Tracking of custom events

GitLab Performance Monitoring is now able to track custom events not
directly related to application performance. These events include the
number of tags pushed, repositories created, builds registered, etc.

The use of these events is to get a better overview of how a GitLab
instance is used and how that may affect performance. For example, a
large number of Git pushes may have a negative impact on the underlying
storage engine.

Events are stored in the "events" measurement and are not prefixed with
"rails_" or "sidekiq_", this makes it easier to query events with the
same name triggered from different parts of the application. All events
being stored in the same measurement also makes it easier to downsample
data.

Currently the following events are tracked:

* Creating repositories
* Removing repositories
* Changing the default branch of a repository
* Pushing a new tag
* Removing an existing tag
* Pushing a commit (along with the branch being pushed to)
* Pushing a new branch
* Removing an existing branch
* Importing a repository (along with the URL we're importing)
* Forking a repository (along with the source/target path)
* CI builds registered (and when no build could be found)
* CI builds being updated
* Rails and Sidekiq exceptions

Fixes gitlab-org/gitlab-ce#13720

4 files changed, 34 insertions, 4 deletions

diff --git a/lib/gitlab/metrics/metric.rb b/lib/gitlab/metrics/metric.rb
index f23d67e1e38..bd0afe53c51 100644
--- a/lib/gitlab/metrics/metric.rb
+++ b/lib/gitlab/metrics/metric.rb
@@ -4,15 +4,20 @@ module Gitlab
     class Metric
       JITTER_RANGE = 0.000001..0.001
 
-      attr_reader :series, :values, :tags
+      attr_reader :series, :values, :tags, :type
 
       # series - The name of the series (as a String) to store the metric in.
       # values - A Hash containing the values to store.
       # tags   - A Hash containing extra tags to add to the metrics.
-      def initialize(series, values, tags = {})
+      def initialize(series, values, tags = {}, type = :metric)
         @values = values
         @series = series
         @tags   = tags
+        @type   = type
+      end
+
+      def event?
+        type == :event
       end
 
       # Returns a Hash in a format that can be directly written to InfluxDB.
diff --git a/lib/gitlab/metrics/rack_middleware.rb b/lib/gitlab/metrics/rack_middleware.rb
index e61670f491c..b4493bf44d2 100644
--- a/lib/gitlab/metrics/rack_middleware.rb
+++ b/lib/gitlab/metrics/rack_middleware.rb
@@ -17,6 +17,10 @@ module Gitlab
         begin
           retval = trans.run { @app.call(env) }
 
+        rescue Exception => error # rubocop: disable Lint/RescueException
+          trans.add_event(:rails_exception)
+
+          raise error
         # Even in the event of an error we want to submit any metrics we
         # might've gathered up to this point.
         ensure
diff --git a/lib/gitlab/metrics/sidekiq_middleware.rb b/lib/gitlab/metrics/sidekiq_middleware.rb
index a1240fd33ee..f9dd8e41912 100644
--- a/lib/gitlab/metrics/sidekiq_middleware.rb
+++ b/lib/gitlab/metrics/sidekiq_middleware.rb
@@ -11,6 +11,10 @@ module Gitlab
           # Old gitlad-shell messages don't provide enqueued_at/created_at attributes
           trans.set(:sidekiq_queue_duration, Time.now.to_f - (message['enqueued_at'] || message['created_at'] || 0))
           trans.run { yield }
+        rescue Exception => error # rubocop: disable Lint/RescueException
+          trans.add_event(:sidekiq_exception)
+
+          raise error
         ensure
           trans.finish
         end
diff --git a/lib/gitlab/metrics/transaction.rb b/lib/gitlab/metrics/transaction.rb
index 968f3218950..7bc16181be6 100644
--- a/lib/gitlab/metrics/transaction.rb
+++ b/lib/gitlab/metrics/transaction.rb
@@ -4,7 +4,10 @@ module Gitlab
     class Transaction
       THREAD_KEY = :_gitlab_metrics_transaction
 
-      attr_reader :tags, :values, :methods
+      # The series to store events (e.g. Git pushes) in.
+      EVENT_SERIES = 'events'
+
+      attr_reader :tags, :values, :method, :metrics
 
       attr_accessor :action
 
@@ -55,6 +58,20 @@ module Gitlab
         @metrics << Metric.new("#{Metrics.series_prefix}#{series}", values, tags)
       end
 
+      # Tracks a business level event
+      #
+      # Business level events including events such as Git pushes, Emails being
+      # sent, etc.
+      #
+      # event_name - The name of the event (e.g. "git_push").
+      # tags - A set of tags to attach to the event.
+      def add_event(event_name, tags = {})
+        @metrics << Metric.new(EVENT_SERIES,
+                               { count: 1 },
+                               { event: event_name }.merge(tags),
+                               :event)
+      end
+
       # Returns a MethodCall object for the given name.
       def method_call_for(name)
         unless method = @methods[name]
@@ -101,7 +118,7 @@ module Gitlab
         submit_hashes = submit.map do |metric|
           hash = metric.to_hash
 
-          hash[:tags][:action] ||= @action if @action
+          hash[:tags][:action] ||= @action if @action && !metric.event?
 
           hash
         end