Welcome!

Linux Containers Authors: Liz McMillan, Vaibhaw Pandey, Elizabeth White, Pat Romanski, Yeshim Deniz

Related Topics: @DevOpsSummit, Java IoT, Linux Containers

@DevOpsSummit: Blog Feed Post

Getting Real About Memory Leaks | @DevOpsSummit #APM #DevOps #ContinuousTesting

Modern programming languages tend to separate the programmer from memory management

Getting Real About Memory Leaks
By Matt Heusser

Modern programming languages tend to separate the programmer from memory management; Java programmers don't have to deal with pointers; they just declare variables and let the built-in garbage collector do its thing.

These garbage collectors are smart, but not perfect; they typically work by object reference. When all the references to an object go out of memory, that object can go out of memory too. Yet if two objects point to each other, they will always have a reference count, and never go away. That means the code written in Javascript to run in a browser, or Objective-C to run on a hand-held phone, or ASP to run on a server could very well have a memory leak.

When memory leaks happen on modern Operating Systems, the Operating System isn't going to throw an error. Instead, it will just use more and more memory, eventually going to virtual memory on the disk. When that happens, performance falls apart. People in operations reboot the server and that "seems to fix it"; users close and restart their browser, or reboot their phone.

Consider the Following Example
My first job in software was to create an electronic audit of a telecommunications bill. Some other software, maintained by my coworker Jeff, would read accounts, phones, and calls from a database and then create a text file that could be interpreted by a printer, called a post-script file. If we were smart, we'd have had written the tool in two parts, first to create a bunch of excel-like text files, then a second piece to combine those into bills.

One day, about four months in, the President of our 30-person software company came downstairs to my desk and said "Matt, I want you to take over the telecom bills", doing maintenance and new feature development.

The program was written in C. It read a list of accounts and looped through every account. Not every active account, every account, because an inactive account could still have an unpaid balance. We calculated the balance by adding up all the debits and credits through all time. If that amount added up to zero, we could skip the account. That was no big deal when we were helping a new, competitive regional carrier get started, with forty or fifty accounts and billing for five or six months.

The competitive carrier, however, was good at, well, competing. By the time I took over they had eighteen hundred accounts, and would be in the tens of thousands (and three states) before I left. Performance would become a real problem, but not for the reasons I expected.

The first two problems that hit us were a pointer out of range, then a memory leak.

Memory Out of Bounds
The software needed to store a great deal of data in memory for each account (the buildings, phones, calls, costs, and taxes) then spit it out to disk in post-script format. There are two basic ways to do this in C: Either allocate memory with pointers, which is hard to track, or simulate it using arrays. We didn't have objects, Test Driven Development wasn't really a thing, and I was inheriting code designed to support a very small customer base. What we did have was arrays. So to support two thousand calls, we could do something like this:

struct call {

char inOrOutbound;

datetimestamp timeStart;

datetimestamp timeEnd;

integer billedMinutes;

double cost;

}

char buildings  [200][200];

char phones [200][200][1000][1000];

call calls [200][200][1000][1000];

What's represented here is up to 200 buildings per account, each of which can have 200 phones, each of which can have up to 1000 calls. The variable calls [5][10][25] would contain the fifth call for the tenth phone at the twenty fifth building. Actually, since C is zero-based, it would be the 6th call at the third phone at the eleventh building.

The software was basically a loop. For each account, for each building, for each phone, for each call. The calls needed to be sorted, then the results printed. Everything worked fine until in one run I got a memory out of bounds error. That's probably because the code was trying to access building 201, phone 201, or call 1001. The compiler has range checking built-in by default. To get around this, I moved the size of the data structure up as large as possible, which worked until we got an account that was too big for that.

Then I turned off range checking and declared a large amount of empty data structures, matching the originals in type, below the originals. That is an incredibly foolish thing to do, but it worked. Because the data structures were built into the compiled program (the ".exe file") and would be re-used for every account. Our little program would declare all the memory it needed one time, at the beginning, and use that.

Until we found the system slowing to a crawl on big accounts, like it was choking.

Enter The Memory Leaks
The data structures above are an over-simplification. We also needed to store the addresses of the building, the payments since the last bill, and so on. Like the examples above some of these were declared variables, put in the compiled code, "on the stack". Others were grabbed at run-time, using a C program call named "malloc" and its friend "free." Instead of declaring an array, we'd declare a character pointer, then malloc() some space at that pointer. When the function was done, we could free() the disk space.

If we remembered to do that.

