acjay/atomic-store

Atomic event store for Scala/Akka

#Atomic Store

Meta

• State: development
• Point People: @acjay

WARNING: This is pre-production software. Use at your own risk. While it will be used in a commercial system soon, it is not currently thoroughly tested, and major features are pending.

Atomic Store is a system for managing persistent streams of atomic events. It is intended for systems in which only one event can be admitted to the canonical stream at a time, contingent upon past events. It exists to maintain the atomicity of handling of incoming events, but outsources the actual validation logic back to the event originator. In a sense, the idea here is to do as little as possible to meet this goal, but in a way that is as practical as possible.

Installation

Atomic Store includes a copy of Typesafe Activator, which can be used to load the project prompt with ./activator. You might also choose to install Activator globally on your system.

Running

At the moment, the only thing you can do is execute the tests, by running test from Activator/SBT prompt.

Integrating into a project

Include the following line in your build.sbt:

libraryDependencies ++= Seq(
  "net.artsy" %% "atomic-store" % "0.0.3")

In a project, it's likely you will want some sort of server-push mechanism to notify clients of new events. Rather than containing this logic. This code can likely be located within the same logic that does the validation.

Technology

Atomic Store is built using Scala, the Akka framework, and associated libraries. Specifically, here are the core technologies being used, with links to documentation:

• Scala (see tutorials)
• Akka
  • Actor basics
  • Persistence

Releasing new versions

For testing changes:

1. Bump the version in build.sbt as appropriate, and add -SNAPSHOT to the end of the version number.
2. Update the libraryDependencies line above in anticipation of the next version.
3. Use the sbt publish-signed task to push snapshots to Maven Central.
4. Update the Changelog as noteworthy changes are made.
5. During the testing period, merge new changes into the development branch, so that the master branch on Github always reflects the latest version on Maven Central.

For releasing new versions:

1. Remove the -SNAPSHOT suffix in build.sbt.
2. Publish to Maven Central staging using sbt publish-signed.
3. Follow the Maven Central workflow for releasing the next version, logging in to Maven Central Nexus with an account set up with the privilege to publish to the Open Source Project Repository Atomic Store entry.
4. Merge development into master to update the canonical version on Github.

For reference on this process, you may want to see the following links:

• SBT: Deploying to Sonatype
• SBT-PGP Usage docs
• The Central Repository: Releasing The Deployment

Todos

• Akka Clustering support for failover.
• Document support for configurable serialization.
• Testing of complicated random flows of events, validations, and timeouts.

Changelog

0.0.3

• Factor out transient state data from what is persisted. It is unlikely to be of any use upon recovery, anyway. Important: this will break compatibility with any existing data that's stored.
• Set up Akka Cluster Singleton for EventLog actors

0.0.2

• Remove Timestamped. It's not crucial to the logic of this library, so let the client own all of the metadata it wants to associate with its events.
• Allow Akka Persistence plugin to be selected at run-time.
• Upgrade to Scala compiler 2.11.8.

0.0.1

• Initial release.