Orleans: An Object Framework for Cloud Computing From Microsoft Research
Earlier this week Microsoft Research published a paper outlining a framework for Cloud Computing codenamed Orleans. The framework is intended for cloud computing applications where a client such as a PC, smartphone or embedded device is employed. In Orleans, the basic premise is to use concurrency patterns and lightweight transactions on an actor-like model with a declarative specification for persistence, replication and consistency.
a simple programming model built around grains, logical units of computation with private state that communicate exclusively by sending messages ….
The system as a whole can process multiple requests concurrently in distinct grain activations, but these computations are isolated, except at the clearly identified points where grains commit state changes to persistent storage and make them globally visible
Summary of Orleans Definitions:
- Grain – an atomic unit of isolation, distribution and durability.
- Activations –multiple instantiations of a grain which process multiple independent requests to a service in parallel.
- Grain Domain – a logical isolated workspace which delimits the set of grains it can directly access. Hierarchical and nested in nature.
- Promises – asynchronous primitive that represents a promise to future completion.
- Turns – a grain activation operates in discrete units of work and finishes each unit before moving to the next unit.
The Microsoft Research team built Orleans as a cloud computing pattern meant to address the need for scale, multi-tenancy and both reliability and availability. The intention is for the grain model to mimic at a programmatic level the sharded data stores they represent and their inherent capability of flexibility as the application changes over time. Further, to address availability and reliability, the use of grains represented as computations or datums, provides failover capabilities built into the system while preserving consistency and separation of logic.
Orleans has three main components; a programming model or framework outlined in the publication, Orleans: A Framework for Cloud Computing, programming language and tool support and a runtime system. Currently Orleans provides support for C# and they are actively working on F#. The runtime delivers core cloud computing functionality such as persistence, replication, consistency and full life cycle management for versioning, debugging, deployment and monitoring. The team has an informal discussion on Channel 9 which walks through the logical architecture.
This first look at Orlean’s internals is very instructional as to how to architect and build a cloud scale application as the software development world moves from Enterprise computing to Internet scale computing above the transport layer.
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