Welcome!

SDN Journal Authors: Olivier Huynh Van, David Paquette, Elizabeth White, Pat Romanski, Liz McMillan

Related Topics: Java IoT, Microservices Expo, Microsoft Cloud, Server Monitoring, @CloudExpo, SDN Journal

Java IoT: Blog Feed Post

NoSQL and Partition Tolerance

While NoSQL implementations are aware that nodes have left, they are not aware that said nodes have formed a separate partition

I came across an article discussing NoSQL and partition tolerance.

The NoSQL Partition Tolerance Myth (link)

I may not entirely agree with the author.

But what most NoSQL systems offer is a peculiar behavior that is not partition tolerant, but partition oblivious instead.

 

No argument here. While NoSQL implementations are aware that nodes have left, they are not aware that said nodes have formed a separate partition.

In this case, we would want failure detection and carry out those transfers where the accounts are both on the same side of the partition, while denying or deferring transfers that cross the chasm.

The author is assuming that the account is only on one side of the partition. If that is that is case, is doesn’t matter whether the NoSQL implementation is eventually consistent or not. If the account is on both sides of the partition, the solution the author provides still results in an inconsistent state.

In such cases, it is almost always better to build services that degrade gracefully under partitions.

Bingo! The author implies that all NoSQL implementations sacrifice consistency in the event of a partition. That is not true. There are AP implementations (available & partition tolerant), and there are CP implementations (consistent & partition tolerant). However, an AP implementation can function as a CP implementation depending on the configuration and the application. For example, if accounts do not have multiple owners and the application can not withdraw funds from or deposit funds to an account if it can not access the account.

This post is not perfect and it is a bit outdated, but I think its helpful nonetheless.

Visual Guide to NoSQL Systems (link)

If I were to build a bank based on Dynamo, the granddaddy of all first-generation NoSQL data stores, it would silently split into two halves, like a lobotomized patient.

I would not say that Amazon Dynamo is the grandparent of all NoSQL implementations. I would say that there are two parents: Amazon Dynamo and Google BigTable. Then there are the grandparents…

A Brief History of NoSQL (link)

In this scenario, the hypothetical backend for Banko Dynamo would not only not provide any indication of failure, but allow a customer to create as many new accounts as there are partitions, one in each.

Why is the author now using account creation instead of withdrawals and deposits, and what is the relevance of creating multiple accounts? If my debit card does not work, I do not create a new account. That, and I maintain two checking accounts and one savings account with the same bank.

Let’s go back to withdrawals and deposits. If the accounts do not have multiple owners, it does not matter whether the NoSQL implementation is eventually consistent or not. If the accounts do have multiple owners, it depends on the NoSQL implementation. If it is inspired by Google BigTable (e.g. Apache HBase) or both Google BigTable and Amazon Dynamo (e.g. Apache Cassandra), it does not matter. These NoSQL implementations are CP, or can be configured to be CP. If it inspired only by Amazon Dynamo and it is eventually consistent, it may or may not matter…

Let’s assume that account withdrawals / deposits are separate from the accounts themselves and that the account is both consistent and available during a partition. The account has multiple owners but it is more or less read only.

My account has a balance of $100 (calculated from the withdrawals and deposits). Now, there are two partitions: A and B. I purchase $50 of St. Bernardus Abt 12 at Binny’s via partition A. Partition A now has withdrawal #1. I have dinner at Baume & Brix for $75 via partition B. Partition B now has withdrawal #2. My account has a balance of $50 in partition A. It has a balance of $25 in partition B. My account should have a balance of minus $25.

Does it matter? My account may not have a balance of minus $25, but it will. When the partition is repaired, the application will be able to access all of the withdrawals and deposits on my account. I may be charged an overlimit fee.

What if the NoSQL implementation sacrificed availability? My payment at Binny’s did not go through. That’s not a problem. No St. Bernardus Abt 12 for me. My payment at Baume & Brix did not go through. That’s a problem. I can’t pay for dinner. Baume & Brix can’t accept my payment nor that of any other customer paying with a debit card from the same bank as me via partition B.

What if I made a deposit of $25 at an ATM via partition A? My account will have a balance of $0 after the partition is repaired. I will not be charged an overlimit fee.

There are other scenarios. Perhaps I’m charged an insufficient funds fee and Baume & Brix does not receive payment. Perhaps Baume & Brix later resubmits the payment and receives payment.

Do you really want to sell tickets from both halves of your system? By definition, there is no way you can guarantee uniqueness of those tickets. There will be customers holding identical tickets with identical seat numbers.

Maybe, maybe not. If there is only a single owner per ticket, then yes. However, there may be availability issues. For example, partition A has tickets 1-150 and partition B has tickets 151-200. If all the tickets in partition B have been purchased, visitors may be unable to purchase tickets despite the fact that there may be tickets available in partition A. If there are multiple owners per ticket, I would prefer a NoSQL implementation that is CP. In this case, I would prefer to sacrifice availability rather than consistency.

