Loopback: Cant get current accesToken in operation hook

[swfredrik]

How can I get the current user in an operation hook? I've tried the guide using context vice versa but can't get it to work. Also reading that the loopback-contex is depricated.

https://docs.strongloop.com/display/public/LB/Using+current+context#Usingcurrentcontext-Configurecontextpropagation

Here is my operation hook:
Model.observe('before save', function (ctx, next) {
ctx.accessToken....
}

[fabien]

Normally, you'd use something like this:

Model.observe('before save', function (ctx, next) {
  // Note: ctx !== currentCtx
  var currentCtx = LoopBackContext.getCurrentContext();
  var accessToken = currentCtx && currentCtx.get('accessToken');
});

However, loopback-context is deprecated, and for good reason. I was bitten hard by depending on this functionality, from when it was first introduced in mid-2014. Seemed a great idea back then - just spent a couple of weeks (!) fixing all the occurrences in my(fairly large) code-base ...

[vijay22sai]

@fabien Is there anyway to access http request object inside an operation hook? How did you fix issues with loopback-context? I tried using cls-hooked but faced same issues as cls. I am looking for a workaround to replace loopback-context with a better mechanism. I am thinking of setting all context variables on req.context and consuming those values in other chain of functions. But I couldn't access http request object in operation hooks.

Can you please guide me on these lines. It would be of a great help, Thanks.

[josieusa]

@vijay22sai Hello,
regarding the package cls-hooked you mentioned, I'm curious about how did you use it.
The up-to-date approach for cls-hooked is this PR, and it's only waiting for merge (you can already try it, see the link for more info):
https://github.com/strongloop/loopback-context/pull/11
The trick is to require cls-hooked before everything, but my PR adds some more stuff.
If you try it, please let me know if it works for you, thanks.

[vijay22sai]

@josieusa Thanks for your suggestions.

I tried to use your proposed PR as mentioned here. But still it didn't solve the concurrency issue which i have been facing.

Here is the code snippet to reproduce the issue. I have a /test endpoint which gets requestId in query object. this code works fine as expected at concurrency level 10.
package.json => "loopback-context": "github:josieusa/loopback-context#feature/cls-hooked-3",

const LoopBackContext = require('loopback-context');
app.use((req, res, next) => {
  console.log('SET query: ', req.query);
  LoopBackContext.getCurrentContext().set('query', req.query);
  next();
});

app.get('/test', (req, res, next) => {
  const promise = new Promise((resolve, reject) => {
    setImmediate(() => {
      resolve();
    });
  });

  promise.then(() => {
    console.log('get query: ', LoopBackContext.getCurrentContext().get('query'));
    res.status(200).send('ok');
  });
});

output on console for the above code looks like below (correct output):

SET query:  { randomNumber: '4965906666', rid: '37' }
SET query:  { randomNumber: '4657916975', rid: '38' }
SET query:  { randomNumber: '1995611512', rid: '39' }
get query:  { randomNumber: '4965906666', rid: '37' }
get query:  { randomNumber: '4657916975', rid: '38' }
get query:  { randomNumber: '1995611512', rid: '39' }

Now, when i replace ES6 promise with a when.js promise, context is getting messed up. At concurrency 10, only 1 or 2 requests are having original context and for other requests, context is wrong (here context is logged query). code is below.

const LoopBackContext = require('loopback-context');
const when = require('when');
app.use((req, res, next) => {
  console.log('SET query: ', req.query);
  LoopBackContext.getCurrentContext().set('query', req.query);
  next();
});

app.get('/test', (req, res, next) => {
  const promise = when.promise((resolve, reject) => {
    setImmediate(() => {
      resolve();
    });
  });

  promise.then(() => {
    console.log('get query: ', LoopBackContext.getCurrentContext().get('query'));
    res.status(200).send('ok');
  });
});

and console looks like below (wrong output):

SET query:  { randomNumber: '2942547297', rid: '35' }
SET query:  { randomNumber: '4785037287', rid: '36' }
SET query:  { randomNumber: '4075411892', rid: '37' }
SET query:  { randomNumber: '3243179957', rid: '38' }
SET query:  { randomNumber: '2582260715', rid: '39' }
get query:  { randomNumber: '2942547297', rid: '35' }
get query:  { randomNumber: '2942547297', rid: '35' }
get query:  { randomNumber: '2942547297', rid: '35' }
get query:  { randomNumber: '2942547297', rid: '35' }
get query:  { randomNumber: '2942547297', rid: '35' }

Please let me know if there is anything wrong in my usage, Thanks.

[josieusa]

@vijay22sai Thanks, I'll take a look.
Meanwhile, you may double-check if you followed the updated README:
https://github.com/josieusa/loopback-context/blob/feature/cls-hooked-3/README.md
Thanks

[josieusa]

@vijay22sai I can confirm that I get the same output :(
It's strange because, if you write your async code using a different library than when, for example async, the problem disappears (it's even tested: see https://github.com/josieusa/loopback-context/blob/feature/cls-hooked-3/test/main.test.js#L107).
I'm going to read the source code of when to discover where the context gets lost, i.e. at what line of code inside when source code, and see if it's possible to fix it or not.
I'll take care of opening an issue in loopback-context to keep track of the problem, and reproducing the bug using loopback-sandbox. Thanks a lot for pointing out the issue.

[vijay22sai]

@josieusa, Thanks for confirming the issue. Please let me know once you created the issue so that i can keep an eye on it. Also you may know that loopback-context is deprecated and https://github.com/strongloop/loopback/pull/3023 is replacing it. I am waiting for https://github.com/strongloop/loopback/pull/3048 patch because i am using loopback 2.x version in my application.

Were you able to get correct context in operation hooks as well? Can you test that once? Thanks a lot.

[josieusa]

@vijay22sai Yes, I know. I linked the issue I just created. No, the only way I know to do that in operation hooks is to use my PR 11 of strongloop/loopback-context, and that is what I'm using while I wait for a proper fix (maybe refactoring my app in order to stop using operation hooks, I don't know yet).

[vijay22sai]

@josieusa Thanks for creating an issue on loopback-context repo. BTW what promises library you use for async flow which works with cls-hooked? I am a heavy user of when. I want mainly this kind of functionality: when.all(bunchOfPromisesArray).resolve(resolverFunction)
Could you suggest similar promise library which also works with cls-hooked, Thanks.

[josieusa]

@vijay22sai Yes, I just tested for you that[email protected] passes your concurrency test (I'm going to reproduce it in the aforementioned issue). I didn't test its Promise.all method though (similar to when.all).
(if you haven't read it yet, remember to read the updated README of loopback-context).
Luckily, bluebird is one of the most used Promise libraries, so this is good to know.

[vijay22sai]

@josieusa Thank you very much 👍 . I will test it myself and update you.

[vijay22sai]

@josieusa By using your PR and with [email protected], I have solved loopback-context bugs. I tested Promise.all of bluebird and it works great with context. Tested it at high concurrency (10-50 requests) and everything works great. Thanks a lot for your inputs.

I will port to use official solution whenever it is mature and stable meanwhile I will continue using your forked version. please keep me in a loop if anything interesting is happening around this area, Thank you.

[josieusa]

@vijay22sai I posted an alternative solution on strongloop/loopback-context#17

[bajtos]

FWIW, #3048 has been released today. I am closing this issue, please open a new one in loopback-context if there is anything more to discuss in relation to the old getCurrentContext API.