Sunday, December 23, 2007

Blog Archive Carousel Widget

I've played around with blogspots' widget system and came up with a nice blog archive carousel widget. The widget is based on the standard blog archive widget and jcarousel, a jquery plugin.
DISCLAIMER: Use at your own discretion.
How to use:

  • Go to your blog's Template -> Edit HTML.

  • Download Full Template for backup and save it somewhere you'll remember.

  • Go go Template -> Page elements and add a blog archive widget, save the page.

  • Go back to Template -> Edit HTML.

  • Make sure Expand Widget Templates is not checked.

  • Just below the <data:blog.pagetitle/> add the code below

    <!-- archive carousel -->
    <script src=''/>
    <script src=''/>
    <script type='text/javascript'>
    jQuery(document).ready(function() {
    jQuery('#mycarousel').jcarousel({ vertical: true, scroll: 3}); });
    <!-- //archive carousel -->

  • At the end of the <skin> section, just above the ]]></b:skin>add the code below

    /* new archive */
    UL.posts LI { font-size:80%; width:170px; padding-right:2px; border-bottom:1px solid silver;}
    .jcarousel-container { position: relative; }
    .jcarousel-clip { z-index: 2; padding: 0; margin: 0; overflow: hidden; position: relative; }
    .jcarousel-list { z-index: 1; overflow: hidden; position: relative; top: 0; left: 0; margin: 0; padding: 0; }
    .jcarousel-item { float: left; list-style: none; width: 170px; xheight: 18px; }
    .jcarousel-next { z-index: 3; display: none; }
    .jcarousel-prev { z-index: 3; display: none; }
    .jcarousel-skin-tango.jcarousel-container { -moz-border-radius: 10px; background: #F0F6F9; border: 1px solid #346F97; }
    .jcarousel-skin-tango.jcarousel-container-vertical { width: 170px; height: 170px; padding: 40px 20px; }
    .jcarousel-skin-tango .jcarousel-clip-vertical { width: 190px; height: 170px; }
    .jcarousel-skin-tango .jcarousel-item { width: 170px; xheight: 18px; }
    .jcarousel-skin-tango .jcarousel-item-vertical { margin-bottom: 10px; }
    .jcarousel-skin-tango .jcarousel-item-placeholder { background: #fff; color: #000; }
    .jcarousel-skin-tango .jcarousel-next-vertical { position: absolute; bottom: 5px; left: 99px; width: 32px; height: 32px; cursor: pointer; background: transparent url( no-repeat 0 0; }
    .jcarousel-skin-tango .jcarousel-next-vertical:hover { background-position: 0 -32px; }
    .jcarousel-skin-tango .jcarousel-next-vertical:active { background-position: 0 -64px; }
    .jcarousel-skin-tango .jcarousel-next-disabled-vertical,
    .jcarousel-skin-tango .jcarousel-next-disabled-vertical:hover,
    .jcarousel-skin-tango .jcarousel-next-disabled-vertical:active { cursor: default; background-position: 0 -96px; }
    .jcarousel-skin-tango .jcarousel-prev-vertical { position: absolute; top: 5px; left: 99px; width: 32px; height: 32px; cursor: pointer; background: transparent url( no-repeat 0 0; }
    .jcarousel-skin-tango .jcarousel-prev-vertical:hover { background-position: 0 -32px; }
    .jcarousel-skin-tango .jcarousel-prev-vertical:active { background-position: 0 -64px; }
    .jcarousel-skin-tango .jcarousel-prev-disabled-vertical,
    .jcarousel-skin-tango .jcarousel-prev-disabled-vertical:hover,
    .jcarousel-skin-tango .jcarousel-prev-disabled-vertical:active { cursor: default; background-position: 0 -96px; }

  • find the
    <b:widget id="'BlogArchive1'" locked="'false'" title="'Blog" type="'BlogArchive'/">
    and replace this line with the following code

