Storing of application metrics in InfluxDB

This adds the ability to write application metrics (e.g. SQL timings) to
InfluxDB. These metrics can in turn be visualized using Grafana, or
really anything else that can read from InfluxDB. These metrics can be
used to track application performance over time, between different Ruby
versions, different GitLab versions, etc.

== Transaction Metrics

Currently the following is tracked on a per transaction basis (a
transaction is a Rails request or a single Sidekiq job):

* Timings per query along with the raw (obfuscated) SQL and information
  about what file the query originated from.
* Timings per view along with the path of the view and information about
  what file triggered the rendering process.
* The duration of a request itself along with the controller/worker
  class and method name.
* The duration of any instrumented method calls (more below).

== Sampled Metrics

Certain metrics can't be directly associated with a transaction. For
example, a process' total memory usage is unrelated to any running
transactions. While a transaction can result in the memory usage going
up there's no accurate way to determine what transaction is to blame,
this becomes especially problematic in multi-threaded environments.

To solve this problem there's a separate thread that takes samples at a
fixed interval. This thread (using the class Gitlab::Metrics::Sampler)
currently tracks the following:

* The process' total memory usage.
* The number of file descriptors opened by the process.
* The amount of Ruby objects (using ObjectSpace.count_objects).
* GC statistics such as timings, heap slots, etc.

The default/current interval is 15 seconds, any smaller interval might
put too much pressure on InfluxDB (especially when running dozens of
processes).

== Method Instrumentation

While currently not yet used methods can be instrumented to track how
long they take to run. Unlike the likes of New Relic this doesn't
require modifying the source code (e.g. including modules), it all
happens from the outside. For example, to track `User.by_login` we'd add
the following code somewhere in an initializer:

    Gitlab::Metrics::Instrumentation.
      instrument_method(User, :by_login)

to instead instrument an instance method:

    Gitlab::Metrics::Instrumentation.
      instrument_instance_method(User, :save)

Instrumentation for either all public model methods or a few crucial
ones will be added in the near future, I simply haven't gotten to doing
so just yet.

== Configuration

By default metrics are disabled. This means users don't have to bother
setting anything up if they don't want to. Metrics can be enabled by
editing one's gitlab.yml configuration file (see
config/gitlab.yml.example for example settings).

== Writing Data To InfluxDB

Because InfluxDB is still a fairly young product I expect the worse.
Data loss, unexpected reboots, the database not responding, you name it.
Because of this data is _not_ written to InfluxDB directly, instead it's
queued and processed by Sidekiq. This ensures that users won't notice
anything when InfluxDB is giving trouble.

The metrics worker can be started in a standalone manner as following:

    bundle exec sidekiq -q metrics

The corresponding class is called MetricsWorker.

Author: Yorick Peterse

Gemfile

@@ -208,6 +208,12 @@ gem 'select2-rails',      '~> 3.5.9'
 gem 'virtus',             '~> 1.0.1'
 gem 'net-ssh',            '~> 3.0.1'
 
+# Metrics
+group :metrics do
+  gem 'influxdb', '~> 0.2', require: false
+  gem 'connection_pool', '~> 2.0', require: false
+end
+
 group :development do
   gem "foreman"
   gem 'brakeman', '3.0.1', require: false

