Momy

Momy is a simple cli tool for replicating MongoDB to MySQL in realtime.

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Installation

$ npm install -g momy

or install it within the project locally:

$ npm install --save momy

Preparation

MongoDB

Momy uses Replica Set feature in MongoDB. But you don't have to replicate between MongoDB actually. Just follow the steps below.

Start a new mongo instance with no data:

$ mongod --replSet "rs0" --oplogSize 100

Open another terminal, and go to MongoDB Shell:

$ mongo
....
> rs.initiate()

rs.initiate() command prepare the collections that is needed for replication.

MySQL

Launch MySQL instance, and create the new database to use. The tables will be created or updated when syncing. You'll see mongo_to_mysql, too. This is needed to store the information for syncing. (don't remove it)

Configuration

Create a new momyfile.json file like this:

{
  "src": "mongodb://localhost:27017/dbname",
  "dist": "mysql://root@localhost:3306/dbname",
  "prefix": "t_",
  "case": "camel",
  "collections": {
    "collection1": {
      "_id": "number",
      "createdAt": "DATETIME",
      "field1": "number",
      "field2": "string",
      "field3": "boolean",
      "field4.subfield": "string"
    },
    "collection2": {
      "_id": "string",
      "createdAt": "DATETIME",
      "field1": "number",
      "field2": "string",
      "field3": "boolean"
    }
  }
}

src: the URL of the MongoDB server
dist: the URL of the MySQL server
prefix: optional prefix for table name. The name of the table would be t_collection1 in the example above.
case: optional. snake or camel
collections: set the collections and fields to sync

_id field is required for each collection and should be string or number.

Field names and types

"<field_name>": "<field_tipe>"

or, field_name could be dot-concatenated:

"<field_name>.<sub_name>": "<field_tipe>"

For example, if you have { a: { b: { c: 'hey!' } } } then "a.b.c": "string"

Currently these native types are supported:

BIGINT
TINYINT
VARCHAR
DATE
DATETIME
TIME

There're also some aliases:

number => BIGINT
boolean => TINYINT
string => VARCHAR

Usage

At the first run, we need to import all the data from MongoDB:

$ momy --config momyfile.json --import

Then start the daemon to streaming data:

$ momy --config momyfile.json

$ forever momy --config momyfile.json

License

MIT

This library was originally made by @doubaokun as MongoDB-to-MySQL and rewritten by @cognitom.

jbarker7 / momy