Welcome!

IoT User Interface Authors: Liz McMillan, Sanjay Zalavadia, Elizabeth White, Pat Romanski, AppDynamics Blog

Related Topics: Java IoT, Open Source Cloud, IoT User Interface

Java IoT: Blog Post

Long Polling Explained

How long polling could be used in Spring MVC web applications

This article defines long polling and presents a few techniques on how long polling could be used in Spring MVC web applications. Discussion covers both the AJAX and the server part of the solution as well as outlines a few possible options for implementation. The article compares performance of the two server side approaches and describes a practical example of long polling application.

Introduction

On daily basis we are using third party web applications, such as Gmail, or Google docs, which update web page content in real time. How can this be done in our own applications? There are a few techniques that can show real live updates in the web application: server push, long polling, web events, and web sockets to name a few. This article will specifically focus on long polling as a potential solution for real time web updates.

Implementations of long polling is also known as Comet.  Long polling emulates server push mechanism. It is a technique to update the page content by continuously polling the server for new information. The page first initiates the request to the server, and the server then holds on to the request until the new information is available, or until the request expires. As server responds to the request, the information is displayed on the web page. As request is processed, the page issues another request to the server. This article will discuss a few examples of long polling implementation and will explore both sides of the processing logic AJAX on front end and server side code.

News Polling App, pre Servlet 3.0

The first example explores a long polling solution on pre-Servlet 3.0 web server, a server where asynchronous servlets are not supported. In this example the server to broadcast news, and a web page that continuously updates as the news becomes available.  The solution implemented as a web application that consists of 3 components: news publishing service that generates news; long wait controller -- a Spring MVC controller that handles the web requests; and a web page that displays the news and has AJAX code that continuously polls for news. To emulate the real time updates without inundating the web server with requests, the web server needs to hold on to the request and not respond to the user until new information is available. To do this, the thread handling the request needs to be paused. It's not the ideal situation, since each web server only has so many threads available to process request, but that's the only way long polling is done without asynchronous servlets.

polling image

 

More Stories By Henry Naftulin

Henry Naftulin is seasoned, result-oriented enterprise senior software developer with 10 years of experience in enterprise scale software applications. He is highly skilled in Java (J2EE), Web and database enterprise application development. Recognized as strong team player, technical leader and mentor for junior team members. Latest interests include e-Logistics/Supply Chain, financial applications and performance tuning.

