Optimise limits

config.go

@@ -69,17 +69,17 @@ var DefLimits = Limits{
 	DownloadRetries: 3, // this shouldn't even happen, as we have no limiter on files download.
 	Tier2: TierLimit{
 		Boost:   20, // seems to work fine with this boost
-		Burst:   1,  // limiter will wait indefinitely if it is less than 1.
+		Burst:   3,  // limiter will wait indefinitely if it is less than 1.
 		Retries: 20, // see issue #28, sometimes slack is being difficult
 	},
 	Tier3: TierLimit{
 		Boost:   120, // playing safe there, but generally value of 120 is fine.
-		Burst:   1,   // safe value, who would ever want to modify it? I don't know.
+		Burst:   5,   // safe value, who would ever want to modify it? I don't know.
 		Retries: 3,   // on Tier 3 this was never a problem, even with limiter-boost=120
 	},
 	Tier4: TierLimit{
 		Boost:   10,
-		Burst:   1,
+		Burst:   7,
 		Retries: 3,
 	},
 	Request: RequestLimit{

internal/network/limiter.go

@@ -1,6 +1,10 @@
 package network
 
-import "golang.org/x/time/rate"
+import (
+	"time"
+
+	"golang.org/x/time/rate"
+)
 
 // Tier represents rate limit Tier:
 // https://api.slack.com/docs/rate-limits
@@ -14,16 +18,15 @@ const (
 	Tier2 Tier = 20
 	Tier3 Tier = 50
 	Tier4 Tier = 100
-
-	// secPerMin is the number of seconds in a minute, it is here to allow easy
-	// modification of the program, should this value change.
-	secPerMin = 60.0
 )
 
 // NewLimiter returns throttler with rateLimit requests per minute.
 // optionally caller may specify the boost
 func NewLimiter(t Tier, burst uint, boost int) *rate.Limiter {
-	callsPerSec := float64(int(t)+boost) / secPerMin
-	l := rate.NewLimiter(rate.Limit(callsPerSec), int(burst))
+	l := rate.NewLimiter(rate.Every(every(t, boost)), int(burst))
 	return l
 }
+
+func every(t Tier, boost int) time.Duration {
+	return time.Minute / time.Duration(int(t)+int(boost))
+}

internal/network/limiter_test.go

@@ -1,7 +1,9 @@
 package network
 
 import (
+	"reflect"
 	"testing"
+	"time"
 
 	"golang.org/x/time/rate"
 )
@@ -36,3 +38,31 @@ func TestNewLimiter(t *testing.T) {
 		})
 	}
 }
+
+func Test_every(t *testing.T) {
+	type args struct {
+		t     Tier
+		boost int
+	}
+	tests := []struct {
+		name string
+		args args
+		want time.Duration
+	}{
+		{
+			name: "tier 2",
+			args: args{
+				t:     Tier2,
+				boost: 0,
+			},
+			want: time.Minute / 20,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := every(tt.args.t, tt.args.boost); !reflect.DeepEqual(got, tt.want) {
+				t.Errorf("every() = %s, want %s", got, tt.want)
+			}
+		})
+	}
+}