From November 2009

I just got home from a very impressive Massive Attack concert. I have to say that this show totally blew me away. The sound quality, the light show, the paragraphs on the LED wall, the band and all was an extremely uplifting experience. They played, among the older classic song, a couple of new ones from their Splitting the Atom EP and some very new ones. Some I never heard before, but they are simply amazing. More groovy then the older ones.

Also, the live versions of Teardrop and Angel are amazing and I really do wish that they make a live DVD of this tour. This is definitely a live band. I love when a band does not play the songs as on their records. I think just about every song at the concert was different then from the record. Psyche was very slow but at the same time you heard this underlining beat that made you want to move faster then her singing, if you know what I mean.

For this year, this was the last show. They are on tour again on February 8th. If you can, go see them, you won’t be disappointed. Here are some images from tonight and of their tour in general. Sorry, for the bad quality, but the iPhone does not have the best camera… (the images on the bottom are from their website). Update: This blog has some more high quality images.

I had to spent way too much time the last time to set up ImageMagick and Ghostscript together that I simply jump right in so you don’t have to waste time on this, like I did.

Creating thumbnails and images from a PDF is one of the most used features within Razuna. But the other day, when we run the normal convert command we were faced with an error message within our web application of:

Error: Uncaught exception ‘ImagickException’ with message ‘Postscript delegate failed....: No such file or directory

Of course, the first thing I did was to see if we have a error in the shell. Strangely, there was NO error when running the same command in the shell! Needless to say, I spent many hours looking for a solution, trying out different things from reinstalling ImageMagick and Ghostscript to looking all over the web for an answer.

In the end, it boiled down to that web applications (be it CFML, PHP, etc.), are looking for a different executable path then when you run command from the shell. Since Ghostscript installed the executable in the “/usr/local/bin/gs” path the web application could not find it. So the solution to “hours of pain” was to simply create a symbolic link to the “gs” library in the “/usr/bin” directory with:

ln -s /usr/local/bin/gs /usr/bin/gs

Hope this helps the next seeker!

I have to admit, I love databases. To hold data in a central place and be able to hook up any application from wherever you are to it, is just convenient to say the least. But there are moments I wish that vendors would “follow” a standard. I guess, when it came down to paging, every vendor thought his way of doing it is the best. No wonder, paging is the one SQL syntax that differs the most. Thus I dedicate, this post to paging and outlining the difference, meaning the solution to achieve it with Oracle, MySQL and MS SQL.

Paging with Oracle

Oracle knows of the internal column “ROWNUM”. Thus with “rownum” we can page trough the records, but have to do this with subselects. Look at the example;

SELECT rn, columns
   FROM (
  SELECT ROWNUM AS rn, columns
    FROM (
      SELECT columns
      FROM table
      WHERE id = 1
      AND something = 2
      ORDER BY columns
    WHERE ROWNUM <= 10
WHERE rn > 0

In this example we select the first 10 records, if you want to select the next 10 records then you will need to increase the values for “ROWNUM” with 20 and for “rn” to 10.

Paging with MySQL

There is one thing I like MySQL, that is the “LIMIT” clause. Not only can you limit how many records to retrieve, but can also add a offset to the limit clause. Thus we can do very elegant paging with “LIMIT offset, number”. Again, we limit the query below to return us 10 records:

SELECT columns
FROM table
WHERE id = 1
AND something = 2
ORDER BY columns
LIMIT 0, 10

Now, this will return the first 10 records. So, what if we want to do a paging here? Actually, quite easy, all we have to do is to increase the offset by one. It is important to know, that the offset start with a “0″ (think of it as the FIRST page), thus if we want to retrieve the next 10 records we use the limit with “LIMIT 1, 10″. This will give us the next 10 records. Elegant, no?

Paging with MS SQL

Now paging with MS SQL took me some time to figure out, since some said that MS SQL know of “rownumber” as well, but honestly, I couldn’t get anything to work with it. So the most easy method to do paging in MS SQL is to use the TOP syntax combined with a NOT IN subselect. Makes sense, right? Here is the example;

SELECT TOP 10 columns
FROM table
WHERE xxxx
  FROM table
  WHERE xxxx

As in the Oracle example above, if you would like to retrieve the next 10 records you would have to increase the TOP values by 10 records, meaning the FIRST TOP would have a value of 20 and the inner select TOP a value of 10.

So here you have it. How paging works for Oracle, MySQL and MS SQL.

My two other posts on FFmpeg entitled “Installing ffmpeg on CentOS 5” and “SELinux with ffmpeg” already explained in deep how to get FFmpeg up and running.

