Juju Charm - Keystone
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This charm provides Keystone, the OpenStack identity service. Its target platform is (ideally) Ubuntu LTS + OpenStack.


The following interfaces are provided:

  • nrpe-external-master: Used to generate Nagios checks.

  • identity-service: OpenStack API endpoints request an entry in the Keystone service catalog + endpoint template catalog. When a relation is established, Keystone receives: service_name, region, public_url, admin_url and internal_url. It first checks that the requested service is listed as a supported service. This list should stay updated to support current OpenStack core services. If the service is supported, an entry in the service catalog is created, an endpoint template is created and an admin token is generated. The other end of the relation receives the token as well as info on which ports Keystone is listening on.

  • keystone-service: This is currently only used by Horizon/dashboard as its interaction with Keystone is different from other OpenStack API services. That is, Horizon requests a Keystone role and token exists. During a relation, Horizon requests its configured default role and Keystone responds with a token and the auth + admin ports on which Keystone is listening.

  • identity-admin: Charms use this relation to obtain the credentials for the admin user. This is intended for charms that automatically provision users, tenants, etc. or that otherwise automate using the OpenStack cluster deployment.

  • identity-notifications: Used to broadcast messages to any services listening on the interface.

  • identity-credentials: Charms use this relation to obtain keystone credentials without creating a service catalog entry. Set ‘username’ only on the relation and keystone will set defaults and return authentication details. Possible relation settings:

    • username Username to be created.
    • project Project (tenant) name to be created. Defaults to services project.
    • requested_roles Comma delimited list of roles to be created.
    • requested_grants Comma delimited list of roles to be granted. Defaults to Admin role.
    • domain Keystone v3 domain the user will be created in. Defaults to the Default domain.


Keystone requires a database. The charm supports relation to a shared database server through the mysql-shared interface. When a new data store is configured, the charm ensures the minimum administrator credentials exist (as configured in charm configuration)


There are two mutually exclusive high availability options: using virtual IP(s) or DNS. In both cases, a relationship to hacluster is required which provides the corosync backend HA functionality.

To use virtual IP(s), the clustered nodes must be on the same subnet such that the VIP is a valid IP on the subnet for one of the node’s interfaces and each node has an interface in said subnet. The VIP becomes a highly-available API endpoint.

At a minimum, the config option vip must be set in order to use virtual IP HA. If multiple networks are being used, a VIP should be provided for each network, separated by spaces. Optionally, vip_iface or vip_cidr may be specified.

To use DNS high availability, there are several prerequisites. However, DNS HA does not require the clustered nodes to be on the same subnet. Currently, the DNS HA feature is only available for MAAS 2.0 or greater environments. MAAS 2.0 requires Juju 2.0 or greater. The clustered nodes must have static or “reserved” IP addresses registered in MAAS. The DNS hostname(s) must be pre-registered in MAAS before use with DNS HA.

At a minimum, the configuration option dns-ha must be set to true and at least one of os-public-hostname, os-internal-hostname or os-admin-hostname must be set in order to use DNS HA. One or more of the above hostnames may be set.

The charm will throw an exception in the following circumstances:

  • If neither vip nor dns-ha is set and the charm is related to hacluster

  • If both vip and dns-ha are set as they are mutually exclusive

  • If dns-ha is set and none of the os-{admin,internal,public}-hostname configuration options are set


Support for TLS and HTTPS endpoints can be enabled through configuration options.

To enable TLS and HTTPS endpoints with a certificate signed by your own Certificate Authority, set the following configuration options:

  • ssl_ca

  • ssl_cert

  • ssl_key

Example bundle usage:

  charm: cs:keystone
  num_units: 1
    ssl_ca:   include-base64://path-to-base64-encoded-ca-data
    ssl_cert: include-base64://path-to-base64-encoded-certificate-data
    ssl_key:  include-base64://path-to-base64-encoded-key-data

NOTE: If your certificate is signed by a Certificate Authority present in the CA Certificate Store in operating systems used in your deployment, you do not need to provide the ssl_ca configuration option.

Network Space Support

This charm supports the use of Juju Network Spaces, allowing the charm to be bound to network space configurations managed directly by Juju. This is only supported with Juju 2.0 and above.

