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Message #85797
[Bug 1799298] Re: Metadata API cross joining instance_metadata and instance_system_metadata
** Changed in: nova/ussuri
Status: In Progress => Fix Released
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https://bugs.launchpad.net/bugs/1799298
Title:
Metadata API cross joining instance_metadata and
instance_system_metadata
Status in OpenStack Compute (nova):
Fix Released
Status in OpenStack Compute (nova) ocata series:
Triaged
Status in OpenStack Compute (nova) pike series:
Triaged
Status in OpenStack Compute (nova) queens series:
In Progress
Status in OpenStack Compute (nova) rocky series:
In Progress
Status in OpenStack Compute (nova) stein series:
In Progress
Status in OpenStack Compute (nova) train series:
In Progress
Status in OpenStack Compute (nova) ussuri series:
Fix Released
Status in OpenStack Compute (nova) victoria series:
Fix Released
Status in OpenStack Security Advisory:
Won't Fix
Bug description:
Description
===========
While troubleshooting a production issue we identified that the Nova
metadata API is fetching a lot more raw data from the database than
seems necessary. The problem appears to be caused by the SQL query
used to fetch instance data, which joins the "instance" table with,
among others, two metadata tables: "instance_metadata" and
"instance_system_metadata". Below is a simplified version of this
query which was captured by adding extra logging (the full query is
listed at the end of this bug report):
SELECT ...
FROM (SELECT ...
FROM `instances`
WHERE `instances` . `deleted` = ?
AND `instances` . `uuid` = ?
LIMIT ?) AS `anon_1`
LEFT OUTER JOIN `instance_system_metadata` AS `instance_system_metadata_1`
ON `anon_1` . `instances_uuid` = `instance_system_metadata_1` . `instance_uuid`
LEFT OUTER JOIN (`security_group_instance_association` AS `security_group_instance_association_1`
INNER JOIN `security_groups` AS `security_groups_1`
ON `security_groups_1` . `id` = `security_group_instance_association_1` . `security_group_id`
AND `security_group_instance_association_1` . `deleted` = ?
AND `security_groups_1` . `deleted` = ? )
ON `security_group_instance_association_1` . `instance_uuid` = `anon_1` . `instances_uuid`
AND `anon_1` . `instances_deleted` = ?
LEFT OUTER JOIN `security_group_rules` AS `security_group_rules_1`
ON `security_group_rules_1` . `parent_group_id` = `security_groups_1` . `id`
AND `security_group_rules_1` . `deleted` = ?
LEFT OUTER JOIN `instance_info_caches` AS `instance_info_caches_1`
ON `instance_info_caches_1` . `instance_uuid` = `anon_1` . `instances_uuid`
LEFT OUTER JOIN `instance_extra` AS `instance_extra_1`
ON `instance_extra_1` . `instance_uuid` = `anon_1` . `instances_uuid`
LEFT OUTER JOIN `instance_metadata` AS `instance_metadata_1`
ON `instance_metadata_1` . `instance_uuid` = `anon_1` . `instances_uuid`
AND `instance_metadata_1` . `deleted` = ?
The instance table has a 1-to-many relationship to both
"instance_metadata" and "instance_system_metadata" tables, so the
query is effectively producing a cross join of both metadata tables.
