Conferences I have visited in May'17

Riga DevDays

Riga DevDays - a perfect conference of an Estonian to visit: not too far away (45 minutes flight), nice city, very good event!

There, I have presented a talk about Java class reloading, which covers the different options for reloading Java classes and explains the fundamental differences of those.

Riga DevDays 2017 - The hitchhiker’s guide to Java class reloading from Anton Arhipov

GeeCON, Krakow

I have presented at GeeCON before. The vibe of the event is quite energising! :) I have presented a talk about TestContainers which seemed to spark a lot of the interest from the attendees. Almost a full room and a lot of questions after the talk. Looks like integration testing is in demand these days!

GeeCON 2017 - TestContainers. Integration testing without the hassle from Anton Arhipov

JUG.ua & JEEConf, Kiev

The visit to Kiev (Kyiv) was super-productive. I've visited EMAP offices of the on-site presentation as well as a local JUG meetup just before the conference. Very good attendance: 100+ people came to the meetup. Interestingly enough, in Ukraine (as well as in Russia) people ask questions in an interesting way: they usually start the question with "What if ...". They are always curious to find the limitations of the technology, the approach, the method, etc - almost like trying to break things. I think this critical mindset is very helpful when you have to develop software these days.

JUG.ua 20170225 - Java bytecode instrumentation from Anton Arhipov

At the JEEConf I have presented 3 talks: 2 on my own, and 1 with Anton Keks, helping to deliver the Kotlin Puzzlers talk. This was a very well organized conference: super-nice view in the center of Kiev, well crafted schedule with the interesting and useful talks, good athmosphere... I recommend :)

I had a pleasure to deliver a live coding session about Javassist, though I still have the slides just as a reference for those who attended the session. I don't find this talk to be very useful for the developers, however, attendees still find it interesting, so I'm puzzled with this a bit :) Here are the slides:

JEEConf 2017 - Having fun with Javassist from Anton Arhipov

As for the Java class reloading talk, I had some time to update the content since Riga DevDays -- removed boring parts and added a few other things. Lots of "What if.." questions after the talk -- I love this crowd! :)

JEEConf 2017 - The hitchhiker’s guide to Java class reloading from Anton Arhipov

HotSwap vs hot deploy

It is the year 2016 and one still has to explain that HotSwap and hot deploy in Java IDEs is not the same thing.

Stackoverflow is full of questions about avoiding restarts of Java applications. So of the answers suggests that “Eclipse can update code without restarting the application” or “IntelliJ IDEA can hot update running applications” or “NetBeans automatically updates running code in debugger”. But the ultimate solution for this problem is JRebel, of course.

UPD: You can also read about various solutions to the redeployment problem in my Stackoverflow answer.

One fundamental thing that people don’t understand is that it is not even the capability of an IDE to be able to update applications. The IDE is just a medium -- it only triggers the update, and then the runtime environment is the one responsible for updating the code.

Repeat after me: 

HotSwap and Hot deploy is not the same thing!

What is HotSwap?

HotSwap (тм) is the technology in HotSpot JVM that is tailored at updating class definitions at runtime. Most importantly, "HotSwap adds functionality to the Java Platform Debugger Architecture (JPDA) to allow a class to be updated while under the control of a debugger”.

So when it comes to IDEs, once an application is started in a debug mode, the IDE can trigger class redefinition in a running JVM by utilizing JPDA.

If you are interested in the intimate details of HotSwap, read the “Safe class and data evolution in large and long-lived java applications” paper by M. Dmitriev.

It is important to understand the limitations of HotSwap: it is limited only to updating statements of code inside methods. Can’t change method signatures, can’t add new methods, fields, etc. Some JVM implementations are able to do a bit more. For instance, with IBM J9 JVM it is possible to add new methods to an existing class. Nevertheless, HotSwap capabilities are minimal. A JEP for enhanced class redefinition has been submitted long ago, and even a research project was sponsored by Oracle, but no further progress was made.

