Based on: https://bulletproofmeteor.com/database-modeling/aggregation-pipeline

server.coffee

# on the server: server.coffee
Metrics = (name, aggregationQuery, collection, interval) ->
  @name = name
  @aggregationQuery = aggregationQuery
  @collection = collection
  @interval = interval or 1000*10
  @_collectionName = 'metrics-transport'

Metrics.prototype._getCollectionName = -> "metrics-#{@name}"

Metrics.prototype._publishCursor = (sub) ->
  result = @collection.aggregate @aggregationQuery
  sub.added @_collectionName, @name, result: result
  sub.ready()
  handle = Meteor.setInterval =>
    result = @collection.aggregate @aggregationQuery
    sub.changed @_collectionName, @name, result: result
  , @interval
  sub.onStop -> Meteor.clearTimeout handle