Steps to reproduce
==================
To illustrate the impact of this query, add 2 properties to a running
instance and verify that it has 2 records in "instance_metadata", as
well as other records in "instance_system_metadata" such as base image
properties:
> select instance_uuid,`key`,value from instance_metadata where instance_uuid = 'a6cf4a6a-effe-4438-9b7f-d61b23117b9b';
+--------------------------------------+-----------+--------+
| instance_uuid | key | value |
+--------------------------------------+-----------+--------+
| a6cf4a6a-effe-4438-9b7f-d61b23117b9b | property1 | value1 |
| a6cf4a6a-effe-4438-9b7f-d61b23117b9b | property2 | value |
+--------------------------------------+-----------+--------+
2 rows in set (0.61 sec)
> select instance_uuid,`key`,valusystem_metadata where instance_uuid = 'a6cf4a6a-effe-4438-9b7f-d61b23117b9b';
+------------------------+--------------------------------------+
| key | value |
+------------------------+--------------------------------------+
| image_disk_format | qcow2 |
| image_min_ram | 0 |
| image_min_disk | 20 |
| image_base_image_ref | 39cd564f-6a29-43e2-815b-62097968486a |
| image_container_format | bare |
+------------------------+--------------------------------------+
5 rows in set (0.00 sec)
For this particular instance, the generated query used by the metadata
API will fetch 10 records from the database:
+--------------------------------------+-------------------------+---------------------------+--------------------------------+--------------------------------------+
| anon_1_instances_uuid | instance_metadata_1_key | instance_metadata_1_value | instance_system_metadata_1_key | instance_system_metadata_1_value |
+--------------------------------------+-------------------------+---------------------------+--------------------------------+--------------------------------------+
| a6cf4a6a-effe-4438-9b7f-d61b23117b9b | property1 | value1 | image_disk_format | qcow2 |
| a6cf4a6a-effe-4438-9b7f-d61b23117b9b | property2 | value | image_disk_format | qcow2 |
| a6cf4a6a-effe-4438-9b7f-d61b23117b9b | property1 | value1 | image_min_ram | 0 |
| a6cf4a6a-effe-4438-9b7f-d61b23117b9b | property2 | value | image_min_ram | 0 |
| a6cf4a6a-effe-4438-9b7f-d61b23117b9b | property1 | value1 | image_min_disk | 20 |
| a6cf4a6a-effe-4438-9b7f-d61b23117b9b | property2 | value | image_min_disk | 20 |
| a6cf4a6a-effe-4438-9b7f-d61b23117b9b | property1 | value1 | image_base_image_ref | 39cd564f-6a29-43e2-815b-62097968486a |
| a6cf4a6a-effe-4438-9b7f-d61b23117b9b | property2 | value | image_base_image_ref | 39cd564f-6a29-43e2-815b-62097968486a |
| a6cf4a6a-effe-4438-9b7f-d61b23117b9b | property1 | value1 | image_container_format | bare |
| a6cf4a6a-effe-4438-9b7f-d61b23117b9b | property2 | value | image_container_format | bare |
+--------------------------------------+-------------------------+---------------------------+--------------------------------+--------------------------------------+
10 rows in set (0.00 sec)
Of course this is only a problem when instances have a lot of metadata
records. An instance with 50 rows in "instance_metadata" and 50 rows
in "instance_system_metadata" will fetch 50 x 50 = 2,500 rows from the
database. It's not difficult to see how this can escalate quickly.
This can be a particularly significant problem in a HA scenario with
multiple API nodes pulling data from multiple database nodes.
This issue is affecting clusters running OpenStack Mitaka. I verified
that this is not an issue on clusters running Icehouse because, in
Icehouse, instance data is pulled as needed, executing separate
queries for each table. However, I as far as I could see, this issue
could be affecting every release since Mitaka.
Full SQL
========
The generated SQL query below was captured by adding extra logging to
_build_instance_get in
https://github.com/openstack/nova/blob/mitaka-
eol/nova/db/sqlalchemy/api.py#L2005
SELECT `anon_1` . `instances_created_at` AS `anon_1_instances_created_at`,
