|By Ben Forta||
|October 18, 1999 12:00 AM EDT||
No one wants to write buggy code, at least no one I choose to know. Bugs are annoying, bugs are embarrassing. And bugs can cost you (and your clients) lots of time and money.
Bugfree code is the ideal all developers strive for - at least should strive for - but it's a lofty goal not easily attained.
To write bugfree code it's important to understand how bugs are introduced. I'd like to explore what I believe to be one of the primary causes for the introduction of bugs into your code: failure to expect the unexpected. While many of these ideas apply to application development in general, the positioning of this column relates specifically to ColdFusion.
Flow? What Flow?
Applications are designed with a particular program flow in mind. Users start at point A, go to point B, then to point C. Program flow is an important part of any application, and when developers write they anticipate a particular program flow.
Here are some examples.
In each of these examples there's a logical starting point, then a series of steps. The search dialog must be displayed before the search can be performed, users must select items from the product catalog before the order can be processed, and login information must be provided before access can be authenticated.
In traditional application development, programmers had total control over program flow. Users had no way to access screens out of order, nor could they start from a screen other than the one they were supposed to start at. But Web applications, for better or worse, behave differently. As every Web page has a unique address (its URL), it's indeed possible for users to execute pages out of order, just as it's possible for them to start from the wrong page.
How could this occur? There are several ways. Users could bookmark pages directly, search engines might index pages below your root, and newer browsers feature an auto-fill option that completes URLs for users but frequently uses the most recently visited page in the site (often the wrong page).
To understand this better, look at the following code:
<!--- Perform search --->
<CFQUERY DATASOURCE="ds" NAME="search">
SELECT title FROM books
WHERE title LIKE %#FORM.title#%'
<!--- Create page --->
<!--- Display search results --->
Actually, this is fairly typical ColdFusion code (it's even commented). It performs a simple database search and displays the results. The search itself is driven by a form that contains a field named "title"
And that's what's wrong. The code makes two dangerous assumptions - that the page will be called from a form and that the form contains a field named "title". If either assumption turns out to be incorrect, ColdFusion throws an error because #FORM.title# would refer to a variable that didn't exist.
What's the solution? There are a couple of things you can and should do. The first is always check for the existence of variables before using them, initializing them with default values if needed. The ColdFusion <CFPARAM> tag is very useful for this, and good programming practices demand that every variable be initialized this way so they always exist (either as submitted FORM or URL values, or as locally created variables). If the following code were inserted above the code example, the page would always execute correctly, regardless of how it was invoked and what fields were passed:
<CFPARAM NAME="FORM.title" DEFAULT="">
Sometimes you may not want to use default values. For example, in the preceding code you may not want to display the entire contents of the table if the page is executed directly. If a user ends up on this page without having filled in the form to perform the search, you'd want to send them to the search page instead. Here's one way you could do this (assuming the search page was named search.cfm):
<!--- Is form field present? --->
<CFIF NOT IsDefined("FORM.title")>
<!--- Not present, redirect to search screen --->
With this snippet at the top of the page your code is now safe. If users try to execute the page directly, you'll programmatically redirect them to where they really should be.
The truth is, every page on your site should be written so that it's safe to execute directly. That way you'll never make assumptions about program flow, and your code won't break when the unexpected occurs.
Are you up for a challenge? How about writing code that uses <CFDIRECTORY> to traverse your code tree to find all CFM pages, then looping through each one, executing it via <CFHTTP> to see which ones throw errors and which work. You could call this code daily (or weekly or monthly) and e-mail yourself the results so you'll know as soon as possible if things might break.
Changes in Site Usage
Another phenomenon that's part of Web site use is the frequency with which that use changes. Programmers anticipate that their site will be used in one way, but, inevitably, users find another way to use it. That's not a bad thing in and of itself, but it does present an interesting problem.
All applications, not just Web-based applications, are designed so that particular parts perform better than others. This is usually because certain parts of the application are more critical and get more use, so the time and effort needed to improve and enhance the site tends to be best spent on these parts.
The application hums along nicely, handling the load thrown at it, and everything works well until those pesky users start using your site in ways you didn't expect. Suddenly the efficient and highly optimized parts are being executed less and less, and the less fine-tuned (I'm being generous) parts start to buckle under the growing load.
This is actually a very common problem. Some of the largest and most impressive sites on the Internet have fallen victim to it.
The good news is that ColdFusion provides you with an invaluable (and frequently overlooked) tool you can use to identify these potential trouble spots. The ColdFusion Administrator (starting in version 4) features a checkbox that, when checked, allows you to log page requests that take longer than a specified amount of time.
Again, the key here is to expect the unexpected and be ready when it occurs. Individual log entries aren't necessarily indicative of a problem, but repeated entries most definitely are. I'd strongly advise all site administrators to enable this option, even on production sites. Determine what the "normal" response time should be (and then pad that number a little) and have ColdFusion log all page requests that take longer. If specific pages start appearing in the log repeatedly, you'll know where to spend your fine-tuning and performance-enhancing efforts.
Up for another challenge? Write a scheduled event that checks this log file daily for new entries. If it finds any, it should e-mail them to you so you'll know about them immediately.
When Bad Things Happen
You've cleaned up your site. You no longer expect specific program flow, nor do you expect specific usage patterns. That's great, but it's not enough.
