InfoQ Homepage event sourcing Content on InfoQ
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Basic Concepts and the Future of Axon, a CQRS and Event Sourcing Framework
At the recent Event-Driven Microservices Conference in Amsterdam, Allard Buijze described in a presentation the basic concepts, the history and future of Axon, a framework for systems based on DDD, event sourcing and CQRS. The adoption of Axon Framework is growing rapidly and recently hit one million downloads.
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Continuous Delivery Implemented with Event Sourcing at eBay
Using an event-centric approach, the Continuous Delivery team at eBay has built an orchestrator for continuous delivery, which is able to scale to handle the increasing amount of work in their build pipelines, John Long and Nataraj Sundar write in two blog posts describing their view on the overall benefits of event sourcing and the advantages they have seen in their application development.
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Axon Framework 3.3 with a Subscription Query API and Kafka Support
Version 3.3 of the Axon framework was recently released with a subscription query API for subscribing to query model updates, a manager for scheduling the publishing of deadline messages, and an Axon-Kafka module allowing for the use of Kafka to send and receive events. An updated version, 3.3.2, has also been released, and for those on version 3.3 an upgrade is strongly recommended.
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QCon NY: Jonas Bonér on Designing Events-First Microservices
Events-first domain driven design (DDD) and event streaming are critical in developing a resilient and scalable microservices architecture. Jonas Bonér from LightBend engineering team spoke at QCon New York 2018 Conference last week about the events-first design.
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Experiences from Building an Event-Sourced System with Kafka Streams
At the recent JEEConf conference in Kiev, Amitay Horwitz described how he and his team implemented an event-sourced invoice system, the challenges they experienced after running in production for 2 ½ years, and how they implemented a new design using Kafka Streams. The new design is still under assessment, but they do heavily use Kafka in production.
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Events Are Reshaping the Future of Distributed Systems: Jonas Bonér at QCon London
There are many reasons why you should care about events; they drive autonomy, increase stability, help you move faster and allow for time travel, Jonas Bonér noted in his presentation at QCon London 2018, where he explored how events are reshaping modern system.
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AxonDB, a New Implementation of an Event Store
AxonDB is a new data storage purpose-built for event sourcing with support for transactions and pushed-based event publishing that recently was released by AxonIQ, the company behind the Axon Framework. To make sure performance is constant, the architecture is specifically targeting reading data — according to AxonIQ the performance is stable even with huge amounts of events stored.
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Retroactive and Future Events in an Event Sourced System
When Thomas Pierrain started a new project with an asset management company, one important requirement was the ability to go back in time to understand why they took decisions that today look strange. At the recent DDD Europe 2018 conference in Amsterdam, Pierrain discussed his experiences when building an event sourced system that included some temporal challenges.
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Events Should Be a First-Class Tool for Developers
We should use events much more often in software systems, Randy Shoup declared in a recent blog post about how events should be first-class citizens in systems. He believes we often underestimate the value of events as a tool. One example is that they can help us decouple parts of a system so that we can reason about them independently.
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Event Sourcing in an Unreliable World
Examples of event sourced systems are often from process-oriented domains, like e-commerce, with incoming commands that generate events. But there are domains without processes that are intrinsically unreliable where we are collecting events from external event sources with transports that are unreliable, Lorenzo Nicora explained at the recent Microservices Conference µCon London 2017.
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Designing Event Sourced Microservices
Event sourced microservices is an area that hasn’t been explored nearly as much as it should be, Greg Young claimed at the recent Microservices Conference µCon London 2017, but he also strongly emphasized that you should not event source all your microservices. Instead, he recommends looking at individual services and applying the event sourcing pattern to services that actually benefit from it.
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Event Architectures and Event Streaming
When moving from a monolithic system to a distributed or microservices system, you commonly also move from a single source of truth in one database to many databases and thus many sources of truth. Using an event architecture and persisting all events as a stream can give back the single source of truth, Ben Stopford claims in one of a series of blog posts about events, event streams and Kafka.
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Selecting an Event Architecture
When designing a distributed system, maybe based on microservices, and you are considering an event architecture, there are several models and technologies available. When choosing how to implement the architecture the non-functional requirements are a main factor, David Dawson claims when describing different styles of event architectures in a recent blog post.
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QCon New York 2017: Scaling Event Sourcing for Netflix Downloads
Phillipa Avery, senior software engineer at Netflix, and Robert Reta, senior software engineer at Netflix, presented their Cassandra-backed event sourcing architecture at QCon New York 2017. Currently, it powers the download feature in Netflix, and was summarised as something which improved the flexibility, reliability, scalability and debuggability of their services.
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Versioning of Events in Event Sourced Systems
A challenge with event sourced systems is that events put in the event store years ago must be readable today, even though the software has gone through numerous changes, Greg Young stated in his presentation at this year’s DDD eXchange conference. If a system can be taken down, versioning of events is relatively simple. The real challenge comes when a system can’t be taken down.