Netflix Eureka

Eureka is a REST-based service registry built at Netflix for the discovery, load balancing and failover of middle-tier servers running in the AWS cloud, where it plays a critical role in Netflix's own infrastructure. It is published as open source on GitHub, is community driven, and builds with Java 8 while keeping source and target compatibility at Java 7.

Its origin explains its design. Eureka was written for an environment where instances appear and disappear constantly and where the naming a traditional load balancer expects does not hold, so the registry is deliberately tolerant of stale information rather than strictly consistent. A client would rather have a slightly outdated list of servers than no list at all, which is the correct trade for a service that must keep serving during a partition.

Being embedded in the Spring Cloud ecosystem is how most teams meet it. Spring Cloud Netflix made Eureka the default registry for a generation of Java microservices, which is why the project appears in far more architectures than its own repository traffic would suggest.

Maintenance is community driven and the maintainers ask that non-trivial changes start with an issue. A team adopting it should read that as it is meant: this is proven infrastructure rather than actively expanding software.