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当前server实例不在哈希环上时，依旧遍历实例列表 #1203

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qnnn opened this issue Aug 13, 2023 · 5 comments · Fixed by qnnn/polaris#2 · May be fixed by #1241
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当前server实例不在哈希环上时，依旧遍历实例列表 #1203

qnnn opened this issue Aug 13, 2023 · 5 comments · Fixed by qnnn/polaris#2 · May be fixed by #1241

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@qnnn
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qnnn commented Aug 13, 2023

部分服务端节点被隔离或不健康时，即当前server实例不在哈希环上，依旧会去遍历实例列表。

if d.continuum != nil {
	d.svr.cacheProvider.RangeHealthCheckInstances(func(itemChecker ItemWithChecker, instance *model.Instance) {
		instanceId := instance.ID()
		host := d.continuum.Hash(itemChecker.GetHashValue())
		if host == d.svr.localHost {
			nextInstances[instanceId] = itemChecker.(*InstanceWithChecker)
		}
	})
}

在心跳分派处理上，可能只希望部分server实例参与心跳健康处理，未参与心跳分派的server实例不需要遍历实例列表。
@qnnn qnnn mentioned this issue Aug 13, 2023
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@qnnn
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qnnn commented Aug 14, 2023

大佬，顺便问下心跳健康检测时间轮添加任务前，delayMilli为什么需要加一个随机数getRandDelayMilli()。是有什么作用吗。

func (c *CheckScheduler) addUnHealthyCallback(instance *itemValue) {
	delaySec := instance.expireDurationSec
	if c.maxCheckIntervalSec > 0 && int64(delaySec) > c.maxCheckIntervalSec {
		delaySec = uint32(c.maxCheckIntervalSec)
	}
	host := instance.host
	port := instance.port
	instanceId := instance.id
	delayMilli := delaySec*1000 + getRandDelayMilli()
	log.Debugf("[Health Check][Check]add unhealthy callback, %s is %s:%d, id is %s, delay is %d(ms)",
		instance.ItemType.String(), host, port, instanceId, delayMilli)
	if instance.ItemType == itemTypeClient {
		c.timeWheel.AddTask(delayMilli, instanceId, c.checkCallbackClient)
	} else {
		c.timeWheel.AddTask(delayMilli, instanceId, c.checkCallbackInstance)
	}
}

@xiaolaji422
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getRandDelayMilli 这个方法可以让时间轮上的单位时间执行的任务更分散。

@qnnn
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qnnn commented Aug 25, 2023

getRandDelayMilli 这个方法可以让时间轮上的单位时间执行的任务更分散。

实测的时候没发现有能达到散列的作用呀。毫秒级的随机数。时间轮又是每秒一slot，实例的ttl也是int类型。代码里加完之后还是整数。

func (tw *TimeWheel) getSlots(d time.Duration) (pos int, circle int) {
	delayTime := int(d.Seconds())
	interval := int(tw.interval.Seconds())
	circle = int(delayTime / interval / tw.slotNum)
	pos = int(tw.currentPos+delayTime/interval) % tw.slotNum
	return
}

@xiaolaji422
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还有一个可能是，当delaySec = 0时，避免AddTask的任务被跳过执行

@xiaolaji422
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具体要看他们官方给出的结论-_-

@qnnn qnnn mentioned this issue Sep 7, 2023
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@qnnn qnnn mentioned this issue Sep 7, 2023
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