Merge branch 'migration-downtime-tags' into 'master'

Added checks for migration downtime

This adds a set of checks that check/list which migrations require downtime (or not). It also comes with a CI task that fails should a migration not be tagged properly.

Fixes #14545

See merge request !4911

4 files changed, 140 insertions, 0 deletions

diff --git a/lib/gitlab/downtime_check.rb b/lib/gitlab/downtime_check.rb
new file mode 100644
index 00000000000..ab9537ed7d7
--- /dev/null
+++ b/lib/gitlab/downtime_check.rb
@@ -0,0 +1,71 @@
+module Gitlab
+  # Checks if a set of migrations requires downtime or not.
+  class DowntimeCheck
+    # The constant containing the boolean that indicates if downtime is needed
+    # or not.
+    DOWNTIME_CONST = :DOWNTIME
+
+    # The constant that specifies the reason for the migration requiring
+    # downtime.
+    DOWNTIME_REASON_CONST = :DOWNTIME_REASON
+
+    # Checks the given migration paths and returns an Array of
+    # `Gitlab::DowntimeCheck::Message` instances.
+    #
+    # migrations - The migration file paths to check.
+    def check(migrations)
+      migrations.map do |path|
+        require(path)
+
+        migration_class = class_for_migration_file(path)
+
+        unless migration_class.const_defined?(DOWNTIME_CONST)
+          raise "The migration in #{path} does not specify if it requires " \
+            "downtime or not"
+        end
+
+        if online?(migration_class)
+          Message.new(path)
+        else
+          reason = downtime_reason(migration_class)
+
+          unless reason
+            raise "The migration in #{path} requires downtime but no reason " \
+              "was given"
+          end
+
+          Message.new(path, true, reason)
+        end
+      end
+    end
+
+    # Checks the given migrations and prints the results to STDOUT/STDERR.
+    #
+    # migrations - The migration file paths to check.
+    def check_and_print(migrations)
+      check(migrations).each do |message|
+        puts message.to_s # rubocop: disable Rails/Output
+      end
+    end
+
+    # Returns the class for the given migration file path.
+    def class_for_migration_file(path)
+      File.basename(path, File.extname(path)).split('_', 2).last.camelize.
+        constantize
+    end
+
+    # Returns true if the given migration can be performed without downtime.
+    def online?(migration)
+      migration.const_get(DOWNTIME_CONST) == false
+    end
+
+    # Returns the downtime reason, or nil if none was defined.
+    def downtime_reason(migration)
+      if migration.const_defined?(DOWNTIME_REASON_CONST)
+        migration.const_get(DOWNTIME_REASON_CONST)
+      else
+        nil
+      end
+    end
+  end
+end
diff --git a/lib/gitlab/downtime_check/message.rb b/lib/gitlab/downtime_check/message.rb
new file mode 100644
index 00000000000..4446e921e0d
--- /dev/null
+++ b/lib/gitlab/downtime_check/message.rb
@@ -0,0 +1,28 @@
+module Gitlab
+  class DowntimeCheck
+    class Message
+      attr_reader :path, :offline, :reason
+
+      OFFLINE = "\e[32moffline\e[0m"
+      ONLINE = "\e[31monline\e[0m"
+
+      # path - The file path of the migration.
+      # offline - When set to `true` the migration will require downtime.
+      # reason - The reason as to why the migration requires downtime.
+      def initialize(path, offline = false, reason = nil)
+        @path = path
+        @offline = offline
+        @reason = reason
+      end
+
+      def to_s
+        label = offline ? OFFLINE : ONLINE
+
+        message = "[#{label}]: #{path}"
+        message += ": #{reason}" if reason
+
+        message
+      end
+    end
+  end
+end
diff --git a/lib/tasks/downtime_check.rake b/lib/tasks/downtime_check.rake
new file mode 100644
index 00000000000..30a2e9be5ce
--- /dev/null
+++ b/lib/tasks/downtime_check.rake
@@ -0,0 +1,26 @@
+desc 'Checks if migrations in a branch require downtime'
+task downtime_check: :environment do
+  # First we'll want to make sure we're comparing with the right upstream
+  # repository/branch.
+  current_branch = `git rev-parse --abbrev-ref HEAD`.strip
+
+  # Either the developer ran this task directly on the master branch, or they're
+  # making changes directly on the master branch.
+  if current_branch == 'master'
+    if defined?(Gitlab::License)
+      repo = 'gitlab-ee'
+    else
+      repo = 'gitlab-ce'
+    end
+
+    `git fetch https://gitlab.com/gitlab-org/#{repo}.git --depth 1`
+
+    compare_with = 'FETCH_HEAD'
+  # The developer is working on a different branch, in this case we can just
+  # compare with the master branch.
+  else
+    compare_with = 'master'
+  end
+
+  Rake::Task['gitlab:db:downtime_check'].invoke(compare_with)
+end
diff --git a/lib/tasks/gitlab/db.rake b/lib/tasks/gitlab/db.rake
index 7230b9485be..0ec19e1a625 100644
--- a/lib/tasks/gitlab/db.rake
+++ b/lib/tasks/gitlab/db.rake
@@ -46,5 +46,20 @@ namespace :gitlab do
         Rake::Task['db:seed_fu'].invoke
       end
     end
+
+    desc 'Checks if migrations require downtime or not'
+    task :downtime_check, [:ref] => :environment do |_, args|
+      abort 'You must specify a Git reference to compare with' unless args[:ref]
+
+      require 'shellwords'
+
+      ref = Shellwords.escape(args[:ref])
+
+      migrations = `git diff #{ref}.. --name-only -- db/migrate`.lines.
+        map { |file| Rails.root.join(file.strip).to_s }.
+        select { |file| File.file?(file) }
+
+      Gitlab::DowntimeCheck.new.check_and_print(migrations)
+    end
   end
 end