Commit f2ed82fa authored by Timothy Andrew's avatar Timothy Andrew

Implement final review comments from @DouweM and @rymai

- Have `Uniquify` take a block instead of a Proc/function. This is more
  idiomatic than passing around a function in Ruby.

- Block a user before moving their issues to the ghost user. This avoids a data
  race where an issue is created after the issues are migrated to the ghost user,
  and before the destroy takes place.

- No need to migrate issues (to the ghost user) in a transaction, because
  we're using `update_all`

- Other minor changes
parent 3bd2a98f
class Uniquify
# Return a version of the given 'base' string that is unique
# by appending a counter to it. Uniqueness is determined by
# repeated calls to `exists_fn`.
# repeated calls to the passed block.
#
# If `base` is a function/proc, we expect that calling it with a
# candidate counter returns a string to test/return.
def string(base, exists_fn)
def string(base)
@base = base
@counter = nil
increment_counter! while exists_fn[base_string]
increment_counter! while yield(base_string)
base_string
end
......@@ -24,6 +24,7 @@ class Uniquify
end
def increment_counter!
@counter = @counter ? @counter.next : 1
@counter ||= 0
@counter += 1
end
end
......@@ -99,7 +99,7 @@ class Namespace < ActiveRecord::Base
path = "blank" if path.blank?
uniquify = Uniquify.new
uniquify.string(path, -> (s) { Namespace.find_by_path_or_name(s) })
uniquify.string(path) { |s| Namespace.find_by_path_or_name(s) }
end
end
......
......@@ -346,43 +346,7 @@ class User < ActiveRecord::Base
# Return (create if necessary) the ghost user. The ghost user
# owns records previously belonging to deleted users.
def ghost
ghost_user = User.find_by_ghost(true)
ghost_user ||
begin
# Since we only want a single ghost user in an instance, we use an
# exclusive lease to ensure than this block is never run concurrently.
lease_key = "ghost_user_creation"
lease = Gitlab::ExclusiveLease.new(lease_key, timeout: 1.minute.to_i)
until uuid = lease.try_obtain
# Keep trying until we obtain the lease. To prevent hammering Redis too
# much we'll wait for a bit between retries.
sleep(1)
end
# Recheck if a ghost user is already present (one might have been)
# added between the time we last checked (first line of this method)
# and the time we acquired the lock.
ghost_user = User.find_by_ghost(true)
return ghost_user if ghost_user.present?
uniquify = Uniquify.new
username = uniquify.string("ghost", -> (s) { User.find_by_username(s) })
email = uniquify.string(
-> (n) { "ghost#{n}@example.com" },
-> (s) { User.find_by_email(s) }
)
User.create(
username: username, password: Devise.friendly_token,
email: email, name: "Ghost User", state: :blocked, ghost: true
)
ensure
Gitlab::ExclusiveLease.cancel(lease_key, uuid)
end
User.find_by_ghost(true) || create_ghost_user
end
end
......@@ -1052,4 +1016,38 @@ class User < ActiveRecord::Base
super
end
end
def self.create_ghost_user
# Since we only want a single ghost user in an instance, we use an
# exclusive lease to ensure than this block is never run concurrently.
lease_key = "ghost_user_creation"
lease = Gitlab::ExclusiveLease.new(lease_key, timeout: 1.minute.to_i)
until uuid = lease.try_obtain
# Keep trying until we obtain the lease. To prevent hammering Redis too
# much we'll wait for a bit between retries.
sleep(1)
end
# Recheck if a ghost user is already present. One might have been
# added between the time we last checked (first line of this method)
# and the time we acquired the lock.
ghost_user = User.find_by_ghost(true)
return ghost_user if ghost_user.present?
uniquify = Uniquify.new
username = uniquify.string("ghost") { |s| User.find_by_username(s) }
email = uniquify.string(-> (n) { "ghost#{n}@example.com" }) do |s|
User.find_by_email(s)
end
User.create(
username: username, password: Devise.friendly_token,
email: email, name: "Ghost User", state: :blocked, ghost: true
)
ensure
Gitlab::ExclusiveLease.cancel(lease_key, uuid)
end
end
......@@ -37,13 +37,18 @@ module Users
end
private
def move_issues_to_ghost_user(user)
# Block the user before moving issues to prevent a data race.
# If the user creates an issue after `move_issues_to_ghost_user`
# runs and before the user is destroyed, the destroy will fail with
# an exception. We block the user so that issues can't be created
# after `move_issues_to_ghost_user` runs and before the destroy happens.
user.block
ghost_user = User.ghost
Issue.transaction do
user.issues.update_all(author_id: ghost_user.id)
end
user.issues.update_all(author_id: ghost_user.id)
user.reload
end
......
require 'spec_helper'
describe Uniquify, models: true do
let(:uniquify) { described_class.new }
describe "#string" do
it 'returns the given string if it does not exist' do
uniquify = Uniquify.new
result = uniquify.string('test_string', -> (s) { false })
result = uniquify.string('test_string') { |s| false }
expect(result).to eq('test_string')
end
it 'returns the given string with a counter attached if the string exists' do
uniquify = Uniquify.new
result = uniquify.string('test_string', -> (s) { true if s == 'test_string' })
result = uniquify.string('test_string') { |s| s == 'test_string' }
expect(result).to eq('test_string1')
end
it 'increments the counter for each candidate string that also exists' do
uniquify = Uniquify.new
result = uniquify.string('test_string', -> (s) { true if s == 'test_string' || s == 'test_string1' })
result = uniquify.string('test_string') { |s| s == 'test_string' || s == 'test_string1' }
expect(result).to eq('test_string2')
end
it 'allows passing in a base function that defines the location of the counter' do
uniquify = Uniquify.new
result = uniquify.string(
-> (counter) { "test_#{counter}_string" },
-> (s) { true if s == 'test__string' }
)
result = uniquify.string(-> (counter) { "test_#{counter}_string" }) do |s|
s == 'test__string'
end
expect(result).to eq('test_1_string')
end
......
......@@ -47,6 +47,10 @@ describe Users::DestroyService, services: true do
expect(migrated_issue.author).to eq(User.ghost)
end
it 'blocks the user before migrating issues to the "Ghost User' do
expect(user).to be_blocked
end
end
context "for an issue the user was assigned to" do
......
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