ictx's Introduction

ictx (Invocation Context)

Globally maintains context throughout a invocation/request lifecycle, using cls-hooked under the hood.

Context can be set and retrieved during the entire lifetime a request, through all chains of function calls, even if defined in another module entirely.

Examples

Context.Middlware (for Express)

import Context from 'ictx';
import express from 'express';

function getCurrentUser() {
  return User.findById(Context.get('userId'));
}

const app = express();

app.use(Context.Middleware);

app.get('/me', async (req, res) => {
  // Request header `x-user-id` was set as '123'

  Context.get('userId'); // => '123'
  Context.userId(); // => '123'

  const currentUser = getCurrentUser();

  res.json(currentUser);
});

Certain headers will be automatically assigned as context properties:

x-user-id can be accessed via Context.get('userId') or Context.userId()
x-invocation-id / x-request-id can be accessed via Context.get('invocationId') or Context.invocationId()

Context.Provider

Generic provider. Works much like Context.Middlware, except you don't need to pass req and res.

import Context from 'ictx';

Context.Provider({ userId: 'abc' }, () => {
  Context.get('userId'); // => 'abc'
});

Typed Context

import Container from 'typedi';
import { ContextFactory } from 'ictx';

const Context = ContextFactory<{ userId: string }>({
  initialValues: { userId: 123 },
  beforeHook: ({ invocationId }) => {
    Container.of(invocationId).set('connection', new DBConnection());
  },
  afterHook: ({ invocationId }) => {
    Container.reset(invocationId);
  },
});

Context.Provider(() => {
  // Defines methods for values
  Context.userId(); // => 123
  Context.userId(999);
  Context.userId(); // => 999
});

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