    <b:widget id='BlogArchiveCarousel' locked='false' title='Blog Archive' type='BlogArchive'>
    <b:includable id='toggle' var='interval'>
    <b:if cond='data:interval.toggleId'>
    <b:if cond='data:interval.expclass == "expanded"'>
    <a class='toggle' expr:href='data:widget.actionUrl + "&amp;action=toggle" + "&amp;dir=close&amp;toggle=" + data:interval.toggleId + "&amp;toggleopen=" + data:toggleopen'>
    <span class='zippy toggle-open'>&#9660; </span>
    <a class='toggle' expr:href='data:widget.actionUrl + "&amp;action=toggle" + "&amp;dir=open&amp;toggle=" + data:interval.toggleId + "&amp;toggleopen=" + data:toggleopen'>
    <span class='zippy'>
    <b:if cond='data:blog.languageDirection == "rtl"'>
    <b:includable id='interval' var='intervalData'>
    <b:loop values='data:intervalData' var='i'>
    <b:if cond=''>
    <b:include data='' name='interval'/>
    <b:if cond='data:i.posts'>
    <b:include data='i.posts' name='posts'/>
    <b:includable id='menu' var='data'>
    <select expr:id='data:widget.instanceId + "_ArchiveMenu"'>
    <option value=''><data:title/></option>
    <b:loop values='data:data' var='i'>
    <option expr:value='data:i.url'><> (<>)</option>
    <b:includable id='flat' var='data'>
    <b:loop values='data:data' var='i'>
    <li class='archivedate'>
    <a expr:href='data:i.url'><></a> (<>)
    <b:includable id='posts' var='posts'>
    <b:loop values='data:posts' var='i'>
    <li>&amp;nbsp;<a expr:href='data:i.url'><data:i.title/></a></li>
    <b:includable id='main'>
    <b:if cond='data:title'>
    <div class='widget-content'>
    <div id='ArchiveList'>
    <div expr:id='data:widget.instanceId + "_ArchiveList"'>
    <ul class='jcarousel-skin-tango posts' id='mycarousel'>
    <b:include data='data' name='interval'/>
    <b:include name='quickedit'/>

  • Preview the template

  • If all looks well, you can save your template. You might get prompted to confirm that BlogArchive1 will be deleted. Allow it (we changed it's name to "BlogArchiveCarousel")

Tuesday, December 18, 2007

MySQL 5.1 Clustering Might Just Actually Work

As I previously wrote mysql 5.0 clustering was a big issue for us since all data as placed in memory. It seems that mysql 5.1 clustering is going to be much better, including the ability to store non-index columns on disk (indexes and indexed columns are still stored in-memory), do (limited) cluster-to-cluster replication, and better varchar support for memory columns. Pitty it's only release candidate at the moment. can't wait for the GA to come out.

Monday, December 17, 2007

Tomcat Cannot assign requested address

I had a very strange error today when I tried to startup tomcat on some linux box that used to work. Since google was no help I figured I should document this somewhere.

Tomcat startup gave the notorious Cannot assign requested address. This usually means that another process is listening on the same port on this machine. I started with ps -ef grep java to make sure that no other tomcat process was running on the machine. Nothing.

I suspected that maybe some other web server was holding the port, but netstat -an showed that nothing binds this address. Moreover, telnet localhost 80 showed that no one is listening.

Looking at the server.xml I found out that the connector was binding to the hostname "demoserver" on port 80.

<Connector className="org.apache.coyote.tomcat4.CoyoteConnector"
address="demoserver" port="80"
minProcessors="5" maxProcessors="75"
enableLookups="true" redirectPort="8443"
acceptCount="100" debug="0" connectionTimeout="20000"
useURIValidationHack="false" disableUploadTimeout="true" />

trying to ping demoserver gave me errors, but nslookup demoserver gave me the right ip address.

After a few minutes I noticed that some clown added demoserver to /etc/hosts with the wrong ip address. Fixing /etc/hosts to have the right ip address for demoserver made tomcat work smooth and nice.

Sunday, December 9, 2007

PHP Allowed memory size of 8388608 bytes exhausted

If you try to install PHP PECL package and get an "Allowed memory size of 8388608 bytes exhausted" you should know that pecl ignores php.ini memory_limit directive. As suggested in
this post, you should use pear instead of pecl to install you package. For example, instead of doing

[root@hostname tmp]# pecl -v install APC

you should do

[root@hostname tmp]# pecl -v download APC
[root@hostname tmp]# pear -v install APC-3.0.15.tgz

Wednesday, November 21, 2007

Java TTL Cache, the Quick and Dirty Way

There are many caching systems in java. I really like some of them (especially Ian Schumacher's LRU Cache). But sometimes you just to drop a quick few lines to get something in a local cache. Here is one way of doing it:

private static Map urlItemCache = Collections.synchronizedMap(new HashMap());
private static Map urlItemCacheTtl = Collections.synchronizedMap(new HashMap());
private static final long TTL=1000*60*60;//one hour in milliseconds

public static String findItemByUrl( String url) {
String item="";
Long now=Long.valueOf(Calendar.getInstance().getTimeInMillis());

