Split '_other' into discourse/ember; init metrics to 0

app/controllers/deprecation_collector/collector_controller.rb

@@ -31,25 +31,13 @@ def log
         if !DeprecationCollector::List.include?(key)
           # We only collect data for a bound set of deprecation-ids so that clients
           # can't inflate our prometheus metrics by sending bogus data.
-          key = "_other"
+          key = key.start_with?("discourse") ? "_other_discourse" : "_other_ember"
         end
 
-        add_to_counter(key, 1)
+        DeprecationCollector.add_to_counter(key, 1)
       end
 
       render json: success_json
     end
-
-    private
-
-    def add_to_counter(name, value)
-      metric = DiscoursePrometheus::InternalMetric::Custom.new
-      metric.type = "Counter"
-      metric.labels = { db: RailsMultisite::ConnectionManagement.current_db, deprecation_id: name }
-      metric.name = "js_deprecation_count"
-      metric.description = "js deprecations reported by clients"
-      metric.value = value
-      $prometheus_client.send_json(metric.to_h)
-    end
   end
 end

plugin.rb

@@ -9,6 +9,21 @@
 
 module ::DeprecationCollector
   PLUGIN_NAME = "discourse-deprecation-collector"
+
+  def self.add_to_counter(name, value)
+    metric = DiscoursePrometheus::InternalMetric::Custom.new
+    metric.type = "Counter"
+    metric.labels = { db: RailsMultisite::ConnectionManagement.current_db, deprecation_id: name }
+    metric.name = "js_deprecation_count"
+    metric.description = "js deprecations reported by clients"
+    metric.value = value
+    $prometheus_client.send_json(metric.to_h)
+  end
 end
 
 require_relative "lib/deprecation_collector/engine"
+
+on(:web_fork_started) do
+  # initialize counters so that `rate()` works correctly in prometheus
+  DeprecationCollector::List.each { |key| DeprecationCollector.add_to_counter(key, 0) }
+end

spec/system/deprecation_collector_spec.rb

@@ -12,8 +12,7 @@
     test_deprecation_id = DeprecationCollector::List.first
 
     stub =
-      DeprecationCollector::CollectorController
-        .any_instance
+      DeprecationCollector
         .stubs(:add_to_counter)
         .with do |value|
           logged_deprecations << value
@@ -30,6 +29,8 @@
     # Refresh the page to trigger the collector
     page.refresh
 
-    try_until_success { expect(logged_deprecations).to include(test_deprecation_id, "_other") }
+    try_until_success do
+      expect(logged_deprecations).to include(test_deprecation_id, "_other_discourse")
+    end
   end
 end