@CloudExpo Stories
Your business relies on your applications and your employees to stay in business. Whether you develop apps or manage business critical apps that help fuel your business, what happens when users experience sluggish performance? You and all technical teams across the organization – application, network, operations, among others, as well as, those outside the organization, like ISPs and third-party providers – are called in to solve the problem.
"delaPlex is a software development company. We do team-based outsourcing development," explained Mark Rivers, COO and Co-founder of delaPlex Software, in this SYS-CON.tv interview at 18th Cloud Expo, held June 7-9, 2016, at the Javits Center in New York City, NY.
In his general session at 18th Cloud Expo, Lee Atchison, Principal Cloud Architect and Advocate at New Relic, discussed cloud as a ‘better data center’ and how it adds new capacity (faster) and improves application availability (redundancy). The cloud is a ‘Dynamic Tool for Dynamic Apps’ and resource allocation is an integral part of your application architecture, so use only the resources you need and allocate /de-allocate resources on the fly.
University of Colorado Athletics has selected FORTRUST, Colorado’s only Tier III Gold certified data center, as their official data center and colocation services provider, FORTRUST announced today. A nationally recognized and prominent collegiate athletics program, CU provides a high quality and comprehensive student-athlete experience. The program sponsors 17 varsity teams and in their history, the Colorado Buffaloes have collected an impressive 28 national championships. Maintaining uptime...
CenturyLink has announced that application server solutions from GENBAND are now available as part of CenturyLink’s Networx contracts. The General Services Administration (GSA)’s Networx program includes the largest telecommunications contract vehicles ever awarded by the federal government. CenturyLink recently secured an extension through spring 2020 of its offerings available to federal government agencies via GSA’s Networx Universal and Enterprise contracts. GENBAND’s EXPERiUS™ Application...
Connected devices and the industrial internet are growing exponentially every year with Cisco expecting 50 billion devices to be in operation by 2020. In this period of growth, location-based insights are becoming invaluable to many businesses as they adopt new connected technologies. Knowing when and where these devices connect from is critical for a number of scenarios in supply chain management, disaster management, emergency response, M2M, location marketing and more. In his session at @Th...
Machine Learning helps make complex systems more efficient. By applying advanced Machine Learning techniques such as Cognitive Fingerprinting, wind project operators can utilize these tools to learn from collected data, detect regular patterns, and optimize their own operations. In his session at 18th Cloud Expo, Stuart Gillen, Director of Business Development at SparkCognition, discussed how research has demonstrated the value of Machine Learning in delivering next generation analytics to imp...
The idea of comparing data in motion (at the sensor level) to data at rest (in a Big Data server warehouse) with predictive analytics in the cloud is very appealing to the industrial IoT sector. The problem Big Data vendors have, however, is access to that data in motion at the sensor location. In his session at @ThingsExpo, Scott Allen, CMO of FreeWave, discussed how as IoT is increasingly adopted by industrial markets, there is going to be an increased demand for sensor data from the outermos...
"SpeedyCloud's specialty lies in providing cloud services - we provide IaaS for Internet and enterprises companies," explained Hao Yu, CEO and co-founder of SpeedyCloud, in this SYS-CON.tv interview at 18th Cloud Expo, held June 7-9, 2016, at the Javits Center in New York City, NY.
It's easy to assume that your app will run on a fast and reliable network. The reality for your app's users, though, is often a slow, unreliable network with spotty coverage. What happens when the network doesn't work, or when the device is in airplane mode? You get unhappy, frustrated users. An offline-first app is an app that works, without error, when there is no network connection. In his session at 18th Cloud Expo, Bradley Holt, a Developer Advocate with IBM Cloud Data Services, discussed...
In his keynote at 18th Cloud Expo, Andrew Keys, Co-Founder of ConsenSys Enterprise, provided an overview of the evolution of the Internet and the Database and the future of their combination – the Blockchain. 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 sett...
IoT is rapidly changing the way enterprises are using data to improve business decision-making. In order to derive business value, organizations must unlock insights from the data gathered and then act on these. In their session at @ThingsExpo, Eric Hoffman, Vice President at EastBanc Technologies, and Peter Shashkin, Head of Development Department at EastBanc Technologies, discussed how one organization leveraged IoT, cloud technology and data analysis to improve customer experiences and effi...
"Avere Systems is a hybrid cloud solution provider. We have customers that want to use cloud storage and we have customers that want to take advantage of cloud compute," explained Rebecca Thompson, VP of Marketing at Avere Systems, in this SYS-CON.tv interview at 18th Cloud Expo, held June 7-9, 2016, at the Javits Center in New York City, NY.
There are several IoTs: the Industrial Internet, Consumer Wearables, Wearables and Healthcare, Supply Chains, and the movement toward Smart Grids, Cities, Regions, and Nations. There are competing communications standards every step of the way, a bewildering array of sensors and devices, and an entire world of competing data analytics platforms. To some this appears to be chaos. In this power panel at @ThingsExpo, moderated by Conference Chair Roger Strukhoff, Bradley Holt, Developer Advocate a...
The U.S. Army Intelligence and Security Command (INSCOM) has awarded BAE Systems a five-year contract worth as much as $75 million to provide enhanced geospatial intelligence technical and analytical support. The award was issued under the INSCOM Global Intelligence indefinite delivery, indefinite quantity contract.
More and more companies are looking to microservices as an architectural pattern for breaking apart applications into more manageable pieces so that agile teams can deliver new features quicker and more effectively. What this pattern has done more than anything to date is spark organizational transformations, setting the foundation for future application development. In practice, however, there are a number of considerations to make that go beyond simply “build, ship, and run,” which changes ho...
In addition to all the benefits, IoT is also bringing new kind of customer experience challenges - cars that unlock themselves, thermostats turning houses into saunas and baby video monitors broadcasting over the internet. This list can only increase because while IoT services should be intuitive and simple to use, the delivery ecosystem is a myriad of potential problems as IoT explodes complexity. So finding a performance issue is like finding the proverbial needle in the haystack.
Creating replica copies to tolerate a certain number of failures is easy, but very expensive at cloud-scale. Conventional RAID has lower overhead, but it is limited in the number of failures it can tolerate. And the management is like herding cats (overseeing capacity, rebuilds, migrations, and degraded performance). Download Slide Deck: ▸ Here In his general session at 18th Cloud Expo, Scott Cleland, Senior Director of Product Marketing for the HGST Cloud Infrastructure Business Unit, discusse...
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, wh...
What does it look like when you have access to cloud infrastructure and platform under the same roof? Let’s talk about the different layers of Technology as a Service: who cares, what runs where, and how does it all fit together. In his session at 18th Cloud Expo, Phil Jackson, Lead Technology Evangelist at SoftLayer, an IBM company, spoke about the picture being painted by IBM Cloud and how the tools being crafted can help fill the gaps in your IT infrastructure.