`anon_1` . `instances_updated_at` AS `anon_1_instances_updated_at`,
`anon_1` . `instances_deleted_at` AS `anon_1_instances_deleted_at`,
`anon_1` . `instances_deleted` AS `anon_1_instances_deleted`,
`anon_1` . `instances_id` AS `anon_1_instances_id`,
`anon_1` . `instances_user_id` AS `anon_1_instances_user_id`,
`anon_1` . `instances_project_id` AS `anon_1_instances_project_id`,
`anon_1` . `instances_image_ref` AS `anon_1_instances_image_ref`,
`anon_1` . `instances_kernel_id` AS `anon_1_instances_kernel_id`,
`anon_1` . `instances_ramdisk_id` AS `anon_1_instances_ramdisk_id`,
`anon_1` . `instances_hostname` AS `anon_1_instances_hostname`,
`anon_1` . `instances_launch_index` AS `anon_1_instances_launch_index`,
`anon_1` . `instances_key_name` AS `anon_1_instances_key_name`,
`anon_1` . `instances_key_data` AS `anon_1_instances_key_data`,
`anon_1` . `instances_power_state` AS `anon_1_instances_power_state`,
`anon_1` . `instances_vm_state` AS `anon_1_instances_vm_state`,
`anon_1` . `instances_task_state` AS `anon_1_instances_task_state`,
`anon_1` . `instances_memory_mb` AS `anon_1_instances_memory_mb`,
`anon_1` . `instances_vcpus` AS `anon_1_instances_vcpus`,
`anon_1` . `instances_root_gb` AS `anon_1_instances_root_gb`,
`anon_1` . `instances_ephemeral_gb` AS `anon_1_instances_ephemeral_gb`,
`anon_1` . `instances_ephemeral_key_uuid` AS `anon_1_instances_ephemeral_key_uuid`,
`anon_1` . `instances_host` AS `anon_1_instances_host`,
`anon_1` . `instances_node` AS `anon_1_instances_node`,
`anon_1` . `instances_instance_type_id` AS `anon_1_instances_instance_type_id`,
`anon_1` . `instances_user_data` AS `anon_1_instances_user_data`,
`anon_1` . `instances_reservation_id` AS `anon_1_instances_reservation_id`,
`anon_1` . `instances_launched_at` AS `anon_1_instances_launched_at`,
`anon_1` . `instances_terminated_at` AS `anon_1_instances_terminated_at`,
`anon_1` . `instances_availability_zone` AS `anon_1_instances_availability_zone`,
`anon_1` . `instances_display_name` AS `anon_1_instances_display_name`,
`anon_1` . `instances_display_description` AS `anon_1_instances_display_description`,
`anon_1` . `instances_launched_on` AS `anon_1_instances_launched_on`,
`anon_1` . `instances_locked` AS `anon_1_instances_locked`,
`anon_1` . `instances_locked_by` AS `anon_1_instances_locked_by`,
`anon_1` . `instances_os_type` AS `anon_1_instances_os_type`,
`anon_1` . `instances_architecture` AS `anon_1_instances_architecture`,
`anon_1` . `instances_vm_mode` AS `anon_1_instances_vm_mode`,
`anon_1` . `instances_uuid` AS `anon_1_instances_uuid`,
`anon_1` . `instances_root_device_name` AS `anon_1_instances_root_device_name`,
`anon_1` . `instances_default_ephemeral_device` AS `anon_1_instances_default_ephemeral_device`,
`anon_1` . `instances_default_swap_device` AS `anon_1_instances_default_swap_device`,
`anon_1` . `instances_config_drive` AS `anon_1_instances_config_drive`,
`anon_1` . `instances_access_ip_v4` AS `anon_1_instances_access_ip_v4`,
`anon_1` . `instances_access_ip_v6` AS `anon_1_instances_access_ip_v6`,
`anon_1` . `instances_auto_disk_config` AS `anon_1_instances_auto_disk_config`,
`anon_1` . `instances_progress` AS `anon_1_instances_progress`,
`anon_1` . `instances_shutdown_terminate` AS `anon_1_instances_shutdown_terminate`,
`anon_1` . `instances_disable_terminate` AS `anon_1_instances_disable_terminate`,
`anon_1` . `instances_cell_name` AS `anon_1_instances_cell_name`,
`anon_1` . `instances_internal_id` AS `anon_1_instances_internal_id`,
`anon_1` . `instances_cleaned` AS `anon_1_instances_cleaned`,
`instance_system_metadata_1` . `created_at` AS `instance_system_metadata_1_created_at`,
`instance_system_metadata_1` . `updated_at` AS `instance_system_metadata_1_updated_at`,
`instance_system_metadata_1` . `deleted_at` AS `instance_system_metadata_1_deleted_at`,
`instance_system_metadata_1` . `deleted` AS `instance_system_metadata_1_deleted`,
`instance_system_metadata_1` . `id` AS `instance_system_metadata_1_id`,
`instance_system_metadata_1` . `key` AS `instance_system_metadata_1_key`,
