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VMOD_VSTHROTTLE(3) VMOD_VSTHROTTLE(3)

NAME

vmod_vsthrottle - Throttling VMOD

SYNOPSIS

import vsthrottle [from "path"] ;

DESCRIPTION

A Varnish vmod for rate-limiting traffic on a single Varnish server. Offers a simple interface for throttling traffic on a per-key basis to a specific request rate.

Keys can be specified from any VCL string, e.g. based on client.ip, a specific cookie value, an API token, etc.

The request rate is specified as the number of requests permitted over a period. To keep things simple, this is passed as two separate parameters, 'limit' and 'period'.

This VMOD implements a token-bucket algorithm. State associated with the token bucket for each key is stored in-memory using BSD's red-black tree implementation.

Memory usage is around 100 bytes per key tracked.

CONTENTS

•
func_is_denied

is_denied

BOOL is_denied(STRING jey, INT limit, DURATION period)


Arguments
key: A unique identifier to define what is being throttled - more examples below limit: How many requests in the specified period period: The time period
Description
Can be used to rate limit the traffic for a specific key to a maximum of 'limit' requests per 'period' time. A token bucket is uniquely identified by the triplet of its key, limit and period, so using the same key multiple places with different rules will create multiple token buckets.
Example

sub vcl_recv {
        if (vsthrottle.is_denied(client.identity, 15, 10s)) {
                # Client has exceeded 15 reqs per 10s
                return (synth(429, "Too Many Requests"));
        }
        # ...
}