The purpose of this feature is to allow administrators to selectively control which API calls are throttled, without having to rebuild and deploy a new version every time a throttle is changed.
The current frequency throttle is only able to throttle each user's total call frequency using a semaphore. The UserThrottleFilter uses an InMemoryTimeBlockCountingSemaphore that maps from a key(user id in this case) to a SimpleSemaphore, which keeps a count of calls made and the the after which the count will reset. The UserThrottleFilter then compares the user's call count to the maximum allowed.
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When an request comes in, the request URI will be normalized using normalizeMethodSignature() AccessRecordUtils of the Synapse-Warehouse-Records project (copy it over).
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