async-local-storage

async-local-storage

I want something like thread-local storage in threaded programming and async_hooks is usable in node.js 8.0, so there is an easy way to use thread-local.

API

const als = require('async-local-storage');
als.enable();
setTimeout(() => {
  als.scope();
  const id = randomBytes(8);
  als.set('id', id);
  delay().then(() => {
    assert.equal(als.get('id'), id);
    return readfilePromise(__filename);
  }).then(() => {
    assert.equal(als.get('id'), id);
    return superagent.get('http://www.baidu.com/');
  }).then(() => {
    assert.equal(als.get('id'), id);
  });
}, 100);

enable

enable the async hooks

const als = require('async-local-storage');
als.enable();

disable

disable the async hooks

const als = require('async-local-storage');
als.enable();
setTimeout(() => {
  als.disable();
}, 100);

size

get the size of storage

const als = require('async-local-storage');
als.enable();
setTimeout(() => {
  console.info(als.size());
}, 100);

scope

change the scope of call chain, it will be the call chain top (remove the parent of itself)

const als = require('async-local-storage');
const Koa = require('koa');
const assert = require('assert');

const app = new Koa();
app.use(async (ctx, next) => {
  const id = ctx.get('X-Request-Id');
  als.scope();
  als.set('id', id);
  await next();
});

app.use(async (ctx, next) => {
  const id = ctx.get('X-Request-Id');
  assert.equal(als.get('id'), id);
  await next();
});

app.use((ctx) => {
  ctx.body = 'OK';
});

set

set the value by key for the current id

• key the key
• value the value
• linkedTop set the value linked to top

als.enable()
setTimeout(() => {
  als.scope();
  const id = randomBytes();
  setTimeout(() => {
    als.set('id', id, true);
  }, 1);
  setTimeout(() => {
    assert.equal(als.get('id'), id);
  }, 10);
}, 10);

get

get the value by key, if will find from parent, self --> parent --> parent, until the value is not undefined

• key the key

als.enable();
setTimeout(() => {
  als.scope();
  const id = randomBytes();
  setTimeout(() => {
    als.set('id', id, true);
  }, 1);
  setTimeout(() => {
    assert.equal(als.get('id'), id);
  }, 10);
}, 10);

enableLinkedTop

enable linked top for default (default is disabled)

als.enable();
als.enableLinkedTop();
setTimeout(() => {
  als.scope();
  setTimeout(() => {
    // the same as als.set('id', 'a', true)
    als.set('id', 'a');
  }, 10);
}, 10);

disableLinkedTop

disable linked top for default

als.enable();
als.enableLinkedTop();
setTimeout(() => {
  als.disableLinkedTop();
  als.scope();
  setTimeout(() => {
    // the same as als.set('id', 'a', false)
    als.set('id', 'a');
  }, 10);
}, 10);

currentId

get the current id

const assert = require('assert');
als.enable();
setTimeout(() => {
  console.info(als.currentId());
}, 10);

use

get the use time of id

• id The tigger id, default is als.currentId()

als.enable()
setTimeout(() => {
  const id = als.currentId();
  console.info(als.use(id));
}, 10);