# An alternative Mongodb driver for Elixir
[](https://travis-ci.org/zookzook/elixir-mongodb-driver)
[](https://hex.pm/packages/mongodb_driver)
[](https://hex.pm/packages/mongodb_driver)
[](https://hex.pm/packages/mongodb_driver)
[](https://hex.pm/packages/mongodb_driver)
This is an alternative development from the [original](https://github.com/ankhers/mongodb), which was the starting point
and already contained very nice code.
I have made a number of changes to understand how the driver works. For example, I reduced cursor modules to just one cursor and
replaced some op code calls with command calls.
This is currently under development and there is no version management yet. The main goal is to simplify the API and
to implement the current requirements for the driver.
[Documentation](https://hexdocs.pm/mongodb_driver/readme.html)
## Motivation
* [ ] Refactoring old code into new
* [x] Simplify code: remove raw_find (raw_find called from cursors, raw_find called with "$cmd"), so raw_find is more calling a command than a find query.
* [x] Better support for new MongoDB version, for example the ability to use views
* [x] Upgrade to ([DBConnection 2.x](https://github.com/elixir-ecto/db_connection))
* [x] Removed depreacated op codes ([See](https://docs.mongodb.com/manual/reference/mongodb-wire-protocol/#request-opcodes))
* [x] Support for SCRAM-SHA-256 (MongoDB 4.x)
* [x] Support for change streaming api ([See](https://github.com/mongodb/specifications/blob/master/source/change-streams/change-streams.rst))
* [x] Add `op_msg` support ([See](https://docs.mongodb.com/manual/reference/mongodb-wire-protocol/#op-msg))
* [ ] driver sessions ([See](https://github.com/mongodb/specifications/blob/master/source/sessions/driver-sessions.rst))
* [ ] driver transactions ([See](https://github.com/mongodb/specifications/blob/master/source/transactions/transactions.rst))
* [ ] Because the driver is used in production environments, quick adjustments are necessary.
## Features
* Supports MongoDB versions 3.2, 3.4, 3.6, 4.0
* Connection pooling ([through DBConnection 2.x](https://github.com/elixir-ecto/db_connection))
* Streaming cursors
* Performant ObjectID generation
* Follows driver specification set by 10gen
* Safe (by default) and unsafe writes
* Aggregation pipeline
* Replica sets
## Data representation
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.
## Usage
### Installation:
Add `mongodb_driver` to your mix.exs `deps` and `:applications`.
```elixir
def application do
[applications: [:mongodb_driver]]
end
defp deps do
[{:mongodb_driver, "~> 0.5.0"}]
end
```
Then run `mix deps.get` to fetch dependencies.
```elixir
# 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
```
### Connection pooling
The driver supports pooling by DBConnection (2.x). By default `mongodb_driver` will start a single
connection, but it also supports pooling with the `:pool_size` option. For 3 connections add the `pool_size: 3` option to `Mongo.start_link` and to all
function calls in `Mongo` using the pool:
```elixir
# Starts an pooled connection
{:ok, conn} = Mongo.start_link(url: "mongodb://localhost:27017/db-name", pool_size: 3)
# 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:
```elixir
def start(_type, _args) do
import Supervisor.Spec
children = [
worker(Mongo, [[name: :mongo, database: "test", pool_size: 3]])
]
opts = [strategy: :one_for_one, name: MyApp.Supervisor]
Supervisor.start_link(children, opts)
end
```
Due to the mongodb specification, an additional connection is always set up for the monitor process.
### Replica Sets
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.
```elixir
{: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.
### Auth mechanisms
For versions of Mongo 3.0 and greater, the auth mechanism defaults to SCRAM.
If you'd like to use [MONGODB-X509](https://docs.mongodb.com/manual/tutorial/configure-x509-client-authentication/#authenticate-with-a-x-509-certificate)
authentication, you can specify that as a `start_link` option.
```elixir
{:ok, pid} = Mongo.start_link(database: "test", auth_mechanism: :x509)
```
### AWS, TLS and Erlang SSL ciphers
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`:
```elixir
{:ok, pid} = Mongo.start_link(database: "test",
ssl_opts: [
ciphers: ['AES256-GCM-SHA384'],
cacertfile: "...",
certfile: "...")
]
)
```
### Examples
Using `$and`
```elixir
Mongo.find(:mongo, "users", %{"$and" => [%{email: "my@email.com"}, %{first_name: "first_name"}]})
```
Using `$or`
```elixir
Mongo.find(:mongo, "users", %{"$or" => [%{email: "my@email.com"}, %{first_name: "first_name"}]})
```
Using `$in`
```elixir
Mongo.find(:mongo, "users", %{email: %{"$in" => ["my@email.com", "other@email.com"]}})
```
## Contributing
The SSL test suite is enabled by default. You have two options. Either exclude
the SSL tests or enable SSL on your Mongo server.
### Disable the SSL tests
`mix test --exclude ssl`
### Enable SSL on your Mongo server
```bash
$ 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`
## License
Copyright 2015 Eric Meadows-Jönsson and Justin Wood
Copyright 2019 Michael Maier
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.