Here is a better example. What if I report my debit card stolen? Sacrificing availability is not appropriate. What if customer service is accessing my account via the partition with no availability? My debit card must be reported stolen or the thief can continue to make purchases with it. Sacrificing consistency is not appropriate. The thief can continue to make purchases with my debit card via the partition where my account has not been reported stolen. Perhaps account information should not be stored in a distributed system.

And if they did, the first-generation NoSQL stores usually take the ultimate punt by presenting all versions of the divergent objects to the application, and let the application resolve the mess.

No argument here.

But if your data is that soft and inconsequential, why not just use memcached? It’s wicked fast, far faster than Mongo.

Perhaps because MongoDB is a document store and as such provides features that are not provided by key / value stores.

A lot of NoSQL developers pretend that being partition oblivious is a difficult thing to implement. This is false. It’s easy to make a program oblivious to a particular event; namely, you write no code to handle that event.

No argument here.

The thing that greatly helps first generation NoSQL data stores, the thing that enables them to package partition obliviousness as if it were equivalent to partition tolerance, is that they provide a very weak service guarantee in the first place. These systems cannot guarantee that, on a good day, your GET will return the latest PUT.

Sure they can.

In fact, eventual consistency means that a GET can return any previous value, including the Does Not Exist response from the very initial state of the system.

No argument here. Of course, not all NoSQL implementations are eventually consistent.


With all this being said, a NoSQL implementation may or may not be appropriate. To be more specific, a NoSQL implementation that is eventually consistent and sacrifices consistency in the event of a partition may or may not be appropriate. The behaviour is determined by the NoSQL implementation, its configuration, and the application that reads and writes to it. Whether that behaviour is appropriate or not depends on the business requirements.

Read the original blog entry...

More Stories By Daniel Thompson

I curate the content on this page, but the credit goes to my talented colleagues for the posts that you see here. Much of what you read on this page is the work of friends at How to JBoss, and I encourage you to drop by the site at http://www.howtojboss.com for some of the best JBoss technical and non-technical content for developers, architects and technology executives on the Web.

