db919aa15f
ignore instance task state and continue with vm evacutaion Closes-Bug: #1978983 Change-Id: I5540df6c7497956219c06cff6f15b51c2c8bc29d
113 lines
4.3 KiB
ReStructuredText
113 lines
4.3 KiB
ReStructuredText
==================
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Evacuate instances
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==================
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If a hardware malfunction or other error causes a cloud compute node to fail,
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you can evacuate instances to make them available again.
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To preserve user data on the server disk, configure shared storage on the
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target host. When you evacuate the instance, Compute detects whether shared
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storage is available on the target host. Also, you must validate that the
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current VM host is not operational. Otherwise, the evacuation fails.
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There are two different ways to evacuate instances from a failed compute
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node. The first one using the :command:`nova evacuate` command can be used to
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evacuate a single instance from a failed node. In some cases where the node
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in question hosted many instances it might be easier to use
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:command:`nova host-evacuate` to evacuate them all in one shot.
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Evacuate a single instance
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~~~~~~~~~~~~~~~~~~~~~~~~~~
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The procedure below explains how to evacuate a single instance from a failed
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compute node. Please be aware that these steps describe a post failure
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scenario and should not be used if the instance is still up and running.
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#. To find a host for the evacuated instance, list all hosts:
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.. code-block:: console
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$ openstack host list
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#. Evacuate the instance. You can use the ``--password PWD`` option to pass the
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instance password to the command. If you do not specify a password, the
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command generates and prints one after it finishes successfully. The
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following command evacuates a server from a failed host to ``HOST_B``.
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.. code-block:: console
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$ nova evacuate EVACUATED_SERVER_NAME HOST_B
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The command rebuilds the instance from the original image or volume and
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returns a password. The command preserves the original configuration, which
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includes the instance ID, name, uid, IP address, and so on.
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.. code-block:: console
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+-----------+--------------+
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| Property | Value |
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+-----------+--------------+
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| adminPass | kRAJpErnT4xZ |
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+-----------+--------------+
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Optionally you can omit the ``HOST_B`` parameter and let the scheduler
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choose a new target host.
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#. To preserve the user disk data on the evacuated server, deploy Compute with
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a shared file system. To configure your system, see
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:ref:`section_configuring-compute-migrations`. The following example does
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not change the password.
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.. code-block:: console
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$ nova evacuate EVACUATED_SERVER_NAME HOST_B --on-shared-storage
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.. note:: Starting with the 2.14 compute API version, one no longer needs
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to specify ``--on-shared-storage`` even if the server is on a
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compute host which is using shared storage. The compute service
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will automatically detect if it is running on shared storage.
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Evacuate all instances
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~~~~~~~~~~~~~~~~~~~~~~
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The procedure below explains how to evacuate all instances from a failed compute
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node. Please note that this method should not be used if the host still has
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instances up and running.
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#. To find a host for the evacuated instances, list all hosts:
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.. code-block:: console
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$ openstack host list
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#. Evacuate all instances from ``FAILED_HOST`` to ``TARGET_HOST``:
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.. code-block:: console
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$ nova host-evacuate --target_host TARGET_HOST FAILED_HOST
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The option ``--target_host`` is optional and can be omitted to let the
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scheduler decide where to place the instances.
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The above argument ``FAILED_HOST`` can also be a pattern
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to search for instead of an exact hypervisor hostname but it is
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recommended to use a fully qualified domain name to make sure no
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hypervisor host is getting evacuated by mistake. As long as you are not
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using a pattern you might want to use the ``--strict`` flag which got introduced
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in version 10.2.0 to make sure nova matches the ``FAILED_HOST``
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exactly.
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.. note::
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.. code-block:: bash
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+------+--------+--------------+
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| Name | Status | Task State |
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+------+--------+--------------+
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| vm_1 | ACTIVE | powering-off |
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+------------------------------+
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If the instance task state is not None, evacuation will be possible. However,
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depending on the ongoing operation, there may be clean up required in other
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services which the instance was using, such as neutron, cinder, glance, or
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the storage backend. |