Home » Java » Enterprise Java » Making Sense Out of Datomic, The Revolutionary Non-NoSQL Database

About Jakub Holy

Jakub Holy
Jakub is an experienced Java[EE] developer working for a lean & agile consultancy in Norway. He is interested in code quality, developer productivity, testing, and in how to make projects succeed.

Making Sense Out of Datomic, The Revolutionary Non-NoSQL Database

I have finally managed to understand one of the most unusual databases of today, Datomic, and would like to share it with you. Thanks to Stuart Halloway and his workshop!

Why? Why?!?

As we shall see shortly, Datomic is very different from the traditional RDBMS databases as well as the various NoSQL databases. It even isn’t a database – it is a database on top of a database. I couldn’t wrap my head around that until now. The key to the understanding of Datomic and its unique design and advantages is actually simple.

The mainstream databases (and languages) have been designed around the following constraints of 1970s:

  • memory is expensive
  • storage is expensive
  • it is necessary to use dedicated, expensive machines

Datomic is essentially an exploration of what database we would have designed if we hadn’t these constraints. What design would we choose having gigabytes of RAM, networks with bandwidth and speed matching and exceeding harddisk access, the ability to spin and kill servers at a whim.

But Datomic isn’t an academical project. It is pragmatic, it wants to fit into our existing environments and make it easy for us to start using its futuristic capabilities now. And it is not as fresh and green as it might seem. Rich Hickey, the master mind behind Clojure and Datomic, has reportedly thought about both these projects for years and the designs have been really well thought through.

The Weird Architecture of Datomic

  1. Datomic is a database on top of another database (or rather storage) – in-memory, a file system, a traditional RDBMS, Amazon Dynamo.
  2. You do not send your query to the server and get back the result. Instead, you get back all the data you need to execute the query and run the query – and all subsequent queries – locally. Thus, “joins” are pretty cheap and you can do plenty of otherwise impossible things (combine data from multiple databases and local data structures, run any code on them, …). Each application using Datomic – a “peer” – will have the data it needs, based on its unique needs and usage patterns, close to itself.
  3. All writes go through one component, called Transactor, which essentially serializes the writes, thus ensuring ACID. It might sound as a bottleneck but it isn’t for most practical purposes[1] given the design and typical application needs. (Reportedly, Datomic could handle all transactions for all credit cards in the world. Listen to the experiences of Room Key with their rather write-heavy load in the Relevance Podcast with Kurt Zimmer (Podcast Episode 033).)
  4. Datomic works quite similarly to a version control system such as Git. It never overwrites data, there are no updates. You only mark the data as not valid anymore and add new data, which produces a new version of the database (think of git hash / svn revision number). You can then query the latest state of the database or the state as of a particular version. (Of course the whole database isn’t copied whenever you add a fact to it. Datomic is smart and efficient.)
  5. It is not a single, monolithic server, the storage, transactor, and peers are physically separate pieces.

What has made this possible?

  • Network access as fast as or faster then disk access => can fetch all the data over the network
  • Plenty of memory => can store a substantial subset of it on each peer according to its actual needs
  • Storage is huge and cheap => we can easily store historical data
  • Experiences with efficient, immutable, “persistent” data structures used in modern FP languages => cheap creation of new “database values”

The Unique Value Proposition And Capabilities of Datomic

We have now learned about and hopefully understood the unique design of Datomic. But what does it give to us, what does it distinguish from other databases?

