Welcome!

Java Authors: Pat Romanski, Liz McMillan, Elizabeth White, Trevor Parsons, Jason Bloomberg

Related Topics: Java, SOA & WOA, AJAX & REA, Web 2.0

Java: Article

Don’t Let Load Balancers Ruin Your Holiday Business

Proactive performance management

An eCommerce site that crashes seven times during the Christmas season being down for up to five hours each time it crashes is a site that loses a lot of money and reputation. It happened to one of our customers who told this story at our annual performance conference earlier this month. Among the several reasons that led to these crashes I want to share more details on one of them that I see more often with other websites as well. Load balancers on a round-robin instead of least-busy can easily lead to app server crashes caused by heap memory exhaustion. Let's dig into some details on how to identify these problems and how to avoid it.

The Symptom: Crashing Tomcat Instances
The website is deployed on six Tomcats with three front-end Apache Web Servers. During peak load hours individual Tomcat instances started showing growing response times and a growing number of requests in the Tomcat processing queue. After a while these instances crashed due to out-of-memory exceptions and with that also brought down the rest of the site as load couldn't be handled any more with the remaining servers. Figure 1 shows the actual flow of transactions through the system highlighting unevenly distributed response time in the application servers and functional errors being reported on all tiers (red-colored server icon):

Even with equally distributed load (Round Robin Load Balancer Setting) one of the Tomcats spiked in Response Time Contribution before crashing

Once the App Server started rejecting incoming connections we can observe the first ripple effect of errors. We can see a very high number of exceptions in the database layer, exceptions thrown between application tiers with the web app responding with HTTP 500s:

Within 30 minutes the application serves 43000 pages with an HTTP 500 Response correlating to Exceptions in the Database and Inter-Tier Communication

The Root Cause: Inefficient Database Statements and Connection Pool Usage
The exceptions caught in the Database Layer (JDBC) were already a very good hint of the root cause of this problem. A closer look at the Exceptions shows that connection pools are exhausted, which causes problems in the different components of the application:

Exhausted Connection Pool causes Exceptions that impact Data Access Layer as well as Widget Rendering

Looking at the performance breakdown by application layer reveals how much performance impact connection pooling has on the overall transaction response time:

Due to the connection pool problem a single request had to wait 3.8s on average to obtain a connection from the pool

Now - it was not only the size of the pool that was the problem - but - several very inefficient database statements that took long to execute for certain business transactions of the application. This caused the application server to hold on to the connection longer than normal. As the load balancer was configured with Round Robin the app server still got additional requests served. Eventually - just by the random nature of incoming requests - one app server received several of these requests that executed these inefficient database calls. Once the connection pool was exhausted the application started throwing exceptions that ultimately also led to a crash of the JVM. Once the first app server crashed, it didn't take too long to take the other app servers down as well.

The Solution: Optimizing App and Load Balancer
The problem was fixed by looking at the slowest database statements and optimizing them for performance by, e.g, adding indices on the database or making the SQL statements more efficient. They also optimized the pool size to accommodate the expected load during peak hours.

 

They started by optimizing SQL Statements that took long to execute and those that got executed several times within the same transaction

They also changed the load balancer setting from Round-Robin to Least-Busy, which was the preferred setting from the LB vendor but had simply forgotten to configure in the production environment.

The Result: Site Has Not Been Down Since
Since they made the changes to the application and the load balancer the site has never gone down since. Now - the next holiday season is coming up and they are ready for the next seasonal spikes. Even though they are really confident that everything will work without any problems, they learned their lesson and are approaching performance proactively through proper load testing.

Next Steps: Proactive Performance Management
The lesson learned was that these problems could have been found prior to the holiday shopping season by doing proper load testing. They did load testing before but never encountered this problem because of two reasons: 1) they didn't test using expected peak volumes for long enough sessions and 2) didn't use a tool that simulated real customer behavior variations (too few scripts and the scripts were too simple) that tested their highly interactive web site.

Their strategy for proactive performance management is that they:

  1. Perform load tests on the production system during low traffic hours (2 a.m.-6 a.m.), accepting the risk of minor sales losses in case of a crash, versus major sales losses during the holiday shopping season.
  2. Multiply the hourly load test volume by 2.5 since their actual peaks are 10 hours long.
  3. Use a load testing service that uses real browsers in different locations around the U.S.
  4. Use an APM solution that identifies problems within the application while running the load test.

