rename all remaining packages to internal/ (#12418)

This is to ensure that there are no projects
that try to import `minio/minio/pkg` into
their own repo. Any such common packages should
go to `https://github.com/minio/pkg`

internal/bucket/bandwidth/throttle.go

@@ -0,0 +1,121 @@
+// Copyright (c) 2015-2021 MinIO, Inc.
+//
+// This file is part of MinIO Object Storage stack
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+package bandwidth
+
+import (
+	"context"
+	"sync"
+	"sync/atomic"
+	"time"
+)
+
+const (
+	throttleInternal = 250 * time.Millisecond
+)
+
+// throttle implements the throttling for bandwidth
+type throttle struct {
+	generateTicker   *time.Ticker    // Ticker to generate available bandwidth
+	freeBytes        int64           // unused bytes in the interval
+	bytesPerSecond   int64           // max limit for bandwidth
+	bytesPerInterval int64           // bytes allocated for the interval
+	clusterBandwidth int64           // Cluster wide bandwidth needed for reporting
+	cond             *sync.Cond      // Used to notify waiting threads for bandwidth availability
+	goGenerate       int64           // Flag to track if generate routine should be running. 0 == stopped
+	ctx              context.Context // Context for generate
+}
+
+// newThrottle returns a new bandwidth throttle. Set bytesPerSecond to 0 for no limit
+func newThrottle(ctx context.Context, bytesPerSecond int64, clusterBandwidth int64) *throttle {
+	if bytesPerSecond == 0 {
+		return &throttle{}
+	}
+	t := &throttle{
+		bytesPerSecond:   bytesPerSecond,
+		generateTicker:   time.NewTicker(throttleInternal),
+		clusterBandwidth: clusterBandwidth,
+		ctx:              ctx,
+	}
+
+	t.cond = sync.NewCond(&sync.Mutex{})
+	t.SetBandwidth(bytesPerSecond, clusterBandwidth)
+	t.freeBytes = t.bytesPerInterval
+	return t
+}
+
+// GetLimitForBytes gets the bytes that are possible to send within the limit
+// if want is <= 0 or no bandwidth limit set, returns want.
+// Otherwise a value > 0 will always be returned.
+func (t *throttle) GetLimitForBytes(want int64) int64 {
+	if want <= 0 || atomic.LoadInt64(&t.bytesPerInterval) == 0 {
+		return want
+	}
+	t.cond.L.Lock()
+	defer t.cond.L.Unlock()
+	for {
+		var send int64
+		freeBytes := atomic.LoadInt64(&t.freeBytes)
+		send = want
+		if freeBytes < want {
+			send = freeBytes
+			if send <= 0 {
+				t.cond.Wait()
+				continue
+			}
+		}
+		atomic.AddInt64(&t.freeBytes, -send)
+
+		// Bandwidth was consumed, start generate routine to allocate bandwidth
+		if atomic.CompareAndSwapInt64(&t.goGenerate, 0, 1) {
+			go t.generateBandwidth(t.ctx)
+		}
+		return send
+	}
+}
+
+// SetBandwidth sets a new bandwidth limit in bytes per second.
+func (t *throttle) SetBandwidth(bandwidthBiPS int64, clusterBandwidth int64) {
+	bpi := int64(throttleInternal) * bandwidthBiPS / int64(time.Second)
+	atomic.StoreInt64(&t.bytesPerInterval, bpi)
+}
+
+// ReleaseUnusedBandwidth releases bandwidth that was allocated for a user
+func (t *throttle) ReleaseUnusedBandwidth(bytes int64) {
+	atomic.AddInt64(&t.freeBytes, bytes)
+}
+
+// generateBandwidth periodically allocates new bandwidth to use
+func (t *throttle) generateBandwidth(ctx context.Context) {
+	for {
+		select {
+		case <-t.generateTicker.C:
+			if atomic.LoadInt64(&t.freeBytes) == atomic.LoadInt64(&t.bytesPerInterval) {
+				// No bandwidth consumption stop the routine.
+				atomic.StoreInt64(&t.goGenerate, 0)
+				return
+			}
+			// A new window is available
+			t.cond.L.Lock()
+			atomic.StoreInt64(&t.freeBytes, atomic.LoadInt64(&t.bytesPerInterval))
+			t.cond.Broadcast()
+			t.cond.L.Unlock()
+		case <-ctx.Done():
+			return
+		}
+	}
+}