Gossiperl Erlang client library
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README.md

Erlang gossiperl client

This is an Erlang gossiperl client library.

Installation

Add this to rebar.config file:

{gossiperl_client, ".*",
  {git, "https://github.com/gossiperl/gossiperl-client-erlang.git", "master"}},

Run rebar get-deps, the application should be installed.

Running

application:start(asn1)
application:start(crypto),
application:start(public_key),
application:start(jsx),
application:start(erlsha2),
application:start(thrift),
application:start(quickrand),
application:start(uuid),
application:start(lager),
lager:start(),
application:start(gossiperl_client).

Connecting to an overlay

To connect a client to an overlay:

gossiperl_client_sup:connect( [
          { overlay_name, <<"overlay-name">> },
          { overlay_port, OverlayPort },
          { client_name, <<"client-name">> },
          { client_port, ClientPort },
          { client_secret, <<"client-secret">> },
          { symmetric_key, <<"symmetric-key">> },
          { listener, ModuleName } ] ).

Listener is a module implementing a gossiperl_client_listener behaviour. This behaviour can be found in gossiperl-core-erlang. Listener setting is optional. If not given, a default implementation will be used.

A client may be connected to multiple overlays.

Subscribing / unsubscribing

Subscribing:

gossiperl_client_sup:subscribe( <<"overlay-name">>,
                                [ event, event ] ).

Unsubscribing:

gossiperl_client_sup:unsubscribe( <<"overlay-name">>,
                                  [ event, event ] ).

Disconnecting from an overlay

gossiperl_client_sup:disconnect( <<"overlay-name">> ).

This will attempt a graceful exit from an overlay.

Additional operations

Checking current client state

gossiperl_client_sup:check_state( <<"overlay-name">> ).

Getting the list of current subscriptions

gossiperl_client_sup:subscriptions( <<"overlay-name">> ).

Receiving notifications

To receive notifications a connection with the ListenerPid needs to be started. An example is provided with unit tests, in test/test_listener.erl file.

Sending arbitrary digests

gossiperl_client_sup:send( <<"overlay-name">>, DigestType, DigestData ).

where

  • DigestType is a digest type atom, other than one of the internally recognised digest types
  • DigestData is a structure describing Thrift packet, values, types and positions

Thrift packet structures

An example of a structure describing a simple packet with 2 properties:

  • some_data of type string

  • some_port_number of type integer

    DigestData = [ { some_data, <<"some data to send">>, string, 1 }, { some_port_number, 1234, i32, 2 } ].

Each item of the list maps to: { field_name, value_to_send, data_type, order }. Supported Thrift types:

  • bool
  • byte
  • double
  • i16
  • i32
  • i64
  • string

Reading custom digests

Once a forwarded message is recieved, it can be read in the following manner (assuming the message presented in the above DigestData):

gossiperl_client_sup:read( DigestType, BinaryEnvelope, DigestInfo ).

Where:

  • DigestType is an atom representing expected digest type

  • BinaryEnvelope and envelope received as forwarded message

  • DigestInfo is a Thrift data structure, example below

    DigestInfo = [ { 1, string }, { 2, i32 } ].

Running tests

rebar clean get-deps compile && rebar eunit skip_deps=true

Tests assume an overlay with the details specified in the test/gossiperl_client_test.erl running.

License

The MIT License (MIT)

Copyright (c) 2014 Radoslaw Gruchalski radek@gruchalski.com

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.