Java IoT Authors: Liz McMillan, Sematext Blog, Carmen Gonzalez, Yeshim Deniz, Jim Kaskade

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This post is not perfect and it is a bit outdated, but I think its helpful nonetheless.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

@ThingsExpo Stories
Intelligent machines are here. Robots, self-driving cars, drones, bots and many IoT devices are becoming smarter with Machine Learning. In her session at @ThingsExpo, Sudha Jamthe, CEO of IoTDisruptions.com, will discuss the next wave of business disruption at the junction of IoT and AI, impacting many industries and set to change our lives, work and world as we know it.
SYS-CON Events announced today that Enzu 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. Enzu’s mission is to be the leading provider of enterprise cloud solutions worldwide. Enzu enables online businesses to use its IT infrastructure to their competitive advantage. By offering a suite of proven hosting and management services, Enzu wants companies to focus on the core of their online busine...
The explosion of new web/cloud/IoT-based applications and the data they generate are transforming our world right before our eyes. In this rush to adopt these new technologies, organizations are often ignoring fundamental questions concerning who owns the data and failing to ask for permission to conduct invasive surveillance of their customers. Organizations that are not transparent about how their systems gather data telemetry without offering shared data ownership risk product rejection, regu...
The Open Connectivity Foundation (OCF), sponsor of the IoTivity open source project, and AllSeen Alliance, which provides the AllJoyn® open source IoT framework, today announced that the two organizations’ boards have approved a merger under the OCF name and bylaws. This merger will advance interoperability between connected devices from both groups, enabling the full operating potential of IoT and representing a significant step towards a connected ecosystem.
November 1–3, 2016, at the Santa Clara Convention Center in Santa Clara, CA. Penta Security is a leading vendor for data security solutions, including its encryption solution, D’Amo. By using FPE technology, D’Amo allows for the implementation of encryption technology to sensitive data fields without modification to schema in the database environment. With businesses having their data become increasingly more complicated in their mission-critical applications (such as ERP, CRM, HRM), continued ...
SYS-CON Events announced today that Embotics, the cloud automation company, 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. Embotics is the cloud automation company for IT organizations and service providers that need to improve provisioning or enable self-service capabilities. With a relentless focus on delivering a premier user experience and unmatched customer support, Embotics is the fas...
SYS-CON Events announced today that Cloudbric, a leading website security provider, 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. Cloudbric is an elite full service website protection solution specifically designed for IT novices, entrepreneurs, and small and medium businesses. First launched in 2015, Cloudbric is based on the enterprise level Web Application Firewall by Penta Security Sys...
Smart Cities are here to stay, but for their promise to be delivered, the data they produce must not be put in new siloes. In his session at @ThingsExpo, Mathias Herberts, Co-founder and CTO of Cityzen Data, will deep dive into best practices that will ensure a successful smart city journey.
Data is the fuel that drives the machine learning algorithmic engines and ultimately provides the business value. In his session at Cloud Expo, Ed Featherston, a director and senior enterprise architect at Collaborative Consulting, will discuss the key considerations around quality, volume, timeliness, and pedigree that must be dealt with in order to properly fuel that engine.
SYS-CON Events announced today that MathFreeOn 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. MathFreeOn is Software as a Service (SaaS) used in Engineering and Math education. Write scripts and solve math problems online. MathFreeOn provides online courses for beginners or amateurs who have difficulties in writing scripts. In accordance with various mathematical topics, there are more tha...
Successful digital transformation requires new organizational competencies and capabilities. Research tells us that the biggest impediment to successful transformation is human; consequently, the biggest enabler is a properly skilled and empowered workforce. In the digital age, new individual and collective competencies are required. In his session at 19th Cloud Expo, Bob Newhouse, CEO and founder of Agilitiv, will draw together recent research and lessons learned from emerging and established ...
In his general session at 19th Cloud Expo, Manish Dixit, VP of Product and Engineering at Dice, will discuss how Dice leverages data insights and tools to help both tech professionals and recruiters better understand how skills relate to each other and which skills are in high demand using interactive visualizations and salary indicator tools to maximize earning potential. Manish Dixit is VP of Product and Engineering at Dice. As the leader of the Product, Engineering and Data Sciences team a...
Virgil consists of an open-source encryption library, which implements Cryptographic Message Syntax (CMS) and Elliptic Curve Integrated Encryption Scheme (ECIES) (including RSA schema), a Key Management API, and a cloud-based Key Management Service (Virgil Keys). The Virgil Keys Service consists of a public key service and a private key escrow service. 

The best way to leverage your Cloud Expo presence as a sponsor and exhibitor is to plan your news announcements around our events. The press covering Cloud Expo and @ThingsExpo will have access to these releases and will amplify your news announcements. More than two dozen Cloud companies either set deals at our shows or have announced their mergers and acquisitions at Cloud Expo. Product announcements during our show provide your company with the most reach through our targeted audiences.
@ThingsExpo has been named the Top 5 Most Influential Internet of Things Brand by Onalytica in the ‘The Internet of Things Landscape 2015: Top 100 Individuals and Brands.' Onalytica analyzed Twitter conversations around the #IoT debate to uncover the most influential brands and individuals driving the conversation. Onalytica captured data from 56,224 users. The PageRank based methodology they use to extract influencers on a particular topic (tweets mentioning #InternetofThings or #IoT in this ...
More and more brands have jumped on the IoT bandwagon. We have an excess of wearables – activity trackers, smartwatches, smart glasses and sneakers, and more that track seemingly endless datapoints. However, most consumers have no idea what “IoT” means. Creating more wearables that track data shouldn't be the aim of brands; delivering meaningful, tangible relevance to their users should be. We're in a period in which the IoT pendulum is still swinging. Initially, it swung toward "smart for smar...
Web Real-Time Communication APIs have quickly revolutionized what browsers are capable of. In addition to video and audio streams, we can now bi-directionally send arbitrary data over WebRTC's PeerConnection Data Channels. With the advent of Progressive Web Apps and new hardware APIs such as WebBluetooh and WebUSB, we can finally enable users to stitch together the Internet of Things directly from their browsers while communicating privately and securely in a decentralized way.
In past @ThingsExpo presentations, Joseph di Paolantonio has explored how various Internet of Things (IoT) and data management and analytics (DMA) solution spaces will come together as sensor analytics ecosystems. This year, in his session at @ThingsExpo, Joseph di Paolantonio from DataArchon, will be adding the numerous Transportation areas, from autonomous vehicles to “Uber for containers.” While IoT data in any one area of Transportation will have a huge impact in that area, combining sensor...
With an estimated 50 billion devices connected to the Internet by 2020, several industries will begin to expand their capabilities for retaining end point data at the edge to better utilize the range of data types and sheer volume of M2M data generated by the Internet of Things. In his session at @ThingsExpo, Don DeLoach, CEO and President of Infobright, discussed the infrastructures businesses will need to implement to handle this explosion of data by providing specific use cases for filterin...
What happens when the different parts of a vehicle become smarter than the vehicle itself? As we move toward the era of smart everything, hundreds of entities in a vehicle that communicate with each other, the vehicle and external systems create a need for identity orchestration so that all entities work as a conglomerate. Much like an orchestra without a conductor, without the ability to secure, control, and connect the link between a vehicle’s head unit, devices, and systems and to manage the ...