`instance_system_metadata_1` . `value` AS `instance_system_metadata_1_value`,
`instance_system_metadata_1` . `instance_uuid` AS `instance_system_metadata_1_instance_uuid`,
`security_groups_1` . `created_at` AS `security_groups_1_created_at`,
`security_groups_1` . `updated_at` AS `security_groups_1_updated_at`,
`security_groups_1` . `deleted_at` AS `security_groups_1_deleted_at`,
`security_groups_1` . `deleted` AS `security_groups_1_deleted`,
`security_groups_1` . `id` AS `security_groups_1_id`,
`security_groups_1` . `name` AS `security_groups_1_name`,
`security_groups_1` . `description` AS `security_groups_1_description`,
`security_groups_1` . `user_id` AS `security_groups_1_user_id`,
`security_groups_1` . `project_id` AS `security_groups_1_project_id`,
`security_group_rules_1` . `created_at` AS `security_group_rules_1_created_at`,
`security_group_rules_1` . `updated_at` AS `security_group_rules_1_updated_at`,
`security_group_rules_1` . `deleted_at` AS `security_group_rules_1_deleted_at`,
`security_group_rules_1` . `deleted` AS `security_group_rules_1_deleted`,
`security_group_rules_1` . `id` AS `security_group_rules_1_id`,
`security_group_rules_1` . `parent_group_id` AS `security_group_rules_1_parent_group_id`,
`security_group_rules_1` . `protocol` AS `security_group_rules_1_protocol`,
`security_group_rules_1` . `from_port` AS `security_group_rules_1_from_port`,
`security_group_rules_1` . `to_port` AS `security_group_rules_1_to_port`,
`security_group_rules_1` . `cidr` AS `security_group_rules_1_cidr`,
`security_group_rules_1` . `group_id` AS `security_group_rules_1_group_id`,
`instance_info_caches_1` . `created_at` AS `instance_info_caches_1_created_at`,
`instance_info_caches_1` . `updated_at` AS `instance_info_caches_1_updated_at`,
`instance_info_caches_1` . `deleted_at` AS `instance_info_caches_1_deleted_at`,
`instance_info_caches_1` . `deleted` AS `instance_info_caches_1_deleted`,
`instance_info_caches_1` . `id` AS `instance_info_caches_1_id`,
`instance_info_caches_1` . `network_info` AS `instance_info_caches_1_network_info`,
`instance_info_caches_1` . `instance_uuid` AS `instance_info_caches_1_instance_uuid`,
`instance_extra_1` . `flavor` AS `instance_extra_1_flavor`,
`instance_extra_1` . `created_at` AS `instance_extra_1_created_at`,
`instance_extra_1` . `updated_at` AS `instance_extra_1_updated_at`,
`instance_extra_1` . `deleted_at` AS `instance_extra_1_deleted_at`,
`instance_extra_1` . `deleted` AS `instance_extra_1_deleted`,
`instance_extra_1` . `id` AS `instance_extra_1_id`,
`instance_extra_1` . `instance_uuid` AS `instance_extra_1_instance_uuid`,
`instance_metadata_1` . `created_at` AS `instance_metadata_1_created_at`,
`instance_metadata_1` . `updated_at` AS `instance_metadata_1_updated_at`,
`instance_metadata_1` . `deleted_at` AS `instance_metadata_1_deleted_at`,
`instance_metadata_1` . `deleted` AS `instance_metadata_1_deleted`,
`instance_metadata_1` . `id` AS `instance_metadata_1_id`,
`instance_metadata_1` . `key` AS `instance_metadata_1_key`,
`instance_metadata_1` . `value` AS `instance_metadata_1_value`,
`instance_metadata_1` . `instance_uuid` AS `instance_metadata_1_instance_uuid`
FROM (SELECT `instances` . `created_at` AS `instances_created_at`,
`instances` . `updated_at` AS `instances_updated_at`,
`instances` . `deleted_at` AS `instances_deleted_at`,
`instances` . `deleted` AS `instances_deleted`,
`instances` . `id` AS `instances_id`,
`instances` . `user_id` AS `instances_user_id`,
`instances` . `project_id` AS `instances_project_id`,
`instances` . `image_ref` AS `instances_image_ref`,
`instances` . `kernel_id` AS `instances_kernel_id`,
`instances` . `ramdisk_id` AS `instances_ramdisk_id`,
`instances` . `hostname` AS `instances_hostname`,
`instances` . `launch_index` AS `instances_launch_index`,
`instances` . `key_name` AS `instances_key_name`,
`instances` . `key_data` AS `instances_key_data`,
`instances` . `power_state` AS `instances_power_state`,
`instances` . `vm_state` AS `instances_vm_state`,
