DB HELPER

Purpose

This present model class is designed to simplify the development of object oriented projects using the native MongoDB Node JS driver.

It provides abstract classes for models and collection. It provides overrides for main insert, find and update functions.

It also allows developer to set up a cache and to define specific pre insert, pre update and post save behaviors.

This module also provides a cache client generator based on ioredis.

Provided to Model constructor, it allows you to use a Redis cache to store responses to Mongo queries in order to improve performances.

Quick start

First you need to create a class extending the Model.

The constructor needs to be overridden. The native constructor takes 3 arguments:

• dbInstance is the instance of a Mongo Db
• foo is the collection name this class is related to
• cacheClient is the ioredis cache client this object is going to use. This param is not mandatory

Foo.class:

const Model = require('@bonjourjohn/dbhelper').Model;

module.exports = class Foo extends Model {
  constructor(dbInstance, cacheClient) {
    super(dbInstance, 'foo', cacheClient);
  }
};

In your code, where you need your object instance:

without cache:

const MongoClient = require('mongodb').MongoClient;

const FooClass = require('./path/to/Foo.class');
const Mclient = new MongoClient(SERVER, OPTIONS).connect();
const MDB = Mclient.db(DBNAME);

const Foo = new FooClass(MDB);
Foo.init(); //loads the dedicated MongoCollection into object instance

with cache:

const MongoClient = require('mongodb').MongoClient;

const FooClass = require('./path/to/Foo.class');
const Mclient = new MongoClient(SERVER, OPTIONS).connect();
const cacheClient = require('@bonjourjohn/dbhelper').Cache(CACHEOPTS);

const MDB = Mclient.db(DBNAME);

const Foo = new FooClass(MDB, cacheClient);
Foo.init(); //loads the dedicated MongoCollection into object instance

Model native properties list

Here are the properties you can find in an instaciated Model object once it's been initiated (it's ready to work):

• this.dbInstance instance of Mongodb Db
• this.collection instance of Mongodb Collection
• this.collecionName string, equivalent to this.collection.collectionName
• this.cacheClient instance of Redis client (if cacheClient set, not mandatory)
• this.useCache bool, true if this.cacheClient is set and ready, false otherwise. It can be set to false if you want to skip cache.

Temporary properties:

• this.doc JSON object, document that is going to be inserted in collection. It will exist only during insert process (from _preInsert to _postSave)
• this.docs JSON object, documents that are going to be inserted in collection. It will exist only during insert process (from _preInsert to _postSave)
• this.update JSON object, update query that will be used by an update method. It will exist only during update process (from _preUpdate to _postSave)

Model methods list

Here are the methods provided by this Model class, and the desciption of their usefulness.

Constructor

constructor(dbInstance, collectionName, cacheClient)

Creates a new Model object.

Params:

• dbInstance Mongodb Db object
• collectionName name of the collection the current instance has to be linked to
• cacheClient not mandatory Redis cache client

init

init()

Get the collectionName collection in given Db and set it as an object instance local var this.collection.

setCacheClient

setCacheClient(cacheClient)

Store given cache client into this.cacheClient. Set this.useCache to true if cache client is ready. Attach listeners:

• on('ready') to set this.useCache to true
• on('end') to set this.useCache to false
• on('error') to set this.useCache to false

Params

• cacheClient instance of Redis client

_preInsert()

Called in insertOne and insertMany methods. Execute all pre insert actions.

It can be overriden. Native behavior consist in adding timestamps fields createdAt and updatedAt to document(s).

_preUpdate()

Called in findOneAndUpdate, updateMany and updateOne methods. Execute all pre update actions.

It can be overriden. Native behavior consist in added the update of updatedAt field in update query if it's not already present.

_postSave()

Called at then end of all saving process: insertOne, insertMany, findOneAndUpdate, updateMany and updateOne. Execute all post save actions.

It can be overriden. Native behavior consist in clearing cache if cache is on.

_postDelete()

Called at then end of all deleting process: remove, findOneAndDelete. Execute all post delete actions.

It can be overriden. Native behavior consist in clearing cache if cache is on.

find(), findOne(), findOneAndDelete(), insertOne(), insertMany(), updateOne(), findOneAndUpdate(), updateMany()

These methods will do the exact same thing as they do when their called on Mongodb Collection objects, except two things:

• they will execute _pre and _post methods before and after process
• they will try to read in cache and/or write result in cache, or flush cache according to the nature of the operation (read, write, delete)

They all take the same arguments their analogue in Mongo Collection object, but you can add this option field:

• skipCache bool, tell method to skip reading in cache and to go straigth to database.

Example:

const results = await Foo.findOne({"fieldName": "value"}, {"skipCache": true});

setupTimestamps()

Add fields createdAt and updatedAt into document stored in this.doc or into documents stored in this.docs.

updateTimestamps()

Add updatedAt to $set part of the query stored in this.update. Create the $set part if it does not exist.

findInCache(query, options)

Check if given query already has a result in cache with given options and return them if it has. Return false otherwise.

Called by read methods when this.useCache is true.

storeInCache(query, options, value)

Stores value into cache under a key generated from given query and options.

Called by read methods when this.useCache is true.

clearCache()

Clears the cache for the current collection name. IE. flush all keys corresponding to the pattern COLLECTIONNAME*

Testing

Requirements

You need a MongoDB and a Redis server running.

Use these Docker images:

• MongoDB
• Redis

docker run --name database -p 27017:27017 -d mongo
docker run --name cache -p 6379:6379 -d redis:3.0.6-32bit

Regarding your needs, you can use your own Redis and Mongo applications/servers/containers.

Once everything is running, just run the tests:

npm test