Click here to close now.


Agile Computing Authors: David Dodd, Brian Daleiden, Dana Gardner, Pat Romanski, Harry Trott

Blog Feed Post

Architecting for the Cloud


The biggest difference between cloud-based applications and the applications running in your data center is scalability. The cloud offers scalability on demand, allowing you to expand and contract your application as load fluctuates. This scalability is what makes the cloud appealing, but it can’t be achieved by simply lifting your existing application to the cloud. In order to take advantage of what the cloud has to offer, you need to re-architect your application around scalability. The other business benefit comes in terms of price, as in the cloud costs scale linearly with demand.

Sample Architecture of a Cloud-Based Application

Designing an application for the cloud often requires re-architecting your application around scalability. The figure below shows what the architecture of a highly scalable cloud-based application might look like.

The Client Tier: The client tier contains user interfaces for your target platforms, which may include a web-based user interface, a mobile user interface, or even a thick client user interface. There will typically be a web application that performs actions such as user management, session management, and page construction. But for the rest of the interactions the client makes RESTful service calls into the server.

Services: The server is composed of both caching services, from which the clients read data, that host the most recently known good state of all of the systems of record, and aggregate services that interact directly with the systems of record for destructive operations (operations that change the state of the systems of record).

Systems of Record: The systems of record are your domain-specific servers that drive your business functions. These may include user management CRM systems, purchasing systems, reservation systems, and so forth. While these can be new systems in the application you’re building, they are most likely legacy systems with which your application needs to interact. The aggregate services are responsible for abstracting your application from the peculiarities of the systems of record and providing a consistent front-end for your application.

ESB: When systems of record change data, such as by creating a new purchase order, a user “liking” an item, or a user purchasing an airline ticket, the system of record raises an event to a topic. This is where the idea of an event-driven architecture (EDA) comes to the forefront of your application: when the system of record makes a change that other systems may be interested in, it raises an event, and any system interested in that system of record listens for changes and responds accordingly. This is also the reason for using topics rather than using queues: queues support point-to-point messaging whereas topics support publish-subscribe messaging/eventing. If you don’t know who all of your subscribers are when building your application (which you shouldn’t, according to EDA) then publishing to a topic means that anyone can later integrate with your application by subscribing to your topic.

Whenever interfacing with legacy systems, it is desirable to shield the legacy system from load. Therefore, we implement a caching system that maintains the currently known good state of all of the systems of record. And this caching system utilizes the EDA paradigm to listen to changes in the systems of record and update the versions of the data it hosts to match the data in the systems of record. This is a powerful strategy, but it also changes the consistency model from being consistent to being eventually consistent. To illustrate what this means, consider posting an update on your favorite social media site: you may see it immediately, but it may take a few seconds or even a couple minutes before your friends see it. The data will eventually be consistent, but there will be times when the data you see and the data your friends see doesn’t match. If you can tolerate this type consistency then you can reap huge scalability benefits.

NoSQL: Finally, there are many storage options available, but if your application needs to store a huge amount of data it is far easier to scale by using a NoSQL document store. There are various NoSQL document stores, and the one you choose will match the nature of your data. For example, MongoDB is good for storing searchable documents, Neo4J is good at storing highly inter-related data, and Cassandra is good at storing key/value pairs. I typically also recommend some form of search index, such as Solr, to accelerate queries to frequently accessed data.

Let’s begin our deep-dive investigation into this architecture by reviewing service-oriented architectures and REST.

REpresentational State Transfer (REST)

The best pattern for dividing an application into tiers is to use a service-oriented architecture (SOA). There are two main options for this, SOAP and REST. There are many reasons to use each protocol that I won’t go into here, but for our purposes REST is the better choice because it is more scalable.

REST was defined in 2000 by Roy Fielding in his doctoral dissertation and is an architectural style that models elements as a distributed hypermedia system that rides on top of HTTP. Rather than thinking about services and service interfaces, REST defines its interface in terms of resources, and services define how we interact with these resources. HTTP serves as the foundation for RESTful interactions and RESTful services use the HTTP verbs to interact with resources, which are summarized as follows:

  • GET: retrieve a resource

  • POST: create a resource

  • PUT: update a resource

  • PATCH: partially update a resource

  • DELETE: delete a resource

  • HEAD: does this resource exist OR has it changed?

  • OPTIONS: what HTTP verbs can I use with this resource

For example, I might create an Order using a POST, retrieve an Order using a GET, change the product type of the Order using a PATCH, replace the entire Order using a PUT, delete an Order using a DELETE, send a version (passing the version as an Entity Tag or eTag) to see if an Order has changed using a HEAD, and discover permissible Order operations using OPTIONS. The point is that the Order resource is well defined and then the HTTP verbs are used to manipulate that resource.

