First, Do No Harm
Let’s face it: not all software developers are superstar programmers (and, trust me, not all luminary developers program in a sane way.) This means that when we maintain existing code, we must be very careful to avoid breaking or degrading the system we work on. Why? Because a failure of a running system can affect operations, people, profits, property, and sometimes even lives. Here are the rules.
Continue reading "First, Do No Harm"
Service Orchestration with Rundeck
Increasingly, software is provided as a service. Managing and controlling the service’s provision is tricky, but tools for service orchestration, such as Rundeck, can make our lives easier. Take software deployment as an example. A well-run IT shop will have automated both the building of its software using tools like make, Ant, and Maven and the configuration of the hosts the software runs on with CFEngine, Chef, or Puppet (see the post “Don’t Install Software by Hand”). Furthermore, version control tools and continuous integration will manage the software and the configuration recipes, handling developer contributions, reviews, traceability, branches, logging, and sophisticated workflows. However, these tools still leave a gap between the software that has been built and is ready to deploy, and the server that has been configured with the appropriate components and libraries and is ready to run the software.
Continue reading "Service Orchestration with Rundeck"
Developing in the Cloud
Running a top-notch software development organization used to be a capital-intensive endeavor, requiring significant technical and organizational resources, all managed through layers of bureaucracy. Not anymore. First, many of the pricey systems and tools that we developers need to work effectively are usually available for free as open source software. More importantly, cheap, cloud-based offerings do away with the setup, maintenance, and user support costs and complexity associated with running these systems. Here are just a few of the services and providers that any developer group can easily tap into
(you can find many more listed here):
Continue reading "Developing in the Cloud"
In the 1920s, the Ford Motor Company embarked on an ill-fated attempt to establish an industrial town in an Amazon rainforest as a way to secure a cultivated rubber supply for its cars’ wheels. At the time, it already owned ore mines, forests, and a steel foundry to produce the raw materials for its cars; today, it buys from external suppliers, even its cars’ electronic control units. How do these two phases of the automotive industry’s history relate to the way we currently develop and adopt infrastructure in our profession?
Continue reading "Bespoke Infrastructures"
The Frictionless Development Environment Scorecard
The environment we work in as developers can make a tremendous difference on our productivity and well-being. I’ve often seen myself get trapped in an unproductive setup through a combination of inertia, sloth, and entropy. Sometimes I put-off investing in new, better tools, at other times I avoid the work required to automate a time-consuming process, and, also, as time goes by, changes in my environment blunt the edge of my setup. I thus occasionally enter into a state where my productivity suffers death by a thousand cuts. I’ve also seen the same situation when working with colleagues: cases where to achieve a simple task they waste considerable time and energy jumping through multiple hoops.
Continue reading "The Frictionless Development Environment Scorecard"
If estimating the time needed for implementing some software is difficult, coming up with a figure for the time required to debug it is nigh on impossible. Bugs can lurk in the most obscure corners of the system, or even in the crevices of third-party libraries and components. Ask some developers for a time estimate, and don’t be surprised if an experienced one snaps back, “I’ve found the bug when I’ve found the bug.” Thankfully, there are some tools that allow methodical debugging, thereby giving you a sense of progress and a visible target. A method I’ve come to appreciate over the past few months is differential debugging. Under it, you compare a known good system with the buggy one, working toward the problem source.
Continue reading "Differential Debugging"
Portability: Goodies vs. the hair shirt
“I don’t know what the language of the year 2000 will look like, but I know it will be called Fortran”
Continue reading "Portability: Goodies vs. the hair shirt"
Systems software is the low-level infrastructure that applications run on: the operating systems, language runtimes, libraries, databases, application servers, and many other components that churn our bits 24/7. It’s the mother of all code. In contrast to application software, which is constructed to meet specific use cases and business objectives, systems software should be able to serve correctly any reasonable workload. Consequently, it must be extremely reliable and efficient. When it works like that, it’s a mighty tool that lets applications concentrate on meeting their users’ needs. When it doesn’t, the failures are often spectacular. Let’s see how we go about creating such software.