//try to get the item from the local cache
item = urlItemCache.get(url);
if ( !isEmpty(item)) {
//urlItemCacheTtl.get(url) is guaranteed to have a value, since it's added at the same time urlItemCache is.
if (now.longValue() - urlItemCacheTtl.get(url).longValue() < TTL ) {
urlItemCacheTtl.put(url, now); //see comment below
return item;
} else {
//not found in cache
//... do you application magic here to get the item ...
if ( !isEmpty(item) ) {
urlItemCache.put(url, item); //add to local cache
urlItemCacheTtl.put(url, now);
return item;
} //else
return null;

Wednesday, September 26, 2007

Reload webapp from ant script

A co-worker asked me how he can reload a web-application from an ant script. GDS was very helpfull finding the line in an old ant script I used to use. In the example below you might want to define $project.output

<property name="project.output" value="WEB-INF/classes"/>
<!-- reload the current webapp to refresh the classes that we just changed -->
<concat><fileset dir="${project.output}/log" includes="reload.log"/></concat>

Monday, September 24, 2007

RequestDispatcher.forward() and filters

If you have read this post then you probably know that if you use RequestDispatcher.forward() (or RequestDispatcher.include()) the filter chain does not get re-called for the forwarded servlet/jsp. However, if you read more closely you see that Craig was talking about the 2.3 servlet spec. Since we are using tomcat 5.5 which conforms to the 2.4 spec, you should know that there's a new <dispatcher> element in the deployment descriptor with possible values REQUEST, FORWARD, INCLUDE, and ERROR. You can add any number of entries to a <filter-mapping> tag and individually decide which filter gets called when. An Example:



Simpler GUI for Jad, The Java Decompiler from As I Learn

This is definitely the most useful two-liner I've seen in a while:
Simpler GUI for Jad, The Java Decompiler.

I naturally customized it to:

jad -o -s java -lnc -d%TEMP% %1
"C:\Program Files\TextPad 5\TextPad.exe" %TEMP%.\

Changed extension to java so that textpad does syntax highlighting; added -lnc so that jad outputs the original line numbers as comments and I can trace the exceptions I get

(after a few questions from people i'm editing this post:)
You will need to download jad and extract the exeutable to somewhere on your path, say C:\windows (or c:\winnt). Then create a new .cmd file, paste the above into the .cmd file, and put it somewhere. Then rightclick any .class file you can find, choose "Open With..."->"Choose Program"->"Browse..." and find the cmd file you created (don't forget to check the "Always use this program"). This way, any .class you'll double-click will decompile and open in textpad.

Monday, September 17, 2007

Using java regular expressions to match groups

It's been demonstrated over and over again, but I always seem to forget the "simple example". So here it is:

import java.util.regex.Matcher;
import java.util.regex.Pattern;
*Going to match a URL that looks like this
* /url/prefix/--sitename--/menu.--menuid--/?param=--itemid--
* and change it into
* /url/prefix/--sitename--/--menuname--/--itemname--
String expr="(/url/prefix/[a-zA-Z0-9_-]+)/menu\\.([a-zA-Z0-9_-]+)/\\?param=([a-zA-Z0-9_-]+)";
Pattern p = Pattern.compile(expr);
Matcher m = p.matcher(uri);
if ( m.matches() ) {
menuitem =;
guid =;
if ( guid != null && prefix != null && menuitem != null ) {

Thursday, September 6, 2007

Does GDS slows my hard disk?

I've a encountred a strange problems that when Google Desktop Search is running on my PC (which it almost always is), my hard disk's read speed is about 1/6th of the normal speed. I'll contact google to see if this is a known issue. I'm using several HD benchmark tools to test the speed, most notably Simpli Software's Hd Tach.

Here are screenshots of my disk's speed with and without GDS running.

Avoding browser history when changing iframe src

We ran into a problem where we needed to have an iframe who's source needed to be changed dynamically by a javascript based on some user data. The issue was that Internet Explorer saved the iframe's old url in the history. The simple solution is to dynamically write the iframe with it's real src instead of having an iframe on the page and then changing it's src.

You do it like this:

var iframeHeaderCell = document.getElementById('wheretoputheiframe');
var dynamicURL = 'http://...' //your url
var iframeHeader = document.createElement('IFRAME'); = 'iframeHeader';
iframeHeader.src = dynamicURL ;
iframeHeader.width = ...;
iframeHeader.height = ...;
iframeHeader.scrolling = 'no';
iframeHeader.frameBorder = 0;
iframeHeader.align = 'center';
iframeHeader.marginwidth = 0;
iframeHeader.marginheight = 0;
iframeHeader.hspace = 0;
iframeHeader.vspace = 0;

Elementry, my dear Watson.