In addition to keeping application resources and interactions clean, using the HTTP verbs can greatly enhance performance. Specifically, if you define a time-to-live (TTL) on your resources, then HTTP GETs can be cached by the client or by an HTTP cache, which offloads the server from constantly rebuilding the same resource.

REST defines three maturity levels, affectionately known as the Richardson Maturity Model (because it was developed by Leonard Richardson):

  1. Define resources

  2. Properly use the HTTP verbs

  3. Hypermedia Controls

Thus far we have reviewed levels 1 and 2, but what really makes REST powerful is level 3. Hypermedia controls allow resources to define business-specific operations or “next states” for resources. So, as a consumer of a service, you can automatically discover what you can do with the resources. Making resources self-documenting enables you to more easily partition your application into reusable components (and hence makes it easier to divide your application into tiers).

Sideline: you may have heard the acronym HATEOAS, which stands for Hypermedia as the Engine of Application State. HATEOAS is the principle that clients can interact with an application entirely through the hypermedia links that the application provides. This is essentially the formalization of level 3 of the Richardson Maturity Model.

RESTful resources maintain their own state so RESTful web services (the operations that manipulate RESTful resources) can remain stateless. Stateless-ness is a core requirement of scalability because it means that any service instance can respond to any request. Thus, if you need more capacity on any service tier, you can add additional virtual machines to that tier to distribute the load. To illustrate why this is important, let’s consider a counter-example: the behavior of stateful servers. When a server is stateful then it maintains some client state, which means that subsequent requests by a client to that server need to be sent to that specific server instance. If that tier becomes overloaded then adding new server instances to the tier may help new client requests, but will not help existing client requests because the load cannot be easily redistributed.

Furthermore, the resiliency requirements of stateful servers hinder scalability because of fail-over options. What happens if the server to which your client is connected goes down? As an application architect, you want to ensure that client state is not lost, so how to we gracefully fail-over to another server instance? The answer is that we need to replicate client state across multiple server instances (or at least one other instance) and then define a fail-over strategy so that the application automatically redirects client traffic to the failed-over server. The replication overhead and network chatter between replicated servers means that no matter how optimal the implementation, scalability can never be linear with this approach.

Stateless servers do not suffer from this limitation, which is another benefit to embracing a RESTful architecture. REST is the first step in defining a cloud-based scalable architecture. The next step is creating an event-driven architecture.

Deploying to the Cloud

This paper has presented an overview of a cloud-based architecture and provided a cursory look at REST and EDA. Now let’s review how such an application can be deployed to and leverage the power of the cloud.

Deploying RESTful Services

RESTful web services, or the operations that manage RESTful resources, are deployed to a web container and should be placed in front of the data store that contains their data. These web services are themselves stateless and only reflect the state of the underlying data they expose, so you are able to use as many instances of these servers as you need. In a cloud-based deployment, start enough server instances to handle your normal load and then configure the elasticity of those services so that new server instances are added as these services become saturated and the number of server instances is reduced when load returns to normal. The best indicator of saturation is the response time of the services, although system resources such as CPU, physical memory, and VM memory are good indicators to monitor as well. As you are scaling these services, always be cognizant of the performance of the underlying data stores that the services are calling and do not bring those data stores to their knees.

The above graphics shows that the services that interact with Document Store 1 can be deployed separately, and thus scaled independently, from the services that interact with Document Store 2. If Service Tier 1 needs more capacity then add more server instances to Service Tier 1 and then distribute load to the new servers.

Deploying an ESB

The choice of whether or not to use an ESB will dictate the EDA requirements for your cloud-based deployment. If you do opt for an ESB, consider partitioning the ESB based on function so that excessive load on one segment does not take down other segments.

 The importance of segmentation is to isolate the load generated by System 1 from the load generated by System 2. Or stated another way, if System 1 generates enough load to slow down the ESB, it will slow down its own segment, but not System 2’s segment, which is running on its own hardware. In our initial deployment we had all of our systems publishing to a single segment, which exhibited just this behavior! Additionally, with segmentations, you are able to scale each segment independently by adding multiple servers to that segment (if your ESB vendor supports this).

Cloud-based applications are different from traditional applications because they have different scalability requirements. Namely, cloud-based applications must be resilient enough to handle servers coming and going at will, must be loosely-coupled, must be as stateless as possible, must expect and plan for failure, and must be able to scale from a handful of server to tens of thousands of servers.

There is no single correct architecture for cloud-based applications, but this paper presented an architecture that has proven successful in practice making use of RESTful services and an event-driven architecture. While there is much, much more you can do with the architecture of your cloud application, REST and EDA are the basic tools you’ll need to build a scalable application in the cloud.