@CloudExpo Stories
Digital innovation is the next big wave of business transformation based on digital technologies of which IoT and Big Data are key components, For example: Business boundary innovation is a challenge to excavate third-party business value using IoT and BigData, like Nest Business structure innovation may propose re-building business structure from scratch, as Uber does in the taxicab industry The social model innovation is also a big challenge to the new social architecture with the design fr...
Fifty billion connected devices and still no winning protocols standards. HTTP, WebSockets, MQTT, and CoAP seem to be leading in the IoT protocol race at the moment but many more protocols are getting introduced on a regular basis. Each protocol has its pros and cons depending on the nature of the communications. Does there really need to be only one protocol to rule them all? Of course not. In his session at @ThingsExpo, Chris Matthieu, co-founder and CTO of Octoblu, walk you through how Oct...
We’ve been doing it for years, decades for some. How many websites have you created accounts on? Your bank, your credit card companies, social media sites, hotels and travel sites, online shopping sites, and that’s just the start. We do it often without even thinking about it, quickly entering our personal information, our data, in a plethora of systems. Sometimes we’re not even aware of the information we are providing. It could be very personal information (think of the security questions you ...
Complete Internet of Things (IoT) embedded device security is not just about the device but involves the entire product’s identity, data and control integrity, and services traversing the cloud. A device can no longer be looked at as an island; it is a part of a system. In fact, given the cross-domain interactions enabled by IoT it could be a part of many systems. Also, depending on where the device is deployed, for example, in the office building versus a factory floor or oil field, security ha...
Is your aging software platform suffering from technical debt while the market changes and demands new solutions at a faster clip? It’s a bold move, but you might consider walking away from your core platform and starting fresh. ReadyTalk did exactly that. In his General Session at 19th Cloud Expo, Michael Chambliss, Head of Engineering at ReadyTalk, will discuss why and how ReadyTalk diverted from healthy revenue and over a decade of audio conferencing product development to start an innovati...
All clouds are not equal. To succeed in a DevOps context, organizations should plan to develop/deploy apps across a choice of on-premise and public clouds simultaneously depending on the business needs. This is where the concept of the Lean Cloud comes in - resting on the idea that you often need to relocate your app modules over their life cycles for both innovation and operational efficiency in the cloud. In his session at @DevOpsSummit at19th Cloud Expo, Valentin (Val) Bercovici, CTO of So...
SYS-CON Events announced today that Niagara Networks will exhibit at the 19th International Cloud Expo, which will take place on November 1–3, 2016, at the Santa Clara Convention Center in Santa Clara, CA. Niagara Networks offers the highest port-density systems, and the most complete Next-Generation Network Visibility systems including Network Packet Brokers, Bypass Switches, and Network TAPs.
Data is an unusual currency; it is not restricted by the same transactional limitations as money or people. In fact, the more that you leverage your data across multiple business use cases, the more valuable it becomes to the organization. And the same can be said about the organization’s analytics. In his session at 19th Cloud Expo, Bill Schmarzo, CTO for the Big Data Practice at EMC, will introduce a methodology for capturing, enriching and sharing data (and analytics) across the organizati...
SYS-CON Events announced today that Commvault, a global leader in enterprise data protection and information management, has been named “Bronze Sponsor” of SYS-CON's 19th International Cloud Expo, which will take place on November 1–3, 2016, at the Santa Clara Convention Center in Santa Clara, CA. Commvault is a leading provider of data protection and information management solutions, helping companies worldwide activate their data to drive more value and business insight and to transform moder...
There is little doubt that Big Data solutions will have an increasing role in the Enterprise IT mainstream over time. Big Data at Cloud Expo - to be held November 1-3, 2016, at the Santa Clara Convention Center in Santa Clara, CA - has announced its Call for Papers is open. Cloud computing is being adopted in one form or another by 94% of enterprises today. Tens of billions of new devices are being connected to The Internet of Things. And Big Data is driving this bus. An exponential increase is...
IoT is fundamentally transforming the auto industry, turning the vehicle into a hub for connected services, including safety, infotainment and usage-based insurance. Auto manufacturers – and businesses across all verticals – have built an entire ecosystem around the Connected Car, creating new customer touch points and revenue streams. In his session at @ThingsExpo, Macario Namie, Head of IoT Strategy at Cisco Jasper, will share real-world examples of how IoT transforms the car from a static p...
SYS-CON Events announced today that Tintri Inc., a leading producer of VM-aware storage (VAS) for virtualization and cloud environments, will exhibit at the 19th International Cloud Expo, which will take place on November 1–3, 2016, at the Santa Clara Convention Center in Santa Clara, CA. Tintri VM-aware storage is the simplest for virtualized applications and cloud. Organizations including GE, Toyota, United Healthcare, NASA and 6 of the Fortune 15 have said “No to LUNs.” With Tintri they mana...
Creating replica copies to tolerate a certain number of failures is easy, but very expensive at cloud-scale. Conventional RAID has lower overhead, but it is limited in the number of failures it can tolerate. And the management is like herding cats (overseeing capacity, rebuilds, migrations, and degraded performance). Download Slide Deck: ▸ Here In his general session at 18th Cloud Expo, Scott Cleland, Senior Director of Product Marketing for the HGST Cloud Infrastructure Business Unit, discusse...
Whether they’re located in a public, private, or hybrid cloud environment, cloud technologies are constantly evolving. While the innovation is exciting, the end mission of delivering business value and rapidly producing incremental product features is paramount. In his session at @DevOpsSummit at 19th Cloud Expo, Kiran Chitturi, CTO Architect at Sungard AS, will discuss DevOps culture, its evolution of frameworks and technologies, and how it is achieving maturity. He will also cover various st...
If you had a chance to enter on the ground level of the largest e-commerce market in the world – would you? China is the world’s most populated country with the second largest economy and the world’s fastest growing market. It is estimated that by 2018 the Chinese market will be reaching over $30 billion in gaming revenue alone. Admittedly for a foreign company, doing business in China can be challenging. Often changing laws, administrative regulations and the often inscrutable Chinese Interne...
Internet of @ThingsExpo, taking place November 1-3, 2016, at the Santa Clara Convention Center in Santa Clara, CA, is co-located with the 19th International Cloud Expo and will feature technical sessions from a rock star conference faculty and the leading industry players in the world and ThingsExpo Silicon Valley Call for Papers is now open.
SYS-CON Events has announced today that Roger Strukhoff has been named conference chair of Cloud Expo and @ThingsExpo 2016 Silicon Valley. The 19th Cloud Expo and 6th @ThingsExpo will take place on November 1-3, 2016, at the Santa Clara Convention Center in Santa Clara, CA. "The Internet of Things brings trillions of dollars of opportunity to developers and enterprise IT, no matter how you measure it," stated Roger Strukhoff. "More importantly, it leverages the power of devices and the Interne...
"We have several customers now running private clouds. They're not as large as they should be but it's getting there. The adoption challenge has been pretty simple. Look at the world today of virtualization vs cloud," stated Nara Rajagopalan, CEO of Accelerite, in this SYS-CON.tv interview at 18th Cloud Expo, held June 7-9, 2016, at the Javits Center in New York City, NY.
"My role is working with customers, helping them go through this digital transformation. I spend a lot of time talking to banks, big industries, manufacturers working through how they are integrating and transforming their IT platforms and moving them forward," explained William Morrish, General Manager Product Sales at Interoute, in this SYS-CON.tv interview at 18th Cloud Expo, held June 7-9, 2016, at the Javits Center in New York City, NY.
In his keynote at 18th Cloud Expo, Andrew Keys, Co-Founder of ConsenSys Enterprise, provided an overview of the evolution of the Internet and the Database and the future of their combination – the Blockchain. Andrew Keys is Co-Founder of ConsenSys Enterprise. He comes to ConsenSys Enterprise with capital markets, technology and entrepreneurial experience. Previously, he worked for UBS investment bank in equities analysis. Later, he was responsible for the creation and distribution of life sett...