ExDgraph

This is work in progress and not functional as of now. If you want to help, please drop me a message. Any help is greatly appreciated!

ExDgraph is a gRPC based client for the Dgraph database. It uses the DBConnection behaviour to support transactions and connection pooling via Poolboy. Works with Dgraph v1.0.4 (latest).

WORK IN PROGRESS.

Dgraph is an open source, horizontally scalable and distributed graph database, providing ACID transactions, consistent replication and linearizable reads. [...] Dgraph's goal is to provide Google production level scale and throughput, with low enough latency to be serving real time user queries, over terabytes of structured data. (Source)

If you want to learn more about Dgraph watch this talk.

Contribute

This is under development and contributions are very welcome. Please add a comment under this issue to discuss how to help. Please also read the roadmap at the bottom of this Readme to see where I stand and what the next steps are.

A good start would be to improve test coverage. Run mix coveralls to see where work is needed.

Design principles

Performance and stability first
Work as closely to GraphQL+ as possible
Keep it simple and allow a maximum of flexibility for the user while providing enough syntactic sugar to make it simple to use. Also for people new to Dgraph

Installation

Add the package ex_dgraph to your list of dependencies in mix.exs:

def deps do
  [
    {:ex_dgraph, "~> 0.2.0-alpha.3"}
  ]
end

And add the application to your list of applications in mix.exs:

def application do
  [
    applications: [
      :ex_dgraph
    ]
  ]
end

Then, update your dependencies:

$ mix deps.get

Usage with Phoenix

Add the configuration to your respective configuration file:

config :ex_dgraph, ExDgraph,
  hostname: 'localhost',
  port: 9080,
  pool_size: 5,
  max_overflow: 1

And finally don't forget to add ExDgraph to the supervisor tree of your app:

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

  # Define workers and child supervisors to be supervised
  children = [
    # Start the endpoint when the application starts
    {ExDgraph, Application.get_env(:ex_dgraph, ExDgraph)},
    supervisor(MyApp.Endpoint, [])
  ]

  # See https://hexdocs.pm/elixir/Supervisor.html
  # for other strategies and supported options
  opts = [strategy: :one_for_one, name: MyApp.Supervisor]
  Supervisor.start_link(children, opts)
end

Important: Please also note the instructions further down on how to run ExDgraph with Phoenix 1.3. It requires Cowboy 2 which means you have to change some things.

Usage

Again, this is work in progress. I'll add more examples on how to use this on the go. So far you can connect to a server and run a simple query. I recommend installing and running Dgraph locally with Docker. You find information on how to do that here. To use this simple example you first have to import the example data. You can just open http://localhost:8000 in your browser when Dgraph is running to execute and visualize queries using Ratel.

At the moment simple queries, mutations and operations are supported via the DBConnection behaviour. Everything else is done directly via the Protobuf API. This will change. Check the tests for examples.

Example for a query

query = """
  {
      starwars(func: anyofterms(name, "VI"))
      {
        uid
        name
        release_date
        starring
        {
          name
        }
      }
  }
"""

conn = ExDgraph.conn()
{:ok, msg} = ExDgraph.query(conn, query)

Examples for a mutation

starwars_schema = "id: string @index(exact).
    name: string @index(exact, term) @count .
    age: int @index(int) .
    friend: uid @count .
    dob: dateTime ."

starwars_creation_mutation = """
   _:luke <name> "Luke Skywalker" .
   _:leia <name> "Princess Leia" .
   _:han <name> "Han Solo" .
   _:lucas <name> "George Lucas" .
   _:irvin <name> "Irvin Kernshner" .
   _:richard <name> "Richard Marquand" .

   _:sw1 <name> "Star Wars: Episode IV - A New Hope" .
   _:sw1 <release_date> "1977-05-25" .
   _:sw1 <revenue> "775000000" .
   _:sw1 <running_time> "121" .
   _:sw1 <starring> _:luke .
   _:sw1 <starring> _:leia .
   _:sw1 <starring> _:han .
   _:sw1 <director> _:lucas .

   _:sw2 <name> "Star Wars: Episode V - The Empire Strikes Back" .
   _:sw2 <release_date> "1980-05-21" .
   _:sw2 <revenue> "534000000" .
   _:sw2 <running_time> "124" .
   _:sw2 <starring> _:luke .
   _:sw2 <starring> _:leia .
   _:sw2 <starring> _:han .
   _:sw2 <director> _:irvin .

   _:sw3 <name> "Star Wars: Episode VI - Return of the Jedi" .
   _:sw3 <release_date> "1983-05-25" .
   _:sw3 <revenue> "572000000" .
   _:sw3 <running_time> "131" .
   _:sw3 <starring> _:luke .
   _:sw3 <starring> _:leia .
   _:sw3 <starring> _:han .
   _:sw3 <director> _:richard .

   _:st1 <name> "Star Trek: The Motion Picture" .
   _:st1 <release_date> "1979-12-07" .
   _:st1 <revenue> "139000000" .
   _:st1 <running_time> "132" .
"""

conn = ExDgraph.conn()
{:ok, operation_msg} = ExDgraph.operation(conn, %{schema: starwars_schema})
{:ok, mutation_msg} = ExDgraph.mutation(conn, starwars_creation_mutation)

Example for inserting a map

map = %{
  name: "Alice",
  friends: %{
    name: "Betty"
  }
}

conn = ExDgraph.conn()
ExDgraph.set_map(conn, map)
{:ok, mutation_msg} = ExDgraph.set_map(conn, map)

ExDgraph.set_map/2 returns the data you have passed it but populates every node in your map with the respective uids returned from Dgraph. For example:

%{
  context: %ExDgraph.Api.TxnContext{
    aborted: false,
    commit_ts: 1703,
    keys: [],
    lin_read: %ExDgraph.Api.LinRead{ids: %{1 => 1508}},
    start_ts: 1702
  },
  result: %{
    friends: [%{name: "Betty", uid: "0xd82"}],
    name: "Alice",
    uid: "0xd81"
  },
  uids: %{
    "763d617a-af34-4ff9-9863-e072bf85146d" => "0xd82",
    "e94713a5-54a7-4e36-8ab8-0d3019409892" => "0xd81"
  }
}

You can also use ExDgraph.set_map/2 to update an existing node or add new edges by passing a uid in your map:

user = %{name: "bob", occupation: "dev"}
{:ok, res} = ExDgraph.set_map(conn, user)

other_mutation = %{
  uid: res.result.uid,
  friends: [%{name: "Paul", occupation: "diver"}, %{name: "Lisa", occupation: "consultant"}]
}

{:ok, res2} = ExDgraph.set_map(conn, other_mutation)

# Content of res2. As you can see the original user has been updated.

%{
  context: %ExDgraph.Api.TxnContext{
    aborted: false,
    commit_ts: 3271,
    keys: [],
    lin_read: %ExDgraph.Api.LinRead{ids: %{1 => 2905}},
    start_ts: 3270
  },
  result: %{
    friends: [
      %{name: "Paul", occupation: "diver", uid: "0x19c6"},
      %{occupation: "consultant", name: "Lisa", uid: "0x19c7"}
    ],
    uid: "0x19c5"
  },
  uids: %{
    "7086397d-aa39-4257-a70e-3ad4e63abc14" => "0x19c7",
    "a66d77fa-afc0-478f-b838-ea1a97a20c11" => "0x19c6"
  }
}

Examples for an operation

# Connect
conn = ExDgraph.conn()

# Drop all entries from the database
ExDgraph.operation(conn, %{drop_all: true})

# Create schema
@testing_schema "id: string @index(exact).
  name: string @index(exact, term) @count .
  age: int @index(int) .
  friend: uid @count .
  dob: dateTime ."

# Run operation
ExDgraph.operation(conn, %{schema: @testing_schema})

Example for a raw query

# Connect to Server
{:ok, channel} = GRPC.Stub.connect("#localhost:9080")

# Define query (for now just a string)
query = """
  {
      starwars(func: anyofterms(name, "VI"))
      {
        uid
        name
        release_date
        starring
        {
          name
        }
      }
  }
"""

# Build request
request = ExDgraph.Api.Request.new(query: query)

# Send request to server
{:ok, msg} = channel |> ExDgraph.Api.Dgraph.Stub.query(request)

# Parse result
json = Poison.decode!(msg.json)

Using with Phoenix 1.3

Since grpc-elixir needs Cowboy 2 you need to upgrade your Phoenix app to work with Cowboy 2.

