Merge branch 'dm-sidekiq-sigstp' into 'master'

Send SIGSTP before SIGTERM to actually give Sidekiq jobs 30s to finish when the memory killer kicks in

See merge request gitlab-org/gitlab-ce!15102

doc/administration/operations/sidekiq_memory_killer.md

@@ -28,7 +28,7 @@ The MemoryKiller is controlled using environment variables.
   delayed shutdown is triggered. The default value for Omnibus packages is set
   [in the omnibus-gitlab
   repository](https://gitlab.com/gitlab-org/omnibus-gitlab/blob/master/files/gitlab-cookbooks/gitlab/attributes/default.rb).
-- `SIDEKIQ_MEMORY_KILLER_GRACE_TIME`: defaults 900 seconds (15 minutes). When
+- `SIDEKIQ_MEMORY_KILLER_GRACE_TIME`: defaults to 900 seconds (15 minutes). When
   a shutdown is triggered, the Sidekiq process will keep working normally for
   another 15 minutes.
 - `SIDEKIQ_MEMORY_KILLER_SHUTDOWN_WAIT`: defaults to 30 seconds. When the grace
@@ -36,5 +36,3 @@ The MemoryKiller is controlled using environment variables.
   Existing jobs get 30 seconds to finish. After that, the MemoryKiller tells
   Sidekiq to shut down, and an external supervision mechanism (e.g. Runit) must
   restart Sidekiq.
-- `SIDEKIQ_MEMORY_KILLER_SHUTDOWN_SIGNAL`: defaults to `SIGKILL`. The name of
-  the final signal sent to the Sidekiq process when we want it to shut down.

lib/gitlab/sidekiq_middleware/memory_killer.rb

@@ -7,7 +7,6 @@ module Gitlab
       GRACE_TIME = (ENV['SIDEKIQ_MEMORY_KILLER_GRACE_TIME'] || 15 * 60).to_s.to_i
       # Wait 30 seconds for running jobs to finish during graceful shutdown
       SHUTDOWN_WAIT = (ENV['SIDEKIQ_MEMORY_KILLER_SHUTDOWN_WAIT'] || 30).to_s.to_i
-      SHUTDOWN_SIGNAL = (ENV['SIDEKIQ_MEMORY_KILLER_SHUTDOWN_SIGNAL'] || 'SIGKILL').to_s
 
       # Create a mutex used to ensure there will be only one thread waiting to
       # shut Sidekiq down
@@ -15,6 +14,7 @@ module Gitlab
 
       def call(worker, job, queue)
         yield
+
         current_rss = get_rss
 
         return unless MAX_RSS > 0 && current_rss > MAX_RSS
@@ -23,32 +23,45 @@ module Gitlab
           # Return if another thread is already waiting to shut Sidekiq down
           return unless MUTEX.try_lock
 
-          Sidekiq.logger.warn "current RSS #{current_rss} exceeds maximum RSS "\
-            "#{MAX_RSS}"
-          Sidekiq.logger.warn "this thread will shut down PID #{Process.pid} - Worker #{worker.class} - JID-#{job['jid']} "\
-            "in #{GRACE_TIME} seconds"
-          sleep(GRACE_TIME)
+          Sidekiq.logger.warn "Sidekiq worker PID-#{pid} current RSS #{current_rss}"\
+            " exceeds maximum RSS #{MAX_RSS} after finishing job #{worker.class} JID-#{job['jid']}"
+          Sidekiq.logger.warn "Sidekiq worker PID-#{pid} will stop fetching new jobs in #{GRACE_TIME} seconds, and will be shut down #{SHUTDOWN_WAIT} seconds later"
 
-          Sidekiq.logger.warn "sending SIGTERM to PID #{Process.pid} - Worker #{worker.class} - JID-#{job['jid']}"
-          Process.kill('SIGTERM', Process.pid)
+          # Wait `GRACE_TIME` to give the memory intensive job time to finish.
+          # Then, tell Sidekiq to stop fetching new jobs.
+          wait_and_signal(GRACE_TIME, 'SIGSTP', 'stop fetching new jobs')
 
