Congress Introduction and Installation

1. What is Congress

Congress is an open policy framework for the cloud. With Congress, a cloud operator can declare, monitor, enforce, and audit “policy” in a heterogeneous cloud environment. Congress gets inputs from a cloud’s various cloud services; for example in OpenStack, Congress fetches information about VMs from Nova, and network state from Neutron, etc. Congress then feeds input data from those services into its policy engine where Congress verifies that the cloud’s actual state abides by the cloud operator’s policies. Congress is designed to work with any policy and any cloud service.

2. Why is Policy Important

The cloud is a collection of autonomous services that constantly change the state of the cloud, and it can be challenging for the cloud operator to know whether the cloud is even configured correctly. For example,

  • The services are often independent from each other and do not support transactional consistency across services, so a cloud management system can change one service (create a VM) without also making a necessary change to another service (attach the VM to a network). This can lead to incorrect behavior.
  • Other times, we have seen a cloud operator allocate cloud resources and then forget to clean them up when the resources are no longer in use, effectively leaving garbage around the system and wasting resources.
  • The desired cloud state can also change over time. For example, if a security vulnerability is discovered in Linux version X, then all machines with version X that were ok in the past are now in an undesirable state. A version number policy would detect all the machines in that undesirable state. This is a trivial example, but the more complex the policy, the more helpful a policy system becomes.

Congress’s job is to help people manage that plethora of state across all cloud services with a succinct policy language.

3. Using Congress

Setting up Congress involves writing policies and configuring Congress to fetch input data from the cloud services. The cloud operator writes policy in the Congress policy language, which receives input from the cloud services in the form of tables. The language itself resembles datalog. For more detail about the policy language and data format see Policy.

To add a service as an input data source, the cloud operator configures a Congress “driver,” and the driver queries the service. Congress already has drivers for several types of service, but if a cloud operator needs to use an unsupported service, she can write a new driver without much effort and probably contribute the driver to the Congress project so that no one else needs to write the same driver.

Finally, when using Congress, the cloud operator must choose what Congress should do with the policy it has been given:

  • monitoring: detect violations of policy and provide a list of those violations
  • proactive enforcement: prevent violations before they happen (functionality that requires other services to consult with Congress before making changes)
  • reactive enforcement: correct violations after they happen (a manual process that Congress tries to simplify)

In the future, Congress will also help the cloud operator audit policy (analyze the history of policy and policy violations).

Congress is free software and is licensed with Apache.

  • Free software: Apache license

4. Installing Congress

There are 2 ways to install Congress.

  • As part of DevStack. Get Congress running alongside other OpenStack services like Nova and Neutron, all on a single machine. This is a great way to try out Congress for the first time.
  • Separate install. Get Congress running alongside an existing OpenStack deployment

4.1 Devstack-install

For integrating Congress with DevStack:

  1. Download DevStack
$ git clone
$ cd devstack
  1. Configure DevStack to use Congress and any other service you want. To do that, modify the local.conf file (inside the DevStack directory). Here is what our file looks like:

enable_plugin congress
enable_plugin ceilometer
enable_service h-eng h-api h-api-cfn h-api-cw
disable_service n-net
enable_service neutron
enable_service q-svc
enable_service q-agt
enable_service q-dhcp
enable_service q-l3
enable_service q-meta
enable_service s-proxy s-object s-container s-account
  1. Run The default configuration expects the passwords to be ‘password’ without the quotes
$ ./

4.2 Separate install

Install the following software, if you haven’t already.

$ sudo apt-get install git gcc python-dev libxml2 libxslt1-dev libzip-dev mysql-server python-mysqldb build-essential libssl-dev libffi-dev

Clone Congress

$ git clone
$ cd congress

Install requirements

$ sudo pip install .

Install Source code

$ sudo python install

Configure Congress (Assume you put config files in /etc/congress)

$ sudo mkdir -p /etc/congress
$ sudo mkdir -p /etc/congress/snapshot
$ sudo cp etc/api-paste.ini /etc/congress
$ sudo cp etc/policy.json /etc/congress
$ sudo touch /etc/congress/congress.conf

Add drivers in /etc/congress/congress.conf [DEFAULT] section:

drivers = congress.datasources.neutronv2_driver.NeutronV2Driver,congress.datasources.glancev2_driver.GlanceV2Driver,congress.datasources.nova_driver.NovaDriver,congress.datasources.keystone_driver.KeystoneDriver,congress.datasources.ceilometer_driver.CeilometerDriver,congress.datasources.cinder_driver.CinderDriver,congress.datasources.swift_driver.SwiftDriver,congress.datasources.plexxi_driver.PlexxiDriver,congress.datasources.vCenter_driver.VCenterDriver,congress.datasources.murano_driver.MuranoDriver,congress.datasources.ironic_driver.IronicDriver

Modify [keystone_authtoken] and [database] according to your environment.

