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March 12, 2015 Volume 13, issue 3 PDF Reliable Cron across the Planet ...or How I stopped worrying and learned to love time Štěpán Davidovič, Kavita Guliani, Google This article describes Google's implementation of a distributed Cron service, serving the vast majority of internal teams that need periodic scheduling of compute jobs. During its existence, we have learned many lessons on how to desig

TABLE 1 Generators and Synchrony: Orthogonal dimensions Unfortunately, control structures in contemporary languages are optimized for simple synchronous calls, and as soon as the need arises to compose asynchronous methods, developers are left to their own devices, forced to write explicit CPS (continuation passing style) code by hand as if they were human compilers. Matters are even worse for cod

March 10, 2015 Volume 13, issue 3 PDF There is No Now Problems with simultaneity in distributed systems Justin Sheehy "Now." The time elapsed between when I wrote that word and when you read it was at least a couple of weeks. That kind of delay is one that we take for granted and don't even think about in written media. "Now." If we were in the same room and instead I spoke aloud, you might have a

The Bike Shed January 6, 2015 Volume 13, issue 2 PDF HTTP/2.0 — The IETF is Phoning It In Bad protocol, bad politics Poul-Henning Kamp A very long time ago —in 1989 —Ronald Reagan was president, albeit only for the final 19½ days of his term. And before 1989 was over Taylor Swift had been born, and Andrei Sakharov and Samuel Beckett had died. In the long run, the most memorable event of 1989 will

August 18, 2011 Volume 9, issue 8 PDF Abstraction in Hardware System Design Applying lessons from software languages to hardware languages using Bluespec SystemVerilog Rishiyur S. Nikhil, Bluespec Inc., USA The history of software engineering is one of continuing development of abstraction mechanisms designed to tackle ever-increasing complexity. Hardware design, however, is not as current. For ex

There’s a lot we can learn from CORBA’s mistakes. MICHI HENNING, ZeroC Depending on exactly when one starts counting, CORBA is about 10-15 years old. During its lifetime, CORBA has moved from being a bleeding-edge technology for early adopters, to being a popular middleware, to being a niche technology that exists in relative obscurity. It is instructive to examine why CORBA—despite once being her

July 23, 2014 Volume 12, issue 7 PDF The Network is Reliable An informal survey of real-world communications failures Peter Bailis, UC Berkeley Kyle Kingsbury, Jepsen Networks "The network is reliable" tops Peter Deutsch's classic list, "Eight fallacies of distributed computing" (https://blogs.oracle.com/jag/resource/Fallacies.html), "all [of which] prove to be false in the long run and all [of wh

April 26, 2014 Volume 12, issue 4 PDF The Curse of the Excluded Middle "Mostly functional" programming does not work. Erik Meijer There is a trend in the software industry to sell "mostly functional" programming as the silver bullet for solving problems developers face with concurrency, parallelism (manycore), and, of course, Big Data. Contemporary imperative languages could continue the ongoing t

December 3, 2013 Volume 11, issue 10 PDF Making the Web Faster with HTTP 2.0 HTTP continues to evolve Ilya Grigorik HTTP (Hypertext Transfer Protocol) is one of the most widely used application protocols on the Internet. Since its publication, RFC 2616 (HTTP 1.1) has served as a foundation for the unprecedented growth of the Internet: billions of devices of all shapes and sizes, from desktop compu

October 7, 2013 Volume 11, issue 8 PDF Online Algorithms in High-frequency Trading The challenges faced by competing HFT algorithms Jacob Loveless, Sasha Stoikov, and Rolf Waeber HFT (high-frequency trading) has emerged as a powerful force in modern financial markets. Only 20 years ago, most of the trading volume occurred in exchanges such as the New York Stock Exchange, where humans dressed in br

August 9, 2013 Volume 11, issue 7 PDF NUMA (Non-Uniform Memory Access): An Overview NUMA becomes more common because memory controllers get close to execution units on microprocessors. Christoph Lameter, Ph.D. NUMA (non-uniform memory access) is the phenomenon that memory at various points in the address space of a processor have different performance characteristics. At current processor speeds,

June 2, 2013 Volume 11, issue 5 PDF Proving the Correctness of Nonblocking Data Structures Nonblocking synchronization can yield astonishing results in terms of scalability and realtime response, but at the expense of verification state space. Mathieu Desnoyers, EfficiOS So you've decided to use a nonblocking data structure, and now you need to be certain of its correctness. How can this be achiev

June 11, 2013 Volume 11, issue 5 PDF Nonblocking Algorithms and Scalable Multicore Programming Exploring some alternatives to lock-based synchronization Samy Al Bahra, AppNexus Real-world systems with complicated quality-of-service guarantees may require a delicate balance between throughput and latency to meet operating requirements in a cost-efficient manner. The increasing availability and decr

There's Just No Getting around It: You're Building a Distributed System Building a distributed system requires a methodical approach to requirements. Mark Cavage Distributed systems are difficult to understand, design, build, and operate. They introduce exponentially more variables into a design than a single machine does, making the root cause of an application problem much harder to discover. It

March 4, 2013 Volume 11, issue 2 PDF How Fast is Your Web Site? Web site performance data has never been more readily available. Patrick Meenan The overwhelming evidence indicates that a Web site's performance (speed) correlates directly to its success, across industries and business metrics. With such a clear correlation (and even proven causation), it is important to monitor how your Web site pe

January 31, 2013 Volume 11, issue 1 PDF Making the Mobile Web Faster Mobile performance issues? Fix the back end, not just the client. Kate Matsudaira Mobile clients have been on the rise and will only continue to grow. This means that if you are serving clients over the Internet, you cannot ignore the customer experience on a mobile device. There are many informative articles on mobile performanc

Weathering the Unexpected Failures happen, and resilience drills help organizations prepare for them. Kripa Krishnan, Google Whether it is a hurricane blowing down power lines, a volcanic-ash cloud grounding all flights for a continent, or a humble rodent gnawing through underground fibers—the unexpected happens. We cannot do much to prevent it, but there is a lot we can do to be prepared for it.

Rethinking Passwords Our authentication system is lacking. Is improvement possible? William Cheswick There is an authentication plague upon the land. We have to claim and assert our identity repeatedly to a host of authentication trolls, each jealously guarding an Internet service of some sort. Each troll has specific rules for passwords, and the rules vary widely and incomprehensibly. Password le

October 17, 2012 Volume 10, issue 10 PDF Anatomy of a Solid-state Drive While the ubiquitous SSD shares many features with the hard-disk drive, under the surface they are completely different. Michael Cornwell, Pure Storage Over the past several years, a new type of storage device has entered laptops and data centers, fundamentally changing expectations regarding the power, size, and performance d

Disks from the Perspective of a File System Disks lie. And the controllers that run them are partners in crime. Marshall Kirk McKusick Most applications do not deal with disks directly, instead storing their data in files in a file system, which protects us from those scoundrel disks. After all, a key task of the file system is to ensure that the file system can always be recovered to a consistent

The Bike Shed August 15, 2012 Volume 10, issue 8 PDF A Generation Lost in the Bazaar Quality happens only when someone is responsible for it. Poul-Henning Kamp Thirteen years ago, Eric Raymond's book The Cathedral and the Bazaar (O'Reilly Media, 2001) redefined our vocabulary and all but promised an end to the waterfall model and big software companies, thanks to the new grass-roots open source so