Welcome!

Weblogic Authors: Yeshim Deniz, Elizabeth White, Michael Meiner, Michael Bushong, Avi Rosenthal

Related Topics: Weblogic

Weblogic: Article

Transactions: How Distributed Are Yours?

Talk to your peers

Another discussion based on a weblogic.developer.interest.transaction posting this month. It's a newsgroup that always proves to be a good source of information for the world at large when it comes to transactional behavior (and a good source of inspiration for me when the article time of the month rolls around again).

This particular posting is a great illustration of how an apparently simple assumption can pitch you into the bowels of the infrastructure, if you're not carefully guided by the architecture you're building against, and the possibilities it offers. The original posting ran:

We have to use distributed transactions between an XADataSource configured at the Web tier level in Tomcat 4.1.27 and an XADataSource configured in WebLogic Server 8.1. As a proof of concept, I built a small servlet sample that uses the XADataSource in Tomcat and uses the transaction manager of WebLogic.

When enlisting the XAResource with the javax.transaction.Transaction object, I keep receiving the following exception:

javax.transaction.SystemException: Not implemented at
weblogic.corba.j2ee.transaction.TransactionManagerImpl.enlistResource
(TransactionManagerImpl.java:370)
at com.myco.jta.TestServlet.addSubscription(TestServlet.java:103)
at com.myco.jta.TestServlet.doGet(TestServlet.java:46)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:740)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:853)

We use XAPool from ObjectWeb as the XADataSource implementation. I'd like to know if we are using JTA properly and if we are missing a configuration of some sort at the WebLogic level.

On the face of it, what could be simpler: a distributed architecture, and we want distributed transactions so let's start coding... But these exceptions quickly put a stop to that, and give pause for thought... Let's think this through.

A first observation, at a high level (and at a tangent to the whole point of this article), is the implicit physical splitting of tiers in this posting. Okay, there may be very good reasons in this case why Tomcat is used for the JSP/servlet logic - maybe it's already in production and is being extended - but WebLogic has a perfectly good servlet/JSP capability. It is amazing how many people decide that the fact that Sun describes a Web tier and an EJB tier means that these tiers must be physically separate. Even people using WebLogic for both the Web tier and the EJB tier often decide that they should deploy different WebLogic instances for both. This is not necessarily the case. Calling between processes is costly and a source of complexity in development, configuration management, and production maintenance. Yes, you can make the tiers physically separate, but even if all the tiers are deployed in a single WebLogic instance they are no less logically distinct! Sorry about that rant, this is a subject that really gets my goat. Just be thankful that I fought the temptation to type the whole of this paragraph in bold caps!

That Really Gets My Goat!
So, Ommmmm... Calm, calm, calm... and back to the plot.

At the high level, transactions flow around our J2EE system quite transparently; you start them, make calls, commit them, and take it for granted that the transaction context flowed around with your calls, and the commit processing touched all the resources you ended up using. This sounds like magic, and - of course - like everything else in the world, it isn't. There is a rational explanation. To find it, you just need to look beneath the J2EE surface you're coding to. What happened under the covers is that every time you made a call, the runtime discovered a Transaction object associated with your thread. This discovery prompted the runtime to piggyback the data about the transaction with the request. The piggybacked transaction information has, in turn, caused the infrastructure on the receiving end to do the "right thing" in terms of associating a transaction with its thread of control, and piggybacked data about the resources that got touched to make sure all the bits of transaction know about each other, so when the time comes the transaction co-ordinator can wander by, tell all the resources (which it has collected a list of) to commit, and life is good. All this apparent magic is wonderful, but it does imply a pretty close coupling between the application server's runtime infrastructure and the transaction manager, and this implication is not for nothing - the two are pretty inextricably tied together. So when you start talking about the scenario laid out in the newsgroup, where two different infrastructure implementations are involved, things are going to get a bit hairy if you carry on trying to make the simple assumption that transactions will flow between the containers and "just work" when it comes to commit time.

What it boils down to is that BEA WebLogic cannot make any assumptions about the nature of a client that is calling it but, as I discussed way back in November 2002 (WLDJ, Vol. 1, issue 11), it tries to smooth over the cracks by allowing a client to demarcate transactions whose completion will be delegated to a server-side transaction manager. A Tomcat client is no exception to that; as far as WebLogic is concerned, it is every bit as incapable as an applet.

