Interval Module

The interval module provides interval limiting functionality via an xlat function.

xlat for interval limiting

The module registers an xlat function:

%interval(<interval> [, <key>])

This function returns true if the request is allowed, or false if the interval limit has been exceeded.

interval: Time period for the interval limit (e.g., 1s, 500ms).
key: Optional key to track interval limits separately. If omitted, interval limiting is applied per xlat call site.

Example - Global interval limit of 1 request per second

if (!%interval(1s)) {
    reject
}

Example - Per-user interval limit of 1 request per 5 seconds

if (!%interval(5s, User-Name)) {
    reject
}

The module supports two scopes for interval limit tracking:

global: Interval limits are shared across all worker threads. Use this when you need server-wide interval limiting.
thread: Interval limits are tracked per worker thread. Use this for higher performance when approximate interval limiting is acceptable. If no key argument is specified in thread mode, then the cost is reduced further.

With scope = thread, the effective interval limit is multiplied by the number of worker threads, as each thread tracks independently.

global - Interval limits shared across all threads (requires locking). thread - Interval limits tracked per-thread (higher performance).

This instance uses per-thread interval limiting for higher performance.

interval interval_global {
	scope = global
}
interval interval_thread {
	scope = thread
}