Add latest changes from gitlab-org/gitlab@master

1 files changed, 66 insertions, 0 deletions

diff --git a/lib/gitlab/health_checks/master_check.rb b/lib/gitlab/health_checks/master_check.rb
new file mode 100644
index 00000000000..057bce84ddd
--- /dev/null
+++ b/lib/gitlab/health_checks/master_check.rb
@@ -0,0 +1,66 @@
+# frozen_string_literal: true
+
+module Gitlab
+  module HealthChecks
+    # This check is registered on master,
+    # and validated by worker
+    class MasterCheck
+      extend SimpleAbstractCheck
+
+      class << self
+        def register_master
+          # when we fork, we pass the read pipe to child
+          # child can then react on whether the other end
+          # of pipe is still available
+          @pipe_read, @pipe_write = IO.pipe
+        end
+
+        def finish_master
+          close_read
+          close_write
+        end
+
+        def register_worker
+          # fork needs to close the pipe
+          close_write
+        end
+
+        private
+
+        def close_read
+          @pipe_read&.close
+          @pipe_read = nil
+        end
+
+        def close_write
+          @pipe_write&.close
+          @pipe_write = nil
+        end
+
+        def metric_prefix
+          'master_check'
+        end
+
+        def successful?(result)
+          result
+        end
+
+        def check
+          # the lack of pipe is a legitimate failure of check
+          return false unless @pipe_read
+
+          @pipe_read.read_nonblock(1)
+
+          true
+        rescue IO::EAGAINWaitReadable
+          # if it is blocked, it means that the pipe is still open
+          # and there's no data waiting on it
+          true
+        rescue EOFError
+          # the pipe is closed
+          false
+        end
+      end
+    end
+  end
+end