Documentation for Mongodb is available online.

• Supports MongoDB versions 3.0, 3.2, 3.4, 3.6, 4.0
• Connection pooling (through db_connection)
• Streaming cursors
• Performant ObjectID generation
• Follows driver specification set by 10gen
• Safe (by default) and unsafe writes
• Aggregation pipeline
• Replica sets

• Make sure requests don't go over the 16mb limit
• New 2.6 write queries and bulk writes

• Use meta-driver test suite
• Server selection / Read preference
  • https://www.mongodb.com/blog/post/server-selection-next-generation-mongodb-drivers
  • http://docs.mongodb.org/manual/reference/read-preference

BSON                Elixir
----------          ------
double              0.0
string              "Elixir"
document            [{"key", "value"}] | %{"key" => "value"} (1)
binary              %BSON.Binary{binary: <<42, 43>>, subtype: :generic}
object id           %BSON.ObjectId{value: <<...>>}
boolean             true | false
UTC datetime        %DateTime{}
null                nil
regex               %BSON.Regex{pattern: "..."}
JavaScript          %BSON.JavaScript{code: "..."}
integer             42
symbol              "foo" (2)
min key             :BSON_min
max key             :BSON_max

1. Since BSON documents are ordered Elixir maps cannot be used to fully represent them. This driver chose to accept both maps and lists of key-value pairs when encoding but will only decode documents to lists. This has the side-effect that it's impossible to discern empty arrays from empty documents. Additionally the driver will accept both atoms and strings for document keys but will only decode to strings.

2. BSON symbols can only be decoded.

Add mongodb to your mix.exs deps and :applications (replace >= 0.0.0 in deps if you want a specific version). Mongodb supports the same pooling libraries db_connection does (currently: no pooling, poolboy, and sbroker). If you want to use poolboy as pooling library you should set up your project like this:

def application do
  [applications: [:mongodb, :poolboy]]
end

defp deps do
  [{:mongodb, ">= 0.0.0"},
   {:poolboy, ">= 0.0.0"}]
end

Then run mix deps.get to fetch dependencies.

By default mongodb will start a single connection, but it also supports pooling with the :pool option. For poolboy add the pool: DBConnection.Poolboy option to Mongo.start_link and to all function calls in Mongo using the pool.

# Starts an unpooled connection
{:ok, conn} = Mongo.start_link(url: "mongodb://localhost:27017/db-name")

# Gets an enumerable cursor for the results
cursor = Mongo.find(conn, "test-collection", %{})

cursor
|> Enum.to_list()
|> IO.inspect

If you're using pooling it is recommend to add it to your application supervisor:

def start(_type, _args) do
  import Supervisor.Spec

  children = [
    worker(Mongo, [[name: :mongo, database: "test", pool: DBConnection.Poolboy]])
  ]

  opts = [strategy: :one_for_one, name: MyApp.Supervisor]
  Supervisor.start_link(children, opts)
end

Then you can use the pool as following:

Mongo.find(:mongo, "collection", %{}, limit: 20, pool: DBConnection.Poolboy)

To connect to a Mongo cluster that is using replica sets, it is recommended to use the :seeds list instead of a :hostname and :port pair.

{:ok, pid} = Mongo.start_link(database: "test", seeds: ["hostname1.net:27017", "hostname2.net:27017"])

This will allow for scenarios where the first "hostname1.net:27017" is unreachable for any reason and will automatically try to connect to each of the following entries in the list to connect to the cluster.

For versions of Mongo 3.0 and greater, the auth mechanism defaults to SCRAM. If you'd like to use MONGODB-X509 authentication, you can specify that as a start_link option.

{:ok, pid} = Mongo.start_link(database: "test", auth_mechanism: :x509)

Some MongoDB cloud providers (notably AWS) require a particular TLS cipher that isn't enabled by default in the Erlang SSL module. In order to connect to these services, you'll want to add this cipher to your ssl_opts:

{:ok, pid} = Mongo.start_link(database: "test", 
      ssl_opts: [
        ciphers: ['AES256-GCM-SHA384'],
        cacertfile: "...",
        certfile: "...")
      ]
)

Using $and

Mongo.find(:mongo, "users", %{"$and" => [%{email: "[email protected]"}, %{first_name: "first_name"}]})

Using $or

Mongo.find(:mongo, "users", %{"$or" => [%{email: "[email protected]"}, %{first_name: "first_name"}]})

Using $in

Mongo.find(:mongo, "users", %{email: %{"$in" => ["[email protected]", "[email protected]"]}})

The SSL test suite is enabled by default. You have two options. Either exclude the SSL tests or enable SSL on your Mongo server.

mix test --exclude ssl

$ openssl req -newkey rsa:2048 -new -x509 -days 365 -nodes -out mongodb-cert.crt -keyout mongodb-cert.key
$ cat mongodb-cert.key mongodb-cert.crt > mongodb.pem
$ mongod --sslMode allowSSL --sslPEMKeyFile /path/to/mongodb.pem

• For --sslMode you can use one of allowSSL or preferSSL
• You can enable any other options you want when starting mongod

Copyright 2015 Justin Wood

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.