The architecture, together with few other design decisions, provides the following key characteristics:

  • Programmability – data, schema, query input/output, transaction metadata are all just elementary data structures that you have fully available at the peer and can thus combine and process in powerful ways unimaginable before
  • Persistence/accountability – you never lose history, can annotate transactions with metadata about who/why etc., support for finding out how things were, how they have been changing, performing what-if analysis
  • Elastic scalability – since a lot of the load has been pushed to the peers
  • Flexibility – no rigid schema, easy to navigate and combine and cache data based on each peer’s unique needs, extensibility via data functions

Closing Notes

Datomic has similar goals as relational databases (especially ACID) and could be used in similar use cases. Performance-wise, if writes are more important than reads, if you need to write really a lot of data each second continuously, or if you have over billions of “rows” then you might prefer another solution. Thanks to the design and recommended architecture for heavily loaded installations, i.e. with memcached in front of the storage, the performance of the backend isn’t so important (as the peers have the data they need locally or get it from memcached) so it should be selected more based on the usage-related characteristics.

Summary

The design of Datomic – peers fetching data and running queries locally, a single coordinator of writes (transactor), building on existing databases/storage tools (and keeping all the history) seemed very strange and perhaps inefficient to me until I realized that the traditional databases are designed around constraints that do not exist anymore. Datomic now makes sense to me and seems as a tool with intriguing capabilities and great potential. I hope you see it the same way now.

I have left out some interesting topics such as what data structures can be stored in Datomic and the data model and query model used. To learn about these and more about Datomic, head to Datomic for Five Year Olds and Datomic’s home page.

Bonus Links

[1] Harizopoulos, S., Abadi, D. J., Madden, S., & Stonebraker, M. (2008, June). OLTP through the looking glass, and what we found there. In Proceedings of the 2008 ACM SIGMOD international conference on Management of data (pp. 981-992). ACM. – this paper shows that traditional RDBMS spend nearly 30% time on locking and latching, that could be eliminated with single-threaded access, as is also done in VoltDB. See also the VoltDB whitepaper.
 

Do you want to know how to develop your skillset to become a Java Rockstar?
Subscribe to our newsletter to start Rocking right now!
To get you started we give you our best selling eBooks for FREE!
1. JPA Mini Book
2. JVM Troubleshooting Guide
3. JUnit Tutorial for Unit Testing
4. Java Annotations Tutorial
5. Java Interview Questions
6. Spring Interview Questions
7. Android UI Design
and many more ....
Email address:

Leave a Reply

Be the First to Comment!

