Commit 133f00be authored by Timothy Andrew's avatar Timothy Andrew

Move records to the ghost user in a transaction.

- While deleting a user, some of the user's associated records are moved to the
  ghost user so they aren't deleted. The user is blocked before these records
  are moved, to prevent the user from creating new records while the migration
  is happening, and so preventing a data race.

- Previously, if the migration failed, the user would _remain_ blocked, which is
  not the expected behavior. On the other hand, we can't just stick the block +
  migration into a transaction, because we want the block to be committed before
  the migration starts (for the data race reason mentioned above).

- One solution (implemented in this commit) is to block the user in a parent
  transaction, migrate the associated records in a nested sub-transaction, and
  then unblock the user in the parent transaction if the sub-transaction fails.
parent 6c65b63c
...@@ -15,27 +15,39 @@ module Users ...@@ -15,27 +15,39 @@ module Users
end end
def execute def execute
# Block the user before moving records to prevent a data race. transition = user.block_transition
# For example, if the user creates an issue after `migrate_issues`
# runs and before the user is destroyed, the destroy will fail with
# an exception.
user.block
user.transaction do user.transaction do
# Block the user before moving records to prevent a data race.
# For example, if the user creates an issue after `migrate_issues`
# runs and before the user is destroyed, the destroy will fail with
# an exception.
user.block
# Reverse the user block if record migration fails
if !migrate_records && transition
transition.rollback
user.save!
end
end
user.reload
end
private
def migrate_records
user.transaction(requires_new: true) do
@ghost_user = User.ghost @ghost_user = User.ghost
migrate_issues migrate_issues
migrate_merge_requests migrate_merge_requests
migrate_notes migrate_notes
migrate_abuse_reports migrate_abuse_reports
migrate_award_emoji migrate_award_emojis
end end
user.reload
end end
private
def migrate_issues def migrate_issues
user.issues.update_all(author_id: ghost_user.id) user.issues.update_all(author_id: ghost_user.id)
end end
...@@ -52,7 +64,7 @@ module Users ...@@ -52,7 +64,7 @@ module Users
user.reported_abuse_reports.update_all(reporter_id: ghost_user.id) user.reported_abuse_reports.update_all(reporter_id: ghost_user.id)
end end
def migrate_award_emoji def migrate_award_emojis
user.award_emoji.update_all(user_id: ghost_user.id) user.award_emoji.update_all(user_id: ghost_user.id)
end end
end end
......
...@@ -60,5 +60,23 @@ describe Users::MigrateToGhostUserService, services: true do ...@@ -60,5 +60,23 @@ describe Users::MigrateToGhostUserService, services: true do
end end
end end
end end
context "when record migration fails with a rollback exception" do
before do
expect_any_instance_of(MergeRequest::ActiveRecord_Associations_CollectionProxy)
.to receive(:update_all).and_raise(ActiveRecord::Rollback)
end
context "for records that were already migrated" do
let!(:issue) { create(:issue, project: project, author: user) }
let!(:merge_request) { create(:merge_request, source_project: project, author: user, target_branch: "first") }
it "reverses the migration" do
service.execute
expect(issue.reload.author).to eq(user)
end
end
end
end end
end end
...@@ -35,5 +35,57 @@ shared_examples "migrating a deleted user's associated records to the ghost user ...@@ -35,5 +35,57 @@ shared_examples "migrating a deleted user's associated records to the ghost user
expect(user).to be_blocked expect(user).to be_blocked
end end
context "race conditions" do
context "when #{record_class_name} migration fails and is rolled back" do
before do
expect_any_instance_of(record_class::ActiveRecord_Associations_CollectionProxy)
.to receive(:update_all).and_raise(ActiveRecord::Rollback)
end
it 'rolls back the user block' do
service.execute
expect(user.reload).not_to be_blocked
end
it "doesn't unblock an previously-blocked user" do
user.block
service.execute
expect(user.reload).to be_blocked
end
end
context "when #{record_class_name} migration fails with a non-rollback exception" do
before do
expect_any_instance_of(record_class::ActiveRecord_Associations_CollectionProxy)
.to receive(:update_all).and_raise(ArgumentError)
end
it 'rolls back the user block' do
service.execute rescue nil
expect(user.reload).not_to be_blocked
end
it "doesn't unblock an previously-blocked user" do
user.block
service.execute rescue nil
expect(user.reload).to be_blocked
end
end
it "blocks the user before #{record_class_name} migration begins" do
expect(service).to receive("migrate_#{record_class_name.parameterize('_')}s".to_sym) do
expect(user.reload).to be_blocked
end
service.execute
end
end
end end
end end
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