Add a REST example that streams its response

examples/rest_stream_response/src/rest_stream_response.app.src

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+%% Feel free to use, reuse and abuse the code in this file.
+
+{application, rest_stream_response, [
+	{description, "Cowboy REST with streaming."},
+	{vsn, "1"},
+	{modules, []},
+	{registered, []},
+	{applications, [
+		kernel,
+		stdlib,
+		cowboy
+	]},
+	{mod, {rest_stream_response_app, []}},
+	{env, []}
+]}.

examples/rest_stream_response/src/rest_stream_response.erl

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+%% Feel free to use, reuse and abuse the code in this file.
+
+-module(rest_stream_response).
+
+%% API.
+-export([start/0]).
+
+%% API.
+
+start() ->
+	ok = application:start(crypto),
+	ok = application:start(ranch),
+	ok = application:start(cowboy),
+	ok = application:start(rest_stream_response).

examples/rest_stream_response/src/rest_stream_response_app.erl

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+%% Feel free to use, reuse and abuse the code in this file.
+
+%% @private
+-module(rest_stream_response_app).
+-behaviour(application).
+
+%% API.
+-export([start/2]).
+-export([stop/1]).
+
+%% API.
+
+start(_Type, _Args) ->
+	Table = ets:new(stream_tab, []),
+	generate_rows(Table, 1000),
+	Dispatch = cowboy_router:compile([
+		{'_', [
+			{"/[:v1]", [{v1, int}], toppage_handler, Table}
+		]}
+	]),
+	{ok, _} = cowboy:start_http(http, 100, [{port, 8080}], [
+		{env, [{dispatch, Dispatch}]}
+	]),
+	rest_stream_response_sup:start_link().
+
+stop(_State) ->
+	ok.
+
+generate_rows(_Table, 0) -> ok;
+generate_rows(Table, N) ->
+	ets:insert(Table, {key(), val(), val()}),
+	generate_rows(Table, N - 1).
+
+key() -> key(10).
+key(N) -> key(<< (random:uniform(26) - 1) >>, N - 1).
+key(Acc, 0) -> binary_part(base64:encode(Acc), 0, 8);
+key(Acc, N) -> key(<< Acc/binary, (random:uniform(26) - 1) >>, N - 1).
+val() -> random:uniform(50).

examples/rest_stream_response/src/rest_stream_response_sup.erl

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+%% Feel free to use, reuse and abuse the code in this file.
+
+%% @private
+-module(rest_stream_response_sup).
+-behaviour(supervisor).
+
+%% API.
+-export([start_link/0]).
+
+%% supervisor.
+-export([init/1]).
+
+%% API.
+
+-spec start_link() -> {ok, pid()}.
+start_link() ->
+	supervisor:start_link({local, ?MODULE}, ?MODULE, []).
+
+%% supervisor.
+
+init([]) ->
+	Procs = [],
+	{ok, {{one_for_one, 10, 10}, Procs}}.

examples/rest_stream_response/src/toppage_handler.erl

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+%% Feel free to use, reuse and abuse the code in this file.
+
+%% @doc Streaming handler.
+-module(toppage_handler).
+
+-export([init/3]).
+-export([rest_init/2]).
+-export([content_types_provided/2]).
+-export([streaming_csv/2]).
+
+init(_Transport, _Req, _Table) ->
+	{upgrade, protocol, cowboy_rest}.
+
+rest_init(Req, Table) ->
+	{ok, Req, Table}.
+
+content_types_provided(Req, State) ->
+	{[
+		{{<<"text">>, <<"csv">>, []}, streaming_csv}
+	], Req, State}.
+
+streaming_csv(Req, Table) ->
+	{N, Req1} = cowboy_req:binding(v1, Req, 1),
+	MS = [{{'$1', '$2', '$3'}, [{'==', '$2', N}], ['$$']}],
+
+	{{stream, result_streamer(Table, MS)}, Req1, Table}.
+
+result_streamer(Table, MS) ->
+	fun (Socket, Transport) ->
+			send_records(Socket, Transport, ets:select(Table, MS, 1))
+	end.
+
+send_records(Socket, Transport, {[Rec], Cont}) ->
+	timer:sleep(500),
+	send_line(Socket, Transport, Rec),
+	send_records(Socket, Transport, ets:select(Cont));
+send_records(_Socket, _Transport, '$end_of_table') ->
+	ok.
+
+send_line(Socket, Transport, [Key, V1, V2]) ->
+	Transport:send(Socket,
+		[Key, $,, integer_to_list(V1), $,, integer_to_list(V2), $\r, $\n]).