|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.
After making a doctor’s appointment via your mobile device, you receive a calendar invite. The day of your appointment, you get a reminder with the doctor’s location and contact information. As you enter the doctor’s exam room, the medical team is equipped with the latest tablet containing your medical history – he or she makes real time updates to your medical file. At the end of your visit, you receive an electronic prescription to your preferred pharmacy and can schedule your next appointment.
Mar. 28, 2015 08:00 AM EDT Reads: 515
GENBAND has announced that SageNet is leveraging the Nuvia platform to deliver Unified Communications as a Service (UCaaS) to its large base of retail and enterprise customers. Nuvia’s cloud-based solution provides SageNet’s customers with a full suite of business communications and collaboration tools. Two large national SageNet retail customers have recently signed up to deploy the Nuvia platform and the company will continue to sell the service to new and existing customers. Nuvia’s capabilities include HD voice, video, multimedia messaging, mobility, conferencing, Web collaboration, deskt...
Mar. 28, 2015 01:00 AM EDT Reads: 1,390
The Open Compute Project is a collective effort by Facebook and a number of players in the datacenter industry to bring lessons learned from the social media giant's giant IT deployment to the rest of the world. Datacenters account for 3% of global electricity consumption – about the same as all of Switzerland or the Czech Republic -- according to people I met at the recent Open Compute Summit in San Jose. With increasing mobility at the edge of the cloud and vast new dataflows being predicted with the growth of the Internet of Things (and The Coming Age of Many Zettabytes) in the near...
Mar. 28, 2015 01:00 AM EDT Reads: 1,777
The list of ‘new paradigm’ technologies that now surrounds us appears to be at an all time high. From cloud computing and Big Data analytics to Bring Your Own Device (BYOD) and the Internet of Things (IoT), today we have to deal with what the industry likes to call ‘paradigm shifts’ at every level of IT. This is disruption; of course, we understand that – change is almost always disruptive.
Mar. 27, 2015 08:15 PM EDT Reads: 999
SYS-CON Events announced today that Cisco, the worldwide leader in IT that transforms how people connect, communicate and collaborate, has been named “Gold 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 City, NY. Cisco makes amazing things happen by connecting the unconnected. Cisco has shaped the future of the Internet by becoming the worldwide leader in transforming how people connect, communicate and collaborate. Cisco and our partners are building the platform for the Internet of Everything by connecting the...
Mar. 27, 2015 07:00 PM EDT Reads: 5,117
SYS-CON Media announced today that @WebRTCSummit Blog, the largest WebRTC resource in the world, has been launched. @WebRTCSummit Blog offers top articles, news stories, and blog posts from the world's well-known experts and guarantees better exposure for its authors than any other publication. @WebRTCSummit Blog can be bookmarked ▸ Here @WebRTCSummit conference site can be bookmarked ▸ Here
Mar. 27, 2015 06:00 PM EDT Reads: 1,669
Temasys has announced senior management additions to its team. Joining are David Holloway as Vice President of Commercial and Nadine Yap as Vice President of Product. Over the past 12 months Temasys has doubled in size as it adds new customers and expands the development of its Skylink platform. Skylink leads the charge to move WebRTC, traditionally seen as a desktop, browser based technology, to become a ubiquitous web communications technology on web and mobile, as well as Internet of Things compatible devices.
Mar. 27, 2015 06:00 PM EDT Reads: 1,711
SYS-CON Events announced today that robomq.io will exhibit at SYS-CON's @ThingsExpo, which will take place on June 9-11, 2015, at the Javits Center in New York City, NY. robomq.io is an interoperable and composable platform that connects any device to any application. It helps systems integrators and the solution providers build new and innovative products and service for industries requiring monitoring or intelligence from devices and sensors.
Mar. 27, 2015 06:00 PM EDT Reads: 1,343
Docker is an excellent platform for organizations interested in running microservices. It offers portability and consistency between development and production environments, quick provisioning times, and a simple way to isolate services. In his session at DevOps Summit at 16th Cloud Expo, Shannon Williams, co-founder of Rancher Labs, will walk through these and other benefits of using Docker to run microservices, and provide an overview of RancherOS, a minimalist distribution of Linux designed expressly to run Docker. He will also discuss Rancher, an orchestration and service discovery platf...
Mar. 27, 2015 04:15 PM EDT Reads: 2,358
Sonus Networks introduced the Sonus WebRTC Services Solution, a virtualized Web Real-Time Communications (WebRTC) offer, purpose-built for the Cloud. The WebRTC Services Solution provides signaling from WebRTC-to-WebRTC applications and interworking from WebRTC-to-Session Initiation Protocol (SIP), delivering advanced real-time communications capabilities on mobile applications and on websites, which are accessible via a browser.
