@opentelemetry/context-async-hooks

OpenTelemetry async_hooks-based Context Managers

This package provides two ContextManager implementations built on APIs from Node.js's [async_hooks][async-hooks-doc] module. If you're looking for a ContextManager to use in browser environments, consider opentelemetry-context-zone or opentelemetry-context-zone-peer-dep.

See the definition of the ContextManager interface and the problem it solves.

API

Two ContextManager implementations are exported:

• AsyncLocalStorageContextManager, based on AsyncLocalStorage
• AsyncHooksContextManager, based on AsyncHook. This is deprecated and will be removed in v3 (planned for mid-2025. AsyncLocalStorage is simpler, faster, available in Node.js v14.8.0 and later, and avoids this possible DoS vulnerability.

Prior art

Context propagation is a big subject when talking about tracing in Node.js. If you want more information about it here are some resources:

• https://www.npmjs.com/package/continuation-local-storage (which was the old way of doing context propagation)
• Datadog's own implementation for their JavaScript tracer
• OpenTracing implementation
• Discussion about context propagation by the Node.js Diagnostics Working Group

Useful links

• For more information on OpenTelemetry, visit: https://opentelemetry.io/
• For more about OpenTelemetry JavaScript: https://github.com/open-telemetry/opentelemetry-js
• For help or feedback on this project, join us in GitHub Discussions

License

Apache 2.0 - See LICENSE for more information.

Similar packages

Other packages similar to @opentelemetry/context-async-hooks

cls-hooked

The cls-hooked package provides a similar functionality to @opentelemetry/context-async-hooks by using the async_hooks module to create context-like namespaces that are preserved across asynchronous calls. It differs in its API and is not specifically tailored for OpenTelemetry or tracing but can be used for general context propagation purposes.

async_hooks

While not a separate npm package, Node.js' built-in async_hooks module is the underlying technology that both @opentelemetry/context-async-hooks and cls-hooked rely on for tracking asynchronous operations. It provides the primitives for creating hooks that monitor the lifecycle of asynchronous operations, which can be used directly for custom context propagation implementations.