Continue reading "Systems Software"
Software Tools Research: SPLASH Panel Discussion
Written by Dennis Mancl and Steven Fraser
At the recent SPLASH (Systems, Programming, Languages and Applications: Software for Humanity) conference, one of us (Steven Fraser) organized an international group of experts to discuss challenges in software tools research.1 The panelists included Kendra Cooper (University of Texas, Dallas), Jim “Cope” Coplien (Gertrud & Cope), Junilu Lacar (Cisco Systems), Ruth Lennon (Letterkenny Institute of Technology), Diomidis Spinellis (Athens University of Economics and Business), and Giancarlo Succi (Free University of Bolzano-Bozen).
Continue reading "Software Tools Research: SPLASH Panel Discussion"
The Importance of Being Declarative
A declarative programming style focuses on what you want your program to do rather than how to perform the task. Through diverse programming techniques, libraries, and specialized languages, you end up with code that sidesteps nitty-gritty implementation details, dealing instead with a task’s big picture.
Continue reading "The Importance of Being Declarative"
APIs, Libraries, and Code
Let’s say you want to display a JPEG-compressed image, calculate Pearson’s correlation coefficient, parse an XML file, or create a key-value store. You can often choose between using the functionality of the application’s platform (Java EE or .NET), calling one of several available external libraries, or writing the code on your own. It isn’t an easy choice because you have many factors to consider. Specifically, you must take into account the task’s complexity, as well as the licensing, quality, and support of competing alternatives. See how you can narrow down your choice by eliminating alternatives at the earliest possible decision point.
Continue reading "APIs, Libraries, and Code"
The virtual machine (VM) is the most dazzling comeback in information technology. IBM implemented a VM platform architecture in the late 1960s in its CP/CMS operating system. The company’s goal was to provide the time-sharing capabilities that its batch-oriented System/360 lacked. Thus a simple control program (CP) created a VM environment where multiple instances of the single-user CMS operating system could run in parallel. Thirty years later, virtualization was rediscovered when companies like VMware found ways to virtualize the less accommodating Intel x86 processor architecture. The popularity of Intel’s platform and the huge amount of software running on it made virtualization an attractive proposition, spawning within a decade tens of proprietary and open source virtualization platforms.
Continue reading "Virtualize Me"
Don't Install Software by Hand
An IT system’s setup and configuration is a serious affair. It increasingly affects us developers mainly due to the proliferation and complexity of internet-facing systems. Fortunately, we can control and conquer this complexity by adopting IT-system configuration management tools.
Continue reading "Don't Install Software by Hand"
Even by our field’s dizzying rate of progress I wouldn’t expect to revisit the subject of version control just six years after I first wrote about it in this column (Version Control Systems. Software, 22(5):108–109, September/October 2005). Yet here we are. The new kid on the block is git, a distributed revision control system available on all mainstream development platforms through a Free Software license. Git, a brainchild of Linus Torvalds, began its life in 2005 as the revision management system used for coordinating the development of the Linux kernel. Over the years its functionality, portability, efficiency, and third-party adoption have evolved by leaps and bounds to make it its category’s leader. (Two other systems with similar characteristics are Mercurial and Bazaar.)
Continue reading "Git"
Package Management Systems
DLL hell was a condition that often afflicted unfortunate users of old Microsoft Windows versions. Under it, the installation of one program would render others unusable due to incompatibilities between dynamically linked libraries. Suffering users would have to carefully juggle their conflicting DLLs to find a stable configuration. Similar problems distress any administrator manually installing software that depends on incompatible versions of other helper modules.
Continue reading "Package Management Systems"
Refactoring on the Cheap
The refactorings that a good integrated development environment can perform are impressive. Yet, there are many reasons to master some cheap-and-cheerful alternative approaches. First, there will always be refactorings that your IDE won’t support. Also, although your IDE might offer excellent refactoring support for some programming languages, it could fall short on others. Modern projects increasingly mix and match implementation languages, and switching to a specialized IDE for each language is burdensome and inefficient. Finally, IDE-provided refactorings resemble an intellectual straightjacket. If you only know how to use the ready-made refactorings, you’ll miss out on opportunities for other code improvements.
Continue reading "Refactoring on the Cheap"
Lessons from Space
By Diomidis Spinellis and Henry Spencer
Continue reading "Lessons from Space"
This column is about a tool we no longer have: the continuous rise of the CPU clock frequency. We were enjoying this trend for decades, but in the past few years, progress stalled. CPUs are no longer getting faster because their makers can’t handle the heat of faster-switching transistors. Furthermore, increasing the CPU’s sophistication to execute our instructions more cleverly has hit the law of diminishing returns. Consequently, CPU manufacturers now package the constantly increasing number of transistors they can fit onto a chip into multiple cores—processing elements—and then ask us developers to put the cores to good use.