Monday, August 13, 2007

Updateing your docroot from subversion

We need to update our integration environment from svn every once in a while. At the moment a manual process is required since our svn gets commited into even if not everything is really stable and we only want to update the integration env when we feel the system is stable. We could do it manually by ssh-ing into the machine, but i hate people logging into my box to do stuff that should have a web interface, and we will probably want to extend that interface in the future.

Here is what I did:

First, manually do an svn checkout in the docroot:

su -
cd /var/www/html
svn co --username myusername svn://mysvnhost/svn/repositories/repository-name/projectname projectname
chown -R apache:apache projectname

Second, you will want a small PHP script to do all the work for you, so you will not have to ssh to machine all the time:

$log = "ACTION LOG\n---------------\n\n";
$log .= shell_exec("sudo svn up --username $username --password $password $docroot/$project");
echo "<pre>$log</pre>";

The thing is that since apache does not change it's user properly, svn cannot be properly run as apache, so will need the sudo there.

Third, in order for all of this to work, you will need to setup /etc/sudoers properly so go ahead and add this to it:

apache ALL=NOPASSWD:/usr/bin/svn

This will of course grow into something much more elaborate, that allows you to select projects, update on schedule, etc.

note that if you do what i specified above, then every update from subversion will reset the owner for the files under the docroot to root. This is generally not a good idea, so i suggest you put the svn update line in a shell script and add a "chown -R apache:apache projectname" to that script. then you can just sudo from the php file.

Tuesday, July 31, 2007

If you need to monitor mysql proccesslist, dump the following to a shell script and chmod 755. (ofcourse you will need to add passwords etc. if you have any;)


watch 'mysql<<EOF
show processlist;

(Control+C will let you out)

Two webapps using shared jar - ClassLoader problem

Yeah, yeah, I know it's obvious, but i thought i might be smarter. I am not:

Charles R Caldarale Writes:

[When using Tomcat,] classes from different webapps cannot access each other - no ifs, ands, or buts. Anything that is to be accessed from more than one webapp must be put in a common location [such as tomcat/shared].


Monday, June 18, 2007

Internet Explorer CSS Limit

We just came across a bug that makes IE choke when it needs to handle over 30 <style> objects. If you thought of using a single style object and then @import the other files, it won't work either.

You might want to ask why we need over 30 style objects. Well, since each drupal module tends to add it's own CSS (using drupal_add_css) we very quickly got to 22 CSS's being included. From there the road to 30-32 was quite trivial. Guess we'll have to use Drupal's CSS/JS aggragator to solve this.

Sunday, June 10, 2007

Calcualting Average in UNIX Shell Script

I grabbed a piece of code to calculate an average for data in shell. It didn't work so I had to modify it. This is the result.

while read x
sum=`echo $sum + $x | bc`
if [ "$?" -eq "0" ]; then
n=`expr $n + 1`
echo "scale=2;$sum/$n"| bc

Thursday, June 7, 2007

Server Header in Apache Tomcat

Altough you cannot disable the header, you can change it to anything you like by adding a "server" attribute to the connector tag in server.xml

port="80" address="localhost"

RoundToNearest in Microsoft Excel

This will round the given cells to the nearest number given, pretty neat if you want to produce a repost that is rounded, e.g. to the 0.25.


Thursday, May 31, 2007

MySQL Cluster

I did some research on MySQL cluster so i can recommend one of our customers whether to use it or not. It turns out that the MySQL cluster is very different from other DBMS clustering solutions in that it distributes the data across the nodes (synchronously) and then stores it on the disk (asynchronously). This is all very nice, but at the moment all data is stored in memory, so if I have a 120GB database I would need around 150GB memory on each node, which is silly.

The Wikipedia Page on MySQL Cluster gives more details.

Waiting for MySQL to get better...

UPDATE: It seems that this is no longer the case for the 5.1 version of mysql. See here.

Welcome - eureka

Why this blog?

Post random thoughts about random technology issues. Basically acts as an online(public) notepad, so i can keep track of things i found and do not wish to forget.

Why eureka?
eureka is the greek word for 'I have found (it)', supposedly exclaimed
by Archimedes upon discovering how to measure the volume of an irregular solid
and thereby determine the purity of a gold object. source: