ExDgraph v0.2.0-alpha.3 ExDgraph View Source

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).

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

The available configuration options are:

config :ex_dgraph, ExDgraph,
  hostname: 'localhost',
  port: 9080,
  pool_size: 5,
  max_overflow: 1
  timeout: 15_000,
  pool: DBConnection.Poolboy,
  ssl: false,
  tls_client_auth: false,
  certfile: nil,
  keyfile: nil,
  cacertfile: nil,
  retry_linear_backoff: {delay: 150, factor: 2, tries: 3}

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, "~> 0.1.0", github: "ospaarmann/exdgraph", branch: "master"}
  ]
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.

Link to this section Summary

Functions

Returns a specification to start this module under a supervisor

Returns an environment specific ExDgraph configuration

Returns a pool name which can be used to acquire a connection

Sends the mutation to the server and returns {:ok, result} or {:error, error} otherwise

The same as mutation/2 but raises an ExDgraph.Exception if it fails. Returns the server response otherwise

Sends the operations to the server and returns {:ok, result} or {:error, error} otherwise

The same as operation/2 but raises an ExDgraph.Exception if it fails. Returns the server response otherwise

Sends the query to the server and returns {:ok, result} or {:error, error} otherwise

The same as query/2 but raises a ExDgraph.Exception if it fails. Returns the server response otherwise

Allow you to pass a map to insert into the database. The function sends the mutation to the server and returns {:ok, result} or {:error, error} otherwise. Internally it uses Dgraphs set_json. The result is a map of all values you have passed in but with the field uid populated from the database

The same as set_map/2 but raises an ExDgraph.Exception if it fails. Returns the server response otherwise

Start the connection process and connect to Dgraph

Link to this section Types

Link to this section Functions

Returns a specification to start this module under a supervisor.

See Supervisor.

Returns an environment specific ExDgraph configuration.

Returns a pool name which can be used to acquire a connection.

Link to this function mutation(conn, statement) View Source
mutation(conn(), String.t()) ::
  {:ok, ExDgraph.Response} | {:error, ExDgraph.Error}

Sends the mutation to the server and returns {:ok, result} or {:error, error} otherwise

Examples

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" .
"""
iex> ExDgraph.mutation(conn, starwars_creation_mutation)
%{:ok,
  %{
    context: %ExDgraph.Api.TxnContext{
      aborted: false,
      commit_ts: 60012,
      keys: [],
      lin_read: %ExDgraph.Api.LinRead{ids: %{1 => 6406}},
      start_ts: 60011
    },
    uids: %{
      "han" => "0xea7e",
      "irvin" => "0xea79",
      "leia" => "0xea7d",
      "lucas" => "0xea78",
      "luke" => "0xea77",
      "richard" => "0xea7a",
      "st1" => "0xea76",
      "sw1" => "0xea7b",
      "sw2" => "0xea7c",
      "sw3" => "0xea75"
    }
  }
}
Link to this function mutation!(conn, statement) View Source
mutation!(conn(), String.t()) :: ExDgraph.Response | ExDgraph.Exception

The same as mutation/2 but raises an ExDgraph.Exception if it fails. Returns the server response otherwise.

Link to this function operation(conn, statement) View Source
operation(conn(), String.t()) ::
  {:ok, ExDgraph.Response} | {:error, ExDgraph.Error}

Sends the operations to the server and returns {:ok, result} or {:error, error} otherwise

Examples

Create schema

schema = """
  id: string @index(exact).
  name: string @index(exact, term) @count .
  age: int @index(int) .
  friend: uid @count .
  dob: dateTime .
"""
iex> ExDgraph.operation(conn, %{schema: schema})
%{:ok, %ExDgraph.Api.Payload{Data: ""}}

Drop all entries from the database

iex> ExDgraph.operation(conn, %{drop_all: true})
%{:ok, %ExDgraph.Api.Payload{Data: ""}}
Link to this function operation!(conn, statement) View Source
operation!(conn(), String.t()) :: ExDgraph.Response | ExDgraph.Exception

The same as operation/2 but raises an ExDgraph.Exception if it fails. Returns the server response otherwise.

