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

Related Topics: Weblogic

Weblogic: Article

Distributing Tasks in a Clustered Application Using JMS

Much more than asynchronous data transfer

Distributing Tasks in a Clustered Application Using JMS Much more than asynchronous data transfer

Decoupling and delaying processing in a request-driven environment is one of the key strategies in creating a robust and scalable distributed application. Many services rely on clustering alone to ensure scalability, but they frequently run into trouble when newfound requirements keep application complexity growing.

Although server clustering is an essential technology that facilitates scalability, it can be rather inefficient when all processing is done synchronously. Throughput can be increased, but responsiveness is a tougher nut to crack.

In this article, I discuss asynchronous processing and illustrate how clever task management can increase the performance, availability, scalability, and manageability of your application. We will create a generic task distribution framework that can send any task to either one or every server in your cluster, in a highly configurable fashion. Our framework will implement the well-known Command pattern by using polymorphism and the Java Message Service (JMS).

What Does Decoupling Mean in Practice?
When a server receives a client request, it usually needs to perform several individual tasks before a response can be returned. Decoupling means that instead of performing all tasks at once, some are instead queued and processed asynchronously. Because queuing is normally a low-cost operation, the synchronous request will finish quicker.

And the Benefits?
Processing tasks sequentially and in parallel is generally more efficient than processing them randomly (whenever clients happen to make requests). The positive impact is greater than what is immediately apparent. In theory, decoupling can increase performance in the following areas:

  • Robustness: Increases because requests will rely on fewer processes that can fail
  • Responsiveness: Partial post processing of requests decreases the time between receiving a request and returning a response
  • Scalability: All decoupled processes can grow in complexity without the threat of decreased responsiveness
  • Availability: Failures can be handled without the client ever knowing that something went wrong

Automatic retries are easily configured for situations where subsystems are unavailable.

Naturally, the difference between theory and practice will vary from application to application. However, it is clear that almost every implementation will have at least some of the aforementioned benefits.

Sounds Great, But Are There Any Pitfalls?
As with most good things, there are some caveats. One of the most severe is that you might actually find yourself decreasing availability if you don't ensure that you have enough hardware to clear busy processing queues. Queues grow very rapidly if more asynchronous requests come in than your system is able to process. Care has to be taken in the design, and automated monitoring of queues is certainly advisable. Another obvious problem is that most processes in request-driven environments aren't very good candidates for decoupling. In fact, most of the processing might be required to return a response. Sometimes it will require some out-of-the-box thinking and maybe even a change in the way you serve your clients.

Which Processes Can We Decouple?
From a purely technical perspective, nearly all processes can be decoupled. For instance, you can decouple an ordering transaction by queuing a list of purchased items together with customer details - the asynchronous process will take care of the rest. The downside is that you can't include any processing details in the response. Thus, meticulous prevalidation of data is important to ensure that nothing will go wrong.

An increasingly popular implementation is to queue requests immediately and then keep polling the server to know when a response can be retrieved. Although this approach is actually synchronous in nature and won't improve request processing times, it has the psychological benefit that a progress bar can be displayed during polling.

In addition to decoupling integral business logic (which can be a formidable challenge), less central processes such as logging and sending e-mail are very good candidates to consider. There is no reason to have a client wait for such tasks to complete when performance is of the essence. E-mail in particular is a very good candidate for decoupling. Let's have a closer look.

Case Study: Asynchronous E-mail
Sending e-mail the traditional way (as part of a synchronous request) poses some problems. First of all, connecting to an e-mail server requires a network round-trip and it might be slow, especially if the server is very busy. An overloaded e-mail server can even make a service that relies on e-mail temporarily unavailable.

XA Transaction Support
Another easily overlooked issue is that e-mail servers are commonly nontransactional by nature. This can cause inconsistent notifications when transactions are rolled back - a message can't be cancelled after it has been queued. Fortunately, JMS supports transactions and can fix this problem by delaying the delivery of a message until its underlying transaction is committed.

Take into account that when accessing the database and transaction-aware JMS, you will need to use XA and two-phase commit (2PC) transactions. It is possible to emulate XA with non-XA resources, but you might end up with inconsistent data. Enabling XA is a configuration issue and usually requires no changes in code. See the WebLogic documentation for details.

More Stories By John-Axel Stråhlman

John-Axel Stråhlman is the founder and CEO of Sanda Interactive Ltd (www.stc-interactive.com), a software consulting company based in Espoo, Finland. He is a distributed systems specialist and has been working as a consultant for his clients' projects for more than five years.

Comments (8) View Comments

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.

Most Recent Comments
John-Axel Strahlman 09/10/05 01:59:30 PM EDT

The source code for this article has been updated. You can access it by clicking on the source code link below the article.


mark sisson 08/30/05 12:43:57 PM EDT

I'm trying to find a download of sample code for this article but only found a SMALL link at the bottom of the article that is a link to a little snipet of code.

Is there a full blown example that accompanies this article? It is exactly what I've been looking for !!!

Thanks in advance.

