway Time-out” page from nginx whenever you try to access a PHP page. To open up the port, if you’re using iptables, add something to your iptables startup script like this:
iptables -A INPUT -p tcp -s localhost --dport 9000 -j ACCEPT
2. Somewhere I saw a redirect example to eliminate the www from URLs that caused me to add this to the config file:
server {
listen 80;
server_name www.definingterms.com;
rewrite ^/(.*) http://definingterms.com/%1 permanent;
}
server {
listen 80 default;
server_name definingterms.com;
[...]
}
I’m not sure why I thought I needed this, but it was messing up the loading of static images on this blog. The right thing to do is just list multiple server_names for the host, and let WordPress handle the redirect:
server {
listen 80 default;
server_name definingterms.com www.definingterms.com;
[...]
}
3. Moving most of my sites from Apache to nginx was easy, but there was the problem of rewrite rules. A lot of the software I use (e.g. Wordpress, Mediawiki, Gallery) needs rewrite rules. If you’re using Apache, there’s always an example .htaccess file either in the documentation, or in some user forum. However, the nginx rewrite rules work differently, and you can’t always find an example config, so it took some time and brain power to get them all right. Actually, this is true for all parts of the nginx configuration. The English documentation is sparse and it’s sometimes hard to find examples of what you want to do.
4. nginx doesn’t have CGI support. If you’ve got those one or two sites that use non-PHP CGI, you’ll have to set up a FastCGI instance for each language you want to support. For example, I had a copy of ViewVC running, which is written in Python. With Apache, it was just using CGI. With nginx, I’d have to constantly run a whole Python FastCGI process for the rare event when someone wants to browse ViewVC.
In the end, I think the move to nginx was worth it purely for the performance gains, since it keeps me from having to pay for a heftier VM every month. But, it did take a fair amount of work and if I had slightly more complex needs, it might not have been a good fit for me.
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Posted by Adam on April 11th, 2009 — Posted in General
For quite a while now, I’ve been using a tiered password system for all of the websites where I have accounts. I knew this was bad practice, but it was easy. Recently there have been a number of stories about websites’ databases being leaked, which made me seriously consider doing something better. Password managers have never impressed me much, both because of the security issues of storing all of your passwords in a central location and the danger of losing the database and not being able to reconstruct it. But, when I came across PasswordMaker, I liked what I saw.
Instead of storing the passwords, they’re generated on the fly using a cryptographically secure method. The software is all open source, so you know what’s going on and can reconstruct it if you need to. Finally, there’s also a very convenient browser plugin for Firefox that I can install everywhere. So, I finally bit the bullet and got away from my tiered password system by moving all of my online accounts to using passwords generated by PasswordMaker.
If I’m going to go through all of that trouble, I might as well use a secure password, right? So I decided to use passwords with letters, numbers, and punctuation. That shouldn’t be anything special, it’s just the standard recommendation for password security. Some systems even have that as a minimum requirement.
What surprised me was that a huge number of websites I use don’t allow passwords with punctuation, 20% in fact. Out of the 97 sites where I tried to update my account, 19 of them would not allow it. These ranged from hip web 2.0 sites like digg.com to big, corporate sites like geico.com. Here’s the full list:
So now I have to use a different set of characters for my passwords at these sites. Fortunately, PasswordMaker lets me configure different profiles for different sites, so I can set it up once and forget about it. But, why should I have to do that, especially when it makes my account less secure?
It seems like it just requires more work from the website makers to restrict certain characters, and I can’t think of any good reason to do so. It might make sense to restrict passwords to ASCII characters if their system doesn’t fully support Unicode. But disallowing all punctuation just doesn’t make any sense. The programmers might be worried about allowing escape characters in passwords, but it seems like it would be just as much work to protect the system against them internally as making an additional demand on the user.
If we’re going to expect users to have secure passwords, we need to allow them to do so. I’d like to see the above sites change their password policies, and I want any new sites to allow long, complex passwords.
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Posted by Adam on April 2nd, 2009 — Posted in General
I like Dinosaur Comics. Since the drawings and panels are the same in every comic, I thought of the idea of trying to mix and match panels from different comics to see what comes out. It turns out, Ryan North had already done something similar, but I decided to implement my idea anyway. Here’s the result:
Dinosaur Remix
Dinosaur Remix lets you randomly mix together panels, but also lock in certain panels to make a comic you like. Then you can add clever alt text and save it or send it to a dinosaur-loving friend!