avatar
  Subscribe  
Notify of
Want to take your Java skills to the next level?
Grab our programming books for FREE!
Here are some of the eBooks you will get:
  • Spring Interview QnA
  • Multithreading & Concurrency QnA
  • JPA Minibook
  • JVM Troubleshooting Guide
  • Advanced Java
  • Java Interview QnA
  • Java Design Patterns
The Spring Framework Cookbook
  • Learn the best practices of the Spring Framework
  • Build simple, portable, fast and flexible JVM-based systems and applications
  • Explore specific projects like Boot and Batch
The Spring Data Programming Cookbook
  • Learn how to use data access technologies and cloud-based data services
  • Set up the environment and create a basic project
  • Learn how to handle the various modules (e.g. JPA, MongoDB, Redis etc.)
The Selenium Programming Cookbook
  • Kick-start your own projects using this testing framework for web applications
  • Learn JUnit integration and Standalone Server functionality
  • Find out the most popular Interview Questions about the Selenium Framework
The Mockito Programming Cookbook
  • Kick-start your own web projects using this open source testing framework
  • Write simple test cases using the Mockito Framework
  • Learn how to integrate with JUnit, Maven and other frameworks
The JUnit Programming Cookbook
  • Learn basic usage and configuration of JUnit
  • Create multithreaded tests
  • Learn how to integrate with other testing frameworks
The JSF 2.0 Programming Cookbook
  • Build component-based user interfaces for web applications
  • Set up the environment and create a basic project
  • Learn Internationalization and Facelets Templates
The Amazon S3 Tutorial
  • Develop your own Amazon S3 based applications
  • Learn API usage and pricing
  • Get your own projects up and running in minimum time
Java Design Patterns
  • Learn how Design Patterns are implemented and utilized in Java
  • Understand the reasons why patterns are so important
  • Learn when and how to apply each one of them
Java Concurrency Essentials
  • Dive into the magic of concurrency
  • Learn about concepts like atomicity, synchronization and thread safety
  • Learn about testing concurrent applications
The IntelliJ IDEA Handbook
  • Kick-start your own programming projects using IntelliJ IDEA
  • Learn how to setup and install plugins
  • Create UIs with this Java integrated development environment
The Git Tutorial
  • Learn why Git differs from other version control systems
  • Explore Git's usage and best practises
  • Learn branching strategies
The Eclipse IDE Handbook
  • Explore the most widely used Java IDE
  • Learn how to setup and install plugins
  • Built your own projects up and running in minimum time
The Docker Containerization Cookbook
  • Explore the world’s leading software containerization platform
  • Learn how to wrap a piece of software in a complete filesystem
  • Learn how to use DNS and various commands
Developing Modern Applications With Scala
  • Develop modern Scala applications
  • Build SBT and reactive applications
  • Learn about testing and database access
The Apache Tomcat Cookbook
  • Explore Apache Tomcat open-source web server
  • Learn about installation, configuration, logging and clustering
  • Kick-start your own web projects using Apache Tomcat
The Apache Maven Cookbook
  • Explore the Apache Maven build automation tool
  • Learn about Maven's project structure and configuration
  • Learn about Maven's dependency management and plug-ins
The Apache Hadoop Cookbook
  • Explore the Apache Hadoop open-source software framework
  • Learn distributed caching and streaming
  • Kick-start your own web projects using Apache Hadoop
The Android Programming Cookbook
  • Explore the Android mobile operating system
  • Learn about services and page views
  • Learn about Google Maps and Bluetooth functionality
The Elasticsearch Tutorial
  • Explore the Elasticsearch search engine
  • Develop your own Elasticsearch based applications
  • Learn operations, Java API Integration and reporting
Amazon DynamoDB Tutorial
  • Develop your own Amazon DynamoDB based applications
  • Learn DynamoDB Concepts and Best Practices
  • Get your own projects up and running in minimum time
Java NIO Programming Cookbook
  • Learn features for intensive I/O operations
  • Follow a series of tutorials on Java NIO examples
  • Get knowledge on Java Nio Socket and Asynchronous Channels
JBoss Drools Cookbook
  • Explore Drools business rule management system
  • Follow a series of tutorials on Drools examples
  • Get knowledge on business rules for a shopping domain model
Vaadin Programming Cookbook
  • Explore Vaadin web framework for rich Internet applications
  • Learn the Architecture and Best Practices
  • Get knowledge on Data Binding and Custom Components
Groovy Programming Cookbook
  • Explore Apache Groovy object-oriented programming language
  • Create sample applications and explore interview questions
