Node.js's ThreadLocal -- Async Context Bound

Using Node.js's ThreadLocal to trace request information among middlewares or RPC.

ThreadLocal in Node.js also means "Async Context Bound". Because of event loop in libuv, Async Context Bound has the same effect just like threadlocal storage.

> node.js's version >= 8.9.4

一、快速上手

install

``sh
npm install @rockerjs/tls
`

> @rockerjs/tls only save async context wrapped in promise, #because asyncId and triggerAsyncId related to execution timing, not causality.


示例 1

`typescript
import { ThreadLocal } from '../index';
let tls = new ThreadLocal();

tls.run(async ()=>{
tls.setProp("traceInfo", {
invoke: "noop"
});

await new Promise((res) => {
setTimeout(() => {
console.log('get Traceinfo in timer', tls.getProp("traceInfo"));
res();
}, 20);
});

setTimeout(() => {
console.log('can\'t get Traceinfo in timer', tls.getProp("traceInfo"));
}, 20);

console.log('get Traceinfo in function', tls.getProp("traceInfo"))
});
`


实例2

`typescript
import { ThreadLocal } from '../index';
import * as fs from "fs";
import * as path from "path";
import * as koa from "koa";
let tls = new ThreadLocal();
var app = new koa();
var Logger = {
info(msg) {
console.log(msg, tls.getProp('traceId'));
}
};

let business = async function(ctx){
let v = await new Promise((res)=>{
setTimeout(()=>{
Logger.info('service执行结束')
res(123);
},1000);
});
let c = await new Promise((res, rej)=>{
fs.readFile(path.join(process.cwd(), "package.json"), "utf8", (e,d)=>{
if (e) {
return rej(e);
}
res(d);
});
})
ctx.body = 'hello world' + c;
Logger.info(请求返回, path: ${ctx.url})
};


app.use(async(ctx, next)=>{
await tls.run(async ()=>{
tls.setProp('traceId', Date.now())
await business(ctx);
Logger.info("end of callback...");
});
await next();
});

app.use(async(ctx, next) => {
await tls.run(async ()=>{
tls.setProp('traceId',123123)
Logger.info("last filter...");
});
});

app.listen(8088);

Logger.info(server start, listening port 8088);
``

License

MIT