Gemfile.lock

@@ -65,7 +65,7 @@ GEM
     attr_encrypted (1.3.4)
       encryptor (>= 1.3.0)
     attr_required (1.0.0)
-    autoprefixer-rails (6.1.1)
+    autoprefixer-rails (6.1.2)
       execjs
       json
     awesome_print (1.2.0)
@@ -102,7 +102,7 @@ GEM
     bundler-audit (0.4.0)
       bundler (~> 1.2)
       thor (~> 0.18)
-    byebug (8.2.0)
+    byebug (8.2.1)
     cal-heatmap-rails (0.0.1)
     capybara (2.4.4)
       mime-types (>= 1.16)
@@ -117,6 +117,7 @@ GEM
       activemodel (>= 3.2.0)
       activesupport (>= 3.2.0)
       json (>= 1.7)
+    cause (0.1)
     charlock_holmes (0.7.3)
     chunky_png (1.3.5)
     cliver (0.3.2)
@@ -140,10 +141,10 @@ GEM
       term-ansicolor (~> 1.3)
       thor (~> 0.19.1)
       tins (~> 1.6.0)
-    crack (0.4.2)
+    crack (0.4.3)
       safe_yaml (~> 1.0.0)
     creole (0.5.0)
-    d3_rails (3.5.6)
+    d3_rails (3.5.11)
       railties (>= 3.1.0)
     daemons (1.2.3)
     database_cleaner (1.4.1)
@@ -230,7 +231,7 @@ GEM
       ipaddress (~> 0.5)
       nokogiri (~> 1.5, >= 1.5.11)
       opennebula
-    fog-brightbox (0.9.0)
+    fog-brightbox (0.10.1)
       fog-core (~> 1.22)
       fog-json
       inflecto (~> 0.0.2)
@@ -249,7 +250,7 @@ GEM
       fog-core (>= 1.21.0)
       fog-json
       fog-xml (>= 0.0.1)
-    fog-sakuracloud (1.4.0)
+    fog-sakuracloud (1.5.0)
       fog-core
       fog-json
     fog-softlayer (1.0.2)
@@ -277,11 +278,11 @@ GEM
       ruby-progressbar (~> 1.4)
     gemnasium-gitlab-service (0.2.6)
       rugged (~> 0.21)
-    gemojione (2.1.0)
+    gemojione (2.1.1)
       json
     get_process_mem (0.2.0)
     gherkin-ruby (0.3.2)
-    github-linguist (4.7.2)
+    github-linguist (4.7.3)
       charlock_holmes (~> 0.7.3)
       escape_utils (~> 1.1.0)
       mime-types (>= 1.19)
@@ -298,7 +299,7 @@ GEM
       posix-spawn (~> 0.3)
     gitlab_emoji (0.2.0)
       gemojione (~> 2.1)
-    gitlab_git (7.2.21)
+    gitlab_git (7.2.22)
       activesupport (~> 4.0)
       charlock_holmes (~> 0.7.3)
       github-linguist (~> 4.7.0)
@@ -370,6 +371,9 @@ GEM
     i18n (0.7.0)
     ice_nine (0.11.1)
     inflecto (0.0.2)
+    influxdb (0.2.3)
+      cause
+      json
     ipaddress (0.8.0)
     jquery-atwho-rails (1.3.2)
     jquery-rails (3.1.4)
@@ -416,11 +420,11 @@ GEM
     net-ldap (0.12.1)
     net-ssh (3.0.1)
     netrc (0.11.0)
-    newrelic-grape (2.0.0)
+    newrelic-grape (2.1.0)
       grape
       newrelic_rpm
     newrelic_rpm (3.9.4.245)
-    nokogiri (1.6.7)
+    nokogiri (1.6.7.1)
       mini_portile2 (~> 2.0.0.rc2)
     nprogress-rails (0.1.6.7)
     oauth (0.4.7)
@@ -783,7 +787,7 @@ GEM
       coercible (~> 1.0)
       descendants_tracker (~> 0.0, >= 0.0.3)
       equalizer (~> 0.0, >= 0.0.9)
-    warden (1.2.3)
+    warden (1.2.4)
       rack (>= 1.0)
     web-console (2.2.1)
       activemodel (>= 4.0)
@@ -836,6 +840,7 @@ DEPENDENCIES
   charlock_holmes (~> 0.7.3)
   coffee-rails (~> 4.1.0)
   colorize (~> 0.7.0)
+  connection_pool (~> 2.0)
   coveralls (~> 0.8.2)
   creole (~> 0.5.0)
   d3_rails (~> 3.5.5)
@@ -873,6 +878,7 @@ DEPENDENCIES
   hipchat (~> 1.5.0)
   html-pipeline (~> 1.11.0)
   httparty (~> 0.13.3)
+  influxdb (~> 0.2)
   jquery-atwho-rails (~> 1.3.2)
   jquery-rails (~> 3.1.3)
   jquery-scrollto-rails (~> 1.4.3)

Procfile

@@ -3,5 +3,5 @@
 # lib/support/init.d, which call scripts in bin/ .
 #
 web: bundle exec unicorn_rails -p ${PORT:="3000"} -E ${RAILS_ENV:="development"} -c ${UNICORN_CONFIG:="config/unicorn.rb"}
-worker: bundle exec sidekiq -q post_receive -q mailers -q archive_repo -q system_hook -q project_web_hook -q gitlab_shell -q incoming_email -q runner -q common -q default
+worker: bundle exec sidekiq -q post_receive -q mailers -q archive_repo -q system_hook -q project_web_hook -q gitlab_shell -q incoming_email -q runner -q common -q default -q metrics
 # mail_room: bundle exec mail_room -q -c config/mail_room.yml

app/workers/metrics_worker.rb

@@ -0,0 +1,29 @@
+class MetricsWorker
+  include Sidekiq::Worker
+
+  sidekiq_options queue: :metrics
+
+  def perform(metrics)
+    prepared = prepare_metrics(metrics)
+
+    Gitlab::Metrics.pool.with do |connection|
+      connection.write_points(prepared)
+    end
+  end
+
+  def prepare_metrics(metrics)
+    metrics.map do |hash|
+      new_hash = hash.symbolize_keys
+
+      new_hash[:tags].each do |key, value|
+        new_hash[:tags][key] = escape_value(value)
+      end
+
+      new_hash
+    end
+  end
+
+  def escape_value(value)
+    value.gsub('=', '\\=')
+  end
+end

config/gitlab.yml.example

@@ -421,9 +421,22 @@ production: &base
       #
       # Ban an IP for one hour (3600s) after too many auth attempts
       # bantime: 3600
+  metrics:
+    enabled: false
+    # The name of the InfluxDB database to store metrics in.
+    database: gitlab
+    # Credentials to use for logging in to InfluxDB.
+    # username:
+    # password:
+    # The amount of InfluxDB connections to open.
+    # pool_size: 16
+    # The timeout of a connection in seconds.
+    # timeout: 10
 