The post Architecting for the Cloud written by Dustin.Whittle appeared first on Application Performance Monitoring Blog from AppDynamics.

Read the original blog entry...

More Stories By AppDynamics Blog

In high-production environments where release cycles are measured in hours or minutes — not days or weeks — there's little room for mistakes and no room for confusion. Everyone has to understand what's happening, in real time, and have the means to do whatever is necessary to keep applications up and running optimally.

DevOps is a high-stakes world, but done well, it delivers the agility and performance to significantly impact business competitiveness.

@ThingsExpo Stories
Microservices are a very exciting architectural approach that many organizations are looking to as a way to accelerate innovation. Microservices promise to allow teams to move away from monolithic "ball of mud" systems, but the reality is that, in the vast majority of organizations, different projects and technologies will continue to be developed at different speeds. How to handle the dependencies between these disparate systems with different iteration cycles? Consider the "canoncial problem" in this scenario: microservice A (releases daily) depends on a couple of additions to backend B (re...
I recently attended and was a speaker at the 4th International Internet of @ThingsExpo at the Santa Clara Convention Center. I also had the opportunity to attend this event last year and I wrote a blog from that show talking about how the “Enterprise Impact of IoT” was a key theme of last year’s show. I was curious to see if the same theme would still resonate 365 days later and what, if any, changes I would see in the content presented.
Apps and devices shouldn't stop working when there's limited or no network connectivity. Learn how to bring data stored in a cloud database to the edge of the network (and back again) whenever an Internet connection is available. In his session at 17th Cloud Expo, Ben Perlmutter, a Sales Engineer with IBM Cloudant, demonstrated techniques for replicating cloud databases with devices in order to build offline-first mobile or Internet of Things (IoT) apps that can provide a better, faster user experience, both offline and online. The focus of this talk was on IBM Cloudant, Apache CouchDB, and ...
Container technology is shaping the future of DevOps and it’s also changing the way organizations think about application development. With the rise of mobile applications in the enterprise, businesses are abandoning year-long development cycles and embracing technologies that enable rapid development and continuous deployment of apps. In his session at DevOps Summit, Kurt Collins, Developer Evangelist at, examined how Docker has evolved into a highly effective tool for application delivery by allowing increasingly popular Mobile Backend-as-a-Service (mBaaS) platforms to quickly crea...
Cloud computing delivers on-demand resources that provide businesses with flexibility and cost-savings. The challenge in moving workloads to the cloud has been the cost and complexity of ensuring the initial and ongoing security and regulatory (PCI, HIPAA, FFIEC) compliance across private and public clouds. Manual security compliance is slow, prone to human error, and represents over 50% of the cost of managing cloud applications. Determining how to automate cloud security compliance is critical to maintaining positive ROI. Raxak Protect is an automated security compliance SaaS platform and ma...
The cloud. Like a comic book superhero, there seems to be no problem it can’t fix or cost it can’t slash. Yet making the transition is not always easy and production environments are still largely on premise. Taking some practical and sensible steps to reduce risk can also help provide a basis for a successful cloud transition. A plethora of surveys from the likes of IDG and Gartner show that more than 70 percent of enterprises have deployed at least one or more cloud application or workload. Yet a closer inspection at the data reveals less than half of these cloud projects involve production...
Internet of @ThingsExpo, taking place June 7-9, 2016 at Javits Center, New York City and Nov 1-3, 2016, at the Santa Clara Convention Center in Santa Clara, CA, is co-located with the 18th International @CloudExpo and will feature technical sessions from a rock star conference faculty and the leading industry players in the world and ThingsExpo New York Call for Papers is now open.
With major technology companies and startups seriously embracing IoT strategies, now is the perfect time to attend @ThingsExpo 2016 in New York and Silicon Valley. Learn what is going on, contribute to the discussions, and ensure that your enterprise is as "IoT-Ready" as it can be! Internet of @ThingsExpo, taking place Nov 3-5, 2015, at the Santa Clara Convention Center in Santa Clara, CA, is co-located with 17th Cloud Expo and will feature technical sessions from a rock star conference faculty and the leading industry players in the world. The Internet of Things (IoT) is the most profound cha...
We are rapidly moving to a brave new world of interconnected smart homes, cars, offices and factories known as the Internet of Things (IoT). Sensors and monitoring devices will touch every part of our lives. Let's take a closer look at the Internet of Things. The Internet of Things is a worldwide network of objects and devices connected to the Internet. They are electronics, sensors, software and more. These objects connect to the Internet and can be controlled remotely via apps and programs. Because they can be accessed via the Internet, these devices create a tremendous opportunity to inte...
