MongoDB library

The MongoDB library allows the Grassroots Server to use the functionality provided by MongoDB. The library uses the C language driver.

Installation

To build this service, you need the grassroots core and grassroots build config installed and configured.

The files to build the MongoDB library are in the build/<platform> directory.

Linux

Enter the build directory

cd build/linux

and create a user.prefs file.

cp example-user.prefs user.prefs

You will need to edit this file to configure where the MongoDB library dependencies are stored. The file content is similar to the following

#
# mongodb dependencies
#
 
# Set this to where you have the mongo-c-driver directory 
# containing "include" and "lib" subdirectories.
export MONGODB_HOME := $(DIR_GRASSROOTS_EXTRAS)/mongodb-c
export BSON_HOME := $(DIR_GRASSROOTS_EXTRAS)/mongodb-c

Adjust the MONGODB_HOME and BSON_HOME variables to where you have the mongo-c-driver installed. You can then build the handler by typing

make all

and then

make install

to install the library into the Grassroots system where it will be available on the server application after it has been restarted.

Usage

One of the facilities that Grassroots system provides is an API to access a MongoDB instance through JSON-based messages. All of the MongoDB messages are accessed using a mongodb key.

Inserting data

The client would send a child insert key with a list of child key-value pairs. These can be in a single object if you just want to insert a single document or as an array if you want to insert multiple documents. For example, both of the following requests are valid:

{
  "mongodb": {
    "collection": "bands",
    "insert": [{
      "band": "spinal tap",
      "volume": 11,
      "recorded in": "dobly"    
    }, {
      "band": "bad news",
      "label": "frilly pink"
    }]  
  }
}

{
  "mongodb": {
    "collection": "bands",
    "insert": {
      "band": "spinal tap",
      "volume": 11,
      "recorded in": "dobly"    
    }
  }
}

The response from the Server will be a list of success values along with the document ids in the same order as they were specified in the incoming request

{
  "mongodb": {
    "response": [{
      "success": true,
      "id": "123456789012345678901234"
    }, {
      "success": false
    }]
  }
}

Deleting documents

To delete documents from a collection, a Client would send a list of the queries that would specify which documents to remove.

{
  "mongodb": {
    "collection": "bands",
    "delete": [{
      "id": "123456789012345678901234"
    }, {
      "id": "1112223334445556667778889"
    }, {
      "crop": "wheat"
    }]
  }
}

Updating documents

Documents that were previously added can be subsequently updated.