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A job offer and a kinda cool puzzle

Written by Jevgeni Kabanov on February 18, 2010 – 3:59 pm

ZeroTurnaround is looking for an infrastructure engineer in Tartu (http://bit.ly/zt-infra-eng). If you want to apply or just have a little fun, solve this puzzle:
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Please don’t post the answer in the comments, but you’re welcome to tell what game is the quote from and how long did it take you to solve it.


Posted in cool | 36 Comments »

Story of a startup: How to Convert a Pair of Glasses into Fame and Fortune?

Written by Ivo Mägi on February 9, 2010 – 9:05 pm

Another guest post from our PHB. Obviously he has been reading too much Techcrunch, just discovered icanhascheezburger.com and slacking off during his day job.

This is a story of a start-up built around the nerdiest glasses on earth. If you wonder why and how we’re doing it, how exactly will we make millions of dollars off of it then you’re in luck. We’re planning to document and publish everything on our website and we have just released the first in the series, Converting a pair of glasses into fame and fortune.


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Posted in cool, humour | No Comments »

Bleeding edge of development – upgrading system and ANT stops working

Written by Toomas Römer on December 28, 2009 – 5:32 pm

I run Debian Unstable as my main desktop system. I shoot myself in the foot couple of times a year with the upgrades but I like using the bleeding edge of development.

Today after my “regular” upgrade I noticed that one of the ANT tasks did not perform as I would have expected.

/home/toomasr/workspace/project/build.xml:459: The following error occurred while executing this line:
/home/toomasr/workspace/project/changelogic-build.xml:72: Please check the correctness of the root url property. The server returned HTTP response code 300 or above for the URL http://172.17.57.242/lib/changelogic-build.xml

A quick ant -debug did not help me much.

/home/toomasr/workspace/project/build.xml:459: The following error occurred while executing this line:
/home/toomasr/workspace/project/changelogic-build.xml:72: Please check the correctness of the root url property. The server returned HTTP response code 300 or above for the URL http://172.17.57.242/lib/changelogic-build.xml                                                                                                                                       
        at org.apache.tools.ant.ProjectHelper.addLocationToBuildException(ProjectHelper.java:508)                                                                                   
        at org.apache.tools.ant.taskdefs.Ant.execute(Ant.java:369)                                                                                                                  
        at org.apache.tools.ant.UnknownElement.execute(UnknownElement.java:288)                                                                                                     
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)                                                                                                              
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)                                                                                            
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)                                                                                    
        at java.lang.reflect.Method.invoke(Method.java:597)                                                                                                                         
        at org.apache.tools.ant.dispatch.DispatchUtils.execute(DispatchUtils.java:106)                                                                                              
        at org.apache.tools.ant.Task.perform(Task.java:348)                                                                                                                         
        at org.apache.tools.ant.Target.execute(Target.java:357)                                                                                                                     
        at org.apache.tools.ant.Target.performTasks(Target.java:385)                                                                                                                
        at org.apache.tools.ant.Project.executeSortedTargets(Project.java:1337)
        at org.apache.tools.ant.Project.executeTarget(Project.java:1306)
        at org.apache.tools.ant.helper.DefaultExecutor.executeTargets(DefaultExecutor.java:41)
        at org.apache.tools.ant.Project.executeTargets(Project.java:1189)
        at org.apache.tools.ant.Main.runBuild(Main.java:758)
        at org.apache.tools.ant.Main.startAnt(Main.java:217)
        at org.apache.tools.ant.launch.Launcher.run(Launcher.java:257)
        at org.apache.tools.ant.launch.Launcher.main(Launcher.java:104)
Caused by: /home/toomasr/workspace/project/changelogic-build.xml:72: Please check the correctness of the root url property. The server returned HTTP response code 300 or above for the URL http://172.17.57.242/lib/changelogic-build.xml
        at org.apache.tools.ant.taskdefs.Exit.execute(Exit.java:142)
        at org.apache.tools.ant.UnknownElement.execute(UnknownElement.java:288)
        at sun.reflect.GeneratedMethodAccessor6.invoke(Unknown Source)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
        at java.lang.reflect.Method.invoke(Method.java:597)
        at org.apache.tools.ant.dispatch.DispatchUtils.execute(DispatchUtils.java:106)
        at org.apache.tools.ant.Task.perform(Task.java:348)
        at org.apache.tools.ant.Target.execute(Target.java:357)
        at org.apache.tools.ant.helper.ProjectHelper2.parse(ProjectHelper2.java:142)
        at org.apache.tools.ant.ProjectHelper.configureProject(ProjectHelper.java:93)
        at org.apache.tools.ant.taskdefs.Ant.execute(Ant.java:367)
        ... 17 more
--- Nested Exception ---
/home/toomasr/workspace/project/changelogic-build.xml:72: Please check the correctness of the root url property. The server returned HTTP response code 300 or above for the URL http://172.17.57.242/lib/changelogic-build.xml
        at org.apache.tools.ant.taskdefs.Exit.execute(Exit.java:142)
        at org.apache.tools.ant.UnknownElement.execute(UnknownElement.java:288)
        at sun.reflect.GeneratedMethodAccessor6.invoke(Unknown Source)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
        at java.lang.reflect.Method.invoke(Method.java:597)
        at org.apache.tools.ant.dispatch.DispatchUtils.execute(DispatchUtils.java:106)
        at org.apache.tools.ant.Task.perform(Task.java:348)
        at org.apache.tools.ant.Target.execute(Target.java:357)
        at org.apache.tools.ant.helper.ProjectHelper2.parse(ProjectHelper2.java:142)
        at org.apache.tools.ant.ProjectHelper.configureProject(ProjectHelper.java:93)
        at org.apache.tools.ant.taskdefs.Ant.execute(Ant.java:367)
        at org.apache.tools.ant.UnknownElement.execute(UnknownElement.java:288)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
        at java.lang.reflect.Method.invoke(Method.java:597)
        at org.apache.tools.ant.dispatch.DispatchUtils.execute(DispatchUtils.java:106)
        at org.apache.tools.ant.Task.perform(Task.java:348)
        at org.apache.tools.ant.Target.execute(Target.java:357)
        at org.apache.tools.ant.Target.performTasks(Target.java:385)
        at org.apache.tools.ant.Project.executeSortedTargets(Project.java:1337)
        at org.apache.tools.ant.Project.executeTarget(Project.java:1306)
        at org.apache.tools.ant.helper.DefaultExecutor.executeTargets(DefaultExecutor.java:41)
        at org.apache.tools.ant.Project.executeTargets(Project.java:1189)
        at org.apache.tools.ant.Main.runBuild(Main.java:758)
        at org.apache.tools.ant.Main.startAnt(Main.java:217)
        at org.apache.tools.ant.launch.Launcher.run(Launcher.java:257)
        at org.apache.tools.ant.launch.Launcher.main(Launcher.java:104)
 
