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Fix bug of zero credit in rate limiter #614

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Fix bug of zero credit in rate limiter #614

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8 changes: 6 additions & 2 deletions utils/rate_limiter.go
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Original file line number Diff line number Diff line change
Expand Up @@ -21,7 +21,7 @@ import (

// RateLimiter is a filter used to check if a message that is worth itemCost units is within the rate limits.
//
// TODO (breaking change) remove this interface in favor of public struct below
// # TODO (breaking change) remove this interface in favor of public struct below
//
// Deprecated, use ReconfigurableRateLimiter.
type RateLimiter interface {
Expand Down Expand Up @@ -55,9 +55,13 @@ type ReconfigurableRateLimiter struct {

// NewRateLimiter creates a new ReconfigurableRateLimiter.
func NewRateLimiter(creditsPerSecond, maxBalance float64) *ReconfigurableRateLimiter {
balance := maxBalance
if creditsPerSecond == 0 {
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seems like it should be invalid condition to instantiate rate limiter with <=0 replenishment rate

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Thanks @yurishkuro.
I feel 0 maybe a valid condition which should have the same effect as {const, 0}.

Supporting zero case will be useful when we want to totally mute the signal from a service endpoint when remotely controlling the sampling from collector using the perOperation strategy. (Setting the probability to 0 is not enough and we have to set the lowerbound to 0 as well).

balance = 0
}
return &ReconfigurableRateLimiter{
creditsPerSecond: creditsPerSecond,
balance: maxBalance,
balance: balance,
maxBalance: maxBalance,
lastTick: time.Now(),
timeNow: time.Now,
Expand Down
16 changes: 16 additions & 0 deletions utils/rate_limiter_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -73,6 +73,22 @@ func TestRateLimiterMaxBalance(t *testing.T) {
assert.False(t, rl.CheckCredit(1.0))
}

func TestRateLimiterZeroCreditsPerSecond(t *testing.T) {
rl := NewRateLimiter(0, 1.0)
// stop time
ts := time.Now()
rl.lastTick = ts
rl.timeNow = func() time.Time {
return ts
}
assert.False(t, rl.CheckCredit(1.0), "on initialization, should not have any credit for 1 message")

rl.timeNow = func() time.Time {
return ts.Add(time.Second * 20)
}
assert.False(t, rl.CheckCredit(1.0))
}

func TestRateLimiterReconfigure(t *testing.T) {
rl := NewRateLimiter(1, 1.0)
assertBalance := func(expected float64) {
Expand Down