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Glossary
Nikos Vasilakis edited this page Nov 13, 2015
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- A means of delivering value to customers by facilitating outcomes customers want to achieve without the ownership of specific costs and risks.
- A collection of components, together with the policies that control its usage, organized to accomplish a specific function or set of functions.
- A single software component, with a HTTP URI and a document describing it state. A service can use other services to offer simplified or advanced functionality. This is the building block of decentralized control plane nodes.
A Xenon Service is defined a by a class (in Java, or a set of methods in Go)
- Each Service class may be instantiated one or more times.
- Each instance is identified and located via a unique path.
/core/examples/one /core/examples/two
The above URI paths refer to two instances of the example service.
Each instance is deployed over a group of Service Hosts (equivalently referred to as 'nodes'). One Service Host may end up hosting zero, or one replicas of the same Service Instance. At any time, a replica may be designated by the runtime as "owner".
- A plain data object, a collection of properties that represent the state of a micro-service. A document can describe a long running task, or a document describing the health and operational status of an entire data center. Many services can use the same document type, but independent instances. Documents can be aggregated through queries.
- An instance of a service host process. A service host is a Java or Go process that hosts micro service instances. Its uniquely identified by a stable id and can be reached on a IP address plus TCP port. A single virtual or physical machine can have multiple nodes (multiple service host processes). We refer to nodes and service host interchangeably.
- For a specific Service Instance, one of the replicas may be designated as owner. The precise guarantees regarding owner consistency and operations associated with it are described in the replication and leader election page
- The Xenon framework code, instantiated as a ServiceHost. The framework manages requests to services, service lifecycle, concurrency, statistics, etc.
- A dynamic state capturing the collection of nodes at some moment in time. Implemented by the node group service
- A local value, held by a node, representing its knowledge of the membership