US Patent 8190593 Dynamic request throttling

Requests for resources can be throttled based on relative allocations, whereby the actual usage of a client or sub-client over time can be monitored in order to make intelligent throttling decisions. A centralized throttling service can maintain throttling information according to a hierarchical allocation tree, and can determine whether to throttle a request based at least in part whether any tokens, or available resource units, are available for a class or node of the tree corresponding to the request. In some cases, an empty token bucket for a node can borrow tokens from a parent node, in order to allow a user to exceed an allocation when the capacity of the system allows for such usage. When a user has been exceeding an allocation or otherwise inappropriately taxing various resources, the system can prevent that user from borrowing tokens for at least a specified period of time.