Commit f0734412 authored by Jan Provaznik's avatar Jan Provaznik

Merge branch 'brodock/reference-counter' into 'master'

Improve reference counter

Closes #198568

See merge request gitlab-org/gitlab!23641
parents 2563b031 e13514e7
# frozen_string_literal: true
module Gitlab
# Reference Counter
#
# A reference counter is used as a mechanism to identify when
# a repository is being accessed by a writable operation.
#
# Maintenance operations would use this as a clue to when it should
# execute significant changes in order to avoid disrupting running traffic
class ReferenceCounter
REFERENCE_EXPIRE_TIME = 600
attr_reader :gl_repository, :key
# Reference Counter instance
#
# @example
# Gitlab::ReferenceCounter.new('project-1')
#
# @see Gitlab::GlRepository::RepoType.identifier_for_repositorable
# @param [String] gl_repository repository identifier
def initialize(gl_repository)
@gl_repository = gl_repository
@key = "git-receive-pack-reference-counter:#{gl_repository}"
end
# Return the actual counter value
#
# @return [Integer] value
def value
Gitlab::Redis::SharedState.with { |redis| (redis.get(key) || 0).to_i }
Gitlab::Redis::SharedState.with do |redis|
(redis.get(key) || 0).to_i
end
end
# Increase the counter
#
# @return [Boolean] whether operation was a success
def increase
redis_cmd do |redis|
redis.incr(key)
......@@ -22,26 +44,51 @@ module Gitlab
end
end
# rubocop:disable Gitlab/RailsLogger
# Decrease the counter
#
# @return [Boolean] whether operation was a success
def decrease
redis_cmd do |redis|
current_value = redis.decr(key)
if current_value < 0
# rubocop:disable Gitlab/RailsLogger
Rails.logger.warn("Reference counter for #{gl_repository} decreased" \
" when its value was less than 1. Reseting the counter.")
" when its value was less than 1. Resetting the counter.")
# rubocop:enable Gitlab/RailsLogger
redis.del(key)
end
end
end
# rubocop:enable Gitlab/RailsLogger
# Reset the reference counter
#
# @private Used internally by SRE and debugging purpose
# @return [Boolean] whether reset was a success
def reset!
redis_cmd do |redis|
redis.del(key)
end
end
# When the reference counter would expire
#
# @api private Used internally by SRE and debugging purpose
# @return [Integer] Number in seconds until expiration or false if never
def expires_in
Gitlab::Redis::SharedState.with do |redis|
redis.ttl(key)
end
end
private
def redis_cmd
Gitlab::Redis::SharedState.with { |redis| yield(redis) }
true
rescue => e
Rails.logger.warn("GitLab: An unexpected error occurred in writing to Redis: #{e}") # rubocop:disable Gitlab/RailsLogger
false
end
end
......
......@@ -2,38 +2,54 @@
require 'spec_helper'
describe Gitlab::ReferenceCounter do
let(:redis) { double('redis') }
let(:reference_counter_key) { "git-receive-pack-reference-counter:project-1" }
describe Gitlab::ReferenceCounter, :clean_gitlab_redis_shared_state do
let(:reference_counter) { described_class.new('project-1') }
before do
allow(Gitlab::Redis::SharedState).to receive(:with).and_yield(redis)
describe '#increase' do
it 'increases and sets the expire time of a reference count for a path' do
expect { reference_counter.increase }.to change { reference_counter.value }.by(1)
expect(reference_counter.expires_in).to be_positive
expect(reference_counter.increase).to be(true)
end
end
it 'increases and set the expire time of a reference count for a path' do
expect(redis).to receive(:incr).with(reference_counter_key)
expect(redis).to receive(:expire).with(reference_counter_key,
described_class::REFERENCE_EXPIRE_TIME)
expect(reference_counter.increase).to be(true)
describe '#decrease' do
it 'decreases the reference count for a path' do
reference_counter.increase
expect { reference_counter.decrease }.to change { reference_counter.value }.by(-1)
end
it 'warns if attempting to decrease a counter with a value of zero or less, and resets the counter' do
expect(Rails.logger).to receive(:warn).with("Reference counter for project-1" \
" decreased when its value was less than 1. Resetting the counter.")
expect { reference_counter.decrease }.not_to change { reference_counter.value }
end
end
it 'decreases the reference count for a path' do
allow(redis).to receive(:decr).and_return(0)
expect(redis).to receive(:decr).with(reference_counter_key)
expect(reference_counter.decrease).to be(true)
describe '#value' do
it 'get the reference count for a path' do
expect(reference_counter.value).to eq(0)
reference_counter.increase
expect(reference_counter.value).to eq(1)
end
end
it 'warns if attempting to decrease a counter with a value of one or less, and resets the counter' do
expect(redis).to receive(:decr).and_return(-1)
expect(redis).to receive(:del)
expect(Rails.logger).to receive(:warn).with("Reference counter for project-1" \
" decreased when its value was less than 1. Reseting the counter.")
expect(reference_counter.decrease).to be(true)
describe '#reset!' do
it 'resets reference count down to zero' do
3.times { reference_counter.increase }
expect { reference_counter.reset! }.to change { reference_counter.value}.from(3).to(0)
end
end
it 'get the reference count for a path' do
allow(redis).to receive(:get).and_return(1)
expect(reference_counter.value).to be(1)
describe '#expires_in' do
it 'displays the expiration time in seconds' do
reference_counter.increase
expect(reference_counter.expires_in).to be_between(500, 600)
end
end
end
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