• Regina allows to run MongoDB 'insert', 'find', 'update', 'delete', 'count', and 'aggregate' methods directly from the client side (such as firebase).

• Regina can track tags based events and send back messages containing the result of the requests and their context to client's sockets subscribed to these tags.

• Regina uses Socket.IO for client-server communication and event tracking.

• npm install -g regina

Run with the default settings (db='localhost:27017/reginadb' and port=3009) :

1. mongod
2. regina
3. open your browser at localhost:3009 and check that you are on the regina home page.

Run with custom settings :

1. mongod --port 5000
2. regina 'localhost:5000/mydb' 6000
3. open your browser at localhost:6000 check that you are on the regina home page.

Import socket.io client and follow these instructions :

1. create a socket instance with the regina server address :

• var socket = io('http://localhost:3009/');

2. send requests to the regina server using one of these type of requests :

• socket.emit('insert', collection, docs, options, meta, ack);
• socket.emit('find', collection, query, options, meta, ack);
• socket.emit('count', collection, query, options, meta, ack);
• socket.emit('update', collection, query, update, options, meta, ack);
• socket.emit('remove', collection, query, options, meta, ack);
• socket.emit('aggregate', collection, pipeline, options, meta, ack);

It is also possible to use IOS and Java clients

  <script src="https://cdnjs.cloudflare.com/ajax/libs/socket.io/2.0.3/socket.io.js"></script>

  <script>
  //create a socket instance with the regina server address 
  var socket = io('http://localhost:3009/');

  //be aware of the misuse of regina methods
  socket.on('regina_noack_callback_error', (msg) => { console.log(msg); })

  //follow the 'new-msg' tag
  socket.on('new-msg', (res, ctx) => { console.log(res, ctx); });

  //send an insert request to the regina server with the 'new-msg' tag
  socket.emit('insert' //CRUD operation
    , 'messages' //collection

    //query|doc|pipeline
    , { msg: "Hello Regina", sender: "Paris MongoDB User Group" }

    , {} //mongo options

    , { "tags": [{ "val" : "new-msg" }] }  //meta (tags)

    , (err, res, ctx) => { console.log(err, res, ctx); } //ack (callback)
  );
</script>

See the full example here.

You can use any tag you want except socket.io reserved events. In the meta parameter, simply add an object containing the tags key and an array of objects each containing the val key.

• {"tags":[{"val":"find-users"}, {"val":"@users-coll"}, {"val":"#users"}]}

You can also specify the kind (scope) for each tag :

• {"tags":[{"val":"find-users","kind":"emit"}, {"val":"#users","kind":"broadcast"}]}

There are 3 kinds of scopes:

• emit : sends a message only to the client that sent the request to the server.
• broadcast : sends a message to all connected clients except the client that sent the request to the server.
• io : sends a message to all connected clients including the client that sent the request to the server. By default the scope is io.