Make dnssd optional dependency

doc/logging.md

@@ -218,6 +218,13 @@
 * ___Explanation___: Problems in hello application initialization.
 * ___Level___: info
 
+#### 4001
+
+* ___Messages___:
+  * [cde9a95372554e5fa65c76a9c62bf9d1] Application dnssd is not started.
+* ___Explanation___: Problems during starting dnssd
+* ___Level___: error
+
 #### 4102
 
 * ___Messages___:

include/hello_log_ids.hrl

@@ -88,3 +88,6 @@
 -define(LOGID61, {ab65930009164e7fb6419b615b4ae4b5, 4102}).
 -define(LOGID62, {bd81f08a8fc94502bcbd07975e952016, 4310}).
 -define(LOGID63, {c796ed5e01f0455fb09c42e0f04198c1, 4310}).
+
+%MESSAGE Ids and SATUS CODEs for optional starting dnssd 
+-define(LOGID64, {cde9a95372554e5fa65c76a9c62bf9d1, 4001}).

mix.exs

@@ -11,8 +11,9 @@ defmodule Hello.Mixfile do
   end
 
   def application do
-    [applications: [:lager, :exometer_core, :cowboy, :ex_uri, :ezmq, :dnssd, :hackney, :jsx],
-     env: [{:metrics, [:packets, :request, :response, :service, :handler, :binding, :listener, :client]},
+    [applications: [:lager, :exometer_core, :cowboy, :ex_uri, :ezmq, :hackney, :jsx],
+     env: [{:dnssd, false},
+           {:metrics, [:packets, :request, :response, :service, :handler, :binding, :listener, :client]},
            {:default_protocol, :hello_proto_jsonrpc},
            {:transports, []},
            {:server_timeout, 10000},
@@ -29,7 +30,7 @@ defmodule Hello.Mixfile do
      {:ezmq,          github: "RoadRunnr/ezmq", branch: "fix-socket-crash"},
      {:jsx,           "~> 2.6.2"},
      {:msgpack,       github: "msgpack/msgpack-erlang", branch: "master"},
-     {:dnssd,         github: "benoitc/dnssd_erlang", branch: "master"},
+     {:dnssd,         github: "benoitc/dnssd_erlang", branch: "master", optional: true},
      {:meck,          "~> 0.8.2", override: true},
      {:exometer_core, github: "Feuerlabs/exometer_core", branch: "master"},
      {:edown,         github: "uwiger/edown", branch: "master", override: true}]

src/hello.app.src

@@ -1,12 +1,13 @@
 % vim: filetype=erlang
 {application, hello,
   [{description, "JSON-RPC API toolkit"},
-   {applications, [kernel, stdlib, lager, exometer_core, cowboy, ex_uri, ezmq, dnssd, hackney, jsx]},
+   {applications, [kernel, stdlib, lager, exometer_core, cowboy, ex_uri, ezmq, hackney, jsx]},
    {registered, [hello_supervisor, hello_stateless_zmq_supervisor]},
    {vsn, git},
    {mod, {hello, []}},
    {env, [
        %% metrics is list of packets | request | response | service | handler | binding | listener | client
+       {dnssd, false},
        {metrics, [packets, request, response, service, handler, binding, listener, client]},
        {default_protocol, hello_proto_jsonrpc},
        {transports, []},

src/hello.erl

@@ -30,6 +30,7 @@
 -export([bind_handler/3, bind/2, bind/3, bind/7, unbind/2]).
 
 -include("hello.hrl").
+-include("hello_log.hrl").
 -include_lib("ex_uri/include/ex_uri.hrl").
 
