koop-provider-mongo

Provider to fetch data from a MongoDb instance. It can access any database/collection on your instance by assigning the id route-parameter a delimited value in the form of database-name::collection-name.

Data considerations

As per MongoDB specifications, each document/record in your dataset will have a unique-identifier, _id. At insert time, you can choose to assign this value manually, or allow Mongo to generate it automatically. In terms of your provider metadata, this means that you could always use _id as the value of your provider's idField (an attribute used to flag which GeoJSON property is the unique-identifier).

If your data has a geometry, you should consider using geospatial index. While not necessary, it will likely speed any queries including a geometry operation.

Usage

Register the provider with Koop:

const Koop = require('@koopjs/koop-core');
const koop = new Koop({ logLevel: 'info'});
const mongoProvider = require('@koopjs/provider-mongodb');

koop.register(mongoProvider, { connnectString, databases });

Registration/Config parameters

The provider can be configured with registration options or the use of the config module with an entry key "mongodb" in the JSON configuration document. See below, for an example of using the config approach

connectString: string

A MongoDB connection string, e.g., mongodb://localhost:27017.

databases: object

A key/value populated object that serves as a metadata lookup/dictionary for any database/collection on your MongoDB instance that you wish to provide access. For example, if imagine you have a database called db1 and it has a collection called my-collection. You can set up the databases object so as to provide metadata for my-collection:

{
  db1: {
    'my-collection': {
      geometryField: 'location', // field holding a record's GeoJSON geometry.
      idField: '_id', // field to treat as the unique-id.  Default: `_id`.
      cacheTtl: 0, // number of seconds to cache results from MongoDb. Default: 0.
      crs: 4326, // Coordinate reference system of geometry. Default: 4326.
      maxRecordCount: 2000, // Max number of records to return in a page. Default: 2000.
    }
  }
}

Note that for each collection, you may configure the options above. If you do not assign a field to geometryField, the collection will be treated like tabular data, and the GeoJSON generated will have no geometry,

definedCollectionsOnly: boolean

This setting determines if the database/collection must appear in the databases parameter to be accessed. Defaults to true.

Setting with the "config" module

Koop allows providers to use the config module. The settings above can be stored in a config JSON under the key mongodb:

{
  "mongodb": {
      "connectString": "mongodb://localhost:27017",
      "databases": {
        "cdf-sample-data": {
          "fires": {
            "geometryField": "location",
            "idField": "_id",
            "cacheTtl": 0,
            "crs": 4326,
            "maxRecordCount": 2000
          }
        }
      }
  }
}

Route parameters

id

Once registered with Koop, the provide will expose routes with an id parameter. For example:

/mongodb/rest/services/:id/FeatureServer

The id parameter should be filled with a :: delimited string with the target <database>::<collection>. For example, a request like:

/mongodb/rest/services/sample-db::fires/FeatureServer/0/query

would return records from the fires collection in the sample-db database.

Demo

The repository includes a demonstration project. To run the demo you will need Docker installed on your computer. Once installed you can following the steps below to create a local Elastic instance and load it with sample data:

> npm install

> cd demo

# use Docker to run Elastic/Kibana
> docker-compose up -d

# load sample data; this will create an MongoDB database called "sample-data' with a collection named "fires"
> node loader.js 

# start the Koop application
> node index.js