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Tutur33
115 lines
4.1 KiB
Markdown
115 lines
4.1 KiB
Markdown
# Knex Dynamic Connection
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This module is meant to patch knex and add support for defining dynamic connection configuration.
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[![gh-workflow-image]][gh-workflow-url] [![npm-image]][npm-url] 
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<!-- START doctoc generated TOC please keep comment here to allow auto update -->
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<!-- DON'T EDIT THIS SECTION, INSTEAD RE-RUN doctoc TO UPDATE -->
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## Table of contents
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- [Why you need it?](#why-you-need-it)
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- [Is it reliable?](#is-it-reliable)
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- [How does it actually work?](#how-does-it-actually-work)
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- [Will this work in the future?](#will-this-work-in-the-future)
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<!-- END doctoc generated TOC please keep comment here to allow auto update -->
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## Why you need it?
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Knex.js doesn't have inbuilt support for read/write connections. One can create two seperate instances of knex for read and write, but that still doesn't completely solve the problem. For example:
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```js
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const Knex = require('knex')
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const writeConfig = {
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client: 'pg',
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connection: {
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}
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}
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const writer = Knex(writeConfig)
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const readConfig = {
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client: 'pg',
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connection: {
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}
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}
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const reader = Knex(readConfig)
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```
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Now, if you want to use multiple servers for read operations, you cannot do that, since knex.js allows only one connection server and will pool connections within that server.
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**Following is not possible**
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```js
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const readConfig = {
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client: 'pg',
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connection: [
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{
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host: ''
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},
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{
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host: ''
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}
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]
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}
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```
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With the help of this module, you can make knex create a connection using the dynamic config for every query.
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```sh
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npm i knex-dynamic-connection
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```
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```js
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const Knex = require('knex')
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const { patchKnex } = require('knex-dynamic-connection')
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const readConfig = {
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client: 'pg',
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connection: {},
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replicas: [
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{
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host: '',
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},
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{
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host: '',
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}
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],
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}
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const knex = Knex(readConfig)
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let roundRobinCounter = 0
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patchKnex(knex, (originalConfig) => {
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const node = roundRobinCounter++ % originalConfig.replicas.length
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return originalConfig.replicas[node]
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})
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```
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The `patchKnex` method overwrites the `acquireRawConnection` on all the dialects and make them fetch the config from your callback vs reading it from a static source.
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## Is it reliable?
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Yes!
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1. I have copied the code of `acquireRawConnection` from the knex codebase and have just made one line of change to read the config from a different source.
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2. I have written tests for `select`, `insert`, `transactions` and `schema` methods.
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3. The code is tested against `mssql`, `mysql`, `mysql2` and `pg`.
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4. The connection is still managed inside the pool, so don't worry about any extra maintaince overhead.
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## How does it actually work?
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Knex.js makes use of [tarn.js](https://github.com/vincit/tarn.js/) for managing pool resources and everytime pool needs a connection, knexjs calls [acquireRawConnection](https://github.com/tgriesser/knex/blob/master/lib/client.js#L258) on the dialect in use.
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The dialect creates a new connection to the database server, **but uses static configuration**. I have just added a patch, which will rely on your closure to return the config vs using the same static config all the time.
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## Will this work in the future?
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I am using Knex.js to write the ORM of https://adonisjs.com/ and will keep a close eye on the releases of Knex to make sure that I incorporate any changes made of the underlying code and keep this module upto date. If knex.js team plans to re-write the entire codebase (which is less likely to happen), then I will pitch this change to be a first class citizen.
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## Can I help?
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Yes, there are currently no tests for oracle. It will be great, if you can help set it up using docker
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[gh-workflow-image]: https://img.shields.io/github/actions/workflow/status/thetutlage/knex-dynamic-connection/test.yml?style=for-the-badge
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[gh-workflow-url]: https://github.com/thetutlage/knex-dynamic-connection/actions/workflows/test.yml "Github action"
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[npm-image]: https://img.shields.io/npm/v/knex-dynamic-connection.svg?style=for-the-badge&logo=npm
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[npm-url]: https://npmjs.org/package/knex-dynamic-connection "npm"
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