Chronon 2.3 released

Posted by Prashant Deva on April 11, 2012

Bugfix release for the Recording Server UI.
This is a bit of a late announcement since the binaries have been available since middle of last week.

If you are using v 2.x of Recording Server, then you can just update the .war file to get the new fixes.

You should no longer see screens like this anymore with v 2.3



Get it now:



Chronon Free for Open Source Projects

Posted by Prashant Deva on April 4, 2012

Last week we won the Eclipse Community Awards for Best Developer Tool. Guess its time we start giving back to the community too.

Thus today we are announcing the long awaited, free open source license program for Chronon!
Read on for more details:

What we are offering

Free licenses of :

  1. Chronon Time Travelling Debugger
  2. Embedded Chronon

Who can get it

There is the obvious requirement of having an Open Source project with an active community
Please don’t just check in a couple of files in github and ask for a free license. 

Apart from that we also ask for the following once your license is approved:

Allow submitting Chronon recordings to your bug repository

That’s it! Just allow users to post Chronon Recordings in your bug repository (as attachments).

This is a benefit to both you and your users:

  1. Your users can easily report bugs as a Chronon Recording instead of trying to figure out and report the exact steps to reproduce the bugs.
  2. You get to fix bugs more easily by just playing back the recordings using the free Chronon Debugger license.
  3. Users can report bugs that occur sporadically or would require a complicated setup on your part to report it. Currently these kind of bugs remain unresolved, but with Chronon that would no longer be the case.

You will need to mention somewhere prominent on either your support/contact page and/or bug tracker that you allow Chronon Recordings.

We will help you with the wording and placement of the text. We will even send you a small badge you can put on your website and link to a page on that will describe to new users what Chronon is and how they can benefit from using it with your project.

For Embedded Chronon licensees

If your open source project has a user facing UI, ie for example its a rich client application or an eclipse plugin, you can use Embedded Chronon and its APIs to add a ‘Record’ button inside your application!

This way, if your user wants to report a bug, but you dont want to have Chronon running all the time in your application:

  1. They can click on a ‘Start Recording’ button to dynamically start the recorder in the running application.
  2. When the bug has occurred, they can click ‘Stop Recording’.
  3. Then they can send you the Chronon recording in your bug repository where you can then easily debug the issue.

Again, a win for both your project and your users!

When can you get it

The free licenses will be available with the release of Chronon 3, however you can start applying for them now.

We believe the performance improvements in Chronon 3 and the resulting small recording file sizes make it much more easy to record applications and share those recordings.

We suggest all interested parties to request the Chronon 3 beta to start trying it out on your projects today.

For those interested in trying the full stack right now, you can download the free 30 day evaluation of Chronon 2.

Where to Apply

Fill the form here to get in the queue for open source licenses right now. 

For more questions, either post a comment or contact [email protected].

Chronon 3 beta: 10x performance improvement

Posted by Prashant Deva on March 23, 2012

Chronon 3 is all about performance.

We have rewritten our Recorder from the ground up to gain an order of magnitude performance improvement! The basic architecture remains the same, but under the hood its an all new engine. We turned a Yugo into a Ferrari!

No more memory issues

The biggest complaint of all users of Chronon 1 and 2 has been high memory usage and OutOfMemory errors. With Chronon 3 our main goal was to get rid of this. And I am proud to say we have blown it out of the ballpark with this one!

Chronon 3 makes absolute minimal use of your Java heap. We have shifted most of our code to native. And this time we made sure that literally every single bit of memory usage is accounted for! This means that you no longer have to fiddle with -Xmx values.

Here is a graph showing memory usage for recording entire Eclipse (namespace org.eclipse.**) with Chronon 2 and Chronon 3 (size in megabytes):


Smaller Recording file size

The Recording file size of Chronon 3 should on avg be 90-95% smaller than that of Chronon 2.

Here is a comparison of recording file size for the startup of eclipse, recording the entire org.eclipse.** namespace (size in megabytes). Note that eclipse has a lengthy, cpu intensive startup so its a good stress test.


Increased Concurrency

Chronon 3 pulls out all the stops to make sure your applications retain all of their concurrency. Highly concurrent applications will instantly see a very noticeable huge performance boost.

Logless Data Center

With the high performance of Chronon 3, you can have the Chronon recorder running all the time. This means you can have for the first time a Logless Data Center!

Consider this, with Chronon on all the time, you no longer need log files or log statements cluttering up your code. If something breaks, just pull out the Chronon recording and put in Post Execution Logging statements wherever you want.

Getting your hands on the beta

To get the beta, please fill out the form here.

We are opening the beta so you test the performance of Chronon 3 on your applications.

Since this is still beta, the recordings made from the Chronon 3 recorder will not open in the Chronon Debugger for now. You will need to use the Chronon Recording Server to record your applications. The only change would be that you would replace the recorder.jar in your Recording Server installation from v2 to v3.

If your existing Recording Server evaluation has expired, dont worry, we will give you a new one.

We would request providing some contact info so we can be in touch with you throughout the beta.

Please provide either a phone number or a skype id , or anything else (put it in the comments section). If providing a phone number, dont forget putting the country code.