The bottom line here is that HotSwap is not a feature of an IDE, it is the ability of a JVM that you use.

What is hot deploy?

Hot deploy is the ability of application container to automatically deploy (web) applications at the startup. Obviously, the same feature can be applied to re-deploy the applications without restarting the JVM process.

Hot deploy is not a feature in any of the IDEs either. IDEs can only trigger (re)deployment of an application by either copying the artefacts to a correct location, or by using hooks if provided by the application server. So this is totally application server specific - this is what server adapters are for! It requires the IDE to be aware of the application server specifics, hence some people affiliate this functionality to their IDE.

Redeploying the application drops its state. Sometimes, application server can serialize/deserialize HTTP session state, but that's about it, not more. It can't preserve the state of the structures inside the application; internal caches have to be warmed up; framework internals have to be reinitialized, etc. The process is time consuming.

Application servers rely on class loader magic to redeploy applications. You can read about it in details in ZeroTurnaround’s blog.

Summary

Make sure you use the terms correctly -- 'HotSwap' and 'hot deploy' is not the same thing! You may other terms, like 'hot update' -- then make sure to ask, what does the person actually means by this, because the devil is in the details.

Another great Java interview question: Singleton

I'm not a big fan to ask to write code at the interviews. But I still find it useful to do some coding exercises at the whiteboard. One of my favourites is the Singleton pattern. Because Singleton is so simple, you can use it as a starter for so many interesting discussions.

it often comes down to the discussions about the Singleton being lazy or eager. And while it leads to the discussion about Java Memory Model, it's not the most interesting one. No one understands Java Memory Model anyway :)

BTW, did you know that a single-element enum type is the best way to implement a Singleton?

Yes! And you can't imagine how many people do fail with this. If you deploy 2 web applications with the same Singleton class, will there be two instances of the same Singleton or one? Of course, there isn't one true answer for this question - you have to ask the details. The the answer depends much on how the class is loaded. If the class is packaged within the WARs, then you get 2 instances of the Singleton.

This is why Singleton is such a great interview question - it opens a lot of topics for further discussion!

XRebel 2.0 with Application Profiling

From the very start, our users requested profiler capabilities in XRebel. As of 2.0, it is possible to get the performance overview for every request and identify the slowest methods.

The profiler view shows the time distribution in the call tree by assigning the percentages to the individual nodes that represent method invocations. The slowest methods are also accompanied with an extra percentage figure that indicates the method own contribution time.

JSP tag mapping is one neat little feature, new in XRebel 2.0. Instead of a cryptic runtime name XRebel displays the real JSP tag.

In 2.0, there are some more notable improvements to the existing features. The session component is now able to handle very large HTTP session snapshots. And of course, there's a ton of little UI improvements -- all to make the profiler more pleasant to use.

Links for XRebel:

• Download
• Features
• Documentation

XRebel 2.0 Beta is available

XRebel 2.0 Beta is available for download! The new version includes profiling capabilities and it is now possible to get an overview of performance breakdown in a single HTTP request. The cool part is that XRebel shows only the minimal relevant information by filtering out a lot of irrelevant stuff. I have tested the new version with a lot of different enterprise-grade applications, including Atlassian Jira, Magnolia CMS, Liferay Portal, eXo Platform... and it works just great!

The greatest feedback so far was that the tool provided the ability to monitor JPA queries and the subsequent JDBC invocations in one go. With the new version, XRebel is turning into a real profiler, yet simple and powerful.

XRebel 1.2

Just released XRebel 1.2. It is amazing, astonishing, splendid, beautiful, awesome, beautiful, beautiful, beautiful! :) I'm most pleased with its ability to show the relation between ORM-level events/queries and the generated SQL queries that are executed via JDBC. Like this:

Or even like this:

The cool part is that even with no special requirements to filtering, the call tree scales very well - the user could see the compact call stack with relevant branching points starting from the incoming HTTP request towards the JDBC calls, or NoSQL... or outgoing HTTP invocations.. even RMI!