What's Needed Is a Peer Relationship
What's needed to flow transactions between implementations in the way that the original poster wanted is a peer relationship between them, not a client/server one. If the two containers can be confident that each can look after itself in terms of transaction logging and recovery, then all that is needed is a shared understanding of how the transactions in one environment map on to those in the other. One way of doing this is via RMI/IIOP. If the containers are both speaking that protocol (as they are mandated to be able to do by J2EE 1.3) then the CORBA OTS specification provides a standard mechanism and interfaces for the transactions to flow through. Each container can handle its own internal implementation, with OTS providing a gateway between them. Internally to WebLogic, this gateway is implemented via a concept called an "Interposed Transaction Manager" - if WebLogic needs to import a transaction via OTS, that actually entails listening for "prepare", "commit", and "rollback" instructions from the remote system and responding appropriately to them. The BEA WebLogic transaction manager simply sits between these instructions and the actual resources participating in the transaction on the WebLogic side - it is interposed between the TM that controls the transaction and the local resources that it manages. If you think about it, responding to begin/prepare/commit/abort commands is exactly what any resource manager does through the xa interface. Wouldn't it be a neat trick if an xa interface could be exposed to WebLogic's transaction manager; then any foreign transaction manager could propagate transactions into WebLogic via xa, as if it were a database or any other xa resource, irrespective of support for any given network protocol.

The good news is that WebLogic's transaction manager offers just such a capability via the getServerInterposedTransactionManager and getClientInterposedTransactionManager methods provided by the weblogic.transaction.TxHelper. These methods give you the ability to get pretty exotic with the propagation of transactions into and out of WebLogic, to help you stitch together the end-to-end propagation of transactions.

As for the bad news... Well, until Tomcat grows a transaction manager of its own as a peer to WebLogic's, the scenario we started from just isn't going to work. Not that that's necessarily a bad thing - client code demarcating transactions can get some transaction architects foaming at the mouth and ranting, but that's a story for another month!

More Stories By Peter Holditch

Peter Holditch is a senior presales engineer in the UK for Azul Systems. Prior to joining Azul he spent nine years at BEA systems, going from being one of their first Professional Services consultants in Europe and finishing up as a principal presales engineer. He has an R&D background (originally having worked on BEA's Tuxedo product) and his technical interests are in high-throughput transaction systems. "Of the pitch" Peter likes to brew beer, build furniture, and undertake other ludicrously ambitious projects - but (generally) not all at the same time!

Comments (0)

Share your thoughts on this story.

Add your comment
You must be signed in to add a comment. Sign-in | Register

In accordance with our Comment Policy, we encourage comments that are on topic, relevant and to-the-point. We will remove comments that include profanity, personal attacks, racial slurs, threats of violence, or other inappropriate material that violates our Terms and Conditions, and will block users who make repeated violations. We ask all readers to expect diversity of opinion and to treat one another with dignity and respect.