Unfortunately, today one of our servers just reported a plain:

ffmpeg: error while loading shared libraries: cannot open shared object file: No such file or directory

when trying to run any ffmpeg command. Now, what was that and foremost why? Especially, since it worked 2 days ago. I guess, “someone” must have done some update. In any case, it was a good lesson to reinstall ffmpeg and bring all libraries up to date.

So, since my last installation, some things must have obviously been changed behind the scenes, because when I tried to configure ffmpeg with the same commands I run into another error which was:

libx264 version must be &gt;= 0.78

Even thought I installed x264 from the latest GIT repository it still showed me the above error! Looking around the website I saw that the nightly snapshots differ in size a lot. So, either their nightly script is broken or something else is going on. In any case, I went with the x264-snapshot-20091031-2245 one.

Configured and installed it. Then did a “ldconfig -v” (in order to see that it really took the latest one) and went on with the ffmpeg configuration (I took the latest code from SVN (Revision 20525)) and low and behold, everything compiled and installed without problem.

Important: Update your libraries after the installation of ffmpeg again with “ldconfig”! Else you will get the “ffmpeg: error while loading shared libraries: ….” error again.

I run into a nasty issue the other day with “alike” directories in my web application.

That is, I had a copy of a “WEB-INF” directory called “WEB-INF–”. While my web application did not bother with copy of the WEB-INF directory, Tomcat threw all kinds of errors in the catalina.out log file. Also, I had some issues with Tomcat restarting and strange Java error messages, like:

com.nary.util.Localization.convertCharSetToCharEncoding(Unknown Source)
com.naryx.tagfusion.cfm.engine.cfEngine.getDefaultEncoding(Unknown Source)
com.naryx.tagfusion.cfm.engine.cfFormData.<init>(Unknown Source)
com.naryx.tagfusion.cfm.engine.cfFormData.<init>(Unknown Source)
com.naryx.tagfusion.cfm.engine.variableStore.<init>(Unknown Source)
com.naryx.tagfusion.cfm.engine.cfSession.<init>(Unknown Source)
com.naryx.tagfusion.cfm.engine.cfEngine.service(Unknown Source)
com.naryx.tagfusion.cfm.cfServlet.service(Unknown Source)

After browsing the log files, I saw that Tomcat tried to read the directory and threw a bunch of critical errors while reading those copied directories. I guess, Tomcat got totally confused and tried to overload libraries.

Lesson learned; Never have any copy of the WEB-INF folder within the web application again.

My favorite choice for running a Linux Server is CentOS, since it is based on the RedHat distribution you can rest assured you will get a top notch enterprise offering and stability. As with all things “enterprise” the priority is on stability and security and not on the latest code releases. This works 99% of the time, but sometimes you still need some update.

In the case of ImageMagick, CentOS comes with version 6.2.8, it was a bug that was fixed with PSD conversion and thus I needed to get the latest version installed. So, here are the steps to install ImageMagick 6.5.7 on CentOS 5.x. Mind you, that you will loose the internal patch upgrading from yum, but all you need to install to the next version is just to follow these steps again.

Uninstall current version
Uninstall the current version with:

yum erase ImageMagick*

This will uninstall ImageMagick 6.2.8 and if you have any other versions installed, like the devel one.

Install the needed dependencies
ImageMagick depends on a couple of additional libraries to convert to different formats. Let us just make sure, that they are all installed with:

yum install tcl-devel libpng-devel libjpeg-devel ghostscript-devel bzip2-devel freetype-devel libtiff-devel

Download and extract latest ImageMagick version
You can always get the latest ImageMagick version directly from their website. Code below will download and extract the file.

tar xcvf ImageMagick.tar.gz
cd ImageMagick-6.5.7-5

Configure and make ImageMagick
With the below configure command we are configuring ImageMagick with the most needed options. Feel free to adjust it to your needs. As always issue a “–help” to see all the available options.

configure --prefix=/usr/local --with-bzlib=yes --with-fontconfig=yes --with-freetype=yes --with-gslib=yes --with-gvc=yes --with-jpeg=yes --with-jp2=yes --with-png=yes --with-tiff=yes

Wait until configure has finished. At the end you will see all the enable options. When you think all went well issue:

Now is a good time to make yourself some coffee or continue coding your next big killer application because make will take some time to finish. When it’s done, issue:
make install

That’s it! You are done. Wasn’t so bad, was it? Check with:

convert --version

That ImageMagick is properly installed and that you got the current version up and running. If all went well you should see something similar to this:
Version: ImageMagick 6.5.7-5 2009-11-08 Q16
Copyright: Copyright (C) 1999-2009 ImageMagick Studio LLC