/me happy! :)

Speaking at JavaOne SF 2013

I've got 4 talks to deliver at JavaOne SF this year:

• UGF10388 - NetBeans Community Tools with JRebel, Jelastic and others. I'll be talking about our NetBeans plugin for JRebel - how it's made and what it does.
• CON2585 - Embedding JVM Scripting Languages. This talk has been brewing in my head for a long time now. It started at a time when I was investigating applicability business rule engines at my previous job. Amazingly, after some time I realized that in order to implement a BRMS, you actually have to have a very very very good reason. In most cases a rule engine can be as easy as a simple dynamic script that follows some conventions. Scripting languages on JVM allow just that! I'll be talking about embedding scripting into a Java app and assessing different options for the implementation. Will cover Groovy, JRuby and a bit of JavaScript too.
• CON2578 - Taming Java Agents. Since JRebel is stands on the shoulders of Instrumentation API and bootstraps via -javaagent VM argument, there's good portion of interesting things that I could talk about. Thankfully, Nikita will assist me as he's involved with Plumbr, which also based largely on Instrumentation API, however, it includes some native code as well. Combined, it will be an interesting overview of the underlying technology that enables us to develop awesome tools for Java platform.
• CON3477 - Apples and Oranges: The Highlights of Eclipse, IntelliJ IDEA, and NetBeans IDE.
This will the showcase of all 3 major IDEs - NetBeans IDE, IntelliJ IDEA, and Eclipse (with JBoss Tools plugin). Geertjan suggested we do it together, so there will be 3 speakers, one for each IDE: Geertjan for NetBeans IDE, Max Andersen for Eclipse, and myself for IntelliJ IDEA.

See You At JavaOne!

Back from 33rd Degree

33rd Degree conference have changed location this year. This time the action took place in Warsaw. It seems that 33rd Degree has outgrown its venue in Krakow and the organizers decided to pursue the possibility to expand the conference.

The venue

I realized that the venue "configuration" counts a lot. This time the conference was located equally on 2 floors of the Gromada Airport hotel. Actually it was a fair separation for both vendors and speakers, but there's a caveat. If the fancier sponsors are on the top floor and the most famous speakers are there as well, then the vendors who locate in the "bunker" should be worried. Actually the speakers who get to speak in the other floor should be worried as well. Literally, on the first day when I arrived, I could not wait in the line for a cup of tea at the top floor and at the same time it was dead empty at the bottom floor. This is just how the crowd moves, and it is very hard to fix it.

My talks

My first talk Do you really get your IDE? happened to take place at the bottom floor at the same time when a beer party was starting at the top floor. I was almost sure that noone will be interested in coming to the talk and my bet was that only 5-10 people would show up. I was totally wrong. The room was full. Very surprising. Since it was a BOF format and a lot time was consumed by conversations in the middle of the talk, I didn't really cover all the cool tricks that I wanted but I would count this talk pretty successful anyway - it was fun and entertaining. I hope I can "sharpen the saw" in delivering this talk a bit more since people really enjoy learning the tools.

My second talk was about JRebel and how it can be used for updating Java applications. Not so many people came this time, probably because JRebel is a well known tool already and Baruch has dragged all the attendees in his talk instead.

Other talks

I usually don't attend that many sessions at the conferences since I know a lot of speakers personally and can learn from them directly in off-line conversations. However, this time I decided to go and listen and learn some cool stuff at the sessions.

Leading the technical change by Nathaniel Schutta. The talk title and abstract did not fire up my curiosity. I just know that Nathaniel has a style delivering the presentations and I wanted to go and learn from his performance. The idea is very simple actually: instead of bullet points Nathaniel creates a slide per bullet point and makes it look attractive so that when the next slides comes he can see it from his laptop screen and then he knows what and how he should say. That is why the delivery is so smooth, no matter which topic he presents. Of course Nathaniel didn't skip the book he co-authored, the Presentation Patterns - very useful book for everyone who wants to present at the conferences.