Total time: 3 seconds

The access log on the server did not show anything for the request. Browsing to the url with FireFox worked just fine. Where to even start debugging this? The simple env did not show any proxies configured either. Quite lost.

At last I decided to trace the problem with strace. strace -f ant my_target > result 2>&1 produced 35 892 lines of output. Searching for the ip showed me the message

35596 [pid 13544] connect(46, {sa_family=AF_INET6, sin6_port=htons(80), inet_pton(AF_INET6, "::ffff:172.17.57.242", &sin6_addr), sin6_flowinfo=0, sin6_scope_id=0}, 28) = -1 ENETUNR      EACH (Network is unreachable)

Weehah, I’m getting somewhere! Googling a bit showed me multiple solutions. Either a system wide sysctl -w net.ipv6.bindv6only=0 or just -Djava.net.preferIPv4Stack=true will do the trick. I hope this helps somebody.


Tags: , ,
Posted in tips | No Comments »

Hacking with IDE plugins – fun art of binary patching

Written by Toomas Römer on December 11, 2009 – 6:34 pm

Today’s software is so much about integration. You can have a cool Java utility but if you don’t have an Eclipse plugin for that, a large % of Eclipse users won’t adopt (IDEA & NetBeans users require plugins just as much). In the consumer market the same goes for browser extensions and iPhone apps that support the main service with better accessibility.

There are different ways for integration. Usually it is done via an API. The host platform offers some hooks into the system and you can use them to add some custom functionality on top of the host (or maybe just integrate your own product with the host). The result of this in the IDE world is a plugin. JRebel (the product our team is spending the most development time on) has plugins for application servers, frameworks and even IDEs.

If you’re in luck you can achieve everything with the API, if not you need other tricks. If the API does not offer certain public methods or access to some internal fields you can go in with reflection and still use them (of course there are no guarantees if the internals stay the same on version changes).