 -type decoded_url() :: #ex_uri{}.
@@ -50,6 +51,7 @@ start() ->
 
 % @doc Callback for application behaviour.
 start(_Type, _StartArgs) ->
+    ok = start_dnssd(),
     {ok, Supervisor} = hello_supervisor:start_link(),
     {ok, Metrics} = application:get_env(hello, metrics),
     hello_metrics:start_subscriptions(Metrics),
@@ -175,3 +177,16 @@ on_ex_uri(URL, Fun) ->
         Other ->
             error(badarg, [URL, Other])
     end.
+
+start_dnssd() ->
+    Reason = case application:get_env(hello, dnssd) of
+        {ok, true} ->
+            case application:ensure_all_started(dnssd) of
+                {ok, _} -> ok;
+                Error -> Error
+            end;
+        _ -> ok
+    end,
+    Reason /= ok andalso ?LOG_ERROR("Application dnssd is not started.", [], 
+                                    [{hello_dnssd_starting_reason, Reason}], ?LOGID64),
+    Reason.

src/hello_lib.erl

@@ -1,5 +1,5 @@
 -module(hello_lib).
--export([get_in/2, to_binary/1, wrap/1, get/2, get/3]).
+-export([get_in/2, to_binary/1, wrap/1, get/2, get/3, is_dnssd_started/0]).
 
 get_in(Map, Path) when is_list(Path) == false -> get_in(Map, Path);
 get_in(Value, []) -> Value;
@@ -23,3 +23,6 @@ to_binary(Term) -> unicode:characters_to_binary(io_lib:format("~p", [Term])).
 
 wrap(Requests) when is_list(Requests) -> Requests;
 wrap(Request) -> [Request].
+
+is_dnssd_started() ->
+    lists:member(dnssd, [App || {App, _, _} <- application:which_applications()]).

src/hello_registry.erl

@@ -185,10 +185,16 @@ do_dnss_register(App, Name, Port) ->
         _ -> ok
     end.
 
-dnss_register(App, Name, Port)
-  when is_list(App), is_list(Name), is_integer(Port) ->
-    do_dnss_register(list_to_binary(App), list_to_binary(Name), Port);
+dnss_register(App, Name, Port) when is_list(App), is_list(Name), is_integer(Port) ->
+    case hello_lib:is_dnssd_started() of
+        true -> do_dnss_register(list_to_binary(App), list_to_binary(Name), Port);
+        false -> ok
+    end;
 dnss_register(_, _, _) -> ok.
 
-dnssd_clean(Ref) when is_reference(Ref) -> dnssd:stop(Ref);
+dnssd_clean(Ref) when is_reference(Ref) -> 
+    case hello_lib:is_dnssd_started() of
+        true -> dnssd:stop(Ref);
+        false -> ok
+    end;
 dnssd_clean(_) -> ok.

src/transports/hello_http_client.erl

@@ -147,9 +147,12 @@ validate_options([_ | R], Opts) ->
 validate_options([], Opts) ->
     {ok, Opts}.
 
-http_connect_url(#ex_uri{authority = #ex_uri_authority{host = Host}, path = [$/|Path]}) ->
-    dnssd:resolve(list_to_binary(Path), <<"_", (list_to_binary(Host))/binary, "._tcp.">>, <<"local.">>),
-    ok;
+http_connect_url(#ex_uri{authority = #ex_uri_authority{host = Host}, path = [$/|Path]} = URI) ->
+    case hello_lib:is_dnssd_started() of
+        true ->
+            dnssd:resolve(list_to_binary(Path), <<"_", (list_to_binary(Host))/binary, "._tcp.">>, <<"local.">>);
+        false -> URI
+    end;
 http_connect_url(URI) ->
     URI.
 

src/transports/hello_zmq_client.erl

@@ -79,8 +79,12 @@ zmq_protocol(#ex_uri{scheme = "zmq-tcp6"}) -> inet6.
 %% use dnssd to resolve port AND host
 %% map host to Type and Path to Name
 ezmq_connect_url(_Socket, #ex_uri{authority = #ex_uri_authority{host = Host, port = undefined}, path = [$/|Path]}) ->
-    dnssd:resolve(list_to_binary(Path), <<"_", (list_to_binary(Host))/binary, "._tcp.">>, <<"local.">>),
-    ok;
+    case hello_lib:is_dnssd_started() of
+        true ->
+            dnssd:resolve(list_to_binary(Path), <<"_", (list_to_binary(Host))/binary, "._tcp.">>, <<"local.">>),
+            ok;
+        false -> {error, port_undefined}
+    end;
 
 ezmq_connect_url(Socket, URI = #ex_uri{authority = #ex_uri_authority{host = Host, port = Port}}) ->
     Protocol = zmq_protocol(URI),