Being Honest - Rethinking Enterprise Java by Adam Bien. Adam is a very energetic speaker and I actually like his presentations about Java EE very much. But this time the technical aspects of the presentation didn't do good. The large room was full, but the screen was way too small for everyone to see the code. Plus the mic wasn't really working and it was quite hard to listen, so I could help myself but leave the room for some other talk.

So I made it to the talk about Kotlin by Hadi Hariri. Kotlin's ecosystem is doing great steps forward. Unfortunately I didn't see the whole talk. In the part that I grasped this time Hadi was talking about the features that allow creating DSLs and he presented his own development, Spek, the specification framework for Kotlin.

Scripted: Embracing Eclipse Orion by Martin Lippert. This was very unfortunate. Very nice talk about very nice tool with almost empty room. I call it "bad marketing". Martin is a good speaker and he talks about interesting topics, but it seems the title of the talk turned off the crowd. Who cares about Eclipse Orion at this kind of conference? Besides, nothing in the talk was really about Eclipse Orion. It was about Scripted - a kick-ass browser based JavaScript editor, very interesting R&D project developed at SpringSource/VMWare.

Programming with Lambda Expressions in Java by Venkat Subramaniam. Venkat's talks are so perfect it is hard to get a seat in the room. Attendees usually occupy the room in advance before the talk starts and those who are late steal the chairs from other rooms in order to get a seat. Nothing really advanced in the topic, but Venkat presents it with passion. Very entertaining.

How we took our server-side application to the Cloud and liked what we got by Baruch Sadogursky. Very interesting talk for those who want to learn the basics of multy-tenancy and approaches in implementation for SaaS. Baruch talked about the solution they chose for the hosted version of Artifactory - what were the challenges and pitfalls.

Overall

33rd Degree was definitely a success for the organizers but still there's plenty of details to improve: technical equipment would be the first on the list. Something needs to be done for managing the crowd - most of the time people are late for the sessions by a lot (with exception for the Venkat's talks). This is very distracting for the speakers, I think, even if they say it is not.

The great thing about 33rd Degree is that Grzegorz works super-hard to organize it all: get the great (NFJS) speakers, cool vendors (Atlassian, Plumbr, JetBrains, etc), and the venue, which is actually very nice: plenty of space, great food, very close to the airport. plus, the price for the conference is still very affordable.

Talking at 33rd Degree conference

Once again, I'm back to 33rd Degree conference, taking place in Warsaw on March 13-15.

I'm going to have 2 talks there:

Do you really get your IDE?, which is actually a BOF. This is my first time experience in running a BOF, so I'm not really sure how it turns out. I want to discuss with the folks, how the IDEs are used and how are the developers using the IDEs. I will play a bit with the code in IntelliJ IDEA and probably jump into other IDEs as well.

Reloading Java applications like a Pro. At many conferences I've been talking about the very root of the turnaround problems in Java, the reasons and pitfalls. But this time I decided that it would be much more fun to showcase what JRebel can do for different types of Java applications. I plan to talk about the mechanics of the updates and what is happening inside Java application when JRebel is doing it work. Hopefully I can fit several demo scenarios into the talk: for Spring based application, for JavaEE, maybe something for non-conventional apps and desktop apps (e.g. JavaFX).

I'm glad that 33rd Degree organizers allowed me to talk about JRebel directly. At many conferences the organizers are actually quite hesitant to accept any talks about commercial products. However, every time I give a talk on some technical topic, the attendees actually are eager to ask questions about JRebel rather than about the talk topic itself. It means that JRebel is more interesting, than, for instance, Java bytecode. So why bother about the commercial side of it?

XPDays Kiev: Continuous Delivery Pipeline With Jenkins, Artifactory And LiveRebel

XPDays in Kiev was a success! Great crowd, interesting talks and fruitful discussions, socializing included.

Embedded are the slides from by import continuous.delivery.* talk which was surprisingly well received and it seems a lot of people are looking for ways to release and deploy continuously, even in the large organizations.

