Nova-specific Rate Limit Class for Turnstile

This package provides the nova_limits Python module, which contains the nova_preprocess() preprocessor, the nova_postprocess() postprocessor, the NovaClassLimit limit class, and the nova_formatter() replacement delay formatter, all for use with Turnstile. These pieces work together to provide class-based rate limiting integration with nova. To use, you must configure the Turnstile middleware with the following configuration:

[filter:turnstile]
use = egg:turnstile#turnstile
enable = nova_limits
formatter = nova_limits
redis.host = <your Redis database host>

Then, simply use the nova_limits rate limit class in your limits configuration.

Using NovaClassLimit

In addition to the other attributes provided by turnstile.limits:Limit, the NovaClassLimit limit class provides one additional required argument: the rate_class. Each tenant is associated with a given rate-limit class through the Redis database. (If no such association is present, the rate-limit class for a tenant is default.) Setting rate_class on NovaClassLimit restricts the limiting action to only those tenants in the given rate-limit class.

Also note that, for nova, the URIs used in configuring rate limiting must include the version identifier, i.e., "/v2/{tenant}/servers/detail".

Quota Classes

If the discovered nova context supports quota classes--that is, if the context object has the quota_class attribute--the quota class for the context will be set to be the same as the selected rate limit class.

Mapping Tenants to Rate Limit Classes

A limit_class command is provided to control the mapping of the tenant ID to the rate limit class. A usage summary follows:

usage: limit_class [-h] [--debug] [--class KLASS] config tenant_id

Set up or query limit classes associated with tenants.

positional arguments:
  config                Name of the configuration file, for connecting to the
                        Redis database.
  tenant_id             ID of the tenant.

optional arguments:
  -h, --help            show this help message and exit
  --debug, -d           Run the tool in debug mode.
  --class KLASS, -c KLASS
                        If specified, sets the class associated with the given
                        tenant ID.