Juju Charm - Glance
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README.md

Overview

The glance charm deploys 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 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. 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 four 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 is used, otherwise it is mysql-innodb-cluster. 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 and ceph-osd 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 three 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 and swift-storage 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 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.

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
  • 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 <backend-name> ...

The default order of precedence is given by the following backend names: 'ceph', 'swift', 's3', 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 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 in the OpenStack Charms Deployment Guide for more information.

Ceph BlueStore compression

This charm supports BlueStore inline 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 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 in the OpenStack Charms Deployment Guide 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 and ceilometer-agent 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. 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:

    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 in the OpenStack Charms Deployment Guide for a thorough treatment of this feature.

Documentation

The OpenStack Charms project maintains two documentation guides:

Bugs

Please report bugs on Launchpad.