Today air travel is a minefield of delays, hassles and customer disappointment. Airlines struggle to revitalize the experience. GE and M2Mi will demonstrate practical examples of how IoT solutions are helping airlines bring back personalization, reduce trip time and improve reliability. In their session at @ThingsExpo, Shyam Varan Nath, Principal Architect with GE, and Dr. Sarah Cooper, M2Mi’s VP Business Development and Engineering, explored the IoT cloud-based platform technologies driving this change including privacy controls, data transparency and integration of real time context with p...
We all know that data growth is exploding and storage budgets are shrinking. Instead of showing you charts on about how much data there is, in his General Session at 17th Cloud Expo, Scott Cleland, Senior Director of Product Marketing at HGST, showed how to capture all of your data in one place. After you have your data under control, you can then analyze it in one place, saving time and resources.
The Internet of Things (IoT) is growing rapidly by extending current technologies, products and networks. By 2020, Cisco estimates there will be 50 billion connected devices. Gartner has forecast revenues of over $300 billion, just to IoT suppliers. Now is the time to figure out how you’ll make money – not just create innovative products. With hundreds of new products and companies jumping into the IoT fray every month, there’s no shortage of innovation. Despite this, McKinsey/VisionMobile data shows "less than 10 percent of IoT developers are making enough to support a reasonably sized team....
Just over a week ago I received a long and loud sustained applause for a presentation I delivered at this year’s Cloud Expo in Santa Clara. I was extremely pleased with the turnout and had some very good conversations with many of the attendees. Over the next few days I had many more meaningful conversations and was not only happy with the results but also learned a few new things. Here is everything I learned in those three days distilled into three short points.
DevOps is about increasing efficiency, but nothing is more inefficient than building the same application twice. However, this is a routine occurrence with enterprise applications that need both a rich desktop web interface and strong mobile support. With recent technological advances from Isomorphic Software and others, rich desktop and tuned mobile experiences can now be created with a single codebase – without compromising functionality, performance or usability. In his session at DevOps Summit, Charles Kendrick, CTO and Chief Architect at Isomorphic Software, demonstrated examples of com...
As organizations realize the scope of the Internet of Things, gaining key insights from Big Data, through the use of advanced analytics, becomes crucial. However, IoT also creates the need for petabyte scale storage of data from millions of devices. A new type of Storage is required which seamlessly integrates robust data analytics with massive scale. These storage systems will act as “smart systems” provide in-place analytics that speed discovery and enable businesses to quickly derive meaningful and actionable insights. In his session at @ThingsExpo, Paul Turner, Chief Marketing Officer at...
In his keynote at @ThingsExpo, Chris Matthieu, Director of IoT Engineering at Citrix and co-founder and CTO of Octoblu, focused on building an IoT platform and company. He provided a behind-the-scenes look at Octoblu’s platform, business, and pivots along the way (including the Citrix acquisition of Octoblu).
In his General Session at 17th Cloud Expo, Bruce Swann, Senior Product Marketing Manager for Adobe Campaign, explored the key ingredients of cross-channel marketing in a digital world. Learn how the Adobe Marketing Cloud can help marketers embrace opportunities for personalized, relevant and real-time customer engagement across offline (direct mail, point of sale, call center) and digital (email, website, SMS, mobile apps, social networks, connected objects).
The Internet of Everything is re-shaping technology trends–moving away from “request/response” architecture to an “always-on” Streaming Web where data is in constant motion and secure, reliable communication is an absolute necessity. As more and more THINGS go online, the challenges that developers will need to address will only increase exponentially. In his session at @ThingsExpo, Todd Greene, Founder & CEO of PubNub, exploreed the current state of IoT connectivity and review key trends and technology requirements that will drive the Internet of Things from hype to reality.
Two weeks ago (November 3-5), I attended the Cloud Expo Silicon Valley as a speaker, where I presented on the security and privacy due diligence requirements for cloud solutions. Cloud security is a topical issue for every CIO, CISO, and technology buyer. Decision-makers are always looking for insights on how to mitigate the security risks of implementing and using cloud solutions. Based on the presentation topics covered at the conference, as well as the general discussions heard between sessions, I wanted to share some of my observations on emerging trends. As cyber security serves as a fou...
Continuous processes around the development and deployment of applications are both impacted by -- and a benefit to -- the Internet of Things trend. To help better understand the relationship between DevOps and a plethora of new end-devices and data please welcome Gary Gruver, consultant, author and a former IT executive who has led many large-scale IT transformation projects, and John Jeremiah, Technology Evangelist at Hewlett Packard Enterprise (HPE), on Twitter at @j_jeremiah. The discussion is moderated by me, Dana Gardner, Principal Analyst at Interarbor Solutions.