openstack/nova
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cb5ad6d3c1
nova/api-guide/source/down_cells.rst
Surya Seetharaman a0b1951d2a Add "links" in the response of "nova show" for a down-cell instance 
The down-cell microversion 2.69 just recently merged and it returns
links in the response for GET /servers/detail and GET /servers but not
for GET /servers/{server_id} which was an oversight because that API
returns links normally.

We should include the links key in the 'nova show' case as well and this
patch does exactly that.

Typically this would require a microversion change but given the code
merged recently and is not yet released we are just fixing this
oversight through this patch without a microversion bump.

Closes-Bug: #1818131
Change-Id: I2ce03df994f59c37b5ce3102c4e7165d17701798
2019-03-01 13:02:14 +00:00

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===================
Handling Down Cells
===================
Starting from microversion 2.69 if there are transient conditions in a
deployment like partial infrastructure failures (for example a cell
not being reachable), some API responses may contain partial results
(i.e. be missing some keys). The server operations which exhibit this
behavior are described below:
* List Servers (GET /servers): This operation may give partial
constructs from the non-responsive portion of the infrastructure. A
typical response, while listing servers from unreachable parts of
the infrastructure, would include only the following keys from
available information:
- status: The state of the server which will be "UNKNOWN".
- id: The UUID of the server.
- links: Links to the servers in question.
A sample response for a GET /servers request that includes one
result each from an unreachable and a healthy part of the
infrastructure is shown below.
Response::
{
"servers": [
{
"status": "UNKNOWN",
"id": "bcc6c6dd-3d0a-4633-9586-60878fd68edb",
"links": [
{
"rel": "self",
"href": "http://openstack.example.com/v2/6f70656e737461636b20342065766572/servers/bcc6c6dd-3d0a-4633-9586-60878fd68edb"
},
{
"rel": "bookmark",
"href": "http://openstack.example.com/6f70656e737461636b20342065766572/servers/bcc6c6dd-3d0a-4633-9586-60878fd68edb"
}
]
},
{
"id": "22c91117-08de-4894-9aa9-6ef382400985",
"name": "test_server",
"links": [
{
"rel": "self",
"href": "http://openstack.example.com/v2/6f70656e737461636b20342065766572/servers/22c91117-08de-4894-9aa9-6ef382400985"
},
{
"rel": "bookmark",
"href": "http://openstack.example.com/6f70656e737461636b20342065766572/servers/22c91117-08de-4894-9aa9-6ef382400985"
}
]
}
]
}
* List Servers Detailed (GET /servers/detail): This operation may give
partial constructs from the non-responsive portion of the
infrastructure. A typical response, while listing servers from
unreachable parts of the infrastructure, would include only the
following keys from available information:
- status: The state of the server which will be "UNKNOWN".
- id: The UUID of the server.
- tenant_id: The tenant_id to which the server belongs to.
- created: The time of server creation.
- links: Links to the servers in question.
A sample response for a GET /servers/details request that includes
one result each from an unreachable and a healthy part of the
infrastructure is shown below.