If you want to read more on common performance problems that are not found prior to moving to production check out my recent series of blogs: Supersized Content, Deployment Mistakes or Excessive Logging

More Stories By Michael Kopp

Michael Kopp has over 12 years of experience as an architect and developer in the Enterprise Java space. Before coming to CompuwareAPM dynaTrace he was the Chief Architect at GoldenSource, a major player in the EDM space. In 2009 he joined dynaTrace as a technology strategist in the center of excellence. He specializes application performance management in large scale production environments with special focus on virtualized and cloud environments. His current focus is how to effectively leverage BigData Solutions and how these technologies impact and change the application landscape.

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
Scott Jenson leads a project called The Physical Web within the Chrome team at Google. Project members are working to take the scalability and openness of the web and use it to talk to the exponentially exploding range of smart devices. Nearly every company today working on the IoT comes up with the same basic solution: use my server and you'll be fine. But if we really believe there will be trillions of these devices, that just can't scale. We need a system that is open a scalable and by using the URL as a basic building block, we open this up and get the same resilience that the web enjoys.
The Internet of Things is tied together with a thin strand that is known as time. Coincidentally, at the core of nearly all data analytics is a timestamp. When working with time series data there are a few core principles that everyone should consider, especially across datasets where time is the common boundary. In his session at Internet of @ThingsExpo, Jim Scott, Director of Enterprise Strategy & Architecture at MapR Technologies, discussed single-value, geo-spatial, and log time series data. By focusing on enterprise applications and the data center, he will use OpenTSDB as an example t...
P2P RTC will impact the landscape of communications, shifting from traditional telephony style communications models to OTT (Over-The-Top) cloud assisted & PaaS (Platform as a Service) communication services. The P2P shift will impact many areas of our lives, from mobile communication, human interactive web services, RTC and telephony infrastructure, user federation, security and privacy implications, business costs, and scalability. In his session at @ThingsExpo, Robin Raymond, Chief Architect at Hookflash, will walk through the shifting landscape of traditional telephone and voice services ...
The Domain Name Service (DNS) is one of the most important components in networking infrastructure, enabling users and services to access applications by translating URLs (names) into IP addresses (numbers). Because every icon and URL and all embedded content on a website requires a DNS lookup loading complex sites necessitates hundreds of DNS queries. In addition, as more internet-enabled ‘Things' get connected, people will rely on DNS to name and find their fridges, toasters and toilets. According to a recent IDG Research Services Survey this rate of traffic will only grow. What's driving t...
Enthusiasm for the Internet of Things has reached an all-time high. In 2013 alone, venture capitalists spent more than $1 billion dollars investing in the IoT space. With "smart" appliances and devices, IoT covers wearable smart devices, cloud services to hardware companies. Nest, a Google company, detects temperatures inside homes and automatically adjusts it by tracking its user's habit. These technologies are quickly developing and with it come challenges such as bridging infrastructure gaps, abiding by privacy concerns and making the concept a reality. These challenges can't be addressed w...
Explosive growth in connected devices. Enormous amounts of data for collection and analysis. Critical use of data for split-second decision making and actionable information. All three are factors in making the Internet of Things a reality. Yet, any one factor would have an IT organization pondering its infrastructure strategy. How should your organization enhance its IT framework to enable an Internet of Things implementation? In his session at Internet of @ThingsExpo, James Kirkland, Chief Architect for the Internet of Things and Intelligent Systems at Red Hat, described how to revolutioniz...
Bit6 today issued a challenge to the technology community implementing Web Real Time Communication (WebRTC). To leap beyond WebRTC’s significant limitations and fully leverage its underlying value to accelerate innovation, application developers need to consider the entire communications ecosystem.
The definition of IoT is not new, in fact it’s been around for over a decade. What has changed is the public's awareness that the technology we use on a daily basis has caught up on the vision of an always on, always connected world. If you look into the details of what comprises the IoT, you’ll see that it includes everything from cloud computing, Big Data analytics, “Things,” Web communication, applications, network, storage, etc. It is essentially including everything connected online from hardware to software, or as we like to say, it’s an Internet of many different things. The difference ...
Cloud Expo 2014 TV commercials will feature @ThingsExpo, which was launched in June, 2014 at New York City's Javits Center as the largest 'Internet of Things' event in the world.
SYS-CON Events announced today that Windstream, a leading provider of advanced network and cloud communications, has been named “Silver Sponsor” of SYS-CON's 16th International Cloud Expo®, which will take place on June 9–11, 2015, at the Javits Center in New York, NY. Windstream (Nasdaq: WIN), a FORTUNE 500 and S&P 500 company, is a leading provider of advanced network communications, including cloud computing and managed services, to businesses nationwide. The company also offers broadband, phone and digital TV services to consumers primarily in rural areas.
"There is a natural synchronization between the business models, the IoT is there to support ,” explained Brendan O'Brien, Co-founder and Chief Architect of Aria Systems, in this SYS-CON.tv interview at the 15th International Cloud Expo®, held Nov 4–6, 2014, at the Santa Clara Convention Center in Santa Clara, CA.
The major cloud platforms defy a simple, side-by-side analysis. Each of the major IaaS public-cloud platforms offers their own unique strengths and functionality. Options for on-site private cloud are diverse as well, and must be designed and deployed while taking existing legacy architecture and infrastructure into account. Then the reality is that most enterprises are embarking on a hybrid cloud strategy and programs. In this Power Panel at 15th Cloud Expo (http://www.CloudComputingExpo.com), moderated by Ashar Baig, Research Director, Cloud, at Gigaom Research, Nate Gordon, Director of T...
An entirely new security model is needed for the Internet of Things, or is it? Can we save some old and tested controls for this new and different environment? In his session at @ThingsExpo, New York's at the Javits Center, Davi Ottenheimer, EMC Senior Director of Trust, reviewed hands-on lessons with IoT devices and reveal a new risk balance you might not expect. Davi Ottenheimer, EMC Senior Director of Trust, has more than nineteen years' experience managing global security operations and assessments, including a decade of leading incident response and digital forensics. He is co-author of t...

