contextsinternal

Contextsinternal is an internal module used by a range of software frameworks to manage execution contexts across asynchronous and concurrent boundaries. It provides low-level primitives for representing, storing, and propagating contextual data while isolating internal concerns from public APIs. The module is designed to be stable yet flexible enough to support different propagation models, including thread-local and ambient-context schemes, depending on the runtime environment.

At its core, contextsinternal defines a minimal context object that carries a map of key-value pairs, along with metadata such as cancellation state and scope lifetime. It exposes utilities to create and clone contexts, attach or detach them to a running task, and retrieve values in a way that minimizes allocations. A central feature is context propagation, which ensures that when a task migrates between threads or asynchronous grains, its ambient data remains available to downstream operations.

The architecture typically comprises: a Context type; a ContextStore for persisting context across await points; a ContextAccessor for reading and writing data in a controlled fashion; and a Propagator component that implements the rules for copying or transferring context across boundaries. Thread-safety is achieved through immutability, copy-on-write semantics, or lock-free primitives, depending on implementation.

Contextsinternal is intended for framework authors and internal components rather than application developers. Changes to its API or behavior may impact public APIs that depend on ambient data semantics, so it adheres to strict versioning and compatibility guarantees.

See also: ExecutionContext, AsyncLocal, Activity (if relevant).