Allow to interrupt running jobs

This adds a middleware to track all threads
for running jobs.

This makes sidekiq to watch for redis-delivered notifications.

This makes be able to send notification to interrupt
running sidekiq jobs.

This does not take into account any native code,
as `Thread.raise` generates exception once the control gets
back to Ruby.

The separate measure should be taken to interrupt gRPC, shellouts,
or anything else that escapes Ruby.

config/initializers/sidekiq.rb

@@ -33,6 +33,7 @@ Sidekiq.configure_server do |config|
   config.redis = queues_config_hash
 
   config.server_middleware do |chain|
+    chain.add Gitlab::SidekiqMiddleware::JobsThreads unless ENV['DISABLE_SIDEKIQ_INTERRUPT_RUNNING_JOBS']
     chain.add Gitlab::SidekiqMiddleware::Metrics if Settings.monitoring.sidekiq_exporter
     chain.add Gitlab::SidekiqMiddleware::ArgumentsLogger if ENV['SIDEKIQ_LOG_ARGUMENTS'] && !enable_json_logs
     chain.add Gitlab::SidekiqMiddleware::MemoryKiller if ENV['SIDEKIQ_MEMORY_KILLER_MAX_RSS']
@@ -57,6 +58,8 @@ Sidekiq.configure_server do |config|
     # Clear any connections that might have been obtained before starting
     # Sidekiq (e.g. in an initializer).
     ActiveRecord::Base.clear_all_connections!
+
+    Gitlab::SidekiqStatus::Monitor.instance.start unless ENV['DISABLE_SIDEKIQ_INTERRUPT_RUNNING_JOBS']
   end
 
   if enable_reliable_fetch?

lib/gitlab/sidekiq_middleware/jobs_threads.rb

@@ -0,0 +1,49 @@
+# frozen_string_literal: true
+
+module Gitlab
+  module SidekiqMiddleware
+    class JobsThreads
+      @@jobs = {} # rubocop:disable Style/ClassVars
+      MUTEX = Mutex.new
+
+      def call(worker, job, queue)
+        jid = job['jid']
+
+        MUTEX.synchronize do
+          @@jobs[jid] = Thread.current
+        end
+
+        return if self.class.cancelled?(jid)
+
+        yield
+      ensure
+        MUTEX.synchronize do
+          @@jobs.delete(jid)
+        end
+      end
+
+      def self.interrupt(jid)
+        MUTEX.synchronize do
+          thread = @@jobs[jid]
+          break unless thread
+
+          thread.raise(Interrupt)
+          thread
+        end
+      end
+
+      def self.cancelled?(jid)
+        Sidekiq.redis {|c| c.exists("cancelled-#{jid}") }
+      end
+
+      def self.mark_job_as_cancelled(jid)
+        Sidekiq.redis {|c| c.setex("cancelled-#{jid}", 86400, 1) }
+        "Marked job as cancelled(if Sidekiq retry within 24 hours, the job will be skipped as `processed`). Jid: #{jid}"
+      end
+
+      def self.jobs
+        @@jobs
+      end
+    end
+  end
+end

lib/gitlab/sidekiq_status/monitor.rb

@@ -0,0 +1,46 @@
+# frozen_string_literal: true
+
+module Gitlab
+  module SidekiqStatus
+    class Monitor < Daemon
+      include ::Gitlab::Utils::StrongMemoize
+
+      NOTIFICATION_CHANNEL = 'sidekiq:cancel:notifications'.freeze
+
+      def start_working
+        Sidekiq.logger.info "Watching sidekiq monitor"
+
+        ::Gitlab::Redis::SharedState.with do |redis|
+          redis.subscribe(NOTIFICATION_CHANNEL) do |on|
+            on.message do |channel, message|
+              Sidekiq.logger.info "Received #{message} on #{channel}..."
+              execute_job_cancel(message)
+            end
+          end
+        end
+      end
+
+      def self.cancel_job(jid)
+        Gitlab::Redis::SharedState.with do |redis|
+          redis.publish(NOTIFICATION_CHANNEL, jid)
+          "Notification sent. Job should be cancelled soon. Check log to confirm. Jid: #{jid}"
+        end
+      end
+
+      private
+
+      def execute_job_cancel(jid)
+        Gitlab::SidekiqMiddleware::JobsThreads.mark_job_as_cancelled(jid)
+
+        thread = Gitlab::SidekiqMiddleware::JobsThreads
+          .interrupt(jid)
+
+        if thread
+          Sidekiq.logger.info "Interrupted thread: #{thread} for #{jid}."
+        else
+          Sidekiq.logger.info "Did not find thread for #{jid}."
+        end
+      end
+    end
+  end
+end

spec/lib/gitlab/sidekiq_middleware/jobs_threads_spec.rb

@@ -0,0 +1,83 @@
+require 'spec_helper'
+
+describe Gitlab::SidekiqMiddleware::JobsThreads do
+  subject { described_class.new }
+
+  let(:worker) { double(:worker, class: Chaos::SleepWorker) }
+  let(:jid) { '581f90fbd2f24deabcbde2f9' }
+  let(:job) { { 'jid' => jid } }
+  let(:jid_thread) { '684f90fbd2f24deabcbde2f9' }
+  let(:job_thread) { { 'jid' => jid_thread } }
+  let(:queue) { 'test_queue' }
+  let(:mark_job_as_cancelled) { Sidekiq.redis {|c| c.setex("cancelled-#{jid}", 2, 1) } }
+
+  def run_job
+    subject.call(worker, job, queue) do
+      sleep 2
+      "mock return from yield"
+    end
+  end
+
+  def run_job_thread
+    Thread.new do
+      subject.call(worker, job_thread, queue) do
+        sleep 3
+        "mock return from yield"
+      end
+    end
+  end
+
+  describe '.call' do
+    context 'by default' do
+      it 'return from yield' do
+        expect(run_job).to eq("mock return from yield")
+      end
+    end
+
+    context 'when job is marked as cancelled' do
+      before do
+        mark_job_as_cancelled
+      end
+
+      it 'return directly' do
+        expect(run_job).to be_nil
+      end
+    end
+  end
+
+  describe '.self.interrupt' do
+    before do
+      run_job_thread
+      sleep 1
+    end
+
+    it 'interrupt the job with correct jid' do
+      expect(described_class.jobs[jid_thread]).to receive(:raise).with(Interrupt)
+      expect(described_class.interrupt jid_thread).to eq(described_class.jobs[jid_thread])
+    end
+
+    it 'do nothing with wrong jid' do
+      expect(described_class.jobs[jid_thread]).not_to receive(:raise)
+      expect(described_class.interrupt 'wrong_jid').to be_nil
+    end
+  end
+
+  describe '.self.cancelled?' do
+    it 'return true when job is marked as cancelled' do
+      mark_job_as_cancelled
+      expect(described_class.cancelled? jid).to be true
+    end
+
+    it 'return false when job is not marked as cancelled' do
+      expect(described_class.cancelled? 'non-exists-jid').to be false
+    end
+  end
+
+  describe '.self.mark_job_as_cancelled' do
+    it 'set Redis key' do
+      described_class.mark_job_as_cancelled('jid_123')
+
+      expect(described_class.cancelled? 'jid_123').to be true
+    end
+  end
+end