ARMONK, N.Y., Nov. 20, 2014 /PRNewswire/ --  IBM (NYSE: IBM) today announced that it is bringing a greater level of control, security and flexibility to cloud-based application development and delivery with a single-tenant version of Bluemix, IBM's platform-as-a-service. The new platform enables developers to build ap...

The security devil is always in the details of the attack: the ones you've endured, the ones you prepare yourself to fend off, and the ones that, you fear, will catch you completely unaware and defenseless. The Internet of Things (IoT) is nothing if not an endless proliferation of details. It's the vision of a world in which continuous Internet connectivity and addressability is embedded into a growing range of human artifacts, into the natural world, and even into our smartphones, appliances, and physical persons. In the IoT vision, every new "thing" - sensor, actuator, data source, data con...
Technology is enabling a new approach to collecting and using data. This approach, commonly referred to as the "Internet of Things" (IoT), enables businesses to use real-time data from all sorts of things including machines, devices and sensors to make better decisions, improve customer service, and lower the risk in the creation of new revenue opportunities. In his General Session at Internet of @ThingsExpo, Dave Wagstaff, Vice President and Chief Architect at BSQUARE Corporation, discuss the real benefits to focus on, how to understand the requirements of a successful solution, the flow of ...
"BSQUARE is in the business of selling software solutions for smart connected devices. It's obvious that IoT has moved from being a technology to being a fundamental part of business, and in the last 18 months people have said let's figure out how to do it and let's put some focus on it, " explained Dave Wagstaff, VP & Chief Architect, at BSQUARE Corporation, in this SYS-CON.tv interview at @ThingsExpo, held Nov 4-6, 2014, at the Santa Clara Convention Center in Santa Clara, CA.
Focused on this fast-growing market’s needs, Vitesse Semiconductor Corporation (Nasdaq: VTSS), a leading provider of IC solutions to advance "Ethernet Everywhere" in Carrier, Enterprise and Internet of Things (IoT) networks, introduced its IStaX™ software (VSC6815SDK), a robust protocol stack to simplify deployment and management of Industrial-IoT network applications such as Industrial Ethernet switching, surveillance, video distribution, LCD signage, intelligent sensors, and metering equipment. Leveraging technologies proven in the Carrier and Enterprise markets, IStaX is designed to work ac...
C-Labs LLC, a leading provider of remote and mobile access for the Internet of Things (IoT), announced the appointment of John Traynor to the position of chief operating officer. Previously a strategic advisor to the firm, Mr. Traynor will now oversee sales, marketing, finance, and operations. Mr. Traynor is based out of the C-Labs office in Redmond, Washington. He reports to Chris Muench, Chief Executive Officer. Mr. Traynor brings valuable business leadership and technology industry expertise to C-Labs. With over 30 years' experience in the high-tech sector, John Traynor has held numerous...
The 3rd International @ThingsExpo, co-located with the 16th International Cloud Expo - to be held June 9-11, 2015, at the Javits Center in New York City, NY - announces that it is now accepting Keynote Proposals. The Internet of Things (IoT) is the most profound change in personal and enterprise IT since the creation of the Worldwide Web more than 20 years ago. All major researchers estimate there will be tens of billions devices - computers, smartphones, tablets, and sensors - connected to the Internet by 2020. This number will continue to grow at a rapid pace for the next several decades.