Response::
{
"servers": [
{
"created": "2018-06-29T15:07:29Z",
"status": "UNKNOWN",
"tenant_id": "940f47b984034c7f8f9624ab28f5643c",
"id": "bcc6c6dd-3d0a-4633-9586-60878fd68edb",
"links": [
{
"href": "http://openstack.example.com/v2.1/6f70656e737461636b20342065766572/servers/bcc6c6dd-3d0a-4633-9586-60878fd68edb",
"rel": "self"
},
{
"href": "http://openstack.example.com/6f70656e737461636b20342065766572/servers/bcc6c6dd-3d0a-4633-9586-60878fd68edb",
"rel": "bookmark"
}
]
},
{
"OS-DCF:diskConfig": "AUTO",
"OS-EXT-AZ:availability_zone": "nova",
"OS-EXT-SRV-ATTR:host": "compute",
"OS-EXT-SRV-ATTR:hostname": "new-server-test",
"OS-EXT-SRV-ATTR:hypervisor_hostname": "fake-mini",
"OS-EXT-SRV-ATTR:instance_name": "instance-00000001",
"OS-EXT-SRV-ATTR:kernel_id": "",
"OS-EXT-SRV-ATTR:launch_index": 0,
"OS-EXT-SRV-ATTR:ramdisk_id": "",
"OS-EXT-SRV-ATTR:reservation_id": "r-y0w4v32k",
"OS-EXT-SRV-ATTR:root_device_name": "/dev/sda",
"OS-EXT-SRV-ATTR:user_data": "IyEvYmluL2Jhc2gKL2Jpbi9zdQplY2hvICJJIGFtIGluIHlvdSEiCg==",
"OS-EXT-STS:power_state": 1,
"OS-EXT-STS:task_state": null,
"OS-EXT-STS:vm_state": "active",
"OS-SRV-USG:launched_at": "2017-10-10T15:49:09.516729",
"OS-SRV-USG:terminated_at": null,
"accessIPv4": "1.2.3.4",
"accessIPv6": "80fe::",
"addresses": {
"private": [
{
"OS-EXT-IPS-MAC:mac_addr": "aa:bb:cc:dd:ee:ff",
"OS-EXT-IPS:type": "fixed",
"addr": "192.168.0.3",
"version": 4
}
]
},
"config_drive": "",
"created": "2017-10-10T15:49:08Z",
"description": null,
"flavor": {
"disk": 1,
"ephemeral": 0,
"extra_specs": {
"hw:cpu_policy": "dedicated",
"hw:mem_page_size": "2048"
},
"original_name": "m1.tiny.specs",
"ram": 512,
"swap": 0,
"vcpus": 1
},
"hostId": "2091634baaccdc4c5a1d57069c833e402921df696b7f970791b12ec6",
"host_status": "UP",
"id": "569f39f9-7c76-42a1-9c2d-8394e2638a6d",
"image": {
"id": "70a599e0-31e7-49b7-b260-868f441e862b",
"links": [
{
"href": "http://openstack.example.com/6f70656e737461636b20342065766572/images/70a599e0-31e7-49b7-b260-868f441e862b",
"rel": "bookmark"
}
]
},
"key_name": null,
"links": [
{
"href": "http://openstack.example.com/v2.1/6f70656e737461636b20342065766572/servers/569f39f9-7c76-42a1-9c2d-8394e2638a6d",
"rel": "self"
},
{
"href": "http://openstack.example.com/6f70656e737461636b20342065766572/servers/569f39f9-7c76-42a1-9c2d-8394e2638a6d",
"rel": "bookmark"
}
],
"locked": false,
"metadata": {
"My Server Name": "Apache1"
},
"name": "new-server-test",
"os-extended-volumes:volumes_attached": [],
"progress": 0,
"security_groups": [
{
"name": "default"
}
],
"status": "ACTIVE",
"tags": [],
"tenant_id": "6f70656e737461636b20342065766572",
"trusted_image_certificates": [
"0b5d2c72-12cc-4ba6-a8d7-3ff5cc1d8cb8",
"674736e3-f25c-405c-8362-bbf991e0ce0a"
],
"updated": "2017-10-10T15:49:09Z",
"user_id": "fake"
}
]
}
**Edge Cases**
* **Filters:** If the user is listing servers using filters, results
from unreachable parts of the infrastructure cannot be tested for
matching those filters and thus no minimalistic construct will be
provided. Note that by default ``openstack server list`` uses the
``deleted=False`` and ``project_id=tenant_id`` filters and since
we know both of these fundamental values at all times, they are
the only allowed filters to be applied to servers with only
partial information available. Hence only doing ``openstack
server list`` and ``openstack server list --all-projects`` (admin
only) will show minimalistic results when parts of the
infrastructure are unreachable. Other filters like ``openstack
server list --deleted`` or ``openstack server list --host xx``
will skip the results depending on the administrator's
configuration of the deployment. Note that the filter ``openstack
server list --limit`` will also skip the results and if not
specified will return 1000 (or the configured default) records
from the available parts of the infrastructure.
* **Marker:** If the user does ``openstack server list --marker`` it will
fail with a 500 if the marker is an instance that is no longer reachable.
* **Sorting:** We exclude the unreachable parts of the infrastructure just like
we do for filters since there is no way of obtaining valid sorted results from
those parts with missing information.
