doseur

Welcome to doseur 👋

Zero-dependency simple queue to run similar operations in batches

Don't want to run db insert for each event generated in your application, but rather to insert them in batches? doseur them!

🏠 Homepage

Features

• written in TypeScript - provides extensive typings for better developer experience
• thoroughly unit-tested
• easy to use - just define what how to handle a batch of items, and then just enqueue & forget.

Install

npm install doseur

Usage

Default export of this package is a factory function that creates a doseur instance. As a rule of thumb, each instance is created to handle similar payloads.

doseur maintains an in-memory queue which is flushed (i.e. passed to a fn callback, see below) when queue outgrows specified size, or a timeout set with the first enqueued item fires.

doseur factory takes 3 mandatory arguments:

• fn: function which takes enqueued items as rest parameters and does something with them (e.g. sent to log stream, or insert to the database)
• maxQueueLength: maximum number of items to store in the queue. When number of enqueued items reaches maxQueueLength, queue is flushed.
• timeoutMs: maximum time (in ms) to wait before flushing the queue starting from the moment when first item is enqueued.

Result of calling doseur is an object with two methods:

• enqueue: takes an item to enqueue
• reset: resets current instance - empties the queue without calling fn, clears currently running timeout.

Example

Here we use doseur to batch API events created by different request handlers and insert them into the database together.

Using the config options provided, each event is saved no longer than 10 seconds after it is created and each batch has no more than 10 items.

const doseur = require('doseur');
 
const saveEventsBatch = (...events) => ApiEvent.insertMany(events);
 
const apiRequestQueue = doseur(saveEventsBatch, 10, 10000);
 
const withEventQueue = (req, res, next) => {
  req.apiRequestQueue = apiRequestQueue;
  next(null);
};
 
router.get('/api/todos', withEventQueue, (req, res) => {
  req.apiRequestQueue.enqueue({
    type: 'GetTodos',
    user: req.user.id
  });
 
  res.send([{ foo: 'bar' }]);
});
 
router.post('/api/todos', withEventQueue, (req, res) => {
  req.apiRequestQueue.enqueue({
    type: 'CreateTodo',
    user: req.user.id,
    body: req.body
  });
 
  res.send([{ foo: 'bar' }]);
});

Let's assume the server above receives 2 calls at the same time from user with id=1:

GET /api/todos

POST /api/todos

{ "foo": "barbaz" }

If no other requests arrive, in 10 seconds these two events will be flushed to ApiEvent.insertMany:

ApiEvent.insertMany([
  {
    type: 'GetTodos',
    user: 1
  },
  {
    type: 'CreateTodo',
    user: 1,
    body: { foo: 'barbaz' }
  }
]);

Otherwise, if during that 10 seconds another 8 requests arrive, events are flushed as soon as 10th request arrives.

Run tests

npm run test

Author

👤 Sergey Lapin

• Github: @svlapin
• https://svlapin.github.io

🤝 Contributing

Contributions, issues and feature requests are welcome!
Feel free to check issues page.

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