All accounts, by default, have a preconfigured set of thresholds (or limits) to manage capacity and prevent abuse of the system. The system recognizes two kinds of limits: rate limits and absolute limits. Rate limits are thresholds that are reset after a certain amount of time passes. Absolute limits are fixed.
Rate limits are specified in terms of both a human-readable wild-card URI and a machine-processable regular expression. The regular expression boundary matcher ‘^’ takes effect after the root URI path. For example, the regular expression ^/v1.0/instances would match the bolded portion of the following URI: https://dfw.blockstorage.api.openstackcloud.com/v1.0/instances.
The following table specifies the default rate limits for all API operations for all GET, POST, PUT, and DELETE calls for volumes:
Table 2.2. Default rate limits
Rate limits are applied in order relative to the verb, going from least to most specific. For example, although the threshold for POST to /v1.0/* is 10 per minute, one cannot POST to /v1.0/* more than 50 times within a single day.
If you exceed the thresholds established for your account, a 413 (Rate Control) HTTP response will be returned with a Retry-After header to notify the client when it can attempt to try again.
The following table shows the absolute limits:
Table 2.3. Absolute limits
Maximum amount of block storage