1 files changed, 104 insertions, 0 deletions
diff --git a/vendor/github.com/eclipse/paho.mqtt.golang/backoff.go b/vendor/github.com/eclipse/paho.mqtt.golang/backoff.go
new file mode 100644
index 0000000..8ee06f6
--- /dev/null
+++ b/vendor/github.com/eclipse/paho.mqtt.golang/backoff.go
@@ -0,0 +1,104 @@
+/*
+ * Copyright (c) 2021 IBM Corp and others.
+ *
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v2.0
+ * and Eclipse Distribution License v1.0 which accompany this distribution.
+ *
+ * The Eclipse Public License is available at
+ *    https://www.eclipse.org/legal/epl-2.0/
+ * and the Eclipse Distribution License is available at
+ *   http://www.eclipse.org/org/documents/edl-v10.php.
+ *
+ * Contributors:
+ *    Matt Brittan
+ *    Daichi Tomaru
+ */
+
+package mqtt
+
+import (
+	"sync"
+	"time"
+)
+
+// Controller for sleep with backoff when the client attempts reconnection
+// It has statuses for each situations cause reconnection.
+type backoffController struct {
+	sync.RWMutex
+	statusMap map[string]*backoffStatus
+}
+
+type backoffStatus struct {
+	lastSleepPeriod time.Duration
+	lastErrorTime   time.Time
+}
+
+func newBackoffController() *backoffController {
+	return &backoffController{
+		statusMap: map[string]*backoffStatus{},
+	}
+}
+
+// Calculate next sleep period from the specified parameters.
+// Returned values are next sleep period and whether the error situation is continual.
+// If connection errors continuouslly occurs, its sleep period is exponentially increased.
+// Also if there is a lot of time between last and this error, sleep period is initialized.
+func (b *backoffController) getBackoffSleepTime(
+	situation string, initSleepPeriod time.Duration, maxSleepPeriod time.Duration, processTime time.Duration, skipFirst bool,
+) (time.Duration, bool) {
+	// Decide first sleep time if the situation is not continual. 
+	var firstProcess = func(status *backoffStatus, init time.Duration, skip bool) (time.Duration, bool) {
+		if skip {
+			status.lastSleepPeriod = 0
+			return 0, false
+		}
+		status.lastSleepPeriod = init
+		return init, false
+	}
+
+	// Prioritize maxSleep.
+	if initSleepPeriod > maxSleepPeriod {
+		initSleepPeriod = maxSleepPeriod
+	}
+	b.Lock()
+	defer b.Unlock()
+
+	status, exist := b.statusMap[situation]
+	if !exist {
+		b.statusMap[situation] = &backoffStatus{initSleepPeriod, time.Now()}
+		return firstProcess(b.statusMap[situation], initSleepPeriod, skipFirst)
+	}
+
+	oldTime := status.lastErrorTime
+	status.lastErrorTime = time.Now()
+
+	// When there is a lot of time between last and this error, sleep period is initialized.
+	if status.lastErrorTime.Sub(oldTime) > (processTime * 2 + status.lastSleepPeriod) {
+		return firstProcess(status, initSleepPeriod, skipFirst)
+	}
+
+	if status.lastSleepPeriod == 0 {
+		status.lastSleepPeriod = initSleepPeriod
+		return initSleepPeriod, true
+	}
+
+	if nextSleepPeriod := status.lastSleepPeriod * 2; nextSleepPeriod <= maxSleepPeriod {
+		status.lastSleepPeriod = nextSleepPeriod
+	} else {
+		status.lastSleepPeriod = maxSleepPeriod
+	}
+
+	return status.lastSleepPeriod, true
+}
+
+// Execute sleep the time returned from getBackoffSleepTime.
+func (b *backoffController) sleepWithBackoff(
+	situation string, initSleepPeriod time.Duration, maxSleepPeriod time.Duration, processTime time.Duration, skipFirst bool,
+) (time.Duration, bool) {
+	sleep, isFirst := b.getBackoffSleepTime(situation, initSleepPeriod, maxSleepPeriod, processTime, skipFirst)
+	if sleep != 0 {
+		time.Sleep(sleep)
+	}
+	return sleep, isFirst
+}