javascript / expert
Snippet
Manual Context Tracking with AsyncResource
While AsyncLocalStorage is the standard for context, AsyncResource provides low-level control for manual context propagation. It is essential when integrating with legacy libraries or event-driven systems where the execution flow doesn't automatically preserve the asynchronous context.
snippet.js
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import { AsyncResource } from 'node:async_hooks';class DatabaseQuery extends AsyncResource {constructor(queryId) {super('DB_QUERY');this.queryId = queryId;}run(callback) {this.runInAsyncScope(callback);}}const query = new DatabaseQuery('req-123');query.run(() => {// Async context is now preserved even through legacy callbacks});
nodejs
Breakdown
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super('DB_QUERY')
Initializes the async resource with a custom type for monitoring and debugging.
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this.runInAsyncScope(callback)
Executes the callback within the asynchronous context associated with this specific resource instance.