Installation¶
Note
Before the Stein release the placement code was in Nova alongside the compute REST API code (nova-api). Make sure that the release version of this document matches the release version you want to deploy.
Steps Overview¶
This subsection gives an overview of the process without going into detail on the methods used.
1. Deploy the API service
Placement provides a placement-api WSGI script for running the service with
Apache, nginx or other WSGI-capable web servers. Depending on what packaging
solution is used to deploy OpenStack, the WSGI script may be in /usr/bin
or /usr/local/bin.
placement-api, as a standard WSGI script, provides a module level
application attribute that most WSGI servers expect to find. This means it
is possible to run it with lots of different servers, providing flexibility in
the face of different deployment scenarios. Common scenarios include:
In all of these scenarios the host, port and mounting path (or prefix) of the
application is controlled in the web server’s configuration, not in the
configuration (placement.conf) of the placement application.
When placement was first added to DevStack it used the mod_wsgi style.
Later it was updated to use mod_proxy_uwsgi. Looking at those changes can
be useful for understanding the relevant options.
DevStack is configured to host placement at /placement on either the
default port for http or for https (80 or 443) depending on whether TLS
is being used. Using a default port is desirable.
By default, the placement application will get its configuration for settings
such as the database connection URL from /etc/placement/placement.conf.
The directory the configuration file will be found in can be changed by setting
OS_PLACEMENT_CONFIG_DIR in the environment of the process that starts the
application. With recent releases of oslo.config, configuration options may
also be set in the environment.
Note
When using uwsgi with a front end (e.g., apache2 or nginx) something needs to ensure that the uwsgi process is running. In DevStack this is done with systemd. This is one of many different ways to manage uwsgi.
This document refrains from declaring a set of installation instructions for the placement service. This is because a major point of having a WSGI application is to make the deployment as flexible as possible. Because the placement API service is itself stateless (all state is in the database), it is possible to deploy as many servers as desired behind a load balancing solution for robust and simple scaling. If you familiarize yourself with installing generic WSGI applications (using the links in the common scenarios list, above), those techniques will be applicable here.
2. Synchronize the database
The placement service uses its own database, defined in the
placement_database section of configuration. The
placement_database.connection option must be set or
the service will not start. The command line tool placement-manage
can be used to migrate the database tables to their correct form, including
creating them. The database described by the connection option must
already exist and have appropriate access controls defined.
Another option for synchronization is to set
placement_database.sync_on_startup to True in
configuration. This will perform any missing database migrations as the
placement web service starts. Whether you choose to sync automaticaly or use
the command line tool depends on the constraints of your environment and
deployment tooling.
Warning
In the Stein release, the placement code was extracted from nova.
If you are upgrading to use the extracted placement you will need
to migrate your placement data from the nova_api database to
the placement database. You can find sample scripts that may
help with this in the placement repository:
mysql-migrate-db.sh and postgresql-migrate-db.sh.
See also Upgrade Notes.
Note
Upgrading to the extracted placement at the same time as the other OpenStack services when upgrading to Stein is an option but is not required. The nova code will continue to have a copy of the placement service in its Stein release. However this copy will be deleted in Train and switching to the extracted version before upgrading to Train (potentially with the help of the scripts above) will be required.
3. Create accounts and update the service catalog
Create a placement service user with an admin role in Keystone.
The placement API is a separate service and thus should be registered under a placement service type in the service catalog. Clients of placement, such as the resource tracker in the nova-compute node, will use the service catalog to find the placement endpoint.
See Configure User and Endpoints for examples of creating the service user and catalog entries.
Devstack sets up the placement service on the default HTTP port (80) with a
/placement prefix instead of using an independent port.
Installation Packages¶
This section provides instructions on installing placement from Linux distribution packages.
Warning
These installation documents are a work in progress. Some of the distribution packages mentioned are not yet available so the instructions will not work.
The placement service provides an HTTP API used to track resource provider inventories and usages. More detail can be found at the placement overview.
Placement operates as a web service over a data model. Installation involves creating the necessary database and installing and configuring the web service. This is a straightforward process, but there are quite a few steps to integrate placement with the rest of an OpenStack cloud.
Note
Placement is required by some of the other OpenStack services, notably nova, therefore it should be installed before those other services but after Identity (keystone).
