Replication

A replication is a Meteor collection that synchronizes with an external source. The synchronization is done by a configurable polling time and is one way. Any changes made directly to the replication will be overwritten on the next sync.

Usage

meteor add alt:replication

Set up a data source for the replication

// server.js
MySql = Npm.require('mysql')

let pool = MySql.createPool({
  connectionLimit:2,
  host: 'localhost',
  database: 'mydb',
  user: 'test',
  password: 'password'
})

let ds = Meteor.Replication.DataSource(pool)

Create replications using the data source

// server.js
let Products = Meteor.Replication('products', ds, 'select * from catalog')

Publish a dataset just like with any Meteor collection

// server.js
Meteor.publish('active_products', () => {
  return Products.find({status: 'active'}, {fields: {name: 1, price: 1, desc: 1}})
})

And subscribe to it on the client as usual

// client.js
let Products = Mogo.Collection('products')
Meteor.subscribe('active_products')

To update the data you need to update the external data and optionally server and client collections. On the server use the Replication.modify method to ensure your change happens immediately.

// server.js
Meteor.methods({
  updateProductPrice(id, price){
    pool.query('update catalog set price = ? where id = ?', [price, id], (err, result) => {
      // optionally update replication or wait for poll
      if(!err){
        Products.modify([id], () => { Products.update({_id: id}, {$set: {price: price}}) })
      }
    })
  }
})

// client.js

// optional client stubs to compensate for latency
Meteor.methods({
  updateProductPrice(id, price){
    Products.update({_id: id}, {$set: {price: price}})
  }
})

Configuration

Meteor.Replication.DataSource(connection [, method [, delay ]] )

Parameter	Description
connection	object that handles retrieving data from external source
method	method on connection to call (defaults to 'query')
delay	minimum number of seconds between sync polls (defaults to 10 seconds)

The method of the connection object is expected to be asynchronous and require a callback as it's last parameter. The callback receives 2 parameters (err, data).

Meteor.Replication( name, data_source, ...args )

Parameter	Description
name	collection name
data_source	instance of Meteor.Replication.DataSource
...args	any number of arguments passed to the datasource method

The rows are assumed to have 'id' as the primary key. Use the id method of DataSource to set a different primary key for each replication.

let Products = Meteor.Replication('products', ds.id('partNum'), 'select * from catalog')
let Orders = Meteor.Replication('orders', ds.id('orderNum'), 'select * from orders where state = ?', ['pending'])

Fast Count

Replication defaults to patching minimongo to provide a faster method of checking for records that need to be deleted on sync. To disable this and only use official published collection api - set the DISABLE_FAST_COUNT environment variable.

DISABLE_FAST_COUNT=true meteor run