Spring Cloud provides tools for developers to quickly build some of the common patterns in distributed systems (e.g. configuration management, service discovery, circuit breakers, intelligent routing, micro-proxy, control bus, one-time tokens, global locks, leadership election, distributed sessions, cluster state). Coordination of distributed systems leads to boiler plate patterns, and using Spring Cloud developers can quickly stand up services and applications that implement those patterns. They will work well in any distributed environment, including the developer's own laptop, bare metal data centres, and managed platforms such as Cloud Foundry.
Spring Cloud builds on Spring Boot by providing a bunch of libraries that enhance the behaviour of an application when added to the classpath. You can take advantage of the basic default behaviour to get started really quickly, and then when you need to, you can configure or extend to create a custom solution.
Spring Cloud focuses on providing good out of box experience for typical use cases and extensibility mechanism to cover others.
Centralized external configuration management backed by a git repository. The configuration resources map directly to Spring `Environment` but could be used by non-Spring applications if desired.
Integration with various Netflix OSS components (Eureka, Hystrix, Zuul, Archaius, etc.).
An event bus for linking services and service instances together with distributed messaging. Useful for propagating state changes across a cluster (e.g. config change events).
Integrates your application with Pivotal Cloudfoundry. Makes it easy to implement SSO and OAuth2 protected resources, and also to create a Cloudfoundry servive broker.
Easy integration with hosted Amazon Web Services. It offers a convenient way to interact with AWS provided services using well-known Spring idioms and APIs, such as the messaging or caching API. Developers can build their application around the hosted services without having to care about infrastructure or maintenance.
Makes it easy for PaaS applications in a variety of platforms to connect to backend services like databases and message brokers (the project formerly known as "Spring Cloud").
Spring Boot-style starter projects to ease dependency management for consumers of Spring Cloud.
Spring Boot CLI plugin for creating Spring Cloud component applications quickly in Groovy
Spring Cloud is an umbrella project consisting of independent projects with, in principle, different release cadences. To manage the protfolio a BOM (Bill of Materials) is published with a curated set of dependencies on the individual project (see below). The release trains have names, not versions, to avoid confusion with the sub-projects. The names are an alphabetic sequence (so you can sort them chronologically) with names of London Tube stations ("Angel" is the first release, "Brixton" is the second). When point releases of the individual projects accumulate to a critical mass, or if there is a critical bug in one of them that needs to be available to everyone, the release train will push out "service releases" with names ending ".SRX", where "X" is a number.
The release train label is actually only used explicitly in one artifact: "spring-cloud-starter-parent" (all the others have normal "Spring" release labels tied to their parent project). The starter parent is the one you can use as a BOM for dependency management or as a parent POM (Maven only). Example using the latest version with the config client and eureka (change the artifact ids to pull in other starters):
Release train contents: