Count wiki page creation

This adds a counter to count page creation, which is reflected in the
usage-data we collect.

The number created is stored in Redis, avoiding DB access.

3 files changed, 51 insertions, 6 deletions

diff --git a/lib/gitlab/usage_data.rb b/lib/gitlab/usage_data.rb
index 43072053e57..db1086c9cae 100644
--- a/lib/gitlab/usage_data.rb
+++ b/lib/gitlab/usage_data.rb
@@ -6,7 +6,9 @@ module Gitlab
 
     class << self
       def data(force_refresh: false)
-        Rails.cache.fetch('usage_data', force: force_refresh, expires_in: 2.weeks) { uncached_data }
+        Rails.cache.fetch('usage_data', force: force_refresh, expires_in: 2.weeks) do
+          uncached_data
+        end
       end
 
       def uncached_data
@@ -128,12 +130,15 @@ module Gitlab
         }
       end
 
+      # @return [Hash<Symbol, Integer>]
       def usage_counters
-        {
-          web_ide_commits: Gitlab::UsageDataCounters::WebIdeCounter.total_commits_count,
-          web_ide_merge_requests: Gitlab::UsageDataCounters::WebIdeCounter.total_merge_requests_count,
-          web_ide_views: Gitlab::UsageDataCounters::WebIdeCounter.total_views_count
-        }
+        usage_data_counters.map(&:totals).reduce({}) { |a, b| a.merge(b) }
+      end
+
+      # @return [Array<#totals>] An array of objects that respond to `#totals`
+      def usage_data_counters
+        [Gitlab::UsageDataCounters::WikiPageCounter,
+         Gitlab::UsageDataCounters::WebIdeCounter]
       end
 
       def components_usage_data
diff --git a/lib/gitlab/usage_data_counters/web_ide_counter.rb b/lib/gitlab/usage_data_counters/web_ide_counter.rb
index 899ad0db9c0..0718c1dd761 100644
--- a/lib/gitlab/usage_data_counters/web_ide_counter.rb
+++ b/lib/gitlab/usage_data_counters/web_ide_counter.rb
@@ -33,6 +33,14 @@ module Gitlab
         def total_views_count
           total_count(VIEWS_COUNT_KEY)
         end
+
+        def totals
+          {
+            web_ide_commits: total_commits_count,
+            web_ide_views: total_views_count,
+            web_ide_merge_requests: total_merge_requests_count
+          }
+        end
       end
     end
   end
diff --git a/lib/gitlab/usage_data_counters/wiki_page_counter.rb b/lib/gitlab/usage_data_counters/wiki_page_counter.rb
new file mode 100644
index 00000000000..c8b59a3160c
--- /dev/null
+++ b/lib/gitlab/usage_data_counters/wiki_page_counter.rb
@@ -0,0 +1,32 @@
+# frozen_string_literal: true
+
+module Gitlab::UsageDataCounters
+  class WikiPageCounter
+    extend RedisCounter
+
+    KNOWN_EVENTS = %w[create update delete].map(&:freeze).freeze
+
+    UnknownEvent = Class.new(StandardError)
+
+    class << self
+      # Each event gets a unique Redis key
+      def redis_key(event)
+        raise UnknownEvent, event unless KNOWN_EVENTS.include?(event.to_s)
+
+        "USAGE_WIKI_PAGES_#{event}".upcase
+      end
+
+      def count(event)
+        increment(redis_key event)
+      end
+
+      def read(event)
+        total_count(redis_key event)
+      end
+
+      def totals
+        KNOWN_EVENTS.map { |e| ["wiki_pages_#{e}".to_sym, read(e)] }.to_h
+      end
+    end
+  end
+end