Remove the obsolete Gitlab::Tracing class

This has been replaced by Labkit::Tracing and is now contained in the
labkit gem.

lib/gitlab/tracing.rb

-# frozen_string_literal: true
-
-module Gitlab
-  module Tracing
-    # Only enable tracing when the `GITLAB_TRACING` env var is configured. Note that we avoid using ApplicationSettings since
-    # the same environment variable needs to be configured for Workhorse, Gitaly and any other components which
-    # emit tracing. Since other components may start before Rails, and may not have access to ApplicationSettings,
-    # an env var makes more sense.
-    def self.enabled?
-      connection_string.present?
-    end
-
-    def self.connection_string
-      ENV['GITLAB_TRACING']
-    end
-
-    def self.tracing_url_template
-      ENV['GITLAB_TRACING_URL']
-    end
-
-    def self.tracing_url_enabled?
-      enabled? && tracing_url_template.present?
-    end
-
-    # This will provide a link into the distributed tracing for the current trace,
-    # if it has been captured.
-    def self.tracing_url
-      return unless tracing_url_enabled?
-
-      # Avoid using `format` since it can throw TypeErrors
-      # which we want to avoid on unsanitised env var input
-      tracing_url_template.to_s
-        .gsub(/\{\{\s*correlation_id\s*\}\}/, Labkit::Correlation::CorrelationId.current_id.to_s)
-        .gsub(/\{\{\s*service\s*\}\}/, Gitlab.process_name)
-    end
-  end
-end

spec/lib/gitlab/tracing_spec.rb

-# frozen_string_literal: true
-
-require 'fast_spec_helper'
-require 'rspec-parameterized'
-
-describe Gitlab::Tracing do
-  using RSpec::Parameterized::TableSyntax
-
-  describe '.enabled?' do
-    where(:connection_string, :enabled_state) do
-      nil                     | false
-      ""                      | false
-      "opentracing://jaeger"  | true
-    end
-
-    with_them do
-      it 'returns the correct state for .enabled?' do
-        expect(described_class).to receive(:connection_string).and_return(connection_string)
-
-        expect(described_class.enabled?).to eq(enabled_state)
-      end
-    end
-  end
-
-  describe '.tracing_url_enabled?' do
-    where(:enabled?, :tracing_url_template, :tracing_url_enabled_state) do
-      false | nil                | false
-      false | ""                 | false
-      false | "http://localhost" | false
-      true  | nil                | false
-      true  | ""                 | false
-      true  | "http://localhost" | true
-    end
-
-    with_them do
-      it 'returns the correct state for .tracing_url_enabled?' do
-        expect(described_class).to receive(:enabled?).and_return(enabled?)
-        allow(described_class).to receive(:tracing_url_template).and_return(tracing_url_template)
-
-        expect(described_class.tracing_url_enabled?).to eq(tracing_url_enabled_state)
-      end
-    end
-  end
-
-  describe '.tracing_url' do
-    where(:tracing_url_enabled?, :tracing_url_template, :correlation_id, :process_name, :tracing_url) do
-      false | "https://localhost"                                              | "123" | "web" | nil
-      true  | "https://localhost"                                              | "123" | "web" | "https://localhost"
-      true  | "https://localhost?service={{ service }}"                        | "123" | "web" | "https://localhost?service=web"
-      true  | "https://localhost?c={{ correlation_id }}"                       | "123" | "web" | "https://localhost?c=123"
-      true  | "https://localhost?c={{ correlation_id }}&s={{ service }}"       | "123" | "web" | "https://localhost?c=123&s=web"
-      true  | "https://localhost?c={{ correlation_id }}"                       | nil   | "web" | "https://localhost?c="
-      true  | "https://localhost?c={{ correlation_id }}&s=%22{{ service }}%22" | "123" | "web" | "https://localhost?c=123&s=%22web%22"
-      true  | "https://localhost?c={{correlation_id}}&s={{service}}"           | "123" | "web" | "https://localhost?c=123&s=web"
-      true  | "https://localhost?c={{correlation_id }}&s={{ service}}"         | "123" | "web" | "https://localhost?c=123&s=web"
-    end
-
-    with_them do
-      it 'returns the correct state for .tracing_url' do
-        expect(described_class).to receive(:tracing_url_enabled?).and_return(tracing_url_enabled?)
-        allow(described_class).to receive(:tracing_url_template).and_return(tracing_url_template)
-        allow(Labkit::Correlation::CorrelationId).to receive(:current_id).and_return(correlation_id)
-        allow(Gitlab).to receive(:process_name).and_return(process_name)
-
-        expect(described_class.tracing_url).to eq(tracing_url)
-      end
-    end
-  end
-end