Link to this function query(conn, statement) View Source
query(conn(), String.t()) :: {:ok, ExDgraph.Response} | {:error, ExDgraph.Error}

Sends the query to the server and returns {:ok, result} or {:error, error} otherwise.

Parameters

  • conn: The pool name from ExDgraph.conn().
  • statement: A GraphQL+ query statement as a string.

Examples

query_statement = """
  {
     starwars(func: anyofterms(name, "VI"))
     {
       uid
       name
       release_date
       starring
       {
         name
       }
     }
   }
"""
iex> ExDgraph.query(conn, query_statement)
%{:ok,
  %{
    result: %{
      starwars: [
        %{
          name: "Star Wars: Episode VI - Return of the Jedi",
          release_date: "1983-05-25",
          starring: [
            %{name: "Princess Leia"},
            %{name: "Luke Skywalker"},
            %{name: "Han Solo"}
          ],
          uid: "0xcdce"
        }
      ]
    },
    schema: [],
    txn: %ExDgraph.Api.TxnContext{
      aborted: false,
      commit_ts: 0,
      keys: [],
      lin_read: %ExDgraph.Api.LinRead{ids: %{1 => 5696}},
      start_ts: 51357
    }
  }
}

iex> ExDgraph.query(conn, invalid_statement)
{:error, [code: 2, message: "while lexing invalid_statement: Invalid operation type: invalid_statement"]}
Link to this function query!(conn, statement) View Source
query!(conn(), String.t()) :: ExDgraph.Response | ExDgraph.Exception

The same as query/2 but raises a ExDgraph.Exception if it fails. Returns the server response otherwise.

Link to this function set_map(conn, map) View Source
set_map(conn(), Map.t()) :: {:ok, ExDgraph.Response} | {:error, ExDgraph.Error}

Allow you to pass a map to insert into the database. The function sends the mutation to the server and returns {:ok, result} or {:error, error} otherwise. Internally it uses Dgraphs set_json. The result is a map of all values you have passed in but with the field uid populated from the database.

Examples

map = %{
   name: "Alice",
   friends: %{
     name: "Betty"
   }
 }
iex> ExDgraph.set_map(conn, map)
%{:ok,
  %{
    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"
    }
  }
}
Link to this function set_map!(conn, map) View Source
set_map!(conn(), Map.t()) :: {:ok, ExDgraph.Response} | {:error, ExDgraph.Error}

The same as set_map/2 but raises an ExDgraph.Exception if it fails. Returns the server response otherwise.

Start the connection process and connect to Dgraph

Options:

  • :hostname - Server hostname (default: DGRAPH_HOST env variable, then localhost);
  • :port - Server port (default: DGRAPH_PORT env variable, then 9080);
  • :username - Username;
  • :password - User password;
  • :pool_size - maximum pool size;
  • :max_overflow - maximum number of workers created if pool is empty
  • :timeout - Connect timeout in milliseconds (default: 15000) Poolboy will block the current process and wait for an available worker, failing after a timeout, when the pool is full;
  • :pool - The connection pool. Defaults to DbConnection.Poolboy.
  • :ssl - If to use ssl for the connection (please see configuration example). If you set this option, you also have to set cacertfile to the correct path.
  • :tls_client_auth - If to use TLS client authentication for the connection (please see configuration example). If you set this option, you also have to set certfile, keyfile and cacertfile to the correct path.
  • :certfile - Path to your client certificate.
  • :keyfile - Path to your client key.
  • :cacertfile - Path to your CA certificate you used to sign the certificate and key. Check the Wiki on how to set this up.
  • :retry_linear_backoff - Retry options. Defaults to {delay: 150, factor: 2, tries: 3}

Example of valid configurations (i.e. defined in config/dev.exs) and usage:

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

With SSL

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'

With TLS client authentication

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',

Example

iex> opts = Application.get_env(:ex_dgraph, ExDgraph)
{:ok, pid} = ExDgraph.start_link(opts)