TD-178: Add Prometheus (#6)

Makefile

@@ -50,7 +50,6 @@ wc-shell: dev-image
 wc-%: dev-image
 	$(DOCKER_RUN) $(DEV_IMAGE_TAG) make $*
 
-#  TODO docker compose down doesn't work yet
 wdeps-shell: dev-image
 	$(DOCKERCOMPOSE_RUN) $(TEST_CONTAINER_NAME) su; \
 	$(DOCKERCOMPOSE_W_ENV) down

config/sys.config

@@ -203,5 +203,9 @@
         % 1 second
         {max_backward_clock_moving, 1000}
         % {machine_id, hostname_hash}
+    ]},
+
+    {prometheus, [
+        {collectors, [default]}
     ]}
 ].

rebar.config

@@ -81,6 +81,12 @@
 {profiles, [
     {prod, [
         {deps, [
+            %% NOTE
+            %% Because of a dependency conflict, prometheus libs are only included in production build for now
+            %% https://github.com/project-fifo/rebar3_lint/issues/42
+            %% https://github.com/valitydev/hellgate/pull/2/commits/884724c1799703cee4d1033850fe32c17f986d9e
+            {prometheus, "4.8.1"},
+            {prometheus_cowboy, "0.1.8"},
             % Introspect a node running in production
             {recon, "2.5.2"},
             {logger_logstash_formatter,
@@ -99,6 +105,8 @@
                 {tools, load},
                 % logger formatter
                 {logger_logstash_formatter, load},
+                prometheus,
+                prometheus_cowboy,
                 token_keeper
             ]},
             {sys_config, "./config/sys.config"},

src/token_keeper.erl

@@ -43,6 +43,10 @@ init([]) ->
     TokenBlacklistSpec = tk_blacklist:child_spec(genlib_app:env(?MODULE, blacklist, #{})),
     TokensSpecs = tk_token:child_specs(genlib_app:env(?MODULE, tokens, #{})),
     StoragesSpecs = tk_storage:child_specs(genlib_app:env(?MODULE, storages, #{})),
+    AdditionalRoutes = [
+        get_prometheus_route(),
+        get_health_route()
+    ],
     HandlerChildSpec = woody_server:child_spec(
         ?MODULE,
         #{
@@ -53,7 +57,7 @@ init([]) ->
             shutdown_timeout => get_shutdown_timeout(),
             event_handler => EventHandlers,
             handlers => get_woody_handlers(AuditPulse),
-            additional_routes => [get_health_route() | get_machinegun_processor_routes(EventHandlers)]
+            additional_routes => AdditionalRoutes ++ get_machinegun_processor_routes(EventHandlers)
         }
     ),
     {ok, {
@@ -147,3 +151,7 @@ get_audit_specs() ->
         disable ->
             {[], []}
     end.
+
+-spec get_prometheus_route() -> {iodata(), module(), _Opts :: any()}.
+get_prometheus_route() ->
+    {"/metrics/[:registry]", prometheus_cowboy2_handler, []}.