As you've probably guessed, we had too many calls to malloc() and not enough to free(). That meant that memory use slowly crept up as we used the software. That's fine for fifty or even five hundred accounts; the memory use would go away when the program finished running. But, we started to get some very big accounts. I noticed that one big account would run, and performance would go down. The kicker, for me, was an out of memory error for our user. I went to Rich, the sysadmin, and asked for more memory for the user. He suggested I tune it instead. After carefully poring over the code, I found some mallocs() that weren't being freed. Adding the calls to free, the program did eventually finish. That account still took too long, but that's enough for today.

You might see how I struggled, but you might not see what that has to do with modern software delivery. Allow me to share just a bit more.

The Lesson for Today
These problems are silent killers, and fixing them is no longer as easy as searching through a program making sure every malloc() has a matching free().

If you write embedded medical software, or avionics, or anything in C, you are probably very familiar with these problems. If you don't, you might not be, but the problems are still there.

If your application degrades over time, the problem might just be memory leaks. The next logical question is how to find them.

Read the original blog entry...

More Stories By SmartBear Blog

As the leader in software quality tools for the connected world, SmartBear supports more than two million software professionals and over 25,000 organizations in 90 countries that use its products to build and deliver the world’s greatest applications. With today’s applications deploying on mobile, Web, desktop, Internet of Things (IoT) or even embedded computing platforms, the connected nature of these applications through public and private APIs presents a unique set of challenges for developers, testers and operations teams. SmartBear's software quality tools assist with code review, functional and load testing, API readiness as well as performance monitoring of these modern applications.