Mar. 27, 2015 04:00 PM EDT Reads: 1,674
SYS-CON Events announced today that Aria Systems, the leading innovator in recurring revenue, has been named “Bronze Sponsor” of SYS-CON's @ThingsExpo, which will take place on June 9–11, 2015, at the Javits Center in New York, NY. Proven by the world’s most demanding enterprises, including AAA NCNU, Constant Contact, Falck, Hootsuite, Pitney Bowes, Telekom Denmark, and VMware, Aria helps enterprises grow their recurring revenue businesses. With Aria’s end-to-end active monetization platform, global brands can get to market faster with a wider variety of products and services, while maximizin...
Mar. 27, 2015 04:00 PM EDT Reads: 1,516
SYS-CON Events announced today that Vitria Technology, Inc. will exhibit at SYS-CON’s @ThingsExpo, which will take place on June 9-11, 2015, at the Javits Center in New York City, NY. Vitria will showcase the company’s new IoT Analytics Platform through live demonstrations at booth #330. Vitria’s IoT Analytics Platform, fully integrated and powered by an operational intelligence engine, enables customers to rapidly build and operationalize advanced analytics to deliver timely business outcomes for use cases across the industrial, enterprise, and consumer segments.
Mar. 27, 2015 03:30 PM EDT Reads: 2,114
SYS-CON Events announced today that Akana, formerly SOA Software, has been named “Bronze Sponsor” of SYS-CON's 16th International Cloud Expo® New York, which will take place June 9-11, 2015, at the Javits Center in New York City, NY. Akana’s comprehensive suite of API Management, API Security, Integrated SOA Governance, and Cloud Integration solutions helps businesses accelerate digital transformation by securely extending their reach across multiple channels – mobile, cloud and Internet of Things. Akana enables enterprises to share data as APIs, connect and integrate applications, drive part...
Mar. 27, 2015 03:15 PM EDT Reads: 1,382
SYS-CON Events announced today that Solgenia will exhibit at SYS-CON's 16th International Cloud Expo®, which will take place on June 9-11, 2015, at the Javits Center in New York City, NY, and the 17th International Cloud Expo®, which will take place on November 3–5, 2015, at the Santa Clara Convention Center in Santa Clara, CA. Solgenia is the global market leader in Cloud Collaboration and Cloud Infrastructure software solutions. Designed to “Bridge the Gap” between Personal and Professional Social, Mobile and Cloud user experiences, our solutions help large and medium-sized organizations dr...
Mar. 27, 2015 03:00 PM EDT Reads: 2,677
SYS-CON Events announced today that Liaison Technologies, a leading provider of data management and integration cloud services and solutions, 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. Liaison Technologies is a recognized market leader in providing cloud-enabled data integration and data management solutions to break down complex information barriers, enabling enterprises to make smarter decisions, faster.
Mar. 27, 2015 03:00 PM EDT Reads: 3,366
The WebRTC Summit 2014 New York, to be held June 9-11, 2015, at the Javits Center in New York, NY, announces that its Call for Papers is open. Topics include all aspects of improving IT delivery by eliminating waste through automated business models leveraging cloud technologies. WebRTC Summit is co-located with 16th International Cloud Expo, @ThingsExpo, Big Data Expo, and DevOps Summit.
Mar. 27, 2015 03:00 PM EDT Reads: 1,373
The 3rd International Internet of @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 its Call for Papers is open. The Internet of Things (IoT) is the biggest idea since the creation of the Worldwide Web more than 20 years ago.
Mar. 27, 2015 02:00 PM EDT Reads: 2,924
SYS-CON Events announced today that CommVault has been named “Bronze 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 City, NY, and the 17th International Cloud Expo®, which will take place on November 3–5, 2015, at the Santa Clara Convention Center in Santa Clara, CA. A singular vision – a belief in a better way to address current and future data management needs – guides CommVault in the development of Singular Information Management® solutions for high-performance data protection, universal availability and sim...
Mar. 27, 2015 02:00 PM EDT Reads: 1,510
Cloud is not a commodity. And no matter what you call it, computing doesn’t come out of the sky. It comes from physical hardware inside brick and mortar facilities connected by hundreds of miles of networking cable. And no two clouds are built the same way. SoftLayer gives you the highest performing cloud infrastructure available. One platform that takes data centers around the world that are full of the widest range of cloud computing options, and then integrates and automates everything. Join SoftLayer on June 9 at 16th Cloud Expo to learn about IBM Cloud's SoftLayer platform, explore se...
Mar. 27, 2015 02:00 PM EDT Reads: 1,534
SYS-CON Media announced today that 9 out of 10 " most read" DevOps articles are published by @DevOpsSummit Blog. Launched in October 2014, @DevOpsSummit Blog offers top articles, news stories, and blog posts from the world's well-known experts and guarantees better exposure for its authors than any other publication. 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 to wait for long development cycles that produce softw...
Mar. 27, 2015 01:00 PM EDT Reads: 2,382