Merge branch 'check-min-schema-migrate' into 'master'

Ensure we are on a supported version before migrating

See merge request gitlab-org/gitlab-ce!29882

.gitlab/ci/rails.gitlab-ci.yml

@@ -244,7 +244,7 @@ migration:path-pg:
   extends: .dedicated-no-docs-and-no-qa-pull-cache-job
   script:
     - bundle exec rake db:migrate VERSION=20170523121229
-    - bundle exec rake db:migrate
+    - bundle exec rake db:migrate SKIP_SCHEMA_VERSION_CHECK=true
   dependencies:
     - setup-test-env
 

changelogs/unreleased/check-min-schema-migrate.yml

@@ -0,0 +1,5 @@
+---
+title: Added a min schema version check to db:migrate
+merge_request: 29882
+author:
+type: added

doc/development/database_debugging.md

@@ -85,3 +85,21 @@ eric             37709   0.0  0.0  2518640   7524 s006  S    Wed11AM   0:00.79 s
 $ kill 87304
 $ kill 37709
 ```
+
+### db:migrate `database version is too old to be migrated` error
+
+Users receive this error when `db:migrate` detects that the current schema version
+is older than the `MIN_SCHEMA_VERSION` defined in the `Gitlab::Database` library
+module.
+
+Over time we cleanup/combine old migrations in the codebase, so it is not always
+possible to migrate GitLab from every previous version.
+
+In some cases you may want to bypass this check. For example, if you were on a version
+of GitLab schema later than the `MIN_SCHEMA_VERSION`, and then rolled back the
+to an older migration, from before. In this case, in order to migrate forward again,
+you should set the `SKIP_SCHEMA_VERSION_CHECK` environment variable.
+
+```sh
+bundle exec rake db:migrate SKIP_SCHEMA_VERSION_CHECK=true
+```

lib/gitlab/database.rb

@@ -13,6 +13,11 @@ module Gitlab
     # https://dev.mysql.com/doc/refman/5.7/en/datetime.html
     MAX_TIMESTAMP_VALUE = Time.at((1 << 31) - 1).freeze
 
+    # Minimum schema version from which migrations are supported
+    # Migrations before this version may have been removed
+    MIN_SCHEMA_VERSION = 20190506135400
+    MIN_SCHEMA_GITLAB_VERSION = '11.11.0'
+
     define_histogram :gitlab_database_transaction_seconds do
       docstring "Time spent in database transactions, in seconds"
     end

lib/tasks/migrate/schema_check.rake

@@ -0,0 +1,20 @@
+# frozen_string_literal: true
+
+# Configures the database by running migrate, or by loading the schema and seeding if needed
+task schema_version_check: :environment do
+  next if ENV['SKIP_SCHEMA_VERSION_CHECK']
+
+  schema_version = ActiveRecord::Migrator.current_version
+
+  # Ensure migrations are being run from a supported schema version
+  # A schema verison of 0 is a fresh db, and should be safe to run migrations
+  # But a database with existing migrations less than our min version is not
+  if schema_version > 0 && schema_version < Gitlab::Database::MIN_SCHEMA_VERSION
+    raise "Your current database version is too old to be migrated. " \
+          "You should upgrade to GitLab #{Gitlab::Database::MIN_SCHEMA_GITLAB_VERSION} before moving to this version. " \
+          "Please see https://docs.gitlab.com/ee/policy/maintenance.html#upgrade-recommendations"
+  end
+end
+
+# Ensure the check is a pre-requisite when running db:migrate
+Rake::Task["db:migrate"].enhance [:schema_version_check]

spec/tasks/migrate/schema_check_rake_spec.rb

@@ -0,0 +1,50 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+require 'rake'
+
+describe 'schema_version_check rake task' do
+  include StubENV
+
+  before :all do
+    Rake.application.rake_require 'active_record/railties/databases'
+    Rake.application.rake_require 'tasks/migrate/schema_check'
+
+    # empty task as env is already loaded
+    Rake::Task.define_task :environment
+  end
+
+  before do
+    # Stub out db tasks
+    allow(ActiveRecord::Tasks::DatabaseTasks).to receive(:migrate).and_return(true)
+    allow(ActiveRecord::Migrator).to receive(:current_version).and_return(Gitlab::Database::MIN_SCHEMA_VERSION)
+
+    # Ensure our check can re-run each time
+    Rake::Task[:schema_version_check].reenable
+  end
+
+  it 'allows migrations on databases meeting the min schema version requirement' do
+    expect { run_rake_task('db:migrate') }.not_to raise_error
+  end
+
+  it 'raises an error when schema version is too old to migrate' do
+    allow(ActiveRecord::Migrator).to receive(:current_version).and_return(25)
+    expect { run_rake_task('db:migrate') }.to raise_error(RuntimeError, /current database version is too old to be migrated/)
+  end
+
+  it 'skips running validation when passed the skip env variable' do
+    stub_env('SKIP_SCHEMA_VERSION_CHECK', 'true')
+    allow(ActiveRecord::Migrator).to receive(:current_version).and_return(25)
+    expect { run_rake_task('db:migrate') }.not_to raise_error
+  end
+
+  it 'allows migrations on fresh databases' do
+    allow(ActiveRecord::Migrator).to receive(:current_version).and_return(0)
+    expect { run_rake_task('db:migrate') }.not_to raise_error
+  end
+
+  def run_rake_task(task_name)
+    Rake::Task[task_name].reenable
+    Rake.application.invoke_task task_name
+  end
+end