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.

    • security_groups: One or more security groups. (Optional)

    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",
                  "id": "bcc6c6dd-3d0a-4633-9586-60878fd68edb",
                  "status": "UNKNOWN",
                  "tenant_id": "940f47b984034c7f8f9624ab28f5643c",
                  "security_groups": [
                      {
                          "name": "default"
                      }
                  ],
                  "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:numa_nodes": "1"
                      },
                      "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:numa_nodes": "1"
                    },
                    "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 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 nova-compute services from available information while the other services like the 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"
            }
        ]
    }