Any spam/incorrect entries will be discarded.

Hidden evils of Java’s boolean array (boolean[])

Posted by Prashant Deva on February 2, 2012

Consider this piece of code which allocates a boolean array of 100,00:

boolean[] array = new boolean[100000];

What should the size of this array be?

Considering that a boolean can just be either true or false, every element in the array only needs a single bit of space each. Thus, the size of our boolean array in bytes should be:


100,000/8 + (overhead of array object) = 12,500 bytes + (overhead of array object)

But there lies the hidden evil….

The Evil Inside

As it turns out, when you allocate a boolean array, Java uses an entire byte for each element in the boolean array!

Thus the size of the boolean array is in fact:

100,000 bytes + (overhead of array object)


So is there any way not to use the 7 extra bytes when you only need the 1 bit? Its here that the java.util.BitSet class comes to rescue.

The BitSet class does indeed use a single bit to represent a true/false boolean value. Its implementation uses an array of ‘long’ values, where each bit of the long value can be individually manipulated to set any position in the entire BitSet to true or false.

The BitSet implementation does add a bit of cpu overhead since it has to shift and or bits together to set the value of the bit in the correct position. Thus you need to weigh the cost of memory savings versus the extra cpu overhead when using this class.


As an example, here is a screenshot from the YourKit profiler, showing the memory used by a boolean array and a bitset object, both 100000 element long:


As can be be seen:

The boolean array takes:
100,000 + 16 (array overhead) = 100,016 bytes

The BitSet object only takes :


100,000 / 64 (size of long) = 1562.5 = 1563 long values after rounding
1563*8 + 16 (array overhead) = 12, 520 bytes

A few extra bytes are added for the BitSet object itself and the extra 2 fields that it contains.

To put things in perspective, here is a graph showing the space occupied by both for 100,000 elements:



As can be seen from the graph above, using the BitSet instead of a boolean[] can save you tons of memory at the cost of just a few extra cpu cycles

Hidden evils of Java’s String.split() and replace()

Posted by Prashant Deva on January 25, 2012

If you code in Java, you have inevitably used the String.split() and String.replace() (including replaceFirst() and replaceAll()) functions.

And why wouldn’t you? They are much more convenient than using the Java Regular Expressions API where you need to create a ‘Pattern‘ object, and possibly a ‘Matcher‘, and then call methods on those.

However, all convenience comes at a price!

The Evil Inside

In this case, the String.split() and String.replace*() methods (with the sole exception of String.replace(char, char) ) internally use the regular expression apis themselves, which can result in performance issues for your application.

Here is the String.split() method:

Notice that each call to String.split() creates and compiles a new Pattern object. The same is true for the String.replace() methods. This compiling of a pattern each time can cause performance issues in your program if you call the split() or replace() functions in a tight loop.


I tried a very simple test case to see how much the performance is affected.


The first case used String.split() a million times:

In the second case, I just changed the loop to use a precompiled Pattern object:

Benchmark Results

Here are the average results of 6 test runs:

Time taken with String.split() : 1600ms
Time taken with precompiled Pattern object: 1195 ms



Note that I used an extremely simple regular expression here which consists of just a single ‘space’ character and it resulted in > 25% decrease in performance.

A longer more complex expression would take longer to compile and thus make the loop containing the split() method even slower compared to its counterpart.

Lesson learned: It is good to know the internals of the APIs you use. Sometimes the convenience comes at the price of a hidden evil which may come to bite you when you are not looking.


Chronon 2.2 released

Posted by Prashant Deva on December 13, 2011

This is mainly a bugfix release for all components.

Some enhancements to the Debugger UI:

Import/Export available for ‘Post Execution Logging’ and ‘Timeline’ views


Servers tab now has ‘Record’ button in main toolbar


Recording Server

Bugfixes for all 3 components: recordingserver.war, controller and recorder.jar.

Each component in this release can be updated indepently.

Thus for example, if you dont want to update the controller on each box, you can just replace the recorder.jar files with the updated one and leave the rest still running.

If however you are updating from a beta version, you will need to update all 3 components at once.

Grab the latest version from our download page now!

Chronon Step-by-Step Tutorial

Posted by Prashant Deva on December 8, 2011

Still don’t think you are utilizing Chronon to its maximum potential?

We have released a Step-by-Step Chronon Tutorial, where you can download a sample eclipse project and have us walk you through debugging it using Chronon, explaining every single feature.

It takes less than 10 minutes to go through the entire tutorial and by the end you will become a master of Time Travel!

GWT support added in Chronon 2.1.2

Posted by Prashant Deva on November 22, 2011

We have updated the Chronon Eclipse plugin to support the Google GWT plugin. You need GWT plugin version 2.4.2 or higher for the Chronon plugin to be enabled for it.

With the GWT support:

  • You can record GWT applications easily in development mode.
  • The GWT ‘Development mode’ view has the Chronon ‘blue’ stop button that is enabled when you are recording a GWT application. Make sure to use that instead of the ‘red’ button to stop your GWT applications, otherwise the recording wont be saved properly.



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