# Overview The glance charm deploys [Glance][upstream-glance], the core OpenStack service that acts as the central repository for virtual machine (VM) images. The charm works alongside other Juju-deployed OpenStack services. # Usage ## Configuration This section covers common and/or important configuration options. See file `config.yaml` for the full list of options, along with their descriptions and default values. See the [Juju documentation][juju-docs-config-apps] for details on configuring applications. #### `openstack-origin` The `openstack-origin` option states the software sources. A common value is an OpenStack UCA release (e.g. 'cloud:bionic-ussuri' or 'cloud:focal-victoria'). See [Ubuntu Cloud Archive][wiki-uca]. The underlying host's existing apt sources will be used if this option is not specified (this behaviour can be explicitly chosen by using the value of 'distro'). #### `pool-type` The `pool-type` option dictates the Ceph storage pool type. See sections 'Ceph pool type' and 'Ceph backed storage' for more information. ## Deployment This section includes five different deployment scenarios (with their respective backends). Each scenario requires these applications to be present: keystone, nova-cloud-controller, nova-compute, and a cloud database. > **Note**: The database application is determined by the series. Prior to focal [percona-cluster][percona-cluster-charm] is used, otherwise it is [mysql-innodb-cluster][mysql-innodb-cluster-charm]. In the example deployments below mysql-innodb-cluster has been chosen. ### Ceph-backed storage Ceph is the recommended storage backend solution for Glance. The steps below assume a pre-existing Ceph cluster (see the [ceph-mon][ceph-mon-charm] and [ceph-osd][ceph-osd-charm] charms). Here, Glance is deployed to a new container on machine '1' and related to the Ceph cluster via the ceph-mon charm: juju deploy --to lxd:1 glance juju add-relation glance:ceph ceph-mon:client Proceed with a group of commands common to all four scenarios: juju add-relation glance:identity-service keystone:identity-service juju add-relation glance:image-service nova-cloud-controller:image-service juju add-relation glance:image-service nova-compute:image-service juju deploy mysql-router glance-mysql-router juju add-relation glance-mysql-router:db-router mysql-innodb-cluster:db-router juju add-relation glance-mysql-router:shared-db glance:shared-db This configuration can be used to support Glance in HA/scale-out deployments. > **Note**: In this scenario Glance acts as a Ceph client, which requires L3 network connectivity to Ceph monitors and OSDs. For MAAS-based deployments this can be addressed with network spaces (see section 'Network spaces' below). ### Object storage-backed storage Glance can use Object storage as its storage backend. OpenStack Swift, Ceph RADOS Gateway, and external S3 are supported, and all resulting configurations can be used to support Glance in HA/scale-out deployments. #### Swift The steps below assume a pre-existing Swift deployment (see the [swift-proxy][swift-proxy-charm] and [swift-storage][swift-storage-charm] charms). Here, Glance is deployed to a new container on machine '1' and related to Swift via the swift-proxy charm: juju deploy --to lxd:1 glance juju add-relation glance:object-store swift-proxy:object-store Proceed with the common group of commands from the Ceph scenario. #### Ceph RADOS Gateway The steps below assume a pre-existing Ceph RADOS Gateway deployment (see the [ceph-radosgw][ceph-radosgw-charm] charm). Here, Glance is deployed to a new container on machine '1' and related to the ceph-radosgw application: juju deploy --to lxd:1 glance juju add-relation glance:object-store ceph-radosgw:object-store Proceed with the common group of commands from the Ceph scenario. #### External S3 The step below assumes an external and pre-existing S3 compatible server available. S3 server information can be passed via charm config options: juju config glance \ s3-store-host='http://my-object-storage.example.com:8080' \ s3-store-access-key='ACCESS_KEY' \ s3-store-secret-key='SECRET_KEY' \ s3-store-bucket='BUCKET_NAME' > **Note**: The S3 backend is supported starting with OpenStack Ussuri. Enabling S3 backend overrides `expose-image-locations` as false not to expose S3 credentials through Glance API. ### Cinder LVM-backed storage Glance can also use Cinder LVM-backed storage as its storage backend, the configuration option cinder-volume-types can be used to specify the volume types in Cinder. The steps below assume a pre-existing Cinder LVM-backed deployment (see the [cinder][cinder-charm] and [cinder-lvm][cinder-lvm-charm] charms). Here, Glance is deployed to machine '1' and related to Cinder: juju deploy --to 1 glance juju add-relation cinder:image-service glance:image-service juju add-relation