Update dependencies in your mix.exs

Open up the mix.exs file and replace the dependencies with this:

defp deps do
  [
    {:phoenix, git: "https://github.com/phoenixframework/phoenix", branch: "master", override: true},
    {:plug, git: "https://github.com/elixir-plug/plug", branch: "master", override: true},
    {:phoenix_pubsub, "~> 1.0"},
    {:phoenix_html, "~> 2.10"},
    {:phoenix_live_reload, "~> 1.0", only: :dev},
    {:gettext, "~> 0.11"},
    {:cowboy, "~> 2.1", override: true},
    {:ex_dgraph, github: "ospaarmann/exdgraph", tag: "v0.1.0"}
  ]
end

Run mix deps.get to retrieve the new dependencies.

Create a self-signed certificate for https

We will need to do this as, although http2 does not specifically require it, browser do expect http2 connections to be secured over TLS.

In your project folder run:

openssl req -new -newkey rsa:4096 -days 365 -nodes -x509 -subj "/C=US/ST=Denial/L=Springfield/O=Dis/CN=www.example.com" -keyout priv/server.key -out priv/server.pem

Add the two generated files to .gitignore.

Now we will need to adjust the Endpoint configuration to use a secure connection and use a Cowboy 2 handler

Replace the configuration with the following.

config :my_app, MyAppWeb.Endpoint,
  debug_errors: true,
  handler: Phoenix.Endpoint.Cowboy2Handler,
  code_reloader: true,
  check_origin: false,
  watchers: [],
  https: [port: 4000, keyfile: "priv/server.key", certfile: "priv/server.pem"]

This tells phoenix to listen on port 4000 with the just generated certificate. Furthermore, the handler tells Phoenix to use Cowboy2.

If you now start the application with mix phx.server and go to https://localhost:4000 the browser will tell that the connection is not secure with for example NET::ERR_CERT_AUTHORITY_INVALID. This is because the certificate is self signed, and not by a certificate authority. You can open the certificate in for example Keychain on Mac OS X and tell your OS to trust the certificate.

Source

Using SSL

If you want to connect to Dgraph using SSL you have to set the :ssl config to true and provide a certificate:

config :ex_dgraph, ExDgraph,
  # default port considered to be: 9080
  hostname: 'localhost',
  pool_size: 5,
  max_overflow: 1,
  ssl: true,
  cacertfile: '/path/to/MyRootCA.pem'

You also have to provide the respective certificates and key to the server and start it with the following options:

command: dgraph server --my=server:7080 --memory_mb=2048 --zero=zero:5080 --tls_on --tls_ca_certs=/path/to/cert/in/container/MyRootCA.pem --tls_cert=/path/to/cert/in/container/MyServer1.pem --tls_cert_key=/path/to/cert/in/container/MyServer1.key

You can read more about how to create self-signed certificates in the Wiki.

Using TLS client authentication

If you want to connect to Dgraph and authenticate the client via TLS you have to set the :tls_client_auth config to true and provide certificates and key:

config :ex_dgraph, ExDgraph,
  # default port considered to be: 9080
  hostname: 'localhost',
  pool_size: 5,
  max_overflow: 1,
  ssl: true,
  cacertfile: '/path/to/MyRootCA.pem',
  certfile: '/path/to/MyClient1.pem',
  keyfile: '/path/to/MyClient1.key',

You also have to provide the respective certificates and key to the server and start it with the following options:

command: dgraph server --my=server:7080 --memory_mb=2048 --zero=zero:5080 --tls_on --tls_ca_certs=/path/to/cert/in/container/MyRootCA.pem --tls_cert=/path/to/cert/in/container/MyServer1.pem --tls_cert_key=/path/to/cert/in/container/MyServer1.key --tls_client_auth=REQUIREANDVERIFY

You can read more about how to create self-signed certificates in the Wiki.

Running tests

You need Dgraph running locally on port 9080. A quick way of running any version of Dgraph, is via Docker:

$ git clone git@github.com:ospaarmann/exdgraph.git
$ cd exdgraph
$ docker-compose up
$ mix test

More info on how to run Dgraph locally.

Roadmap

Notes

Read more on Dgraph here: https://docs.dgraph.io
Read more on gRPC here: https://grpc.io/docs/
Read more on Google Protobuf here: https://developers.google.com/protocol-buffers/
Read more on DBConnection here: https://hexdocs.pm/db_connection/DBConnection.html

I am using tony612/grpc-elixir as Elixir gRPC implementation and tony612/protobuf-elixir as pure Elixir implementation of Google Protobuf.

License

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.

brianbroderick/exdgraph