How to make this cls work with async function

[foreverpw]

I have below test code, executed in nodejs 7.4.0 with --harmony-async-await argument.

function newP(id){
    Promise.resolve().then((data)=>{
        ns.run(function(){
            ns.set('cid',id)
            afn()
        })
    })
}
async function afn(){
    var a1 = await log(1)
    var a1 = await log(2)
}
function log(index){
    return new Promise(function (resolve, reject){
         console.log('cid:'+ns.get('cid')+',index:'+index)
         resolve()
    })
}
newP(1);
newP(2);

and the output is:

cid:1,index:1
cid:2,index:1
cid:undefined,index:2
cid:undefined,index:2

what I think it should be is:

cid:1,index:1
cid:2,index:1
cid:1,index:2
cid:2,index:2

It seems that the context is lost, but when I changed the async function to Generator and ran with co, it works well.

function* gen(){
    var a1 = yield log(1)
    var a2 = yield log(2)
}

function newP(id){
    Promise.resolve().then((data)=>{
        ns.run(function(){
            ns.set('cid',id)
            co(gen);
        })
    })
}

newP(1);
newP(2);

So how can I get it work with async function.

[Qard]

It's because V8 handles awaited promises with some internal magic rather than actually calling the then(...) method. The patches to maintain the continuation do not get applied. Unfortunately there's nothing that can be done about this currently. We're waiting on the V8 team to provide hooks to the microtask queue so async_hooks can support promises properly, then CLS will need to be ported at some point from the old AsyncListener API to async_hooks.

[ofrobots]

V8 promise hooks should ship with V8 5.7 and should be available in Node 8.

[Qard]

@ofrobots Nice! Thanks for the update. 👍

[yizhiheng]

@ofrobots
tried this with Node8, same result

[santiagodoldan]

I'm having the same problem as @yizhiheng, node -v 👉 v8.1.2

[Francisc]

Shouldn't this be logged against V8 as well?

[ofrobots]

This library will need to migrate to async hooks + promise hooks in order to support async functions. I am not aware of anyone working on this at the moment.

[Jeff-Lewis]

See cls-hooked. The plan is to eventually PR this into node-continuation-local-storage when we are comfortable with it.

[carlisliu]

var getNamespace = require('continuation-local-storage').getNamespace;
var nameSpaceName = 'sample';
var sampleKey = 'sampleKey';
var createNamespace = require('continuation-local-storage').createNamespace;
createNamespace(nameSpaceName);

var namespace = getNamespace(nameSpaceName);

const mongoose = require('mongoose');
const config = {
    dbIp: '127.0.0.1',
    dbPort: 27017,
    dbUser: 'root',
    dbPass: 'root',
    db: 'order'
};

let uri;
if (config.dbUser == '') {
    uri = 'mongodb://' + config.dbIp + ':' + config.dbPort + '/' + config.db;
} else {
    uri = 'mongodb://' + config.dbUser + ':' + config.dbPass + '@' + config.dbIp + ':' + config.dbPort + '/' + config.db;
}

mongoose.connect(uri);

mongoose.Promise = global.Promise;

const db = mongoose.connection;

db.on('error', function(err) {
    console.log(err);
    setTimeout(() => {
        mongoose.connect(uri);
    }, 1000 * 3)
}).once('open', function() {
    console.log('mongodb connected!');
});

const Schema = mongoose.Schema;
const ObjectId = Schema.ObjectId;

const ActivitySchema = new Schema({
    author: ObjectId,
    title: String,
    body: String,
    create_date: Date
});

var activityS = mongoose.model('activity', ActivitySchema, 'activity');


var _find = activityS.find;
activityS.find = function() {
    console.log('sampleKey:', namespace.get(sampleKey));
    return _find.apply(this, arguments);
}

async function find(ctx, next) {
    namespace.set(sampleKey, 'sample');
    let activity = await activityS.find({}).then(function() {
        console.log('sampleKey_find_then:', namespace.get(sampleKey));
    });
    console.log('sampleKey_find:', namespace.get(sampleKey));
    return activity;
}

namespace.run(function() {
    find();
});

this code didn't work as i expected. Look like the same problem with this issue.

[Jeff-Lewis]

FYI - trying this with cls-hooked, I received this:

[joepuzzo]

Any updates on this? Was attempting to use this library to keep track of trace information for logging in my GraphQL express app and was disappointed to find that the apollo-server-express uses await and i lose context :(

Nevermind turns out I just needed to include https://github.com/othiym23/cls-middleware

[alexkravets]

Guys, thank you for cls-hooked implementation!