cinder:cinder-volume-service glance:cinder-volume-service Proceed with the common group of commands from the Ceph scenario. > **Note**: To support Cinder LVM-backed storage, Glance unit should be deployed on a baremetal machine or a virtual machine. ### Local storage Glance can simply use the storage available on the application unit's machine to store image data. Here, Glance is deployed to a new container on machine '1': juju deploy --to lxd:1 glance Proceed with the common group of commands from the Ceph scenario. ## Multiple backends Multiple storage backend support allows for one backend of each type: * Ceph * Swift (includes Ceph RADOS Gateway) * S3 * Cinder * local With multiple backends configured, the cloud operator can specify, at image upload time, which backend will be used to store the image. This is done by using the `--store` option to the `glance` CLI client: glance image-create --store ... The default order of precedence is given by the following backend names: 'ceph', 'swift', 's3', 'cinder', and then 'local'. > **Important**: The backend name of 'swift' denotes both object storage solutions: Swift and Ceph RADOS Gateway. Only one of these solutions can therefore be used. ## Actions This section covers Juju [actions][juju-docs-actions] supported by the charm. Actions allow specific operations to be performed on a per-unit basis. To display action descriptions run `juju actions --schema glance`. If the charm is not deployed then see file `actions.yaml`. * `openstack-upgrade` * `pause` * `resume` * `security-checklist` ## Ceph pool type Ceph storage pools can be configured to ensure data resiliency either through replication or by erasure coding. This charm supports both types via the `pool-type` configuration option, which can take on the values of 'replicated' and 'erasure-coded'. The default value is 'replicated'. For this charm, the pool type will be associated with Glance images. > **Note**: Erasure-coded pools are supported starting with Ceph Luminous. ### Replicated pools Replicated pools use a simple replication strategy in which each written object is copied, in full, to multiple OSDs within the cluster. The `ceph-osd-replication-count` option sets the replica count for any object stored within the 'glance' rbd pool. Increasing this value increases data resilience at the cost of consuming more real storage in the Ceph cluster. The default value is '3'. > **Important**: The `ceph-osd-replication-count` option must be set prior to adding the relation to the ceph-mon (or ceph-proxy) application. Otherwise, the pool's configuration will need to be set by interfacing with the cluster directly. ### Erasure coded pools Erasure coded pools use a technique that allows for the same resiliency as replicated pools, yet reduces the amount of space required. Written data is split into data chunks and error correction chunks, which are both distributed throughout the cluster. > **Note**: Erasure coded pools require more memory and CPU cycles than replicated pools do. When using erasure coded pools for Glance images two pools will be created: a replicated pool (for storing RBD metadata) and an erasure coded pool (for storing the data written into the RBD). The `ceph-osd-replication-count` configuration option only applies to the metadata (replicated) pool. Erasure coded pools can be configured via options whose names begin with the `ec-` prefix. > **Important**: It is strongly recommended to tailor the `ec-profile-k` and `ec-profile-m` options to the needs of the given environment. These latter options have default values of '1' and '2' respectively, which result in the same space requirements as those of a replicated pool. See [Ceph Erasure Coding][cdg-ceph-erasure-coding] in the [OpenStack Charms Deployment Guide][cdg] for more information. ## Ceph BlueStore compression This charm supports [BlueStore inline compression][ceph-bluestore-compression] for its associated Ceph storage pool(s). The feature is enabled by assigning a compression mode via the `bluestore-compression-mode` configuration option. The default behaviour is to disable compression. The efficiency of compression depends heavily on what type of data is stored in the pool and the charm provides a set of configuration options to fine tune the compression behaviour. > **Note**: BlueStore compression is supported starting with Ceph Mimic. ## High availability When more than one unit is deployed with the [hacluster][hacluster-charm] application the charm will bring up an HA active/active cluster. There are two mutually exclusive high availability options: using virtual IP(s) or DNS. In both cases the hacluster subordinate charm is used to provide the Corosync and Pacemaker backend HA functionality. See [OpenStack high availability][cdg-ha-apps] in the [OpenStack Charms Deployment