@ThingsExpo Stories
Gemini is Yahoo’s native and search advertising platform. To ensure the quality of a complex distributed system that spans multiple products and components and across various desktop websites and mobile app and web experiences – both Yahoo owned and operated and third-party syndication (supply), with complex interaction with more than a billion users and numerous advertisers globally (demand) – it becomes imperative to automate a set of end-to-end tests 24x7 to detect bugs and regression. In th...
Widespread fragmentation is stalling the growth of the IIoT and making it difficult for partners to work together. The number of software platforms, apps, hardware and connectivity standards is creating paralysis among businesses that are afraid of being locked into a solution. EdgeX Foundry is unifying the community around a common IoT edge framework and an ecosystem of interoperable components.
"MobiDev is a software development company and we do complex, custom software development for everybody from entrepreneurs to large enterprises," explained Alan Winters, U.S. Head of Business Development at MobiDev, in this SYS-CON.tv interview at 21st Cloud Expo, held Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA.
Large industrial manufacturing organizations are adopting the agile principles of cloud software companies. The industrial manufacturing development process has not scaled over time. Now that design CAD teams are geographically distributed, centralizing their work is key. With large multi-gigabyte projects, outdated tools have stifled industrial team agility, time-to-market milestones, and impacted P&L stakeholders.
"Space Monkey by Vivent Smart Home is a product that is a distributed cloud-based edge storage network. Vivent Smart Home, our parent company, is a smart home provider that places a lot of hard drives across homes in North America," explained JT Olds, Director of Engineering, and Brandon Crowfeather, Product Manager, at Vivint Smart Home, in this SYS-CON.tv interview at @ThingsExpo, held Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA.
"Akvelon is a software development company and we also provide consultancy services to folks who are looking to scale or accelerate their engineering roadmaps," explained Jeremiah Mothersell, Marketing Manager at Akvelon, in this SYS-CON.tv interview at 21st Cloud Expo, held Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA.
In his session at 21st Cloud Expo, Carl J. Levine, Senior Technical Evangelist for NS1, will objectively discuss how DNS is used to solve Digital Transformation challenges in large SaaS applications, CDNs, AdTech platforms, and other demanding use cases. Carl J. Levine is the Senior Technical Evangelist for NS1. A veteran of the Internet Infrastructure space, he has over a decade of experience with startups, networking protocols and Internet infrastructure, combined with the unique ability to it...
"IBM is really all in on blockchain. We take a look at sort of the history of blockchain ledger technologies. It started out with bitcoin, Ethereum, and IBM evaluated these particular blockchain technologies and found they were anonymous and permissionless and that many companies were looking for permissioned blockchain," stated René Bostic, Technical VP of the IBM Cloud Unit in North America, in this SYS-CON.tv interview at 21st Cloud Expo, held Oct 31 – Nov 2, 2017, at the Santa Clara Conventi...
"Cloud Academy is an enterprise training platform for the cloud, specifically public clouds. We offer guided learning experiences on AWS, Azure, Google Cloud and all the surrounding methodologies and technologies that you need to know and your teams need to know in order to leverage the full benefits of the cloud," explained Alex Brower, VP of Marketing at Cloud Academy, in this SYS-CON.tv interview at 21st Cloud Expo, held Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clar...
Coca-Cola’s Google powered digital signage system lays the groundwork for a more valuable connection between Coke and its customers. Digital signs pair software with high-resolution displays so that a message can be changed instantly based on what the operator wants to communicate or sell. In their Day 3 Keynote at 21st Cloud Expo, Greg Chambers, Global Group Director, Digital Innovation, Coca-Cola, and Vidya Nagarajan, a Senior Product Manager at Google, discussed how from store operations and ...
"There's plenty of bandwidth out there but it's never in the right place. So what Cedexis does is uses data to work out the best pathways to get data from the origin to the person who wants to get it," explained Simon Jones, Evangelist and Head of Marketing at Cedexis, in this SYS-CON.tv interview at 21st Cloud Expo, held Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA.
SYS-CON Events announced today that CrowdReviews.com has been named “Media Sponsor” of SYS-CON's 22nd International Cloud Expo, which will take place on June 5–7, 2018, at the Javits Center in New York City, NY. CrowdReviews.com is a transparent online platform for determining which products and services are the best based on the opinion of the crowd. The crowd consists of Internet users that have experienced products and services first-hand and have an interest in letting other potential buye...
SYS-CON Events announced today that Telecom Reseller has been named “Media Sponsor” of SYS-CON's 22nd International Cloud Expo, which will take place on June 5-7, 2018, at the Javits Center in New York, NY. Telecom Reseller reports on Unified Communications, UCaaS, BPaaS for enterprise and SMBs. They report extensively on both customer premises based solutions such as IP-PBX as well as cloud based and hosted platforms.
It is of utmost importance for the future success of WebRTC to ensure that interoperability is operational between web browsers and any WebRTC-compliant client. To be guaranteed as operational and effective, interoperability must be tested extensively by establishing WebRTC data and media connections between different web browsers running on different devices and operating systems. In his session at WebRTC Summit at @ThingsExpo, Dr. Alex Gouaillard, CEO and Founder of CoSMo Software, presented ...
WebRTC is great technology to build your own communication tools. It will be even more exciting experience it with advanced devices, such as a 360 Camera, 360 microphone, and a depth sensor camera. In his session at @ThingsExpo, Masashi Ganeko, a manager at INFOCOM Corporation, introduced two experimental projects from his team and what they learned from them. "Shotoku Tamago" uses the robot audition software HARK to track speakers in 360 video of a remote party. "Virtual Teleport" uses a multip...
A strange thing is happening along the way to the Internet of Things, namely far too many devices to work with and manage. It has become clear that we'll need much higher efficiency user experiences that can allow us to more easily and scalably work with the thousands of devices that will soon be in each of our lives. Enter the conversational interface revolution, combining bots we can literally talk with, gesture to, and even direct with our thoughts, with embedded artificial intelligence, whic...
SYS-CON Events announced today that Evatronix will exhibit at SYS-CON's 21st International Cloud Expo®, which will take place on Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. Evatronix SA offers comprehensive solutions in the design and implementation of electronic systems, in CAD / CAM deployment, and also is a designer and manufacturer of advanced 3D scanners for professional applications.
Leading companies, from the Global Fortune 500 to the smallest companies, are adopting hybrid cloud as the path to business advantage. Hybrid cloud depends on cloud services and on-premises infrastructure working in unison. Successful implementations require new levels of data mobility, enabled by an automated and seamless flow across on-premises and cloud resources. In his general session at 21st Cloud Expo, Greg Tevis, an IBM Storage Software Technical Strategist and Customer Solution Architec...
To get the most out of their data, successful companies are not focusing on queries and data lakes, they are actively integrating analytics into their operations with a data-first application development approach. Real-time adjustments to improve revenues, reduce costs, or mitigate risk rely on applications that minimize latency on a variety of data sources. In his session at @BigDataExpo, Jack Norris, Senior Vice President, Data and Applications at MapR Technologies, reviewed best practices to ...
An increasing number of companies are creating products that combine data with analytical capabilities. Running interactive queries on Big Data requires complex architectures to store and query data effectively, typically involving data streams, an choosing efficient file format/database and multiple independent systems that are tied together through custom-engineered pipelines. In his session at @BigDataExpo at @ThingsExpo, Tomer Levi, a senior software engineer at Intel’s Advanced Analytics gr...