Removed tracking of raw SQL queries

This particular setup had 3 problems:

1. Storing SQL queries as tags is very inefficient as InfluxDB ends up
   indexing every query (and they can get pretty large). Storing these
   as values instead means we can't always display the SQL as easily.
2. We already instrument ActiveRecord query methods, thus we already
   have timing information about database queries.
3. SQL obfuscation is difficult to get right and I'd rather not expose
   sensitive data by accident.

config/initializers/metrics.rb

@@ -7,7 +7,6 @@ if Gitlab::Metrics.enabled?
   # 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'
 
   Gitlab::Application.configure do |config|
     config.middleware.use(Gitlab::Metrics::RackMiddleware)

lib/gitlab/metrics/obfuscated_sql.rb

-module Gitlab
-  module Metrics
-    # Class for producing SQL queries with sensitive data stripped out.
-    class ObfuscatedSQL
-      REPLACEMENT = /
-        \d+(\.\d+)?      # integers, floats
-        | '.+?'          # single quoted strings
-        | \/.+?(?<!\\)\/ # regexps (including escaped slashes)
-      /x
-
-      MYSQL_REPLACEMENTS = /
-        ".+?" # double quoted strings
-      /x
-
-      # Regex to replace consecutive placeholders with a single one indicating
-      # the length. This can be useful when a "IN" statement uses thousands of
-      # IDs (storing this would just be a waste of space).
-      CONSECUTIVE = /(\?(\s*,\s*)?){2,}/
-
-      # sql - The raw SQL query as a String.
-      def initialize(sql)
-        @sql = sql
-      end
-
-      # Returns a new, obfuscated SQL query.
-      def to_s
-        regex = REPLACEMENT
-
-        if Gitlab::Database.mysql?
-          regex = Regexp.union(regex, MYSQL_REPLACEMENTS)
-        end
-
-        sql = @sql.gsub(regex, '?').gsub(CONSECUTIVE) do |match|
-          "#{match.count(',') + 1} values"
-        end
-
-        # InfluxDB escapes double quotes upon output, so lets get rid of them
-        # whenever we can.
-        if Gitlab::Database.postgresql?
-          sql = sql.delete('"')
-        end
-
-        sql.tr("\n", ' ')
-      end
-    end
-  end
-end

lib/gitlab/metrics/subscribers/active_record.rb

-module Gitlab
-  module Metrics
-    module Subscribers
-      # Class for tracking raw SQL queries.
-      #
-      # Queries are obfuscated before being logged to ensure no private data is
-      # exposed via InfluxDB/Grafana.
-      class ActiveRecord < ActiveSupport::Subscriber
-        attach_to :active_record
-
-        SERIES = 'sql_queries'
-
-        def sql(event)
-          return unless current_transaction
-
-          values = values_for(event)
-          tags   = tags_for(event)
-
-          current_transaction.add_metric(SERIES, values, tags)
-        end
-
-        private
-
-        def values_for(event)
-          { duration: event.duration }
-        end
-
-        def tags_for(event)
-          sql  = ObfuscatedSQL.new(event.payload[:sql]).to_s
-          tags = { sql: sql }
-
-          file, line = Metrics.last_relative_application_frame
-
-          if file and line
-            tags[:file] = file
-            tags[:line] = line
-          end
-
-          tags
-        end
-
-        def current_transaction
-          Transaction.current
-        end
-      end
-    end
-  end
-end

