When Trove receives a command to create a database instance, it does so by launching a Nova instance based on the appropriate guest image that is stored in Glance. This document shows you the steps to build the guest images.
Note
For testing purpose, the Trove guest images of some specific databases are periodically built and published in http://tarballs.openstack.org/trove/images/ in Trove upstream CI.
Additionally, if you install Trove in devstack environment, a MySQL image
is created and registered in Glance automatically, unless it’s disabled by
setting TROVE_ENABLE_IMAGE_BUILD=false
in devstack local.conf file.
At the most basic level, a Trove Guest Instance is a Nova instance launched by Trove in response to a create command. For most of this document, we will confine ourselves to single instance databases; in other words, without the additional complexity of replication or mirroring. Guest instances and Guest images for replicated and mirrored database instances will be addressed specifically in later sections of this document.
This section describes the various components of a Trove Guest Instance.
A Trove Guest Instance contains at least a functioning Operating System and the database software that the instance wishes to provide (as a Service). For example, if your chosen operating system is Ubuntu and you wish to deliver MySQL version 5.7, then your guest instance is a Nova instance running the Ubuntu operating system and will have MySQL version 5.7 installed on it.
Trove supports multiple databases, some of them are relational (RDBMS) and some are non-relational (NoSQL). In order to provide a common management interface to all of these, the Trove Guest Instance has on it a ‘Guest Agent’. The Trove Guest Agent is a component of the Trove system that is specific to the database running on that Guest Instance.
The purpose of the Trove Guest Agent is to implement the Trove Guest Agent API for the specific database. This includes such things as the implementation of the database ‘start’ and ‘stop’ commands. The Trove Guest Agent API is the common API used by Trove to communicate with any guest database, and the Guest Agent is the implementation of that API for the specific database.
The Trove Guest Agent runs inside the Trove Guest Instance.
When TaskManager launches the guest VM it injects config files into the VM, including:
/etc/trove/conf.d/guest_info.conf
: Contains some information about
the guest, e.g. the guest identifier, the tenant ID, etc.
/etc/trove/conf.d/trove-guestagent.conf
: The config file for the
guest agent service.
The database stores data on persistent storage on Cinder (if
CONF.volume_support=True
) or ephemeral storage on the Nova instance. The
database service is accessible over the tenant network provided when creating
the database instance.
The cloud administrator is able to config management
networks(CONF.management_networks
) that is invisible to the cloud tenants,
but used for communication between database instance and the control plane
services(e.g. the message queue).
trovestack
is the recommended tooling provided by Trove community to build
the guest images. Before running trovestack
command, go to the scripts
folder:
git clone https://opendev.org/openstack/trove
cd trove/integration/scripts
The trove guest agent image could be created by running the following command:
$ ./trovestack build-image \
${datastore_type} \
${guest_os} \
${guest_os_release} \
${dev_mode} \
${guest_username} \
${imagepath}
Currently, only guest_os=ubuntu
and guest_os_release=xenial
are fully
tested and supported.
Default input values:
datastore_type=mysql
guest_os=ubuntu
guest_os_release=xenial
dev_mode=true
guest_username=ubuntu
imagepath=$HOME/images/trove-${guest_os}-${guest_os_release}-${datastore_type}
dev_mode=true
is mainly for testing purpose for trove developers and it’s
necessary to build the image on the trove controller host, because the host
and the guest VM need to ssh into each other without password. In this mode,
when the trove guest agent code is changed, the image doesn’t need to be
rebuilt which is convenient for debugging. Trove guest agent will ssh into
the controller node and download trove code during the service initialization.
if dev_mode=false
, the trove code for guest agent is injected into the
image at the building time. Now dev_mode=false
is still in experimental
and not considered production ready yet.
Some other global variables:
HOST_SCP_USERNAME
: Only used in dev mode, this is the user name used by
guest agent to connect to the controller host, e.g. in devstack
environment, it should be the stack
user.
GUEST_WORKING_DIR
: The place to save the guest image, default value is
$HOME/images
.
TROVE_BRANCH
: Only used in dev mode. The branch name of Trove code
repository, by default it’s master, use other branches as needed such as
stable/train.
For example, in order to build a MySQL image for Ubuntu Xenial operating system in development mode:
$ ./trovestack build-image mysql ubuntu xenial true
Once the image build is finished, the cloud administrator needs to register the
image in Glance and register a new datastore or version in Trove using
trove-manage
command, e.g. after building an image for MySQL 5.7.1:
$ openstack image create ubuntu-mysql-5.7.1-dev \
--public \
--disk-format qcow2 \
--container-format bare \
--file ~/images/ubuntu-xenial-mysql.qcow2
$ trove-manage datastore_version_update mysql 5.7.1 mysql $image_id "" 1
If you see anything error or need help for the image creation, please ask help
either in #openstack-trove
IRC channel or sending emails to
openstack-discuss@lists.openstack.org mailing list.
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