Optimistic Concurrency

The default serialization for API calls must be JSON. There is an effort to use Google's protobuf serialization, but this remains experimental. While we may work with files in a YAML format, they are converted to and from JSON.

Kubernetes uses the resourceVersion value to determine API updates and implement optimistic concurrency. In other words, an object is not locked from the time it has been read until the object is written.

Instead, upon an updated call to an object, the resourceVersion is checked, and a 409 CONFLICT is returned, should the number have changed. The resourceVersion is currently backed via the modifiedIndex parameter in the etcd database, and is unique to the namespace, kind, and server. Operations which do not change an object, such as WATCH or GET, do not update this value.