It’s written in Python, PHP, and JavaScript. It was my first chance to really use jQuery, which is just about as awesome as everyone says it is. All of the code is available on GitHub.
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Posted by Adam on October 3rd, 2008 — Posted in General
Not so long ago, the only help available when translating text from one language to another was a dictionary and a grammar book. That’s how it was when I started learning German. Now, there are a number of tools online to help you in your bilingual quest, but you have to be clever to get the most use out of them. My examples will be in German, but these techniques can be applied to most languages that have a strong online presence.
- A Good Dictionary - This is still your first line of defense against the hostile hoards of foreign words. For German, the best is clearly LEO. The reason it’s better than your trusty Langenscheidt’s or Oxford-Duden is that it’s user created and maintained, so you get idioms, slang, and current events.
- Google for Grammar - If you don’t know which of two or three possible variants is the correct one, Google all of them and see if one has many more hits than the rest. Important here: put the phrase in quotes. This is especially good for things like which preposition to use with more common words. Let’s say you want to translate “I’m going to Chicago.” Which preposition do you use? Try searching for a similar phrase (in this case, altered for geographic relevance) and see if one stands out. Go to google.de and click the “Seiten auf Deutsch” (Pages in German) button. Then try three reasonable guesses:
- “gehe zu Berlin”: 7 hits
- “gehe nach Berlin”: 2,890 hits
- “gehe bei Berlin”: 1 hit
It looks like we have a clear winner. You can be pretty confident translating your sentence as “Ich gehe nach Chicago”. However, this isn’t always foolproof. If you had searched for “gehe in Berlin” you would have gotten 576 hits and the results wouldn’t have been quite as clear. But, after reading the first few hits, you’d have realized that it’s not what you’re looking for.
- Wikipedia - This is especially good for technical terms. Suppose you want to talk about the famous Quicksort algorithm in German. LEO won’t help you. So, go to the English Wikipedia page for Quicksort. Then, look down on the left side of the page in the “languages” box. Click “Deutsch” (if it exists) and you’ll be taken to the equivalent German page. In this case, you find out that Quicksort is the same in English and German, so now you can (not) translate it with confidence.
- Names - You read a foreign name and you’re not sure what gender it is. Sometimes that doesn’t matter, but if you want to talk about this person, it sure is useful to be able to use pronouns. So, to figure it out, do a Google image search, preferably at the Google site for the country, and look at the results. Example: Johannes vs. Johanna (I read this somewhere online, but I’m not sure where. It’s especially helpful for Asian names.)
- Machine Translation - I list this one last because it’s generally the least helpful. The two main free sites are Google Translate and Babelfish. These sites are slowly getting better, but right now they’re still of limited value. They’re good if you want to read something in a language you don’t know at all or it would take you a long time to do the translation yourself and you just want to get the gist of the text.
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Posted by Adam on July 25th, 2008 — Posted in General
Yesterday, I came across this wonderful sentence while reading “Das Parfum” by Patrick Süskind:
Und wenn er auch wußte, daß er den Besitz dieses Duftes mit seinem anschließenden Verlust würde entsetzlich teuer bezahlen müssen, so schienen ihm doch Besitz und Verlust begehrenswerter als der lapidare Verzicht auf beides.
This can be roughly translated as:
And even knowing that the possession of this scent would require him to subsequently pay the terribly high price of its loss, the possession and loss seemed more desirable than the lapidary relinquishment of both.
The interesting part of the sentence is “daß er den Besitz dieses Duftes mit seinem anschließenden Verlust würde entsetzlich teuer bezahlen müssen”. In a word-for-word translation, this is “that he the possession of this scent with its subsequent loss would terribly expensive pay have to”.
In general, English and German have similar sentence structure and word order. But occasionally you see a German sentence that makes you think the author took a sentence, tied it in a knot, and threw it onto the page. Translation of such sentences requires not only translating the meaning into English, but untying the knot so that the English-speaking reader can parse it. And that’s the fun part.
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Posted by Adam on March 31st, 2008 — Posted in General
Here is a simple example of drawing pixels (rather than paths) to a canvas element with JavaScript. The algorithm goes left to right and draws across the canvas, and for each pixel column draws two blue pixels, one for the top half of the circle and one for the bottom half. Then, because this results in sparse drawing for the far left and right edges of the circle, it does another pass from top to bottom, doing the same thing with red pixels. The result is a circle with gradient colors, showing which pass drew more of the circle.
It’s been tested in Firefox 2 and 3, and I think it should work in recent versions of Safari and Opera.