API endpoints can be bound to distinct network spaces supporting the network separation of public, internal and admin endpoints.

Access to the underlying MySQL instance can also be bound to a specific space using the shared-db relation.

To use this feature, use the --bind option when deploying the charm:

juju deploy keystone --bind "public=public-space internal=internal-space admin=admin-space shared-db=internal-space"

Alternatively, these can also be provided as part of a juju native bundle configuration:

  charm: cs:xenial/keystone
  num_units: 1
    public: public-space
    admin: admin-space
    internal: internal-space
    shared-db: internal-space

NOTE: Spaces must be configured in the underlying provider prior to attempting to use them.

NOTE: Existing deployments using os\-\*-network configuration options will continue to function; these options are preferred over any network space binding provided if set.

Token Support

As the keystone charm supports multiple releases of the OpenStack software, it also supports two keystone token systems: UUID and Fernet. The capabilities are:

  • pre ‘ocata’: UUID tokens only.
  • ocata and pike: UUID or Fernet tokens, configured via the ‘token-provider’ configuration parameter.
  • rocky and later: Fernet tokens only.

Fernet tokens were added to OpenStack to solve the problem of keystone being required to persist tokens to a common database (cluster) like UUID tokens, and solve the problem of size for PKI or PKIZ tokens.

For further information, please see Fernet - Frequently Asked Questions.

Theory of Operation

In order to generate tokens, Fernet keys are used. These are generated by keystone and have an expiry date. The key repository is a directory, and each key is an integer number, with the highest number being the primary key. Key ‘0’ is the staged key, that will be the next primary. Other keys are secondary keys.

New tokens are only ever generated from the primary key, whilst the secondary keys are used to validate existing tokens. The staging key is not used to generate tokens but can be used to validate tokens as the staging key might be the new primary key on the master due to a rotation and the keys have not yet been synchronised across all the units.

Fernet keys need to be rotated at periodic intervals, and the keys need to be synchronised to each of the other keystone units. Keys should only be rotated on the master keystone unit and must be synchronised before they are rotated again. Over rotation occurs if a unit rotates its keys such that there is no suitable decoding key on another unit that can decode a token that has been generated on the master. This happens if two key rotations are done on the master before a synchronisation has been successfully performed. This should be avoided. Over rotations can also cause validation keys to be removed before a token’s expiration which would result in failed validations.

There are 3 parts to the Key Rotation Strategy:

  1. The rotation frequency
  2. The token lifespan
  3. The number of active keys

There needs to be at least 3 keys as a minimum. The actual number of keys is determined by the token lifespan and the rotation frequency. The max_active_keys must be one greater than the token lifespan / rotation frequency

To quote from the FAQ:

    The number of max_active_keys for a deployment can be determined by
    dividing the token lifetime, in hours, by the frequency of rotation in
    hours and adding two. Better illustrated as:

Configuring Key Lifetime

In the keystone charm, the rotation frequency is calculated automatically from the token-expiration and the fernet-max-active-keys configuration parameters. For example, with an expiration of 24 hours and 6 active keys, the rotation frequency is calculated as:

token_expiration = 24   # actually 3600, as it's in seconds
max_active_keys = 6
rotation_frequency = token_expiration / (max_active_keys - 2)

Thus, the fernet-max-active-keys can never be less than 3 (which is enforced in the charm), which would make the rotation frequency the same as the token expiration time.

NOTE: To increase the rotation frequency, either increase fernet-max-active-keys or reduce token-expiration, and to decrease rotation frequency, do the opposite.

NOTE: If the configuration parameters are used to significantly reduce the key lifetime, then it is possible to over-rotate the verification keys such that services will hold tokens that cannot be verified but haven’t yet expired. This should be avoided by only making small changes and verifying that current tokens will still be able to be verified. In particular, fernet-max-active-keys affects the rotation time.


When an older keystone charm is upgraded to this version, NO change will occur to the token system. That is, an ocata system will continue to use UUID tokens. In order to change the token system to Fernet, change the token-provider configuration item to fernet. This will switch the token system over. There may be a small outage in the control plane, but the running instances will be unaffected.