The design document for the API can be found below. This document contains the API as of the current release:
There are two top-level concepts in today’s API: Policies and Data-sources.
- Policies have rules that describe the permitted states of the cloud, along with tables representing abstractions of the cloud state.
- Data-sources have tables representing the current state of the cloud.
- The tables of both policies and data-sources have rows that describe their contents.
1. Policy (/v1/)¶
You can create and delete policies. Two policies are provided by the system, and you are not permitted to delete them: classification and action. A policy has the following fields:
- name: a unique name that is human-readable
- abbreviation: a shorter name that appears in traces
- description: an explanation of this policy’s purpose
- kind: either nonrecursive or action. The default is nonrecursive and unless you are writing action descriptions for use with simulate you should always use the default.
|GET||.../policies/<policy-id>||Read policy properties|
|POST||.../policies/<policy-id>||Create new policy|
You can also utilize the simulation API call, which answers hypothetical questions: if we were to change the state of the cloud in this way, what would the answer to this query be? See Monitoring and Enforcement for more details and examples:
POST .../policies/<policy-id> ?action=simulate &query=<query> # string query like: 'error(x)' &sequence=<sequence> # changes to state like: 'p+(1) p-(2)' &action_policy=<action_policy> # name of a policy: 'action' [&delta=true] # return just change in <query> [&trace=true] # also return explanation of result
2. Policy Rules (/v1/policies/<policy-id>/...)¶
Each policy is a collection of rules. Congress supports the usual CRUD operations for changing that collection. A rule has the following fields:
- ID: a unique identifier
- name: a human-friendly identifier
- rule: a string representing the actual rule as described in Policy
|GET||.../rules||List policy rules|
|POST||.../rules||Create policy rule|
|GET||.../rules/<rule-id>||Read policy rule|
|DELETE||.../rules/<rule-id>||Delete policy rule|
3. Policy Tables (/v1/policies/<policy-id>/...)¶
All the tables mentioned in the rules of a policy can be queried via the API. They have only an ID field.
|GET||.../tables/<table-id>||Read table properties|
4. Policy Table Rows (/v1/policies/<policy-id>/tables/<table-id>/...)¶
Rules are used to instruct Congress how to create new tables from existing tables. Congress allows you to query the actual contents of tables at any point in time. Congress will also provide a trace of how it computed a table, to help policy authors understand why certain rows belong to the table and others do not.
|GET||.../rows?trace=true||List rows with explanation (use ‘printf’ to display)|
5. Drivers (/v1/system/)¶
A driver is a piece of code that once instantiated and configured interacts with a specific cloud service like Nova or Neutron. A driver has the following fields.
- ID: a human-friendly unique identifier
- description: an explanation of which type of cloud service this driver interacts with
|GET||.../drivers/<driver-id>||Read driver properties|
6. Data sources (/v1/)¶
A data source is an instantiated and configured driver that interacts with a particular instance of a cloud service (like Nova or Neutron). You can construct multiple datasources using the same driver. For example, if you have two instances of Neutron running, one in production and one in test and you want to write policy over both of them, you would create two datasources using the Neutron driver and give them different names and configuration options. For example, you might call one datasource ‘neutron_prod’ and the other ‘neutron_test’ and configure them with different IP addresses.
A datasource has the following fields.
- ID: a unique identifier
- name: a human-friendly unique that is unique across datasources and policies
- driver: the name of the driver code that this datasource is running
- config: a dictionary capturing the configuration of this datasource
- description: an explanation of the purpose of this datasource
- enabled: whether or not this datasource is functioning (which is always True)
|GET||.../data-sources||List data sources|
|POST||.../data-sources||Create data source|
|DELETE||.../data-sources/<ds-id>||Delete data source|
|GET||.../data-sources/<ds-id>/schema||Show schema (tables and table-columns)|
|GET||.../data-sources/<ds-id>/status||Show data source status|
7. Data source Tables (/v1/data-sources/<ds-id>/...)¶
Each data source maintains a collection of tables (very similar to a Policy). The list of available tables for each data source is available via the API. A table just has an ID field.
|GET||.../tables||List data sources|
|GET||.../tables/<table-id>||Read data source properties|
8. Data source Table Rows (/v1/data-sources/<ds-id>/tables/<table-id>/...)¶
The contents of each data source table (the rows of each table) can be queried via the API as well. A row has just a Data field, which is a list of values.