  • Get knowledge on Callback functionality and various widgets
GWT Programming Cookbook
  • Explore the open source Google Web Toolkit
  • Create sample applications and explore interview questions
  • Create and maintain complex JavaScript front-end applications in Java
Do you want to know how to develop your skillset to become a Java Rockstar?
Subscribe to our newsletter to start Rocking right now!
To get you started we give you our best selling eBooks for FREE!
1. JPA Mini Book
2. JVM Troubleshooting Guide
3. JUnit Tutorial for Unit Testing
4. Java Annotations Tutorial
5. Java Interview Questions
and many more ....
Email address:
Do you want to know how to develop your skillset to become a Java Rockstar?
Subscribe to our newsletter to start Rocking right now!
To get you started we give you our best selling eBooks for FREE!
1. JPA Mini Book
2. JVM Troubleshooting Guide
3. JUnit Tutorial for Unit Testing
4. Java Annotations Tutorial
5. Java Interview Questions
and many more ....
Email address:
Do you want to know how to develop your skillset to become a Java Rockstar?
Subscribe to our newsletter to start Rocking right now!
To get you started we give you our best selling eBooks for FREE!
1. JPA Mini Book
2. JVM Troubleshooting Guide
3. JUnit Tutorial for Unit Testing
4. Java Annotations Tutorial
5. Java Interview Questions
6. Spring Interview Questions
7. Android UI Design
and many more ....
Email address:
Want to be a DynamoDB Master ?
Subscribe to our newsletter and download the Amazon DynamoDB Tutorial right now!
In order to help you master this Amazon NoSQL database service, we have compiled a kick-ass guide with all the major DynamoDB features and use cases! Besides studying them online you may download the eBook in PDF format!
Email address:
Programming Interview Coming Up?
Subscribe to our newsletter and download the Ultimate Multithreading and Concurrency interview questions and answers collection right now!
In order to get you prepared for your next Programming Interview, we have compiled a huge list of relevant Questions and their respective Answers. Besides studying them online you may download the eBook in PDF format!
Email address:
Java Interview Coming Up?
Subscribe to our newsletter and download the Ultimate Spring interview questions and answers collection right now!
In order to get you prepared for your next Java Interview, we have compiled a huge list of relevant Questions and their respective Answers. Besides studying them online you may download the eBook in PDF format!
Email address:
Java Interview Coming Up?
Subscribe to our newsletter and download the Ultimate Java interview questions and answers collection right now!
In order to get you prepared for your next Java Interview, we have compiled a huge list of relevant Questions and their respective Answers. Besides studying them online you may download the eBook in PDF format!
Email address:
Want to be a Java NIO Master ?
Subscribe to our newsletter and download the Java NIO Programming Cookbook right now!
In order to help you master Java NIO Library, we have compiled a kick-ass guide with all the major Java NIO features and use cases! Besides studying them online you may download the eBook in PDF format!
Email address:
Want to be a Drools Master ?
Subscribe to our newsletter and download the JBoss Drools Cookbook right now!
In order to help you master Drools Business Rule Management System, we have compiled a kick-ass guide with all the major Drools features and use cases! Besides studying them online you may download the eBook in PDF format!
Email address:
Want to be an iText Master ?
Subscribe to our newsletter and download the iText Tutorial right now!
In order to help you master iText Library, we have compiled a kick-ass guide with all the major iText features and use cases! Besides studying them online you may download the eBook in PDF format!
Email address:
Want to be an Elasticsearch Master ?
Subscribe to our newsletter and download the Elasticsearch Tutorial right now!
In order to help you master Elasticsearch search engine, we have compiled a kick-ass guide with all the major Elasticsearch features and use cases! Besides studying them online you may download the eBook in PDF format!
Email address:
Want to be a Scala Master ?
Subscribe to our newsletter and download the Scala Cookbook right now!
In order to help you master Scala, we have compiled a kick-ass guide with all the basic concepts! Besides studying them online you may download the eBook in PDF format!
Email address:
Want to be a JUnit Master ?
Subscribe to our newsletter and download the JUnit Programming Cookbook right now!
In order to help you master unit testing with JUnit, we have compiled a kick-ass guide with all the major JUnit features and use cases! Besides studying them online you may download the eBook in PDF format!
Email address:
Want to master Amazon Web Services ?
Subscribe to our newsletter and download the Amazon S3 Tutorial right now!