spec/lib/gitlab/metrics/obfuscated_sql_spec.rb

-require 'spec_helper'
-
-describe Gitlab::Metrics::ObfuscatedSQL do
-  describe '#to_s' do
-    it 'replaces newlines with a space' do
-      sql = described_class.new("SELECT x\nFROM y")
-
-      expect(sql.to_s).to eq('SELECT x FROM y')
-    end
-
-    describe 'using single values' do
-      it 'replaces a single integer' do
-        sql = described_class.new('SELECT x FROM y WHERE a = 10')
-
-        expect(sql.to_s).to eq('SELECT x FROM y WHERE a = ?')
-      end
-
-      it 'replaces a single float' do
-        sql = described_class.new('SELECT x FROM y WHERE a = 10.5')
-
-        expect(sql.to_s).to eq('SELECT x FROM y WHERE a = ?')
-      end
-
-      it 'replaces a single quoted string' do
-        sql = described_class.new("SELECT x FROM y WHERE a = 'foo'")
-
-        expect(sql.to_s).to eq('SELECT x FROM y WHERE a = ?')
-      end
-
-      if Gitlab::Database.mysql?
-        it 'replaces a double quoted string' do
-          sql = described_class.new('SELECT x FROM y WHERE a = "foo"')
-
-          expect(sql.to_s).to eq('SELECT x FROM y WHERE a = ?')
-        end
-      end
-
-      it 'replaces a single regular expression' do
-        sql = described_class.new('SELECT x FROM y WHERE a = /foo/')
-
-        expect(sql.to_s).to eq('SELECT x FROM y WHERE a = ?')
-      end
-
-      it 'replaces regular expressions using escaped slashes' do
-        sql = described_class.new('SELECT x FROM y WHERE a = /foo\/bar/')
-
-        expect(sql.to_s).to eq('SELECT x FROM y WHERE a = ?')
-      end
-    end
-
-    describe 'using consecutive values' do
-      it 'replaces multiple integers' do
-        sql = described_class.new('SELECT x FROM y WHERE z IN (10, 20, 30)')
-
-        expect(sql.to_s).to eq('SELECT x FROM y WHERE z IN (3 values)')
-      end
-
-      it 'replaces multiple floats' do
-        sql = described_class.new('SELECT x FROM y WHERE z IN (1.5, 2.5, 3.5)')
-
-        expect(sql.to_s).to eq('SELECT x FROM y WHERE z IN (3 values)')
-      end
-
-      it 'replaces multiple single quoted strings' do
-        sql = described_class.new("SELECT x FROM y WHERE z IN ('foo', 'bar')")
-
-        expect(sql.to_s).to eq('SELECT x FROM y WHERE z IN (2 values)')
-      end
-
-      if Gitlab::Database.mysql?
-        it 'replaces multiple double quoted strings' do
-          sql = described_class.new('SELECT x FROM y WHERE z IN ("foo", "bar")')
-
-          expect(sql.to_s).to eq('SELECT x FROM y WHERE z IN (2 values)')
-        end
-      end
-
-      it 'replaces multiple regular expressions' do
-        sql = described_class.new('SELECT x FROM y WHERE z IN (/foo/, /bar/)')
-
-        expect(sql.to_s).to eq('SELECT x FROM y WHERE z IN (2 values)')
-      end
-    end
-
-    if Gitlab::Database.postgresql?
-      it 'replaces double quotes' do
-        sql = described_class.new('SELECT "x" FROM "y"')
-
-        expect(sql.to_s).to eq('SELECT x FROM y')
-      end
-    end
-  end
-end

spec/lib/gitlab/metrics/subscribers/active_record_spec.rb

-require 'spec_helper'
-
-describe Gitlab::Metrics::Subscribers::ActiveRecord do
-  let(:transaction) { Gitlab::Metrics::Transaction.new }
-
-  let(:subscriber) { described_class.new }
-
-  let(:event) do
-    double(:event, duration: 0.2,
-                   payload:  { sql: 'SELECT * FROM users WHERE id = 10' })
-  end
-
-  before do
-    allow(subscriber).to receive(:current_transaction).and_return(transaction)
-
-    allow(Gitlab::Metrics).to receive(:last_relative_application_frame).
-      and_return(['app/models/foo.rb', 4])
-  end
-
-  describe '#sql' do
-    it 'tracks the execution of a SQL query' do
-      sql    = 'SELECT * FROM users WHERE id = ?'
-      values = { duration: 0.2 }
-      tags   = { sql: sql, file: 'app/models/foo.rb', line: 4 }
-
-      expect(transaction).to receive(:add_metric).
-        with(described_class::SERIES, values, tags)
-
-      subscriber.sql(event)
-    end
-  end
-end