1 files changed, 45 insertions, 0 deletions
diff --git a/lib/gitlab/sidekiq_signals.rb b/lib/gitlab/sidekiq_signals.rb
new file mode 100644
index 00000000000..82462544d07
--- /dev/null
+++ b/lib/gitlab/sidekiq_signals.rb
@@ -0,0 +1,45 @@
+# frozen_string_literal: true
+
+module Gitlab
+  # As a process group leader, we can ensure that children of sidekiq are killed
+  # at the same time as sidekiq itself, to stop long-lived children from being
+  # reparented to init and "escaping". To do this, we override the default
+  # handlers used by sidekiq for INT and TERM signals
+  module SidekiqSignals
+    REPLACE_SIGNALS = %w[INT TERM].freeze
+
+    SIDEKIQ_CHANGED_MESSAGE =
+      "Intercepting signal handlers: #{REPLACE_SIGNALS.join(", ")} failed. " \
+      "Sidekiq should have registered them, but appears not to have done so."
+
+    def self.install!(sidekiq_handlers)
+      # This only works if we're process group leader
+      return unless Process.getpgrp == Process.pid
+
+      raise SIDEKIQ_CHANGED_MESSAGE unless
+        REPLACE_SIGNALS == sidekiq_handlers.keys & REPLACE_SIGNALS
+
+      REPLACE_SIGNALS.each do |signal|
+        old_handler = sidekiq_handlers[signal]
+        sidekiq_handlers[signal] = ->(cli) do
+          blindly_signal_pgroup!(signal)
+          old_handler.call(cli)
+        end
+      end
+    end
+
+    # The process group leader can forward INT and TERM signals to the whole
+    # group. However, the forwarded signal is *also* received by the leader,
+    # which could lead to an infinite loop. We can avoid this by temporarily
+    # ignoring the forwarded signal. This may cause us to miss some repeated
+    # signals from outside the process group, but that isn't fatal.
+    def self.blindly_signal_pgroup!(signal)
+      old_trap = trap(signal, 'IGNORE')
+      begin
+        Process.kill(signal, 0)
+      ensure
+        trap(signal, old_trap)
+      end
+    end
+  end
+end