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