One step further to the darkside is binary patching. By binary patching I mean adding/changing/removing methods/fields/classes in runtime. This is the approach that we had to take when writing the JRebel NetBeans plugin.

On NetBeans startup we lookup a debugger class and on success try to patch it. In 2009 and using the JVM (not native apps) it is quite an easy task, at least for the most part. No assembler involved (of course you could be using a bytecode generation library), no need to do jumps to correct offsets or even read assembler (or bytecode).

In our case we use the Javassist library. It is a matter of inserting Java code embedded into a String to methods looked up via reflection. For example the following code adds some new code into the beginning of a method.

ctc.getDeclaredMethod("setRequests").insertAfter(
  "org.netbeans.api.debugger.jpda.LineBreakpoint _breakpoint = getBreakpoint();" +
  "java.lang.String _className = _breakpoint.getPreferredClassName();" +
  "if (_className == null) {" +
  "  _className = reader.findCachedClassName(_breakpoint);" +
  "  if (_className == null) {" +
  "    _className = org.netbeans.modules.debugger.jpda.EditorContextBridge.getContext().getClassName (" +
  "      _breakpoint.getURL ()," +
  "      lineNumber);" +
  "    if (_className != null && _className.length() > 0) {" +
  "      reader.storeCachedClassName(_breakpoint, _className);" +
  "    }" +
  "  }" +
  "}"

For the complete source code of the patch see the src folder of the nb-plugin.

In conclusion, the best way to integrate with any system is via the API it provides. If it does not cut it then look into reflection and start using internals. You will lose on maintainability of course. Still not happy? Look into binary patching and have your fingers crossed whenever the target platform releases a new version.

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Posted in cool, tips | 1 Comment »

Configuring Eclipse – “fail fast”

Written by Ivo Mägi on November 27, 2009 – 1:33 pm

Another guest post from our favorite PHB. I don’t have the slightest idea why he has Eclipse installed or better yet, why is he trying to run it. Probably overheard something from devs at the water-cooler and wants some free time from PowerPoint.

My Eclipse instance starts with a warning popup. Well, most likely it picked up a JRE instead of the usual JDK specified in my environment variables. But hey, I know how to handle property files (ed: seriously?), and they are actually pointing me towards the eclipse.ini.

JDK vs JRE

Clicking the link on the warning popup does not open the file itself though, so I have to manually navigate to the C:\Programs\eclipse folder and find eclipse.ini from there containing:

PLAIN TEXT
CODE:
  1. -showsplash
  2. org.eclipse.platform
  3. –launcher.XXMaxPermSize
  4. 256M
  5. -framework
  6. plugins\org.eclipse.osgi_3.4.2.R34x_v20080826-1230.jar
  7. -vmargs
  8. -Dosgi.requiredJavaVersion=1.5
  9. -Xms40m
  10. -Xmx256m

Adding –vm C:\Program Files\Java\jdk1.6.0_14 to the end of the configuration and restarting. Well – nothing has changed. OK, let’s open up Google.

Proposed solution: -vm option has to be specified before the –vmargs option. Still no help, Eclipse will start with the previously mentioned warning.

Second solution – there has to be a line break between –vm and the value specified – BINGO. We are getting somewhere –

Trainwreck

Now let’s just change it to:

PLAIN TEXT
CODE:
  1. -showsplash
  2. org.eclipse.platform
  3. –launcher.XXMaxPermSize
  4. 256M
  5. -framework
  6. plugins\org.eclipse.osgi_3.4.2.R34x_v20080826-1230.jar
  7. -vm
  8. C:\Program Files\Java\jdk1.6.0_14\bin\javaw.exe
  9. -vmargs
  10. -Dosgi.requiredJavaVersion=1.5
  11. -Xms40m
  12. -Xmx256m

And it just works. But for heaven’s sake – why on earth do I have to figure out

  • where is the configuration I have to change
  • in which order do I have to specify the parameters
  • that the key-value options must be separated with the line break

Considering the last warning dialog – why cannot the whole configuration be validated and initialization failed properly? If this were a tool used in-house or only by small number of freaks, then – let it be. But this is Eclipse we are speaking about – there are millions of people working their asses off on a daily bases with this tool. Can’t imagine the time wasted for problems like this …


Posted in cool, rant | 2 Comments »
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