In order to help you master the leading Web Services platform, we have compiled a kick-ass guide with all its major features and use cases! Besides studying them online you may download the eBook in PDF format!
Email address:
Want to master Spring Framework ?
Subscribe to our newsletter and download the Spring Framework Cookbook right now!
In order to help you master the leading and innovative Java framework, we have compiled a kick-ass guide with all its major features and use cases! Besides studying them online you may download the eBook in PDF format!
Email address:
Want to master Eclipse IDE ?
Subscribe to our newsletter and download the Eclipse IDE Handbook right now!
In order to help you master Eclipse, we have compiled a kick-ass guide with all the basic features of the popular IDE! Besides studying them online you may download the eBook in PDF format!
Email address:
Want to master IntelliJ IDEA ?
Subscribe to our newsletter and download the IntelliJ IDEA Handbook right now!
In order to help you master IntelliJ IDEA, we have compiled a kick-ass guide with all the basic features of the popular IDE! Besides studying them online you may download the eBook in PDF format!
Email address:
Want to master Docker ?
Subscribe to our newsletter and download the Docker Containerization Cookbook right now!
In order to help you master Docker, we have compiled a kick-ass guide with all the basic concepts of the Docker container system! Besides studying them online you may download the eBook in PDF format!
Email address:
Want to create a kick-ass Android App ?
Subscribe to our newsletter and download the Android Programming Cookbook right now!
With this book, you will delve into the fundamentals of Android programming. You will understand user input, views and layouts. Furthermore, you will learn how to communicate over Bluetooth and also leverage Google Maps into your application!
Email address:
Want to be a GIT Master ?
Subscribe to our newsletter and download the GIT Tutorial eBook right now!
In order to help you master GIT, we have compiled a kick-ass guide with all the basic concepts of the GIT version control system! Besides studying them online you may download the eBook in PDF format!
Email address:
Want to be a Hadoop Master ?
Subscribe to our newsletter and download the Apache Hadoop Cookbook right now!
In order to help you master Apache Hadoop, we have compiled a kick-ass guide with all the basic concepts of a Hadoop cluster! Besides studying them online you may download the eBook in PDF format!
Email address:
Want to master Spring Data ?
Subscribe to our newsletter and download the Spring Data Ultimate Guide right now!
In order to help you master Spring Data, we have compiled a kick-ass guide with all the major features and use cases! Besides studying them online you may download the eBook in PDF format!
Email address:
Want to create a kick-ass Android App ?
Subscribe to our newsletter and download the Android UI Design mini-book right now!
With this book, you will delve into the fundamentals of Android UI design. You will understand user input, views and layouts, as well as adapters and fragments. Furthermore, you will learn how to add multimedia to an app and also leverage themes and styles!
Email address:
Want to be a Java 8 Ninja ?
Subscribe to our newsletter and download the Java 8 Features Ultimate Guide right now!
In order to get you up to speed with the major Java 8 release, we have compiled a kick-ass guide with all the new features and goodies! Besides studying them online you may download the eBook in PDF format!
Email address:
Want to master Java Annotations ?
Subscribe to our newsletter and download the Java Annotations Ultimate Guide right now!
In order to help you master the topic of Annotations, we have compiled a kick-ass guide with all the major features and use cases! Besides studying them online you may download the eBook in PDF format!
Email address:
Want to be a JUnit Master ?
Subscribe to our newsletter and download the JUnit Ultimate Guide right now!
In order to help you master unit testing with JUnit, we have compiled a kick-ass guide with all the major JUnit features and use cases! Besides studying them online you may download the eBook in PDF format!
Email address:
Want to master Java Abstraction ?
Subscribe to our newsletter and download the Abstraction in Java Ultimate Guide right now!
In order to help you master the topic of Abstraction, we have compiled a kick-ass guide with all the major features and use cases! Besides studying them online you may download the eBook in PDF format!
Email address:
Want to master Java Reflection ?
Subscribe to our newsletter and download the Java Reflection Ultimate Guide right now!
In order to help you master the topic of Reflection, we have compiled a kick-ass guide with all the major features and use cases! Besides studying them online you may download the eBook in PDF format!
