Sengi DocStore MongoDB

This package is part of the Sengi family.

A wrapper for Mongo DB that implements the Sengi document store interface.

Installation

npm install sengi-docstore-mongodb

Usage

The MongoDbDocStore implements the DocStore interface defined in sengi-interfaces.

To instantiate a MongoDbDocStore you have to provide the following parameters:

• mongoUrl - A url that identifies your MongoDB instance. This should be prefixed with mongo://.

• mongoOptions - An object that describes how to connect to mongo. This is passed directly to the MongoClient constructor. See the example below for connecting with a username and password.

• generateDocVersionFunc - A function () => string that returns a string of random characters.

• getDatabaseNameFunc - A function (docTypeName: string, docTypePluralName: string, options: DocStoreOptions) => string that returns the name of a database.

• getCollectionNameFunc - A function (databaseName: string, docTypeName: string, docTypePluralName: string, options: DocStoreOptions) => string that returns the name of a collection.

const mongoDbDocStore = new MongoDbDocStore({
    mongoUrl: 'mongodb://localhost:27017',
    mongoOptions: {
      auth: { user: 'sengi', password: 'sengi' },
      useUnifiedTopology: true
    },
    generateDocVersionFunc: () => crypto.randomBytes(Math.ceil(10)).toString('hex').slice(0, 20),
    getDatabaseNameFunc = (docTypeName, docTypePluralName, options) => 'myDatabase',
    getCollectionNameFunc: (databaseName, docTableName, docTypePluralName, options) => docTypePluralName
  })

This example uses the standard NodeJs crypto library to produce a string of 20 random hex characters for generateDocVersionFunc.

Filters

Filter expressions are expected to be a FilterQuery<Doc> object.

The Mongo documentation explains how to specify filter objects in more detail.

This is an example filter expression returned from a DocType filter implementation:

const filter = {
  heightInCms: { $gt: 200 }
}

Indexes

See the Mongo documentation for setting up secondary indexes on Mongo collections.

Ensure any DocType filters will hit a specific index to ensure performant responses.

Limitations

The current MongoDB client library is connection-based rather than connection-less.

This can lead to some problems determining when to connect and how to handle interruptions to that connection.

Hopefully a connection-less version of the client library will be available in the future.

Setup

To run the tests locally you will need MongoDB listening at mongodb://127.0.0.1:27017 with an admin/root user named sengi and with password sengi.

The database sengi and collection trees, that are used by the automated tests, will be created automatically.

The following command sets up an appropriate local instance of Mongo via docker.

docker run -d --name test-mongo-with-sengi -p 127.0.0.1:27017:27017 \
  -e MONGO_INITDB_ROOT_USERNAME=sengi \
  -e MONGO_INITDB_ROOT_PASSWORD=sengi \
  mongo:4.2.9

You can connect to the server by using the Mongo SH client (mongosh) as per the example below. There is also a GUI tool you can download.

mongosh mongodb://127.0.0.1:27017 -u sengi -p sengi

You can issue the following commands, using Mongo SH client, to work with databases and collections. This is not required.

show databases
use sengi
show collections
db.createCollection('trees')
db.trees.drop()

Development

Tests are written using Jest with 100% coverage.

npm test

Note that the tests run sequentially (jest --runInBand) so that only one test can access the database at a time.

Continuous Deployment

Any pushes or pull-requests on non-master branches will trigger the test runner.

Any pushes to master will cause the family of libraries to be re-published.