-          Sidekiq.logger.warn "waiting #{SHUTDOWN_WAIT} seconds before sending "\
-            "#{SHUTDOWN_SIGNAL} to PID #{Process.pid} - Worker #{worker.class} - JID-#{job['jid']}"
-          sleep(SHUTDOWN_WAIT)
+          # Wait `SHUTDOWN_WAIT` to give already fetched jobs time to finish.
+          # Then, tell Sidekiq to gracefully shut down by giving jobs a few more
+          # moments to finish, killing and requeuing them if they didn't, and
+          # then terminating itself.
+          wait_and_signal(SHUTDOWN_WAIT, 'SIGTERM', 'gracefully shut down')
 
-          Sidekiq.logger.warn "sending #{SHUTDOWN_SIGNAL} to PID #{Process.pid} - Worker #{worker.class} - JID-#{job['jid']}"
-          Process.kill(SHUTDOWN_SIGNAL, Process.pid)
+          # Wait for Sidekiq to shutdown gracefully, and kill it if it didn't.
+          wait_and_signal(Sidekiq.options[:timeout] + 2, 'SIGKILL', 'die')
         end
       end
 
       private
 
       def get_rss
-        output, status = Gitlab::Popen.popen(%W(ps -o rss= -p #{Process.pid}))
+        output, status = Gitlab::Popen.popen(%W(ps -o rss= -p #{pid}))
         return 0 unless status.zero?
 
         output.to_i
       end
+
+      def wait_and_signal(time, signal, explanation)
+        Sidekiq.logger.warn "waiting #{time} seconds before sending Sidekiq worker PID-#{pid} #{signal} (#{explanation})"
+        sleep(time)
+
+        Sidekiq.logger.warn "sending Sidekiq worker PID-#{pid} #{signal} (#{explanation})"
+        Process.kill(signal, pid)
+      end
+
+      def pid
+        Process.pid
+      end
     end
   end
 end

spec/lib/gitlab/sidekiq_middleware/memory_killer_spec.rb

+require 'spec_helper'
+
+describe Gitlab::SidekiqMiddleware::MemoryKiller do
+  subject { described_class.new }
+  let(:pid) { 999 }
+
+  let(:worker) { double(:worker, class: 'TestWorker') }
+  let(:job) { { 'jid' => 123 } }
+  let(:queue) { 'test_queue' }
+
+  def run
+    thread = subject.call(worker, job, queue) { nil }
+    thread&.join
+  end
+
+  before do
+    allow(subject).to receive(:get_rss).and_return(10.kilobytes)
+    allow(subject).to receive(:pid).and_return(pid)
+  end
+
+  context 'when MAX_RSS is set to 0' do
+    before do
+      stub_const("#{described_class}::MAX_RSS", 0)
+    end
+
+    it 'does nothing' do
+      expect(subject).not_to receive(:sleep)
+
+      run
+    end
+  end
+
+  context 'when MAX_RSS is exceeded' do
+    before do
+      stub_const("#{described_class}::MAX_RSS", 5.kilobytes)
+    end
+
+    it 'sends the STP, TERM and KILL signals at expected times' do
+      expect(subject).to receive(:sleep).with(15 * 60).ordered
+      expect(Process).to receive(:kill).with('SIGSTP', pid).ordered
+
+      expect(subject).to receive(:sleep).with(30).ordered
+      expect(Process).to receive(:kill).with('SIGTERM', pid).ordered
+
+      expect(subject).to receive(:sleep).with(10).ordered
+      expect(Process).to receive(:kill).with('SIGKILL', pid).ordered
+
+      run
+    end
+  end
+
+  context 'when MAX_RSS is not exceeded' do
+    before do
+      stub_const("#{described_class}::MAX_RSS", 15.kilobytes)
+    end
+
+    it 'does nothing' do
+      expect(subject).not_to receive(:sleep)
+
+      run
+    end
+  end
+end