Guide][cdg] for details. > **Important**: Glance in an HA configuration must be backed by either Ceph or Swift. ## Glance metering Glance metering can be achieved with Ceilometer. The [rabbitmq-server][rabbitmq-server-charm] and [ceilometer-agent][ceilometer-agent-charm] applications are required to be present. Assuming Glance is deployed, add two relations: juju add-relation glance:amqp rabbitmq-server:amqp juju add-relation glance:amqp ceilometer-agent:amqp juju add-relation glance:juju-info ceilometer-agent:container ## Network spaces This charm supports the use of Juju [network spaces][juju-docs-spaces]. This feature optionally allows specific types of the application's network traffic to be bound to subnets that the underlying hardware is connected to. > **Note**: Spaces must be configured in the backing cloud prior to deployment. API endpoints can be bound to distinct network spaces supporting the network separation of public, internal and admin endpoints. Glance acts as a Ceph client and needs IP connectivity to Ceph monitors and OSDs. Binding the ceph endpoint to a space can solve this problem in case monitors and OSDs are located on a single L2 broadcast domain (if they are not, static or dynamic routes need to be used in addition to spaces). 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 glance --bind \ "public=public-space \ internal=internal-space \ admin=admin-space \ shared-db=internal-space \ ceph=ceph-access-space" Alternatively, these can also be provided as part of a juju native bundle configuration: ```yaml glance: charm: cs:xenial/glance num_units: 1 bindings: public: public-space admin: admin-space internal: internal-space shared-db: internal-space ceph: ceph-access-space ``` > **Note**: Existing glance units configured with the `os-admin-network`, `os-internal-network`, or `os-public-network` options will continue to honour them. Furthermore, these options override any space bindings, if set. ## Policy overrides Policy overrides is an advanced feature that allows an operator to override the default policy of an OpenStack service. The policies that the service supports, the defaults it implements in its code, and the defaults that a charm may include should all be clearly understood before proceeding. > **Caution**: It is possible to break the system (for tenants and other services) if policies are incorrectly applied to the service. Policy statements are placed in a YAML file. This file (or files) is then (ZIP) compressed into a single file and used as an application resource. The override is then enabled via a Boolean charm option. Here are the essential commands (filenames are arbitrary): zip overrides.zip override-file.yaml juju attach-resource glance policyd-override=overrides.zip juju config glance use-policyd-override=true See [Policy overrides][cdg-appendix-n] in the [OpenStack Charms Deployment Guide][cdg] for a thorough treatment of this feature. # Documentation The OpenStack Charms project maintains two documentation guides: * [OpenStack Charm Guide][cg]: for project information, including development and support notes * [OpenStack Charms Deployment Guide][cdg]: for charm usage information # Bugs Please report bugs on [Launchpad][lp-bugs-charm-glance]. [cg]: https://docs.openstack.org/charm-guide [cdg]: https://docs.openstack.org/project-deploy-guide/charm-deployment-guide [cdg-appendix-n]: https://docs.openstack.org/project-deploy-guide/charm-deployment-guide/latest/app-policy-overrides.html [lp-bugs-charm-glance]: https://bugs.launchpad.net/charm-glance/+filebug [hacluster-charm]: https://jaas.ai/hacluster [ceph-mon-charm]: https://jaas.ai/ceph-mon [ceph-osd-charm]: https://jaas.ai/ceph-osd [ceph-radosgw-charm]: https://jaas.ai/ceph-radosgw [swift-proxy-charm]: https://jaas.ai/swift-proxy [swift-storage-charm]: https://jaas.ai/swift-storage [percona-cluster-charm]: https://jaas.ai/percona-cluster [mysql-innodb-cluster-charm]: https://jaas.ai/mysql-innodb-cluster [rabbitmq-server-charm]: https://jaas.ai/rabbitmq-server [ceilometer-agent-charm]: https://jaas.ai/ceilometer-agent [cdg-ha-apps]: https://docs.openstack.org/project-deploy-guide/charm-deployment-guide/latest/app-ha.html#ha-applications [juju-docs-spaces]: https://juju.is/docs/spaces [wiki-uca]: https://wiki.ubuntu.com/OpenStack/CloudArchive [juju-docs-config-apps]: https://juju.is/docs/configuring-applications [cdg-ceph-erasure-coding]: https://docs.openstack.org/project-deploy-guide/charm-deployment-guide/latest/app-erasure-coding.html [ceph-bluestore-compression]: https://docs.ceph.com/en/latest/rados/configuration/bluestore-config-ref/#inline-compression [upstream-glance]: https://docs.openstack.org/glance/latest/ [juju-docs-actions]: https://jaas.ai/docs/actions [cinder-charm]: https://jaas.ai/cinder [cinder-lvm-charm]: https://jaas.ai/cinder-lvm