Continue reading "Faking it"
When the facts change, I change my mind. What do you do, sir?
Continue reading "Agility Drivers"
Choosing and Using Open Source Components
The developers of the SQLite open source database engine estimate that it’s deployed in roughly half a billion systems around the world (users include Airbus, Google, and Skype). Think of the hundreds of thousands of open source components, just one click away from you. If you know how to choose and use them effectively , your project can benefit mightily.
Continue reading "Choosing and Using Open Source Components"
Sure, you can write English right to left. You can also write software code to look like a disc or even a train (see www.ioccc.org/1988/westley.c and 1986/marshall.c). However, you can’t then complain when you have to fight with your magazine’s editor or production staff about accepting your column’s title for publication, or if your colleagues refuse to touch your code with a 10-foot pole. Writing code in a readable and consistent style is difficult, uninteresting, tedious, underappreciated, and, extremely important.
Continue reading "elytS edoC"
Farewell to Disks
A classic web-comic illustrates how idle Wikipedia browsing can lead us from the Tacoma Narrows Bridge to Fatal hilarity (and worse). The comic doesn’t show the path leading from A to B, and finding it is an interesting challenge—think how you would engineer a system that could answer such questions. I believe that this problem and a solution I’ll present demonstrate some programming tools and techniques that will become increasingly important in the years to come.
Continue reading "Farewell to Disks"
The innumerate misleading the illiterate.
— Stan Kelly-Bootle, “The Devil’s DP Dictionary”
A mechanical engineer who sees the symbol ⊥ in a diagram will immediately realize that a feature is specified to be perpendicular to another. In contrast, a software engineer looking at a diagram’s line ending with the symbol ◊ will, at best, wonder whether it denotes aggregation (as in UML), or a “zero or one” cardinality (as in IDEF1X), or something else invented by a creative academic. Worse, many developers will simply scratch their head in bewilderment.
Continue reading "UML, Everywhere"
Technical prose is almost immortal.
Continue reading "Code Documentation"
A generous car reviewer might praise a vehicle’s handling by writing that it turns as if it’s running on railroad tracks. Indeed, tracks offer guidance and support. When you run on tracks you can carry more weight, you can run faster, and you can’t get lost. That’s why engineers, from early childhood to old age, get hooked on trains. Can we get our software to run on tracks?
Continue reading "Software Tracks"
Basic Etiquette of Technical Communication
Parents spend years trying to teach their children to be polite, and some of us had to learn at school how to properly address an archbishop. Yet, it seems that advice on courteousness and politeness in technical communication is in short supply; most of us learn these skills through what is euphemistically called “on the job training.” With enough bruises on my back to demonstrate the amount and variety of my experience in this area (though not my skill), here are some of the things I’ve learned.
Continue reading "Basic Etiquette of Technical Communication"
My colleague, who works for a major equipment vendor, was discussing how his employer was planning to lay off hundreds of developers over the coming months. “But I’m safe,” he said, “as I’m one of the two people in our group who really understand the code.” It seems that writing code that nobody else can comprehend can be a significant job security booster. Here’s some advice.
Continue reading "Job Security"
1 Word = 1 Millipicture
It’s no accident that in all engineering branches, our colleagues often communicate using drawings and diagrams. Given many artifacts’ scale and complexity, a drawing is often the best way to describe them. Uniquely, in software development we can easily derive pictures from code, and sometimes even code from pictures.
Continue reading "Drawing Tools"
Start With the Most Difficult Part
There’s not a lot you can change in the process of constructing a building. You must lay the foundation before you erect the upper floors, and you can’t paint without having the walls in place. In software, we’re blessed with more freedom.
Continue reading "Start With the Most Difficult Part"
Brian Kernighan on 30 Years of Software Tools
As part of the IEEE Software 25th anniversary, Brian Kernighan
graciously agreed to write a Tools of the Trade column.
His article, titled Sometimes the Old Ways are Best, is now freely
through the Computing Now web site.
