npm package discovery and stats viewer.

Discover Tips

  • General search

    [free text search, go nuts!]

  • Package details

    pkg:[package-name]

  • User packages

    @[username]

Sponsor

Optimize Toolset

I’ve always been into building performant and accessible sites, but lately I’ve been taking it extremely seriously. So much so that I’ve been building a tool to help me optimize and monitor the sites that I build to make sure that I’m making an attempt to offer the best experience to those who visit them. If you’re into performant, accessible and SEO friendly sites, you might like it too! You can check it out at Optimize Toolset.

About

Hi, 👋, I’m Ryan Hefner  and I built this site for me, and you! The goal of this site was to provide an easy way for me to check the stats on my npm packages, both for prioritizing issues and updates, and to give me a little kick in the pants to keep up on stuff.

As I was building it, I realized that I was actually using the tool to build the tool, and figured I might as well put this out there and hopefully others will find it to be a fast and useful way to search and browse npm packages as I have.

If you’re interested in other things I’m working on, follow me on Twitter or check out the open source projects I’ve been publishing on GitHub.

I am also working on a Twitter bot for this site to tweet the most popular, newest, random packages from npm. Please follow that account now and it will start sending out packages soon–ish.

Open Software & Tools

This site wouldn’t be possible without the immense generosity and tireless efforts from the people who make contributions to the world and share their work via open source initiatives. Thank you 🙏

© 2024 – Pkg Stats / Ryan Hefner

@jpwilliams/distributed-promise

v0.2.4

Published

Distribute a promise across multiple processes connected via Redis.

Downloads

3

Readme

@jpwilliams/distributed-promise

Distribute a promise across multiple processes connected via Redis. If two seperate processes make the same call, only one will actually do the work, but both promises will return simultaneously with the same data.

Has pretty types and works with any data compatible with JSON.stringify and JSON.parse.

npm install --save @jpwilliams/distributed-promise
import { DistributedPromiseWrapper } from '@jpwilliams/distributed-promise'

const wrapper = new DistributedPromiseWrapper({
	redis: myRedisClient
})

// any function
// can be synchronous or asynchronous
function joinStr (...strs) {
	return strs.join()
}

const sharedJoinStr = wrapper.wrap(joinStr)
const result = await sharedJoinStr('foo', 'bar')
// result = 'foobar'

Why?

This facilitates the memoisation of expensive function calls in a distributed system and helps combat the issue of a cache stampede.

It does this by only allowing a single service per job to actually do the work and makes all other services wait for that result and not compute their own.

How

First, after creating a wrapper via new DistributedPromiseWrapper, you can wrap any functions for use with the library, regardless of what they return. The wrapping process will always return a function that returns a Promise, even if the original function did not.

// (...objs: object[]): object
const combine = (...objs: object[]): object => Object.assign(...objs)

// (...objs: object[]): Promise<object>
const sharedCombine = wrapper.wrap(combine)

Internally, when a wrapped function is called, a simple route is followed:

  1. Get relevant data from cache based on input args. Found data? Return it.
  2. Try to attain a lock to get permission to do the work locally.
  3. If we get the lock, perform work locally, push the result to the cache, publish via Redis and return.
  4. If we didn't get the lock, wait for the data to be published via Redis and return it when it arrives.

In basic terms, if

API

new DistributedPromiseWrapper(config: DistributedPromiseConfig)

Creates a new wrapper to use to wrap functions.

config DistributedPromiseConfig

  • redis: RedisClient The RedisClient instance to use to connect.
  • lockTimeout?: number The amount of time in milliseconds to hold the Redis lock for when doing work locally. Defaults to 30000 (30 seconds).
  • ttl?: number The amount of time in milliseconds before items expire from the cache. Defaults to 1800000 (30 minutes).
  • keyPrefix?: string The prefix to use for all keys the library uses in Redis. Defaults to distributed-promise.
  • lockPrefix?: string The prefix to use for locks in Redis. Defaults to lock.
  • notifPrefix?: string The prefix to use for notifications in Redis. Defaults to notif.
  • keySeperator?: string The seperator to use between the segments of key data in Redis. Defaults to :.

Returns DistributedPromiseWrapper.


DistributedPromiseWrapper.wrap(work: InputFn, config?: WrapConfig | string)

Wraps a function, ready to share. An internal key is needed for caching and data retrieval. If just work is passed, this key will be the name of the function. If it does not have one, the library will throw.

work InputFn

A function. (...args: any) => any - any arguments and any return.

config WrapConfig | string

If undefined, the internal key required will be grabbed from the name of the work function. If it does not have a name, the library will throw.

If a string, the internal key will be set to that string.

To customise your wrap further, you can send a WrapConfig:

  • key: string The internal key to use.
  • timeout?: number The timeout to wait for an external process to do the work before giving up and rejecting the promise.

Returns your wrapped function.

Caveats

Keep in mind that this library can only deal with raw data; you can't make a database connection and magically share it with everyone. ;)

Todo

  • [ ] Detect if work is already happening locally and tap in to the local Promise rather than going to Redis.
  • [ ] If a TTL of 0 is set, still look to Redis for locking and the receipt of data via pubsub, but never actually cache the data.