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|
package sub_coordinator
import (
"fmt"
"github.com/seaweedfs/seaweedfs/weed/mq/pub_balancer"
"time"
)
type PartitionConsumerMapping struct {
currentMapping *PartitionSlotToConsumerInstanceList
prevMappings []*PartitionSlotToConsumerInstanceList
}
// Balance goal:
// 1. max processing power utilization
// 2. allow one consumer instance to be down unexpectedly
// without affecting the processing power utilization
func (pcm *PartitionConsumerMapping) BalanceToConsumerInstances(partitionSlotToBrokerList *pub_balancer.PartitionSlotToBrokerList, consumerInstances []*ConsumerGroupInstance) {
if len(partitionSlotToBrokerList.PartitionSlots) == 0 || len(consumerInstances) == 0 {
return
}
newMapping := NewPartitionSlotToConsumerInstanceList(partitionSlotToBrokerList.RingSize, time.Now())
var prevMapping *PartitionSlotToConsumerInstanceList
if len(pcm.prevMappings) > 0 {
prevMapping = pcm.prevMappings[len(pcm.prevMappings)-1]
} else {
prevMapping = nil
}
newMapping.PartitionSlots = doBalanceSticky(partitionSlotToBrokerList.PartitionSlots, consumerInstances, prevMapping)
if pcm.currentMapping != nil {
pcm.prevMappings = append(pcm.prevMappings, pcm.currentMapping)
if len(pcm.prevMappings) > 10 {
pcm.prevMappings = pcm.prevMappings[1:]
}
}
pcm.currentMapping = newMapping
}
func doBalanceSticky(partitions []*pub_balancer.PartitionSlotToBroker, consumerInstances []*ConsumerGroupInstance, prevMapping *PartitionSlotToConsumerInstanceList) (partitionSlots []*PartitionSlotToConsumerInstance) {
// collect previous consumer instance ids
prevConsumerInstanceIds := make(map[ConsumerGroupInstanceId]struct{})
if prevMapping != nil {
for _, prevPartitionSlot := range prevMapping.PartitionSlots {
if prevPartitionSlot.AssignedInstanceId != "" {
prevConsumerInstanceIds[prevPartitionSlot.AssignedInstanceId] = struct{}{}
}
}
}
// collect current consumer instance ids
currConsumerInstanceIds := make(map[ConsumerGroupInstanceId]struct{})
for _, consumerInstance := range consumerInstances {
currConsumerInstanceIds[consumerInstance.InstanceId] = struct{}{}
}
// check deleted consumer instances
deletedConsumerInstanceIds := make(map[ConsumerGroupInstanceId]struct{})
for consumerInstanceId := range prevConsumerInstanceIds {
if _, ok := currConsumerInstanceIds[consumerInstanceId]; !ok {
deletedConsumerInstanceIds[consumerInstanceId] = struct{}{}
}
}
// convert partition slots from list to a map
prevPartitionSlotMap := make(map[string]*PartitionSlotToConsumerInstance)
if prevMapping != nil {
for _, partitionSlot := range prevMapping.PartitionSlots {
key := fmt.Sprintf("%d-%d", partitionSlot.RangeStart, partitionSlot.RangeStop)
prevPartitionSlotMap[key] = partitionSlot
}
}
// make a copy of old mapping, skipping the deleted consumer instances
newPartitionSlots := make([]*PartitionSlotToConsumerInstance, 0, len(partitions))
for _, partition := range partitions {
newPartitionSlots = append(newPartitionSlots, &PartitionSlotToConsumerInstance{
RangeStart: partition.RangeStart,
RangeStop: partition.RangeStop,
UnixTimeNs: partition.UnixTimeNs,
Broker: partition.AssignedBroker,
FollowerBroker: partition.FollowerBroker,
})
}
for _, newPartitionSlot := range newPartitionSlots {
key := fmt.Sprintf("%d-%d", newPartitionSlot.RangeStart, newPartitionSlot.RangeStop)
if prevPartitionSlot, ok := prevPartitionSlotMap[key]; ok {
if _, ok := deletedConsumerInstanceIds[prevPartitionSlot.AssignedInstanceId]; !ok {
newPartitionSlot.AssignedInstanceId = prevPartitionSlot.AssignedInstanceId
}
}
}
// for all consumer instances, count the average number of partitions
// that are assigned to them
consumerInstancePartitionCount := make(map[ConsumerGroupInstanceId]int)
for _, newPartitionSlot := range newPartitionSlots {
if newPartitionSlot.AssignedInstanceId != "" {
consumerInstancePartitionCount[newPartitionSlot.AssignedInstanceId]++
}
}
// average number of partitions that are assigned to each consumer instance
averageConsumerInstanceLoad := float32(len(partitions)) / float32(len(consumerInstances))
// assign unassigned partition slots to consumer instances that is underloaded
consumerInstanceIdsIndex := 0
for _, newPartitionSlot := range newPartitionSlots {
if newPartitionSlot.AssignedInstanceId == "" {
for avoidDeadLoop := len(consumerInstances); avoidDeadLoop > 0; avoidDeadLoop-- {
consumerInstance := consumerInstances[consumerInstanceIdsIndex]
if float32(consumerInstancePartitionCount[consumerInstance.InstanceId]) < averageConsumerInstanceLoad {
newPartitionSlot.AssignedInstanceId = consumerInstance.InstanceId
consumerInstancePartitionCount[consumerInstance.InstanceId]++
consumerInstanceIdsIndex++
if consumerInstanceIdsIndex >= len(consumerInstances) {
consumerInstanceIdsIndex = 0
}
break
} else {
consumerInstanceIdsIndex++
if consumerInstanceIdsIndex >= len(consumerInstances) {
consumerInstanceIdsIndex = 0
}
}
}
}
}
return newPartitionSlots
}
|