Continue reading "Brian Kernighan on 30 Years of Software Tools"
The Way We Program
If the code and the comments disagree, then both are probably wrong.
Continue reading "The Way We Program"
The tools and processes we use to transform our system’s source code into an application we can deploy or ship were always important, but nowadays they can mean the difference between success and failure. The reasons are simple: larger code bodies, teams that are bigger, more fluid, and wider distributed, richer interactions with other code, and sophisticated tool chains. All these mean that a slapdash software build process will be an endless drain on productivity and an embarrassing source of bugs, while a high-quality one will give us developers more time and traction to build better software.
Continue reading "Software Builders"
Using and Abusing XML
Words are like leaves; and where they most abound,
Much fruit of sense beneath is rarely found.
— Alexander Pope
I was recently gathering GPS coordinates and cell identification data, researching the algorithms hiding behind Google’s “My Location” facility.
While working on this task, I witnessed the great interoperability benefits we get from XML. With a simple 140-line script, I converted the data I gathered into a de facto standard, the XML-based GPS-exchange format called GPX. Then, using a GPS-format converter, I converted my data into Google Earth’s XML data format A few mouse clicks later, I had my journeys and associated cell tower switchovers beautifully superimposed on satellite pictures and maps.
Continue reading "Using and Abusing XML"
Metaprogramming, using programs to manipulate other programs, is as old as programming. From self-modifying machine code in early computers to expressions involving partially applied functions in modern functional-programming languages, metaprogramming is an essential part of an advanced programmer’s arsenal.
Continue reading "Rational Metaprogramming"
A box of crayons and a big sheet of paper provides a more expressive medium for kids than computerized paint programs.
— Clifford Stoll
This column came to life as I was trying to devise an algorithm for
analyzing initializers for C arrays and structures. At the time I was
using the CScout
refactoring browser to look for possible differences
between closed and open source code. I had already processed the
Linux, FreeBSD, and Windows research kernel source codel and only the
OpenSolaris kernel remained. Unlikethe other three code bases, Sun’s
code didn’t appear to use any exotic compiler extensions, so
CScout uncomplainingly devoured one file after the next. Then, after
aspproximately six hours of processing and 80 percent along the way,
it reported a syntax error.
Continue reading "On Paper"
Abstraction and Variation
“Master, a friend told me today that I should never use the editor’s copy-paste functions when programming,” said the young apprentice. “I thought the whole point of programming tools was to make our lives easier,” he continued.
The Master stroked his long grey beard and pressed the busy button on his phone. This was going to be one of those long, important discussions.
Continue reading "Abstraction and Variation"
The Tools we Use
It is impossible to sharpen a pencil with a blunt ax. It is equally vain to try to do it with ten blunt axes instead.
— Edsger W. Dijkstra
Continue reading "The Tools we Use"
Silver Bullets and Other Mysteries
It seemed like a good idea at the time.
—Ken Thomson, on naming the Unix system call to create a file "creat"
When conference participants interrupt a speaker with applause, you know the speaker has struck a chord. This happened when Alan Davis, past editor in chief of IEEE Software, gave a talk on improving the requirements engineering process at the NASSCOM (Indian National Association of Software and Services Companies) Quality Summit in Bangalore in September 2006. He was explaining why a marketing team will often agree with developers on additional features and a compressed delivery schedule that both sides know to be unrealistic. The truth is that this places the two parties in a Machiavellian win-win situation. When the product's delivery is inevitably delayed, the developers will claim that they said from the beginning that they couldn't meet the schedule but that marketing insisted on it. The marketing people also end up with a convenient scapegoat. If the product launch is a flop, they can say they missed a critical marketing time window owing to the product's delay. Where else are we playing such games?
Continue reading "Silver Bullets and Other Mysteries"
Knowledge is power.
—Sir Francis Bacon
The ultimate source of truth regarding a program is its execution. When a program runs everything comes to light: correctness, CPU and memory utilization, even interactions with buggy libraries, operating systems, and hardware. Yet, this source of truth is also fleeting, rushing into oblivion at the tune of billions of instructions per second. Worse, capturing that truth can be a tricky, tortuous, or downright treacherous affair.
Continue reading "I Spy"
Cracking Software Reuse
[Newton] said, "If I have seen further than others, it is because I've stood on the shoulders of giants." These days we stand on each other's feet!
