One day a while back, I started blabbing out loud about some quick ways to experiment with a live placement service and was (very appropriately) reminded that I make a ton of incorrect assumptions about the familiarity people have with things I do most days. Statements like "just spin up the wsgi script against uwsgi and a stubbed out placement.conf and see what happens" are a good example of me being bad.

So, to help, here are some instructions on how to spin up the wsgi script against uwsgi and a stubbed out placement.conf, in case you want to see what happens. The idea here is that you want to experiment with the current placement code, using a live database, but you're not concerned with other services, don't want to deal with devstack, but need a level of interaction with the code and process that something like placedock can't provide.

As ever, even all of the above has lots of assumptions about experience and context. This post assumes you are someone who either is an OpenStack (and probably placement) developer, or would like to be one.

To make this go you need a unix-like OS, with a python3 dev environment, and git and mysql (or postgresql) installed. We'll be doing this work from within a virtualenv, built from the tox.ini in the placement code.

At the time of writing, some required code is not yet merged into placement, so we'll be using a patch that is currently under review. I'll update this document when that code merges so we can skip a step.

Get The Code and Deps

The placement code lives at https://git.openstack.org/cgit/openstack/placement. We want to clone that:

git clone git://git.openstack.org/openstack/placement
cd placement

Then we want to get the extra code mentioned above:

git pull https://git.openstack.org/openstack/placement refs/changes/61/600161/13

Setup The Database

That patch adds a commands to create tables in a database. We need to 1) create the database, 2) create a virtualenv to have the command, 3) use it to create the tables.

The database can have whatever name you like. Whatever you choose, use it throughout this process. I choose placement. You may need a user and password to talk to your database, setting that up is out of scope for this document. I'm using a machine that has had devstack on it before so mysql is configured in what might be a familiar way:

mysql -uroot -psecret -e "DROP DATABASE IF EXISTS placement;"
mysql -uroot -psecret -e "CREATE DATABASE placement CHARACTER SET utf8;"

You may also need to set permissions:

mysql -uroot -psecret \
    -e "GRANT ALL PRIVILEGES ON placement.* TO 'root'@'%' identified by 'secret';"

Get the table create command by updating the virtualenv:

tox -epy36 --notest

Create a bare minimum placement.conf in the /etc/placement directory (which you may need to create):

[placement_database]
connection = mysql+pymysql://root:secret@127.0.0.1/placement?charset=utf8

(Note that when this command matures you will be able to name the location of the configuration file on the command line.)

Run the command to create the tables:

.tox/py36/bin/placement-manage db table_create

You can confirm the tables are there with mysqlshow placement

Run The Service

Now we want to run the service. We need to update placement.conf so it will produce debugging output and use the noauth strategy for authentication (so we don't also have to run Keystone). Make placement.conf look like this (adjusting for your database settings):

[DEFAULT]
debug = True

[placement_database]
connection = mysql+pymysql://root:secret@127.0.0.1/placement?charset=utf8

[api]
auth_strategy = noauth2

We need to install the uwsgi package into the virtualenv:

.tox/py36/bin/pip install uwsgi

And then use uwsgi to run the service. Start it with:

.tox/py36/bin/uwsgi --http :8000 --wsgi-file .tox/py36/bin/placement-api

If that worked you'll see lots of debug output and spawned uWSGI worker 1. Test that things are working from another terminal with curl:

curl -v http://localhost:8000/

Get a list of resource providers with (the x-auth-token header is required, openstack-api-version is optional but makes sure we are getting the latest functionality):

curl -H 'x-auth-token: admin' \
     -H 'openstack-api-version: placement latest' \
     http://localhost:8000/resource_providers

The result ought to look something like this:

{"resource_providers": []}

If it doesn't then something went wrong with the above and there should be more information in the terminal where uwsgi is running.

From here you can experiment with creating resource providers and related placement features. If you change the placement code, ctrl-c to kill the uwsgi process and start it up again. For testing, you might might enjoy placecat.

Here's a script to do the install for you: