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 get 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 appears 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 susinct 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.rst.

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. (See Cloud Services <cloudservices>)

Finally, when using Congress, the cloud operator will need to address violations that Congress detects. Usually, this means fixing the cloud configuration to abide by the policy. In the future Congress will also provide mechanisms to enforce policy (by preventing violations before they occur or correcting violations after the fact) and to audit policy (analyze the history of policy and policy violations).

• Free software: Apache license
• Documentation: http://docs.openstack.org/developer/congress

4. Installing Congress

There are 2 ways to install Congress.

• As part of devstack. This allows you to run Congress alongside live instances of other OpenStack projects like Nova and Neutron.
• Standalone. This allows you to write code and run unit tests, without requiring a full devstack installation.

4.1 Devstack-install

The contrib/devstack/ directory contains the files necessary to integrate Congress with devstack.

To install, make sure you have git installed. Then:

$ git clone https://git.openstack.org/openstack-dev/devstack
 (Or set env variable DEVSTACKDIR to the location to your devstack code)

$ wget http://git.openstack.org/cgit/stackforge/congress/plain/contrib/devstack/prepare_devstack.sh

$ chmod u+x prepare_devstack.sh

$ ./prepare_devstack.sh

Run devstack as normal. Note: the default data source configuration assumes the admin password is 'password':

$ ./stack.sh

Note: If the miminum localrc file required to run congress with keystone requires: ENABLED_SERVICES=congress,key,mysql

4.2 Standalone-install

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

• python 2.7 or above: https://www.python.org/download/releases/2.7/
• pip: https://pip.pypa.io/en/latest/installing.html
• java: http://java.com
• git

Clone Congress:

$ git clone https://github.com/stackforge/congress.git
$ cd congress

Run unit tests:

$ tox -epy27

Read the HTML documentation:

$ make docs
Open doc/html/index.html in a browser