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https://github.com/m-elbably/process-pubsub
A tiny library that enables node applications to publish events to one multiple interested consumers asynchronously, without coupling the producers to the consumers.
https://github.com/m-elbably/process-pubsub
Last synced: 9 days ago
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A tiny library that enables node applications to publish events to one multiple interested consumers asynchronously, without coupling the producers to the consumers.
- Host: GitHub
- URL: https://github.com/m-elbably/process-pubsub
- Owner: m-elbably
- License: mit
- Created: 2022-07-31T19:40:05.000Z (over 2 years ago)
- Default Branch: main
- Last Pushed: 2022-07-31T20:24:05.000Z (over 2 years ago)
- Last Synced: 2024-10-29T17:00:02.202Z (17 days ago)
- Language: TypeScript
- Size: 192 KB
- Stars: 3
- Watchers: 4
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- License: LICENSE
Awesome Lists containing this project
README
# **Process PubSub**
A tiny library that enables node applications to publish events to one multiple interested consumers asynchronously, without coupling the producers to the consumers.
> Works **only** on single process, to provide effective way to decouple producers from consumers
[](https://nodejs.org)
[](https://www.npmjs.com/package/process-pubsub)
[](https://github.com/m-elbably/process-pubsub/workflows/process-pubsub/badge.svg)
[](https://coveralls.io/github/m-elbably/process-pubsub?branch=main)
[](https://raw.githubusercontent.com/m-elbably/process-pubsub/master/LICENSE)
### How Process PubSub works:
## Installation
npm install process-pubsub --save
## Features
- Simplicity & flexibility
- Light weight
## Usage
### Channels & Topics
- **Channel**: is a logical container used to send and receive messages, publishing/receiving messages should be through a channel
- **Topic**: is a logical container within channel used to send and receive messages, publishing/receiving messages should be through a topic registered within a channel
### Subscription
`subscribe` function can be used to subscribe to one or more channels and topics, through `Subscribtion` object:
Subscription:
- `channel` _String_ Channel name
- `topic` _String_ Topic name
- `once` _Boolean_, _optional_, default = `fasle` Get notified about specific event only once
- `callback` _Function(message, metadata)_ Callback function will be invoked when message published to a `channel` and/or `topic`
Simple subscription:
```typescript
import {PubSub} from 'process-pubsub';
const pubsub = new PubSub();
pubsub.subscribe({
channel: 'orders',
topic: 'created',
callback: (message, metadata) => {
console.log(message);
}
});
```
Subscription to get notified for all messages in specific channel is also possible using `*` with `topic` field:
```typescript
import {PubSub} from 'process-pubsub';
const pubsub = new PubSub();
pubsub.subscribe({
channel: 'orders',
topic: '*',
callback: (message, metadata) => {
console.log(message);
}
});
```
> Subscribe to all messages published to any `topic` under `channel` "orders", so `callback` handler will be call if we publish messages to "create", "updated" topic for example or any other topic under "orders" channel
**Once subscription**
Setting `once` field to `true` will notify the subscriber with the event for only one-time, after that the subscription will be removed.
```typescript
import {PubSub} from 'process-pubsub';
const pubsub = new PubSub();
pubsub.subscribe({
channel: 'orders',
topic: 'created',
once: true,
callback: (message, metadata) => {
console.log(message);
}
});
```
#### Message metadata
`callback` function will also receive `metadata` object with message, which includes the following fields:
- `channel` The current message destination channel
- `topic` The current message destination topic (_If subscriber is listening to all topic using `*` under specific channel, metadata will be very useful_)
### Publishing
We can publish directly to specific **channel** and **topic**:
```typescript
import {PubSub} from 'process-pubsub';
const pubsub = new PubSub();
pubsub.publish('orders', 'created', {id: 1, amount: 120});
```
> - This message will be received by all subscribers of **channel** `orders` and **topic** `created`
> - This message will be received also by subscribers of **channel** `orders` and **topic** `*`
We can publish to all topics registered within a specific **channel**, by using `*` for **topic**
```typescript
import {PubSub} from 'process-pubsub';
const pubsub = new PubSub();
pubsub.publish('orders', '*', {id: 1, amount: 120});
```
> This message will be received by all subscribers of **channel** `orders`, whatever the **topic** the subscriber is registered with
#### Synchronous Request-Reply
Synchronous Request-Reply style is also possible using `publishAndGetReply` function, we can publish message and wait for response from first register subscriber, or break the operation if timeout exceeded.
```typescript
import {PubSub} from 'process-pubsub';
const pubsub = new PubSub();
const response = await pubsub.publishAndGetReply('orders', 'created', {id: 1, amount: 120});
```
#### License
MIT