.. _arch_overview_draining: Draining ======== Draining is the process by which Envoy attempts to gracefully shed connections in response to various events. Draining occurs at the following times: * The server has been manually health check failed via the :ref:`healthcheck/fail ` admin endpoint. See the :ref:`health check filter ` architecture overview for more information. * The server is being :ref:`hot restarted `. * Individual listeners are being modified or removed via :ref:`LDS `. Each :ref:`configured listener ` has a :ref:`drain_type ` setting which controls when draining takes place. The currently supported values are: default Envoy will drain listeners in response to all three cases above (admin drain, hot restart, and LDS update/remove). This is the default setting. modify_only Envoy will drain listeners only in response to the 2nd and 3rd cases above (hot restart and LDS update/remove). This setting is useful if Envoy is hosting both ingress and egress listeners. It may be desirable to set *modify_only* on egress listeners so they only drain during modifications while relying on ingress listener draining to perform full server draining when attempting to do a controlled shutdown. Note that although draining is a per-listener concept, it must be supported at the network filter level. Currently the only filters that support graceful draining are :ref:`HTTP connection manager `, :ref:`Redis `, and :ref:`Mongo `.