The other big trouble spot is reliance on other systems and technologies. Whether it's database integration, execution of third-party objects and components, or interaction with other Internet protocols (like HTTP, FTP and NNTP), the more you rely on other systems and technologies, the more room there is for something to go wrong.
Whether it's database failure, the inability to connect to a specific host, or errors and problems in calls resources, they're all your problem because to the end user your site is broken. It's not an ideal world out there; bad things do happen and you'll be blamed. And you're not going to escape this one anytime soon.
So what do you do? Again, ColdFusion (version 4 or later) provides a tool to respond to these situations - try catch error handling. While full coverage of try catch is beyond the scope of this column (I'll devote an entire column to error handling in the future), here's the basic idea.
Try catch error handling allows you to trap errors in your code, then pick up the processing elsewhere when an error occurs. The basic page layout looks like this:
... page goes here ...
... error processing goes here ...
By wrapping an entire page between <CFTRY> and </CFTRY> tags, any error that occurs within that page will be trapped. As soon as an error is caught, processing will be taken over by the catch block (the code between <CFCATCH> and </CFCATCH>). There's no limit to what you can place in the catch block-you can change variables, redirect requests, generate e-mail, write logs and even try to fix error conditions.
Experienced developers take this one step further by nesting try catch error handling. Generic error handling is implemented at the page level, and additional error handling is implemented around specific features or functions. This type of implementation provides the greatest level of control and allows developers to not just expect the unexpected, but also to handle the unexpected.
The Internet is a highly dynamic and configurable environment. With all that flexibility and power comes the need for greater caution and planning to ensure that applications don't suddenly break. Bugfree code is a wonderful ideal, but for most of us, writing good code that doesn't break in unexpected scenarios is as close as we'll get to attaining it.
The bottom line is that as developers writing code for this new environment, we must all expect the unexpected- because it's going to happen and usually at the least opportune time.
Discussions of cloud computing have evolved in recent years from a focus on specific types of cloud, to a world of hybrid cloud, and to a world dominated by the APIs that make today's multi-cloud environments and hybrid clouds possible. In this Power Panel at 17th Cloud Expo, moderated by Conference Chair Roger Strukhoff, panelists addressed the importance of customers being able to use the specific technologies they need, through environments and ecosystems that expose their APIs to make true change and transformation possible.
Nov. 30, 2015 08:00 AM EST Reads: 561
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...
Nov. 30, 2015 07:00 AM EST Reads: 466
Too often with compelling new technologies market participants become overly enamored with that attractiveness of the technology and neglect underlying business drivers. This tendency, what some call the “newest shiny object syndrome” is understandable given that virtually all of us are heavily engaged in technology. But it is also mistaken. Without concrete business cases driving its deployment, IoT, like many other technologies before it, will fade into obscurity.
Nov. 30, 2015 07:00 AM EST Reads: 380
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 Built.io, 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...
Nov. 30, 2015 06:00 AM EST Reads: 386
The Internet of Things is clearly many things: data collection and analytics, wearables, Smart Grids and Smart Cities, the Industrial Internet, and more. Cool platforms like Arduino, Raspberry Pi, Intel's Galileo and Edison, and a diverse world of sensors are making the IoT a great toy box for developers in all these areas. In this Power Panel at @ThingsExpo, moderated by Conference Chair Roger Strukhoff, panelists discussed what things are the most important, which will have the most profound effect on the world, and what should we expect to see over the next couple of years.
Nov. 30, 2015 05:30 AM EST Reads: 493
Growth hacking is common for startups to make unheard-of progress in building their business. Career Hacks can help Geek Girls and those who support them (yes, that's you too, Dad!) to excel in this typically male-dominated world. Get ready to learn the facts: Is there a bias against women in the tech / developer communities? Why are women 50% of the workforce, but hold only 24% of the STEM or IT positions? Some beginnings of what to do about it! In her Day 2 Keynote at 17th Cloud Expo, Sandy Carter, IBM General Manager Cloud Ecosystem and Developers, and a Social Business Evangelist, wil...
Nov. 30, 2015 04:00 AM EST Reads: 607
PubNub has announced the release of BLOCKS, a set of customizable microservices that give developers a simple way to add code and deploy features for realtime apps.PubNub BLOCKS executes business logic directly on the data streaming through PubNub’s network without splitting it off to an intermediary server controlled by the customer. This revolutionary approach streamlines app development, reduces endpoint-to-endpoint latency, and allows apps to better leverage the enormous scalability of PubNub’s Data Stream Network.
Nov. 30, 2015 04:00 AM EST Reads: 347
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 ...
Nov. 30, 2015 03:45 AM EST Reads: 437
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...
Nov. 30, 2015 02:00 AM EST Reads: 447
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.
Nov. 30, 2015 02:00 AM EST Reads: 449
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...
Nov. 30, 2015 12:00 AM EST Reads: 450
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....
Nov. 29, 2015 02:00 PM EST Reads: 488
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.
Nov. 29, 2015 01:00 PM EST Reads: 358
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...
Nov. 29, 2015 12:45 PM EST Reads: 423
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...
Nov. 29, 2015 12:30 PM EST Reads: 428
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).
Nov. 29, 2015 12:00 PM EST Reads: 532
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).
Nov. 29, 2015 11:45 AM EST Reads: 335
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.
Nov. 29, 2015 09:45 AM EST Reads: 455
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...
Nov. 29, 2015 09:15 AM EST Reads: 347
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.
Nov. 29, 2015 08:45 AM EST Reads: 234