"Thread context" emulation for Node.js based on continuation local storage
npm install thread-contextthread-contextcls-hooked to access continuation local storage and provides a thin yet convenient wrapper around it.The threadContext object that can be imported from the thread-context module, is a Proxy object with virtual getter and setter and implements undefined type (for those of you using typescript). It allows storing data of any structure within one stack call ("thread")
You simply call threadContext.init() once in the topmost function of a callstack (e.g. an express handler), giving a context a unique id. The id is later available as threadContext.threadId.
Any read or write to threadContext fields yields same result within one "thread" no matter how deep in call stack execution is.
The threadContext "threads" are disposed automatically, there is nothing you need to do.
index.js
``typescript
import debug from 'debug';
import express from 'express';
import { threadContext } from 'thread-context';
import { generateThreadReport } from './report';
import { generateSuperUniqueId } from './uniqueIdGenerator';
const app = new express.Express();
app.use(async (req, res, next) => {
// start a threadContext and give it a unique ID
await threadContext.init(generateSuperUniqueId());
// or simply threadContext.init();
// store some data for later
threadContext.requestMethod = req.method;
threadContext.requestPath = req.originalPath;
debug.log([${threadContext.threadId}] ${threadContext.requestMethod} ${threadContext.requestPath}: threadContext init);
next();
});
app.get('/thread.json', (req, res, next) => {
res.json(generate);
});
app.get('/someOtherUrl', (req, res, next) => {
debug.log([${threadContext.threadId}] ${threadContext.requestMethod} ${threadContext.requestPath}: still in same threadContext);`
// ...
res.end();
});
report.js
`typescript
import debug from 'debug';
import { threadContext as ctx } from 'thread-context';
export function generateThreadReport() {
debug.log([${ctx.threadId}] ${ctx.requestMethod} ${ctx.requestPath}: generating report);
return {
threadId: ctx.threadId,
requestMethod: ctx.requestMethod,
requestPath: ctx.requestPath,
}
}
``