— Richard Hamming
Sometimes we encounter ideas that inspire us for life. For me, this was a Unix command pipeline I came across in the '80s:
Continue reading "Cracking Software Reuse"
Open Source and Professional Advancement
Doing really first-class work, and knowing it, is as good as wine, women (or men) and song put together.
— Richard Hamming
I recently participated in an online discussion regarding the advantages of the various certification programs. Some voiced skepticism regarding how well one can judge a person's knowledge through answers to narrowly framed multiple choice questions. My personal view is that the way a certification's skills are examined is artificial to the point of uselessness. In practice I often find solutions to problems by looking for answers on the web. Knowing where and how to search for an answer is becoming the most crucial problem-solving skill, yet typical certification exams still test rote learning. Other discussants suggested that certification was a way to enter into a job market where employers increasingly asked for experience in a specific technology. My reaction to that argument was that open source software development efforts offer us professionals a new and very valuable way to obtain significant experience in a wide range of areas. In this column I'll describe how we can advance professionally by contributing to open source projects.
Continue reading "Open Source and Professional Advancement"
Choosing a Programming Language
A language that doesn't have everything is actually easier to program in than some that do.
— Dennis M. Ritchie
Computer languages fascinate me. Like a living person, each one has its own history, personality, interests, and quirks. Once you've learned one, you can use it again after years of neglect, and it's like reconnecting with an old friend: you can continue discussions from the point they were broken off years before. For a task I recently faced I adopted a language I hadn't used for 15 years, and felt enlightened.
Continue reading "Choosing a Programming Language"
Debuggers and Logging Frameworks
As soon as we started programming, we found to our surprise that it wasn't as easy to get programs right as we had thought. Debugging had to be discovered.
— Maurice Wilkes discovers debugging, 1949
The testing, diagnostic, and repair equipment of many professions is horrendously expensive. Think of logic analyzers, CAT scanners, and dry docks. For us the cost of debuggers and logging frameworks is minimal; some of them are even free. All we need to become productive, is to invest some time and effort to learn how to use these tools in the most efficient and effective way.
Continue reading "Debuggers and Logging Frameworks"
Although only a few may originate a policy, we are all able to judge it.
— Pericles of Athens
Popular folklore has our profession's use of the word bug originating from a real insect found in an early electromechanical computer. Indeed, on September 9th of 1947 the Harvard Mark II operators did find a moth obstructing a relay's contacts. They removed it and dutifully taped it in the machine's logbook. However, engineers were using the term "bug" many decades before that incident. For example, in a 1878 letter Edison used the term referring to the faults and difficulties he was facing while moving from an invention's intuition to a commercialisable product.
Continue reading "Bug Busters"
Project Asset Portability
It's said that real computer scientists don't program in assembler; they don't write in anything less portable than a number two pencil. Joking aside, at the end of the 1970s, the number of nonstandard languages and APIs left most programs tied to a very specific and narrow combination of software and hardware. Entire organizations were locked in for life to a specific vendor, unable to freely choose the hardware and software where their code and data would reside. Portability and vendor independence appeared to be a faraway, elusive goal.
Continue reading "Project Asset Portability"
Working with Unix Tools
A successful [software] tool is one that was used to do something undreamed of by its author.
— Stephen C. Johnson
Line-oriented textual data streams are the lowest useful common denominator for a lot of data that passes through our hands. Such streams can be used to represent program source code, web server log data, version control history, file lists, symbol tables, archive contents, error messages, profiling data, and so on. For many routine, everyday tasks, we might be tempted to process the data using a Swiss army knife scripting language, like Perl, Python, or Ruby. However, to do that we often need to write a small, self-contained program and save it into a file. By that point we've lost interest in the task, and end-up doing the work manually, if at all. Often, a more effective approach is to combine programs of the Unix toolchest into a short and sweet pipeline that we can run from our shell's command prompt. With the modern shell command-line editing facilities we can build our command bit by bit, until it molds into exactly the form that suits us. Nowadays, the original Unix tools are available on many different systems, like GNU/Linux, Mac OS X, and Microsoft Windows, so there's no reason why you shouldn't add this approach to your arsenal.