@ThingsExpo Stories
"Space Monkey by Vivent Smart Home is a product that is a distributed cloud-based edge storage network. Vivent Smart Home, our parent company, is a smart home provider that places a lot of hard drives across homes in North America," explained JT Olds, Director of Engineering, and Brandon Crowfeather, Product Manager, at Vivint Smart Home, in this SYS-CON.tv interview at @ThingsExpo, held Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA.
Coca-Cola’s Google powered digital signage system lays the groundwork for a more valuable connection between Coke and its customers. Digital signs pair software with high-resolution displays so that a message can be changed instantly based on what the operator wants to communicate or sell. In their Day 3 Keynote at 21st Cloud Expo, Greg Chambers, Global Group Director, Digital Innovation, Coca-Cola, and Vidya Nagarajan, a Senior Product Manager at Google, discussed how from store operations and ...
"Cloud Academy is an enterprise training platform for the cloud, specifically public clouds. We offer guided learning experiences on AWS, Azure, Google Cloud and all the surrounding methodologies and technologies that you need to know and your teams need to know in order to leverage the full benefits of the cloud," explained Alex Brower, VP of Marketing at Cloud Academy, in this SYS-CON.tv interview at 21st Cloud Expo, held Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clar...
In his session at 21st Cloud Expo, Carl J. Levine, Senior Technical Evangelist for NS1, will objectively discuss how DNS is used to solve Digital Transformation challenges in large SaaS applications, CDNs, AdTech platforms, and other demanding use cases. Carl J. Levine is the Senior Technical Evangelist for NS1. A veteran of the Internet Infrastructure space, he has over a decade of experience with startups, networking protocols and Internet infrastructure, combined with the unique ability to it...
"Akvelon is a software development company and we also provide consultancy services to folks who are looking to scale or accelerate their engineering roadmaps," explained Jeremiah Mothersell, Marketing Manager at Akvelon, in this SYS-CON.tv interview at 21st Cloud Expo, held Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA.
It is of utmost importance for the future success of WebRTC to ensure that interoperability is operational between web browsers and any WebRTC-compliant client. To be guaranteed as operational and effective, interoperability must be tested extensively by establishing WebRTC data and media connections between different web browsers running on different devices and operating systems. In his session at WebRTC Summit at @ThingsExpo, Dr. Alex Gouaillard, CEO and Founder of CoSMo Software, presented ...
"There's plenty of bandwidth out there but it's never in the right place. So what Cedexis does is uses data to work out the best pathways to get data from the origin to the person who wants to get it," explained Simon Jones, Evangelist and Head of Marketing at Cedexis, in this SYS-CON.tv interview at 21st Cloud Expo, held Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA.
WebRTC is great technology to build your own communication tools. It will be even more exciting experience it with advanced devices, such as a 360 Camera, 360 microphone, and a depth sensor camera. In his session at @ThingsExpo, Masashi Ganeko, a manager at INFOCOM Corporation, introduced two experimental projects from his team and what they learned from them. "Shotoku Tamago" uses the robot audition software HARK to track speakers in 360 video of a remote party. "Virtual Teleport" uses a multip...
"IBM is really all in on blockchain. We take a look at sort of the history of blockchain ledger technologies. It started out with bitcoin, Ethereum, and IBM evaluated these particular blockchain technologies and found they were anonymous and permissionless and that many companies were looking for permissioned blockchain," stated René Bostic, Technical VP of the IBM Cloud Unit in North America, in this SYS-CON.tv interview at 21st Cloud Expo, held Oct 31 – Nov 2, 2017, at the Santa Clara Conventi...
Gemini is Yahoo’s native and search advertising platform. To ensure the quality of a complex distributed system that spans multiple products and components and across various desktop websites and mobile app and web experiences – both Yahoo owned and operated and third-party syndication (supply), with complex interaction with more than a billion users and numerous advertisers globally (demand) – it becomes imperative to automate a set of end-to-end tests 24x7 to detect bugs and regression. In th...
SYS-CON Events announced today that Telecom Reseller has been named “Media Sponsor” of SYS-CON's 22nd International Cloud Expo, which will take place on June 5-7, 2018, at the Javits Center in New York, NY. Telecom Reseller reports on Unified Communications, UCaaS, BPaaS for enterprise and SMBs. They report extensively on both customer premises based solutions such as IP-PBX as well as cloud based and hosted platforms.
SYS-CON Events announced today that CrowdReviews.com has been named “Media Sponsor” of SYS-CON's 22nd International Cloud Expo, which will take place on June 5–7, 2018, at the Javits Center in New York City, NY. CrowdReviews.com is a transparent online platform for determining which products and services are the best based on the opinion of the crowd. The crowd consists of Internet users that have experienced products and services first-hand and have an interest in letting other potential buye...
"MobiDev is a software development company and we do complex, custom software development for everybody from entrepreneurs to large enterprises," explained Alan Winters, U.S. Head of Business Development at MobiDev, in this SYS-CON.tv interview at 21st Cloud Expo, held Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA.
A strange thing is happening along the way to the Internet of Things, namely far too many devices to work with and manage. It has become clear that we'll need much higher efficiency user experiences that can allow us to more easily and scalably work with the thousands of devices that will soon be in each of our lives. Enter the conversational interface revolution, combining bots we can literally talk with, gesture to, and even direct with our thoughts, with embedded artificial intelligence, whic...
SYS-CON Events announced today that Evatronix will exhibit at SYS-CON's 21st International Cloud Expo®, which will take place on Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. Evatronix SA offers comprehensive solutions in the design and implementation of electronic systems, in CAD / CAM deployment, and also is a designer and manufacturer of advanced 3D scanners for professional applications.
Leading companies, from the Global Fortune 500 to the smallest companies, are adopting hybrid cloud as the path to business advantage. Hybrid cloud depends on cloud services and on-premises infrastructure working in unison. Successful implementations require new levels of data mobility, enabled by an automated and seamless flow across on-premises and cloud resources. In his general session at 21st Cloud Expo, Greg Tevis, an IBM Storage Software Technical Strategist and Customer Solution Architec...
To get the most out of their data, successful companies are not focusing on queries and data lakes, they are actively integrating analytics into their operations with a data-first application development approach. Real-time adjustments to improve revenues, reduce costs, or mitigate risk rely on applications that minimize latency on a variety of data sources. In his session at @BigDataExpo, Jack Norris, Senior Vice President, Data and Applications at MapR Technologies, reviewed best practices to ...
An increasing number of companies are creating products that combine data with analytical capabilities. Running interactive queries on Big Data requires complex architectures to store and query data effectively, typically involving data streams, an choosing efficient file format/database and multiple independent systems that are tied together through custom-engineered pipelines. In his session at @BigDataExpo at @ThingsExpo, Tomer Levi, a senior software engineer at Intel’s Advanced Analytics gr...
When talking IoT we often focus on the devices, the sensors, the hardware itself. The new smart appliances, the new smart or self-driving cars (which are amalgamations of many ‘things’). When we are looking at the world of IoT, we should take a step back, look at the big picture. What value are these devices providing? IoT is not about the devices, it’s about the data consumed and generated. The devices are tools, mechanisms, conduits. In his session at Internet of Things at Cloud Expo | DXWor...
Everything run by electricity will eventually be connected to the Internet. Get ahead of the Internet of Things revolution. In his session at @ThingsExpo, Akvelon expert and IoT industry leader Sergey Grebnov provided an educational dive into the world of managing your home, workplace and all the devices they contain with the power of machine-based AI and intelligent Bot services for a completely streamlined experience.