fix: change the burst limit to the number of configured events

For example, the configuration value "100/24h" will permit 100
events immediately. It will still continue to refill the bucket
at a rate of 1 token approx every 15 minutes.

This change comes with the caveat that this rate limit is easily
bypassed by restarting the service. You may however achieve
smaller bursts (mitigating circumvention via restarts) by
lowering the overall time interval at the same ratio. For example
you could specify 8/2h to limit the burst to only 8 while still
producing roughly 1 token every 15 minutes.

internal/api/ratelimits.go

@@ -14,7 +14,10 @@ import (
 func newRateLimiter(r conf.Rate) *rate.Limiter {
 	// The rate limiter deals in events per second.
 	eps := r.EventsPerSecond()
-	const burst = 1
+	burst := int(r.Events)
+	if burst <= 0 {
+		burst = 1
+	}
 
 	// NewLimiter will have an initial token bucket of size `burst`. It will
 	// be refilled at a rate of `eps` indefinitely. Note that the expression

internal/api/ratelimits_test.go

@@ -19,14 +19,25 @@ func Example_newRateLimiter() {
 		cfg := conf.Rate{Events: 100, OverTime: time.Hour * 24}
 		rl := newRateLimiter(cfg)
 		cur := now
-		for i := 0; i < 61; i++ {
-			fmt.Printf("%-5v @ %v\n", rl.AllowN(cur, 1), cur)
-			cur = cur.Add(time.Minute)
+		for limited, i := 0, 0; i < 160; i++ {
+			allowed := rl.AllowN(cur, 1)
+			if allowed {
+				limited++
+			}
+
+			switch {
+			case i == 100:
+				fmt.Printf("true  @ %v for last %v events...\n", cur, limited)
+			case i > 100:
+				fmt.Printf("%-5v @ %v\n", allowed, cur)
+				cur = cur.Add(time.Minute)
+			}
 		}
 	}
 
 	// Output:
-	// true  @ 2024-09-24 10:00:00 +0000 UTC
+	// true  @ 2024-09-24 10:00:00 +0000 UTC for last 100 events...
+	// false @ 2024-09-24 10:00:00 +0000 UTC
 	// false @ 2024-09-24 10:01:00 +0000 UTC
 	// false @ 2024-09-24 10:02:00 +0000 UTC
 	// false @ 2024-09-24 10:03:00 +0000 UTC
@@ -55,8 +66,8 @@ func Example_newRateLimiter() {
 	// false @ 2024-09-24 10:26:00 +0000 UTC
 	// false @ 2024-09-24 10:27:00 +0000 UTC
 	// false @ 2024-09-24 10:28:00 +0000 UTC
-	// false @ 2024-09-24 10:29:00 +0000 UTC
-	// true  @ 2024-09-24 10:30:00 +0000 UTC
+	// true  @ 2024-09-24 10:29:00 +0000 UTC
+	// false @ 2024-09-24 10:30:00 +0000 UTC
 	// false @ 2024-09-24 10:31:00 +0000 UTC
 	// false @ 2024-09-24 10:32:00 +0000 UTC
 	// false @ 2024-09-24 10:33:00 +0000 UTC
@@ -70,8 +81,8 @@ func Example_newRateLimiter() {
 	// false @ 2024-09-24 10:41:00 +0000 UTC
 	// false @ 2024-09-24 10:42:00 +0000 UTC
 	// false @ 2024-09-24 10:43:00 +0000 UTC
-	// false @ 2024-09-24 10:44:00 +0000 UTC
-	// true  @ 2024-09-24 10:45:00 +0000 UTC
+	// true  @ 2024-09-24 10:44:00 +0000 UTC
+	// false @ 2024-09-24 10:45:00 +0000 UTC
 	// false @ 2024-09-24 10:46:00 +0000 UTC
 	// false @ 2024-09-24 10:47:00 +0000 UTC
 	// false @ 2024-09-24 10:48:00 +0000 UTC
@@ -84,9 +95,7 @@ func Example_newRateLimiter() {
 	// false @ 2024-09-24 10:55:00 +0000 UTC
 	// false @ 2024-09-24 10:56:00 +0000 UTC
 	// false @ 2024-09-24 10:57:00 +0000 UTC
-	// false @ 2024-09-24 10:58:00 +0000 UTC
-	// false @ 2024-09-24 10:59:00 +0000 UTC
-	// true  @ 2024-09-24 11:00:00 +0000 UTC
+	// true  @ 2024-09-24 10:58:00 +0000 UTC
 
 }