Continue reading "Working with Unix Tools"
Version Control Talk Demystified
One indication of the importance an
endeavor has in our lives is the vocabulary associated with it. If developers employ a tool or a method,
inevitably they will come up with words to describe their corresponding work in
an accurate and concise way. I recently
heard a colleague describe version control systems (also formally known as
configuration management tools) as boring. I hope that this dictionary
will dispel this myth by documenting a rich technical and social
vocabulary. If you donít work with a
VCS I believe this list will give you plenty of reasons to look at what these
systems can do for you and your projects. On the other hand, if you already use a VCS I hope you will find ideas
on how to use it more productively and how to improve your configuration management
process. And, no matter to which group
you belong to, I am sure youíll find here some new words worth knowing.
Continue reading "Version Control Talk Demystified"
Version Control Systems
A source code control system [is] a giant UNDO key—a project wide time machine.
— A. Hunt and D. Thomas
Sane programmers don't write production code without the help of an editor and an interpreter or a compiler, yet I've seen many software projects limping along without using a version control system. We can explain this contrast if we think in terms of the increased startup costs and the delayed gratification associated with the adoption of a VCS. We humans typically discount the future, and therefore implementing version control in a project appears to be a fight against the human nature. It is true that you can't beat the productivity boost that compilers and editors have provided us, but four decades after punched card programming in assembly language has gone out of fashion we must look elsewhere to reap our next gains in efficiency. And if you or your project is not using a VCS, adopting one may well be the single most important improvement you can undertake.
Continue reading "Version Control Systems"
Tool Writing: A Forgotten Art?
Merely adding features does not make it easier for users to do things—it just makes the manual thicker. The right solution in the right place is always more effective than haphazard hacking.
— Brian W. Kernighan and Rob Pike
In 1994 Chidamber and Kemerer defined a set of six simple metrics for object-oriented programs. Although the number of object-oriented metrics swelled to above 300 in the years that followed, I had a case where I preferred to use the original classic metric set for clarity, consistency, and simplicity. Surprisingly, none of the six open-source tools I found and tried to use fitted the bill. Most tools calculated only a subset of the six metrics, some required tweaking to make them compile, others had very specific dependencies on other projects (for example Eclipse), while others were horrendously inefficient. Although none of the tools I surveyed managed to calculate correctly the six classic Chidamber and Kemerer metrics in a straightforward way, most of them included numerous bells and whistles, such as graphical interfaces, XML output, and bindings to tools like ant and Eclipse.
Continue reading "Tool Writing: A Forgotten Art?"
Java Makes Scripting Languages Irrelevant?
Simplicity does not precede complexity, but follows it.
— Alan J. Perlis
In computing we often solve a complex problem by adding another level of indirection. As an example, on Unix file systems an index node, or inode, data structure allows files to be allocated concurrently and sparsely, and yet still provide an efficient random access capability. When we want to customize large and complex systems or express fluid and rapidly changing requirements a common tool we employ is to add a scripting layer on top of the corresponding system. An early instance of this approach was employed in Dan Murphy's TECO editor developed on the DEC PDP-1 computer in 1962–63: its command language also doubled as an arcane (to put it politely) macro language.
Continue reading "Java Makes Scripting Languages Irrelevant?"
Machines should work. People should think.
— Richard Hamming
Continue reading "Dear Editor"
I know that you are nowadays often taken for granted, and that many programmers consider you a relic of an older age. Yet, programmers continue to spend an inordinate amount of time with you, and often listen to your advice. As you have no doubt observed I am often mistreated; in this letter I have written my most common grievances hoping you can convince them programmers to behave better toward me in the future.
The Tools at Hand
The tools we use have a profound (and devious!) influence on our thinking habits, and, therefore, on our thinking abilities.
— Edsger W. Dijkstra
With a shovel excavator a single operator can effortlessly move 720 tons of earth with a single movement; a VLSI fabrication plant allows a designer to create elaborate sub-micron structures. Without tools the thousands employed in a car factory are nothing, with tools they can assemble a car in 18 effort hours. Sometimes, tools can even subsume the importance of their operators. The violinist Ivry Gitlis, considered one of the most talented musicians of his generation, said of his Stradivarius: "I have a violin that was born in 1713. I don't consider it my violin. Rather, I am its violinist; I am passing though its life." Tools are clearly an important and defining element of any profession and activity: tools help us move boulders and atoms, tools help us reach the Moon and our soul.
Continue reading "The Tools at Hand"