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Posted by Adam on March 25th, 2008 — Posted in General
I wrote a few weeks ago about how Rotten Tomatoes did a redesign of their site that broke my primary use case. Since then, they have done an update that makes things a lot better for me, though it’s still not as convenient as the original design. Right now, if you hover over any of the tabs for different groups of ratings, you get a popup that tells you that group’s percentage of positive reviews. In my case, I’m interested in the Top Critics group:
While this does allow you to compare the percentages much more easily, it’s not quite perfect. On the plus side, it displays both percentages at the same time and it’s quite easy to discover. Anyone who is interested in the Top Critics information will move to click on the tab header, and when they move the pointer over it, they’ll see the popup.
On the downside, it does require fairly precise mousing (and holding the mouse still) for the whole time you want to read the number. This makes it much less accessible to those who have trouble acquiring small targets and keeping the pointer still, such as the elderly or disabled using a mouse. Additionally, you have to use the pointer to see it, which makes it inaccessible to those navigating with just the keyboard.
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Posted by Adam on March 24th, 2008 — Posted in General
Ticketmaster has long charged too much in service fees, but this is the first time I’ve seen them almost double the price of a ticket. This is what I saw this morning:
Ticketmaster made the price go from $15.00 to $27.30, and that’s if I print off the ticket on my printer. If I wanted to have a ticket mailed to me, it would cost even more. That’s just out of control. When I saw that, I closed my browser window and decided to buy a ticket at the door and risk it selling out.
In contrast, I had a very good experience at etix, where they charged a $2.50 service fee per ticket. I think that’s reasonable and I wish more venues and artists would use etix and force Ticketmaster to respond to some competition.
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Posted by Adam on February 22nd, 2008 — Posted in General
I haven’t really gotten into the whole online backup thing. I’m not sure I want to spend a week uploading my files on my cable Internet connection, only to depend on some company keeping my files safe and private.
But, yesterday it was announced that Microsoft’s new online backup/file sharing service has come out of beta. It’s free and all you need is a Windows LiveID. I have one of those, so I thought I’d take a minute to try it out.
I was tweaking my .bashrc a couple of days ago, so I thought I’d upload that. It’s a nice small file, so it shouldn’t take long to upload, and it might be useful to have it accessible from a web browser.
So, I downloaded it to my local machine. It was pretty easy to figure out how to upload it to a folder on my SkyDrive, and I just had to pick it from the hard drive using a file browser.
Just click upload and we’re all set!
Clicking on the “Learn why uploading may fail” link was not helpful. My file doesn’t violate any of the rules on the page.
But then I remembered, Windows doesn’t like it if you start a filename with a dot. You can copy a file around that starts with a dot, but you can’t rename files in Windows Explorer to start with dots. Of course, the service surely uses Windows servers, so I bet it has something to do with that. How could I find out if that was the real problem? How about renaming the file to not have the dot and retry?
Wonderful. But now I want to be able to download it with the real filename, so I can just drop it on a Linux machine and go. So I tried to rename it.
Oh, now I get a real error message. At least I know what the problem is.
But that’s a pretty silly restriction to not allow filenames that start or end with dots. I understand that there’s an arbitrary restriction on those files from Windows Explorer, but you can store dotfiles on NTFS partitions without a problem. So the programmers had to add extra code to explicitly disallow these files for no good reason. Why?
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Posted by Adam on January 29th, 2008 — Posted in General
I saw Night Watch a few days ago. The film wasn’t bad; it had great cinematography and decent effects. Sadly, the story was a dim shadow of the one in the book, but I suppose that’s to be expected.
The most interesting part of the movie, for me, was the subtitling. I watched the DVD with the Russian audio and English subtitles. The subtitles were beautiful, dynamic, and surprising. The font was nice to look at and easy to read, even on my 27″ SDTV. The words appeared and disappeared in unexpected ways on the screen. For example, sometimes they would be revealed from behind a character as he moved across the screen. Other times, multiple phrases would fade in and out at different times at different places on the screen. They were not constrained to the bottom of the screen: they would appear at any place on the screen. During conversations, the lines of each character would appear near the person on the screen, so it was easy to tell who said what. One of the most interesting presentations was of “The Call”, the siren song of the vampire to her victim. The words (e.g. “Come to me”) would appear on the screen blood-red, then swirl away like drops in a stream.
Time magazine has an interesting writeup about subtitles that mentions Night Watch, and has a poor quality screenshot of the subtitling of The Call. A DVD Times post has a number of other screenshots that show the subtitles.
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