expose metrics as rest resource

apps/tanodb/src/tanodb_app.erl

@@ -29,7 +29,8 @@ stop(_State) ->
 
 routes() ->
     [
-     {"/ping", tanodb_http_ping, []}
+     {"/ping", tanodb_http_ping, []},
+     {"/metrics", tanodb_http_metrics, []}
     ].
 
 init_http() ->

apps/tanodb/src/tanodb_http_metrics.erl

@@ -0,0 +1,35 @@
+-module(tanodb_http_metrics).
+
+-export([init/3, terminate/3]).
+
+-ignore_xref([init/3, terminate/3]).
+
+-export([rest_init/2,
+         rest_terminate/2,
+         allowed_methods/2,
+         content_types_provided/2,
+         to_json/2]).
+
+-ignore_xref([rest_init/2,
+         rest_terminate/2,
+         allowed_methods/2,
+         content_types_provided/2,
+         to_json/2]).
+
+-record(state, {}).
+
+init(_, _Req, _Opts) -> {upgrade, protocol, cowboy_rest}.
+rest_init(Req, _Opts) -> {ok, Req, #state{}}.
+
+allowed_methods(Req, State) -> {[<<"GET">>], Req, State}.
+
+content_types_provided(Req, State) ->
+    {[{{<<"application">>, <<"json">>, '*'}, to_json}], Req, State}.
+
+to_json(Req, State) ->
+    Metrics = tanodb_metrics:all(),
+    Response = tanodb_json:encode(Metrics),
+    {Response, Req, State}.
+
+rest_terminate(_Req, _State) -> ok.
+terminate(_Reason, _Req, _State) -> ok.

apps/tanodb/src/tanodb_metrics.erl

@@ -3,7 +3,7 @@
 
 -export([core_ping/0]).
 
--define(ENDPOINTS, [<<"ping">>]).
+-define(ENDPOINTS, [<<"ping">>, <<"metrics">>]).
 -define(METRIC_CORE_PING, [tanodb, core, ping]).
 
 all() ->