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ratelimit.go
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/
ratelimit.go
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// Copyright (c) 2022 Gobalsky Labs Limited
//
// Use of this software is governed by the Business Source License included
// in the LICENSE.VEGA file and at https://www.mariadb.com/bsl11.
//
// Change Date: 18 months from the later of the date of the first publicly
// available Distribution of this version of the repository, and 25 June 2022.
//
// On the date above, in accordance with the Business Source License, use
// of this software will be governed by version 3 or later of the GNU General
// Public License.
package ratelimit
import (
"encoding/base64"
)
type Key []byte
func (k Key) String() string {
return base64.StdEncoding.EncodeToString(k)
}
type Rates struct {
block int
requests int
perNBlocks int
entries map[string][]int
}
func New(requests, perNBlocks int) *Rates {
return &Rates{
block: 0,
requests: requests,
perNBlocks: perNBlocks,
entries: map[string][]int{},
}
}
// Count returns the number of requests recorded for a given key
// It returns -1 if the key has been not recorded or evicted.
func (r *Rates) Count(key string) int {
entry, ok := r.entries[key]
if !ok {
return -1
}
var count int
for _, n := range entry {
count += n
}
return count
}
func (r *Rates) NextBlock() {
// compute the next block index
r.block = (r.block + 1) % (r.perNBlocks)
// reset the counters for that particular block index
for _, c := range r.entries {
c[r.block] = 0
}
// We clean up the entries after finishing the block round
if r.block != 0 {
return
}
for key := range r.entries {
if r.Count(key) == 0 {
delete(r.entries, key)
}
}
}
func (r *Rates) Allow(key string) bool {
entry, ok := r.entries[key]
if !ok {
entry = make([]int, r.perNBlocks)
r.entries[key] = entry
}
entry[r.block]++
return r.Count(key) < r.requests
}