Axum (software)

Axum (software)
Name	Axum
Developer	Microsoft
Released	2009 (preview)
Programming language	C#
Operating system	Microsoft Windows
Platform	.NET Framework
License	Microsoft Shared Source or proprietary

Axum (software) Axum is a domain-specific language and runtime developed by Microsoft for building concurrent, actor-based applications on the .NET Framework. It combines influences from research in Concurrent computing, Actor model, Software transactional memory, and languages such as Erlang (programming language), Haskell, and OCaml to provide isolation, agents, and message-passing primitives targeted at scalable service architectures. Axum preview implementations integrated with Visual Studio and targeted developers building servers for Windows Server and cloud platforms like Windows Azure.

Overview

Axum presented a language and runtime that focused on composing isolated units called agents that communicate via message-passing channels; this model was influenced by the Actor model, Communicating sequential processes, and the concurrency constructs investigated in Microsoft Research. Axum's design emphasized safety through isolation similar to Erlang (programming language) processes and transactional messaging inspired by Software transactional memory research and systems such as STM Haskell. The project integrated with the Common Language Runtime and the [.NET Framework] ecosystem to leverage existing libraries from projects like Entity Framework, Windows Communication Foundation, and ASP.NET while providing concurrency abstractions not present in traditional C# (programming language).

History and development

Axum emerged from research efforts within Microsoft Research and engineering teams focused on scalable, concurrent server architectures for Windows Server and cloud services like Windows Azure. Public previews were released around 2009 and showcased at conferences attended by communities around Visual Studio, Mix (Microsoft conference), and PDC (Professional Developers Conference). The project drew on prior Microsoft projects and languages such as Singularity (operating system), CHESS (concurrency testing tool), and the design ethos of Spec#. Key contributors included engineers associated with Microsoft Research and developer evangelists from Microsoft who demonstrated integration with Visual Studio tooling and deployment scenarios involving IIS (Internet Information Services) and Windows Server AppFabric.

Architecture and core concepts

Axum's architecture centered on isolated execution entities called agents that encapsulated state and executed code within a single-threaded environment, echoing isolation approaches seen in Erlang (programming language) and the Actor model. Agents communicated through strongly typed channels reminiscent of channels in Go (programming language) and the message-passing in Scala (programming language)'s Akka framework. The runtime offered explicit routing, mailbox semantics comparable to RabbitMQ or ZeroMQ in message orientation, and coordination facilities akin to Distributed transactions research exemplified by Microsoft Distributed Transaction Coordinator. Axum programs compiled to assemblies loaded by the Common Language Runtime and interoperated with languages like C# (programming language), Visual Basic .NET, and F# from Microsoft Research.

Programming model and features

Axum provided a type-safe, declarative syntax for defining agents, channels, and selectors, with influences traceable to languages such as Haskell and OCaml for functional patterns, and to Erlang (programming language) for supervision and failure isolation. Features included structured concurrency via agents, explicit channel typing similar to the typing systems in ML (programming language), and composition primitives inspired by Communicating sequential processes. Debugging and determinism tools drew from CHESS (concurrency testing tool) techniques for exploring interleavings. The language aimed to reduce common concurrency errors like race conditions and deadlocks, addressing problems long discussed in contexts such as Dijkstra Prize-related work and concurrency models taught alongside Operating System research in universities that use texts influenced by Tony Hoare.

Tooling and ecosystem integration

Microsoft positioned Axum to interoperate with the Visual Studio development environment, providing project templates, debugging support, and integration with build systems like MSBuild. Tooling demonstrations included deployments to IIS (Internet Information Services), monitoring with System Center, and use with Windows Azure services for scalable hosting. Axum assemblies could reference libraries such as Entity Framework for persistence or Windows Communication Foundation for external interoperability, and developers could apply continuous integration workflows using tools like Team Foundation Server and Azure DevOps Services (formerly part of Team Foundation Service). The ecosystem also considered interop with messaging systems like RabbitMQ and integration patterns from Enterprise Integration Patterns literature.

Adoption and use cases

Axum remained largely experimental and preview-stage; adoption was limited compared with mainstream languages and frameworks such as C# (programming language), Java (programming language), Go (programming language), Erlang (programming language), and Scala (programming language) with Akka. Use cases explored by Microsoft and early adopters included high-concurrency servers, scalable cloud services on Windows Azure, telecommunication-style messaging systems inspired by Erlang (programming language) deployments, and research prototypes that compared actor-based designs against thread-based models prominent in POSIX-based server software. The project influenced later thinking about concurrency models in the .NET Foundation ecosystem and informed discussions around concurrency features introduced in subsequent versions of C# (programming language) and runtimes evolving under Microsoft stewardship.

Category:Microsoft software