Email address:
Want to be a JMeter Master ?
Subscribe to our newsletter and download the JMeter Ultimate Guide right now!
In order to help you master load testing with JMeter, we have compiled a kick-ass guide with all the major JMeter features and use cases! Besides studying them online you may download the eBook in PDF format!
Email address:
Want to be a Servlets Master ?
Subscribe to our newsletter and download the Java Servlet Ultimate Guide right now!
In order to help you master programming with Java Servlets, we have compiled a kick-ass guide with all the major servlet API uses and showcases! Besides studying them online you may download the eBook in PDF format!
Email address:
Want to be a JAXB Master ?
Subscribe to our newsletter and download the JAXB Ultimate Guide right now!
In order to help you master XML Binding with JAXB, we have compiled a kick-ass guide with all the major JAXB features and use cases! Besides studying them online you may download the eBook in PDF format!
Email address:
Want to be a JDBC Master ?
Subscribe to our newsletter and download the JDBC Ultimate Guide right now!
In order to help you master database programming with JDBC, we have compiled a kick-ass guide with all the major JDBC features and use cases! Besides studying them online you may download the eBook in PDF format!
Email address:
Want to be a JPA Master ?
Subscribe to our newsletter and download the JPA Ultimate Guide right now!
In order to help you master programming with JPA, we have compiled a kick-ass guide with all the major JPA features and use cases! Besides studying them online you may download the eBook in PDF format!
Email address:
Want to be a Hibernate Master ?
Subscribe to our newsletter and download the Hibernate Ultimate Guide right now!
In order to help you master JPA and database programming with Hibernate, we have compiled a kick-ass guide with all the major Hibernate features and use cases! Besides studying them online you may download the eBook in PDF format!
Email address:
Want to be a JSF Master ?
Subscribe to our newsletter and download the JSF 2.0 Programming Cookbook right now!
In order to get you prepared for your JSF development needs, we have compiled numerous recipes to help you kick-start your projects. Besides reading them online you may download the eBook in PDF format!
Email address:
Want to be a Java Master ?
Subscribe to our newsletter and download the Advanced Java Guide right now!
In order to help you master the Java programming language, we have compiled a kick-ass guide with all the must-know advanced Java features! Besides studying them online you may download the eBook in PDF format!
Email address:
Want to be a Java Master ?
Subscribe to our newsletter and download the Java Design Patterns right now!
In order to help you master the Java programming language, we have compiled a kick-ass guide with all the must-know Design Patterns for Java! Besides studying them online you may download the eBook in PDF format!
Email address:
Want to be a Hadoop Master ?
Subscribe to our newsletter and download the Hadoop Tutorial right now!
In order to help you master Apache Hadoop, we have compiled a kick-ass guide with all the basic concepts of a Hadoop cluster! Besides studying them online you may download the eBook in PDF format!
Email address:
Want to be an Elastic Beanstalk Master ?
Subscribe to our newsletter and download the Amazon Elastic Beanstalk Tutorial right now!
In order to help you master AWS Elastic Beanstalk, we have compiled a kick-ass guide with all the major Elastic Beanstalk features and use cases! Besides studying them online you may download the eBook in PDF format!
Email address:
Amazon Elastic Beanstalk Tutorial
  • Develop your own Amazon Elastic Beanstalk based applications
  • Learn Java Integration and Command Line Interfacing
  • Get your own projects up and running in minimum time
Want to take your Java skills to the next level?
Grab our programming books for FREE!
Here are some of the eBooks you will get:
  • Spring Interview QnA
  • Multithreading & Concurrency QnA
  • JPA Minibook
  • JVM Troubleshooting Guide
  • Advanced Java
  • Java Interview QnA
  • Java Design Patterns
Insiders are already enjoying weekly updates and complimentary whitepapers!
Join them now to gain exclusive access to the latest news in the Java world, as well as insights about Android, Scala, Groovy and other related technologies.
Email address:
Want to be an ActiveMQ Master ?
Subscribe to our newsletter and download the Apache ActiveMQ Cookbook right now!
In order to help you master Apache ActiveMQ JMS, we have compiled a kick-ass guide with all the major ActiveMQ features and use cases! Besides studying them online you may download the eBook in PDF format!
Email address:
Apache ActiveMQ Cookbook
  • Explore Apache ActiveMQ Best Practices
  • Learn ActiveMQ Load Balancing and File Transfer
  • Develop your own Apache ActiveMQ projects