Push Type DataSource Driver


Problem description

Currently DataSource Driver retrieves all cloud service’s info by polling each datasource. The purpose of the polling is just to monitor cloud service periodically. Thus Congress can’t notice a change in cloud service just after the change occurs. It means a policy violation isn’t detected until Congress polls the change. Additionally, Congress calls the service’s API to get the data for a table, so datasource table’s schema depends on API response contents.

In the area of monitoring, tons of well-developed monitoring system have already existed in the world. The systems have an ability to notify a change in cloud services just after a change occurs. And then these monitoring systems can detect many kind of changes in cloud services that Congress can’t do.

Congress should retrieve the notification as a DataSource since it helps Congress to calculate a policy violation faster than now and also enables us to define varied policies and rules.

Proposed change

Following changes are proposed in the BP.

  1. Create PollingDataSourceDriver and PushedDataSourceDriver class. Current

    DataSourceDriver has 2 features. One is converting data to datasource table and sending it to Policy Engine. Another is polling data from datasource. We should separate the polling feature into another class that is subclass of DataSourceDriver named PollingDataSourceDriver. And we create PushedDataSourceDriver, which is subclass of DataSourceDriver and receives data from a monitoring system.

  2. Create HttpReceiverDriver subclass or OsloMsgReceiverDriver subclass

    Both Drivers are a subclass of PushedDataSourceDriver and receive datasource info by the protocol the class name has. DataSourceDriver has to keep datasource status in itself, so the classes will support 2 types of a data receiving method. One is receiving all status data each push time. Another is receiving only delta data that represents which row is deleted or added in the status like REST API.

    First of all, the BP chooses and implements one of them based on an usecase, which needs to use PushedDatasourceDriver.

There are some restrictions as a first implementation.

  • Table definitions

    Ideally speaking, PushedDataSourceDriver should allow admin to change a datasource name, table name, schema and so on by Congress API. PushedDataSourceDriver defines the protocol name as a datasource name in first implementation. Then the admin can define a translator in another python file. In the current architecture, the path is set by ‘config’ key in a call for create datasource API. In the distributed architecture, the path is set by a config file for each datasource driver.


The alternative is that Congress allows admin to add and delete a row by API calls. The API is a REST API, so the benefit is that both create and delete methods are already developed in itself. However, the way has following bad points. First is all request needs an authentication to push data. It means all datasource have to be related to keystone authority. Second is it’s not easy to divide a network segmentation based on each API’s purpose. If Congress enables API to retrieve datasource, the datasource receiver is exposed to user.


Example: define a table that shows service name related to host’s failures

detected by monitoring system.

Assumption: monitoring system pushes data by http. col_1 represents name of

a host where the monitoring system detects some failure. col_2 represents a failure type.


http:table(col_1=host, col_2=”nic_error”)


http:table(col_1=host, col_2=”disk_error”)

failure_effected_service(service, host) :-

nova:service(host_name=host, service=service), host_failures(host=host)

Policy actions


Data sources

Add new datasource model and table.

Data model impact


REST API impact

Creating new datasource name, table name and table schema by API is a future work. It means this feature is out of scope for this BP.

Security impact

It enables others to push datasource row into the datasource driver. It would cause undesired policy violation if malicious users send data on purpose.

Notifications impact


Other end user impact


Performance impact

PushedDataSourceDriver notifies a status change when it receives a change from a monitoring system. If the system frequently sends a notification, it would make Congress busy with calculating policy table.

Other deployer impact

  • Add a config for column number

  • Disable the PushedDataSourceDriver in default because of a reason described in Security Impact section

Developer impact




Primary assignee:


Other contributors:


Work items

  1. Create PollingDataSourceDriver subclass and pull out methods related to polling from DataSourceDriver class into the new Driver

  2. Create PushedDataSourceDriver subclass

  3. Create HttpReceiverDriver or OsloMsgReceiverDriver




  • Add unit tests related to new class

  • Add tempest scenario tests which use pushed data in rules if possible

Documentation impact

DataSource list will be updated if the list is described in docs.