`instances` . `task_state` AS `instances_task_state`,
`instances` . `memory_mb` AS `instances_memory_mb`,
`instances` . `vcpus` AS `instances_vcpus`,
`instances` . `root_gb` AS `instances_root_gb`,
`instances` . `ephemeral_gb` AS `instances_ephemeral_gb`,
`instances` . `ephemeral_key_uuid` AS `instances_ephemeral_key_uuid`,
`instances` . `host` AS `instances_host`,
`instances` . `node` AS `instances_node`,
`instances` . `instance_type_id` AS `instances_instance_type_id`,
`instances` . `user_data` AS `instances_user_data`,
`instances` . `reservation_id` AS `instances_reservation_id`,
`instances` . `launched_at` AS `instances_launched_at`,
`instances` . `terminated_at` AS `instances_terminated_at`,
`instances` . `availability_zone` AS `instances_availability_zone`,
`instances` . `display_name` AS `instances_display_name`,
`instances` . `display_description` AS `instances_display_description`,
`instances` . `launched_on` AS `instances_launched_on`,
`instances` . `locked` AS `instances_locked`,
`instances` . `locked_by` AS `instances_locked_by`,
`instances` . `os_type` AS `instances_os_type`,
`instances` . `architecture` AS `instances_architecture`,
`instances` . `vm_mode` AS `instances_vm_mode`,
`instances` . `uuid` AS `instances_uuid`,
`instances` . `root_device_name` AS `instances_root_device_name`,
`instances` . `default_ephemeral_device` AS `instances_default_ephemeral_device`,
`instances` . `default_swap_device` AS `instances_default_swap_device`,
`instances` . `config_drive` AS `instances_config_drive`,
`instances` . `access_ip_v4` AS `instances_access_ip_v4`,
`instances` . `access_ip_v6` AS `instances_access_ip_v6`,
`instances` . `auto_disk_config` AS `instances_auto_disk_config`,
`instances` . `progress` AS `instances_progress`,
`instances` . `shutdown_terminate` AS `instances_shutdown_terminate`,
`instances` . `disable_terminate` AS `instances_disable_terminate`,
`instances` . `cell_name` AS `instances_cell_name`,
`instances` . `internal_id` AS `instances_internal_id`,
`instances` . `cleaned` AS `instances_cleaned`
FROM `instances`
WHERE `instances` . `deleted` = ?
AND `instances` . `uuid` = ?
LIMIT ?) AS `anon_1`
LEFT OUTER JOIN `instance_system_metadata` AS `instance_system_metadata_1`
ON `anon_1` . `instances_uuid` = `instance_system_metadata_1` . `instance_uuid`
LEFT OUTER JOIN (`security_group_instance_association` AS `security_group_instance_association_1`
INNER JOIN `security_groups` AS `security_groups_1`
ON `security_groups_1` . `id` = `security_group_instance_association_1` . `security_group_id`
AND `security_group_instance_association_1` . `deleted` = ?
AND `security_groups_1` . `deleted` = ? )
ON `security_group_instance_association_1` . `instance_uuid` = `anon_1` . `instances_uuid`
AND `anon_1` . `instances_deleted` = ?
LEFT OUTER JOIN `security_group_rules` AS `security_group_rules_1`
ON `security_group_rules_1` . `parent_group_id` = `security_groups_1` . `id`
AND `security_group_rules_1` . `deleted` = ?
LEFT OUTER JOIN `instance_info_caches` AS `instance_info_caches_1`
ON `instance_info_caches_1` . `instance_uuid` = `anon_1` . `instances_uuid`
LEFT OUTER JOIN `instance_extra` AS `instance_extra_1`
ON `instance_extra_1` . `instance_uuid` = `anon_1` . `instances_uuid`
LEFT OUTER JOIN `instance_metadata` AS `instance_metadata_1`
ON `instance_metadata_1` . `instance_uuid` = `anon_1` . `instances_uuid`
AND `instance_metadata_1` . `deleted` = ?
Environment
===========
1. Exact version of OpenStack you are running.
OpenStack Mitaka
openstack-nova-api.noarch 1:13.1.4-1.el7
Code suggests this could be affecting every release since Mitaka.
2. Which hypervisor did you use?
qemu-kvm.x86_64 10:1.5.3-141.el7_4.6
qemu-kvm-common.x86_64 10:1.5.3-141.el7_4.6
Reference
=========
Discussion on the OpenStack dev mailing list:
http://lists.openstack.org/pipermail/openstack-
dev/2018-October/135945.html
To manage notifications about this bug go to:
https://bugs.launchpad.net/nova/+bug/1799298/+subscriptions
References