For setting Congress with “noauth”: Add the following line to [DEFAULT] section in /etc/congress/congress.conf

auth_strategy = noauth
Also, might want to delete/comment [keystone_authtoken] section in

To use RabbitMQ with Congress, Set the transport_url in [DEFAULT] section in /etc/congress/congress.conf according to your setup.

transport_url = rabbit://$RABBIT_USERID:$RABBIT_PASSWORD@$RABBIT_HOST:5672

A bare-bones congress.conf is as follows (adapt MySQL root password):

drivers = congress.datasources.neutronv2_driver.NeutronV2Driver,congress.datasources.glancev2_driver.GlanceV2Driver,congress.datasources.nova_driver.NovaDriver,congress.datasources.keystone_driver.KeystoneDriver,congress.datasources.ceilometer_driver.CeilometerDriver,congress.datasources.cinder_driver.CinderDriver,congress.datasources.swift_driver.SwiftDriver,congress.datasources.plexxi_driver.PlexxiDriver,congress.datasources.vCenter_driver.VCenterDriver,congress.datasources.murano_driver.MuranoDriver,congress.datasources.ironic_driver.IronicDriver
auth_strategy = noauth
connection = mysql+pymysql://root:password@

For a detailed sample, please follow README-congress.conf.txt

Create database

$ mysql -u root -p
$ mysql> CREATE DATABASE congress;
$ mysql> GRANT ALL PRIVILEGES ON congress.* TO 'congress'@'localhost' IDENTIFIED BY 'CONGRESS_DBPASS';

Configure congress.conf with db information.

Push down schema

$ sudo congress-db-manage --config-file /etc/congress/congress.conf upgrade head
Set up Congress accounts

Use your OpenStack RC file to set and export required environment variables: OS_USERNAME, OS_PASSWORD, OS_PROJECT_NAME, OS_TENANT_NAME, OS_AUTH_URL.

(Adapt parameters according to your environment)

$ ADMIN_ROLE=$(openstack role list | awk "/ admin / { print \$2 }")
$ SERVICE_TENANT=$(openstack project list | awk "/ admin / { print \$2 }")
$ CONGRESS_USER=$(openstack user create --password password --project admin --email "" congress | awk "/ id / {print \$4 }")
$ openstack role add $ADMIN_ROLE --user $CONGRESS_USER --project  $SERVICE_TENANT
$ CONGRESS_SERVICE=$(openstack service create congress --name "policy" --description "Congress Service" | awk "/ id / { print \$4 }")
$ openstack endpoint create $CONGRESS_SERVICE --region RegionOne --publicurl  --adminurl --internalurl
Start Congress
The default behavior is to start the Congress API, Policy Engine, and Datasource in a single node. For HAHT deployment options, please see the HA Overview document.
$ sudo /usr/local/bin/congress-server --debug
Configure datasource drivers
First make sure you have the Congress client (project python-congressclient) installed. Run this command for every service that Congress will poll for data. Please note that the service name $SERVICE should match the ID of the datasource driver, e.g. “neutronv2” for Neutron and “glancev2” for Glance; $OS_USERNAME, $OS_TENANT_NAME, $OS_PASSWORD and $SERVICE_HOST are used to configure the realted datasource driver so that congress knows how to talk with the service.
$ openstack congress datasource create $SERVICE "$SERVICE" --config username=$OS_USERNAME --config tenant_name=$OS_TENANT_NAME --config password=$OS_PASSWORD --config auth_url=http://$SERVICE_HOST:5000/v2.0

Install test harness

$ sudo pip install 'tox<1.7'

Run unit tests

$ tox -epy27
Read the HTML documentation
Install python-sphinx and the oslosphinx extension if missing.
$ sudo pip install sphinx
$ sudo pip install oslosphinx

Build the docs
$ make docs

Open doc/html/index.html in a browser

4.3 Upgrade

Here are the instructions for upgrading to a new release of the Congress server.

  1. Stop the Congress server.
  2. Update the Congress git repo
$ cd /path/to/congress
$ git fetch origin

3. Checkout the release you are interested in, say Mitaka. Note that this step will not succeed if you have any uncommitted changes in the repo.

$ git checkout origin/stable/mitaka

If you have changes committed locally that are not merged into the public repository, you now need to cherry-pick those changes onto the new branch.

  1. Install dependencies
$ sudo pip install
  1. Install source code
$ sudo python install
  1. Migrate the database schema
$ sudo congress-db-manage --config-file /etc/congress/congress.conf upgrade head
  1. (optional) Check if the configuration options you are currently using are still supported and whether there are any new configuration options you would like to use. To see the current list of configuration options, use the following command, which will create a sample configuration file in etc/congress.conf.sample for you to examine.
$ tox -egenconfig
  1. Restart Congress, e.g.
$ sudo /usr/local/bin/congress-server --debug