Charles Steinberg 05/24/05 03:26:05 PM EDT

A question related to the configuration database for WLI 8.1: I am looking for documentation on the sizing of the WLI Database, vs. the Application database. Do you have any information to help establish a baseline?

John-Axel Strahlman 03/28/05 01:52:08 PM EST


You need to configure JMS queues and write an MDB that does the asynchronous processing. The framework will only work on an application running on WebLogic Server 6.1 or newer. Drop me an email if you need more specific instructions.

The link to the performance guide is missing a slash between products and wlserver, sorry about that.


meir 03/24/05 04:02:49 PM EST

1.try to press on:

and no response !!!

2.what kind of weblogic software needed to install?

3.how do i use this code:

Listing 3: Framework sample usage

DistributedLogger logger =
new DistributedLogger();

String text =
"Hello asynchronous execution!"

logger, //Command instance
1000, //delay
true, //runEverywhere
false, //persisted
false, //enableXA
4); //delay.

i mean from a "main" program that includes "weblogic" classes?

Patricia Thomas 03/14/05 04:38:23 PM EST

We're also using JMS for several asynchronous tasks, but never thought of using a generic command processor like this. Until now, we have used dedicated queues and MDBs for each task, but this is clearly a better and more manageable solution! Thanks!

John-Axel Strahlman 03/01/05 03:33:24 AM EST

Yes, all your CommandMessage classes need to be in the classpath of the server (or servers) that does the execution.

Steve Rogers 02/28/05 02:50:21 PM EST

I assume each new type of CommandMessage, like the DistributedLogger, have to be in the Classpath of the Server. Otherwise, can the serialized objects method be executed?

IoT & Smart Cities Stories
Headquartered in Plainsboro, NJ, Synametrics Technologies has provided IT professionals and computer systems developers since 1997. Based on the success of their initial product offerings (WinSQL and DeltaCopy), the company continues to create and hone innovative products that help its customers get more from their computer applications, databases and infrastructure. To date, over one million users around the world have chosen Synametrics solutions to help power their accelerated business or per...
Poor data quality and analytics drive down business value. In fact, Gartner estimated that the average financial impact of poor data quality on organizations is $9.7 million per year. But bad data is much more than a cost center. By eroding trust in information, analytics and the business decisions based on these, it is a serious impediment to digital transformation.
@DevOpsSummit at Cloud Expo, taking place November 12-13 in New York City, NY, is co-located with 22nd international CloudEXPO | first international DXWorldEXPO and will feature technical sessions from a rock star conference faculty and the leading industry players in the world. The widespread success of cloud computing is driving the DevOps revolution in enterprise IT. Now as never before, development teams must communicate and collaborate in a dynamic, 24/7/365 environment. There is no time t...
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, its about the data consumed and generated. The devices are tools, mechanisms, conduits. This paper discusses the considerations when dealing with the...
SYS-CON Events announced today that IoT Global Network has been named “Media Sponsor” of SYS-CON's @ThingsExpo, which will take place on June 6–8, 2017, at the Javits Center in New York City, NY. The IoT Global Network is a platform where you can connect with industry experts and network across the IoT community to build the successful IoT business of the future.
IoT is rapidly becoming mainstream as more and more investments are made into the platforms and technology. As this movement continues to expand and gain momentum it creates a massive wall of noise that can be difficult to sift through. Unfortunately, this inevitably makes IoT less approachable for people to get started with and can hamper efforts to integrate this key technology into your own portfolio. There are so many connected products already in place today with many hundreds more on the h...
CloudEXPO New York 2018, colocated with DXWorldEXPO New York 2018 will be held November 11-13, 2018, in New York City and will bring together Cloud Computing, FinTech and Blockchain, Digital Transformation, Big Data, Internet of Things, DevOps, AI, Machine Learning and WebRTC to one location.
The best way to leverage your Cloud Expo presence as a sponsor and exhibitor is to plan your news announcements around our events. The press covering Cloud Expo and @ThingsExpo will have access to these releases and will amplify your news announcements. More than two dozen Cloud companies either set deals at our shows or have announced their mergers and acquisitions at Cloud Expo. Product announcements during our show provide your company with the most reach through our targeted audiences.
Andrew Keys is Co-Founder of ConsenSys Enterprise. He comes to ConsenSys Enterprise with capital markets, technology and entrepreneurial experience. Previously, he worked for UBS investment bank in equities analysis. Later, he was responsible for the creation and distribution of life settlement products to hedge funds and investment banks. After, he co-founded a revenue cycle management company where he learned about Bitcoin and eventually Ethereal. Andrew's role at ConsenSys Enterprise is a mul...
Disruption, Innovation, Artificial Intelligence and Machine Learning, Leadership and Management hear these words all day every day... lofty goals but how do we make it real? Add to that, that simply put, people don't like change. But what if we could implement and utilize these enterprise tools in a fast and "Non-Disruptive" way, enabling us to glean insights about our business, identify and reduce exposure, risk and liability, and secure business continuity?