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

``js
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);
`

$3

enable the async hooks

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

$3

disable the async hooks

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

$3

get the size of storage

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

$3

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

`js
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';
});
`

$3

set the value by key for the current id

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

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

$3

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

- key the key

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

$3

enable linked top for default (default is disabled)

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

$3

disable linked top for default

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

$3

get the current id

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

$3

get the use time of id

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

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

$3

enable create time of data, default is enabled.

`js
als.enableCreateTime();
`

$3

disable create time of data, it can save memory.

`js
als.disableCreateTime();
``