 development:
   <<: *base
+  metrics:
+    enabled: false
 
 test:
   <<: *base
@@ -466,6 +479,10 @@ test:
         user_filter: ''
         group_base: 'ou=groups,dc=example,dc=com'
         admin_group: ''
+  metrics:
+    enabled: false
 
 staging:
   <<: *base
+  metrics:
+    enabled: false

config/initializers/metrics.rb

@@ -0,0 +1,25 @@
+if Gitlab::Metrics.enabled?
+  require 'influxdb'
+  require 'socket'
+  require 'connection_pool'
+
+  # These are manually require'd so the classes are registered properly with
+  # ActiveSupport.
+  require 'gitlab/metrics/subscribers/action_view'
+  require 'gitlab/metrics/subscribers/active_record'
+  require 'gitlab/metrics/subscribers/method_call'
+
+  Gitlab::Application.configure do |config|
+    config.middleware.use(Gitlab::Metrics::RackMiddleware)
+  end
+
+  Sidekiq.configure_server do |config|
+    config.server_middleware do |chain|
+      chain.add Gitlab::Metrics::SidekiqMiddleware
+    end
+  end
+
+  GC::Profiler.enable
+
+  Gitlab::Metrics::Sampler.new.start
+end

lib/gitlab/metrics.rb

@@ -0,0 +1,52 @@
+module Gitlab
+  module Metrics
+    def self.pool_size
+      Settings.metrics['pool_size'] || 16
+    end
+
+    def self.timeout
+      Settings.metrics['timeout'] || 10
+    end
+
+    def self.enabled?
+      !!Settings.metrics['enabled']
+    end
+
+    def self.pool
+      @pool
+    end
+
+    def self.hostname
+      @hostname
+    end
+
+    def self.last_relative_application_frame
+      root    = Rails.root.to_s
+      metrics = Rails.root.join('lib', 'gitlab', 'metrics').to_s
+
+      frame = caller_locations.find do |l|
+        l.path.start_with?(root) && !l.path.start_with?(metrics)
+      end
+
+      if frame
+        return frame.path.gsub(/^#{Rails.root.to_s}\/?/, ''), frame.lineno
+      else
+        return nil, nil
+      end
+    end
+
+    @hostname = Socket.gethostname
+
+    # When enabled this should be set before being used as the usual pattern
+    # "@foo ||= bar" is _not_ thread-safe.
+    if enabled?
+      @pool = ConnectionPool.new(size: pool_size, timeout: timeout) do
+        db   = Settings.metrics['database']
+        user = Settings.metrics['username']
+        pw   = Settings.metrics['password']
+
+        InfluxDB::Client.new(db, username: user, password: pw)
+      end
+    end
+  end
+end

lib/gitlab/metrics/delta.rb

@@ -0,0 +1,32 @@
+module Gitlab
+  module Metrics
+    # Class for calculating the difference between two numeric values.
+    #
+    # Every call to `compared_with` updates the internal value. This makes it
+    # possible to use a single Delta instance to calculate the delta over time
+    # of an ever increasing number.
+    #
+    # Example usage:
+    #
+    #     delta = Delta.new(0)
+    #
+    #     delta.compared_with(10) # => 10
+    #     delta.compared_with(15) # => 5
+    #     delta.compared_with(20) # => 5
+    class Delta
+      def initialize(value = 0)
+        @value = value
+      end
+
+      # new_value - The value to compare with as a Numeric.
+      #
+      # Returns a new Numeric (depending on the type of `new_value`).
+      def compared_with(new_value)
+        delta  = new_value - @value
+        @value = new_value
+
+        delta
+      end
+    end
+  end
+end

lib/gitlab/metrics/instrumentation.rb

@@ -0,0 +1,47 @@
+module Gitlab
+  module Metrics
+    # Module for instrumenting methods.
+    #
+    # This module allows instrumenting of methods without having to actually
+    # alter the target code (e.g. by including modules).
+    #
+    # Example usage:
+    #
+    #     Gitlab::Metrics::Instrumentation.instrument_method(User, :by_login)
+    module Instrumentation
+      # Instruments a class method.
+      #
+      # mod  - The module to instrument as a Module/Class.
+      # name - The name of the method to instrument.
+      def self.instrument_method(mod, name)
+        instrument(:class, mod, name)
+      end
+
+      # Instruments an instance method.
+      #
+      # mod  - The module to instrument as a Module/Class.
+      # name - The name of the method to instrument.
+      def self.instrument_instance_method(mod, name)
+        instrument(:instance, mod, name)
+      end
+
+      def self.instrument(type, mod, name)
+        return unless Metrics.enabled?
+
+        alias_name = "_original_#{name}"
+        target     = type == :instance ? mod : mod.singleton_class
+
+        target.class_eval do
+          alias_method(alias_name, name)
+
+          define_method(name) do |*args, &block|
+            ActiveSupport::Notifications.
+              instrument("#{type}_method.method_call", module: mod, name: name) do
+                __send__(alias_name, *args, &block)
+              end
+          end
+        end
+      end
+    end
+  end
+end