* **Paging:** We ignore the parts of the deployment which are non-responsive.
For example if we have three cells A (reachable state), B (unreachable state)
and C (reachable state) and if the marker is half way in A, we would get the
remaining half of the results from A, all the results from C and ignore cell B.
.. note:: All the edge cases that are not supported for minimal constructs would
give responses based on the administrator's configuration of the deployment,
either skipping those results or returning an error.
* Show Server Details (GET /servers/{server_id}): This operation may
give partial constructs from the non-responsive portion of the
infrastructure. A typical response while viewing a server from an
unreachable part of the infrastructure would include only the
following keys from available information:
- status: The state of the server which will be "UNKNOWN".
- id: The UUID of the server.
- tenant_id: The tenant_id to which the server belongs to.
- created: The time of server creation.
- user_id: The user_id to which the server belongs to. This may be "UNKNOWN"
for older servers.
- image: The image details of the server. If it is not set like
in the boot-from-volume case, this value will be an empty string.
- flavor: The flavor details of the server.
- availability_zone: The availability_zone of the server if it was specified
during during boot time and "UNKNOWN" otherwise.
- power_state: Its value will be 0 (``NOSTATE``).
- links: Links to the servers in question.
- server_groups: The UUIDs of the server groups to which the server belongs.
Currently this can contain at most one entry. Note that this key will be in
the response only from the "2.71" microversion.
A sample response for a GET /servers/{server_id} request that
includes one server from an unreachable part of the infrastructure
is shown below.
Response::
{
"server": [
{
"created": "2018-06-29T15:07:29Z",
"status": "UNKNOWN",
"tenant_id": "940f47b984034c7f8f9624ab28f5643c",
"id": "bcc6c6dd-3d0a-4633-9586-60878fd68edb",
"user_id": "940f47b984034c7f8f9624ab28f5643c",
"image": {
"id": "70a599e0-31e7-49b7-b260-868f441e862b",
},
"flavor": {
"disk": 1,
"ephemeral": 0,
"extra_specs": {
"hw:cpu_policy": "dedicated",
"hw:mem_page_size": "2048"
},
"original_name": "m1.tiny.specs",
"ram": 512,
"swap": 0,
"vcpus": 1
},
"OS-EXT-AZ:availability_zone": "geneva",
"OS-EXT-STS:power_state": 0,
"links": [
{
"href": "http://openstack.example.com/v2.1/6f70656e737461636b20342065766572/servers/bcc6c6dd-3d0a-4633-9586-60878fd68edb",
"rel": "self"
},
{
"href": "http://openstack.example.com/6f70656e737461636b20342065766572/servers/bcc6c6dd-3d0a-4633-9586-60878fd68edb",
"rel": "bookmark"
}
],
"server_groups": ["0fd77252-4eef-4ec4-ae9b-e05dfc98aeac"]
}
]
}
* List Compute Services (GET /os-services): This operation may give
partial constructs for the services with :program:`nova-compute` as
their binary from the non-responsive portion of the
infrastructure. A typical response while listing the compute
services from unreachable parts of the infrastructure would include
only the following keys for the :program:`nova-compute` services
from available information while the other services like the
:program:`nova-conductor` service will be skipped from the result:
- binary: The binary name of the service which would always be
``nova-compute``.
- host: The name of the host running the service.
- status: The status of the service which will be "UNKNOWN".
A sample response for a GET /servers request that includes two
compute services from unreachable parts of the infrastructure and
other services from a healthy one are shown below.
Response::
{
"services": [
{
"binary": "nova-compute",
"host": "host1",
"status": "UNKNOWN"
},
{
"binary": "nova-compute",
"host": "host2",
"status": "UNKNOWN"
},
{
"id": 1,
"binary": "nova-scheduler",
"disabled_reason": "test1",
"host": "host3",
"state": "up",
"status": "disabled",
"updated_at": "2012-10-29T13:42:02.000000",
"forced_down": false,
"zone": "internal"
},
{
"id": 2,
"binary": "nova-compute",
"disabled_reason": "test2",
"host": "host4",
"state": "up",
"status": "disabled",
"updated_at": "2012-10-29T13:42:05.000000",
"forced_down": false,
"zone": "nova"
}
]
}
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