There are numerous different tools that could be used to organize the continuous delivery pipeline. The pipeline that I've demonstrated was built with Jenkins, Artifactory (Pro) and LiveRebel.

I'm not super happy with the build pipeline plugin in Jenkins. In the talk I had to spend time explaining why the flow is organized the way it is and why the build pipeline plugin behaves the way it behaves. It is just buggy... I should find time to fix it.

Arifactory's Pro version was just primarily because of the fact that artifact promotion feature is a Pro version and some of the REST APIs that I wanted to use were under Pro license. There are alternatives, but with Artifactory it was just much easier to show the relevant stuff.

LiveRebel - well, there's no real alternative to it. The attendees were really impressed how easy it is to deploy via LiveRebel and oversee the target environment.

The cool part is that all the tools integrate well via the REST API (or CLI) and you can build a very flexible pipeline if this kind of integration is available. What I also realized is that although everything can be automated in the pipeline, it shouldn't get on your way still - you should be able to go into any step and re-execute if needed.

Another critical feature is the rollback functionality. It is not just that you select the previous version of the app if something goes wrong. There's more things you have to keep in mind when organizing the pipeline (I'm not revealing it now :P).

Enjoy the slides! :)

I'm speaking at JavaZone again this year. Hope to give an overview of javaagent and Instrumentation API with some referrals to the interesting use cases.

33rd Degree

I'll be speaking at 33rd Degree conference in Krakow, Poland. Looking at the schedule there's plenty of interesting talks I'd like to attend myself - hopefully I will have some time for that.

JFokus & Vaadin Meetup

I'm going to JFokus in February. Is anyone else coming? :)

There's also an awesome opportunity to join the Vaadin team at the boat to Stockholm from Helsinki - don't miss it!

JavaZone 2011: Bytecode for discriminating developers

View more presentations from Anton Arhipov

Destination: JavaZone, Oslo, Norway

I'm presenting at JavaZone the next week.

There's plenty of interesting sessions on the schedule that I'm tempted to attend myself.

JRebel 4.0.x

JRebel 4.0.3 was released just recently. The debugger support is maturing - some features are still missing, like expression evaluation support for the reloaded classes, but stepping functionality and breakpoints installation are quite well polished now.





See the press release.

33rd Degree, 2011, Day 1

ZeroTurnaround is exhibiting at 33rd degree conference in Krakow. In fact, we are the only software product company at the tiny expo here. The others, Luxoft and Tieto are the outsourcing companies, so we feel a bit lonely in this situation. BTW, Luxof has the most meaningless booth I've ever seen - it is huge and it completely ineffective.

Anyways, we've met a lot of smart people asking a lot of smart questions about JRebel and it is tough to answer all kind of questions - I wish I could.

I didn't have much time to attend the sessions myself. However I've managed to escape from the expo area and to attend Ted Neward's talk Busy Developer's Guide to Scala: Patterns. I've got smarter in a way. I've learned about some Scala idioms that diminish some of the classical design patterns that you need to implement in Java from scratch. In fact, I realized that many of the design patterns become obsolete once the target language supports closures.

At the end of the day we've organized the beer party for all the conference attendees. It is a funny thing but people are more interested in JRebel if they're are served with the free beer :)

Presentation Slides: Java Bytecode Fundamentals I - Tech Talk for JUG.lv, March 2011

Java Bytecode Fundamentals I

View more presentations from Anton Arhipov

JRebel 4.0 M1 Released

JRebel 4.0-M1 was released. Grab it while it's hot!

The new features include integration with HotSwap, support for anonymous classes and adding new session beans to JBoss 4.2/5.1 and Glassfish 2/3.

For the new features, I would encourage everyone to give it a try! JRebel already provides the integration for JSF (Mojarra), JAX-RS (Jersey), CDI (Weld), and now the support for EJBs is extended! It is possible to create a JavaEE6 app with almost no redeploys already. Things are improving quite fast!

LiveRebel Product Demo