seaweedfs/weed/mq/pub_balancer/allocate.go
2024-02-29 14:51:06 -08:00

144 lines
4.2 KiB
Go

package pub_balancer
import (
cmap "github.com/orcaman/concurrent-map/v2"
"github.com/seaweedfs/seaweedfs/weed/glog"
"github.com/seaweedfs/seaweedfs/weed/pb/mq_pb"
"math/rand"
"time"
)
func AllocateTopicPartitions(brokers cmap.ConcurrentMap[string, *BrokerStats], partitionCount int32) (assignments []*mq_pb.BrokerPartitionAssignment) {
// divide the ring into partitions
now := time.Now().UnixNano()
rangeSize := MaxPartitionCount / partitionCount
for i := int32(0); i < partitionCount; i++ {
assignment := &mq_pb.BrokerPartitionAssignment{
Partition: &mq_pb.Partition{
RingSize: MaxPartitionCount,
RangeStart: int32(i * rangeSize),
RangeStop: int32((i + 1) * rangeSize),
UnixTimeNs: now,
},
}
if i == partitionCount-1 {
assignment.Partition.RangeStop = MaxPartitionCount
}
assignments = append(assignments, assignment)
}
// pick the brokers
pickedBrokers := pickBrokers(brokers, partitionCount)
// assign the partitions to brokers
for i, assignment := range assignments {
assignment.LeaderBroker = pickedBrokers[i]
}
glog.V(0).Infof("allocate topic partitions %d: %v", len(assignments), assignments)
return
}
// randomly pick n brokers, which may contain duplicates
// TODO pick brokers based on the broker stats
func pickBrokers(brokers cmap.ConcurrentMap[string, *BrokerStats], count int32) []string {
candidates := make([]string, 0, brokers.Count())
for brokerStatsItem := range brokers.IterBuffered() {
candidates = append(candidates, brokerStatsItem.Key)
}
pickedBrokers := make([]string, 0, count)
for i := int32(0); i < count; i++ {
p := rand.Intn(len(candidates))
pickedBrokers = append(pickedBrokers, candidates[p])
}
return pickedBrokers
}
// reservoir sampling select N brokers from the active brokers, with exclusion of the excluded brokers
func pickBrokersExcluded(brokers []string, count int, excludedLeadBroker string, excludedBrokers []string) []string {
// convert the excluded brokers to a map
excludedBrokerMap := make(map[string]bool)
for _, broker := range excludedBrokers {
excludedBrokerMap[broker] = true
}
if excludedLeadBroker != "" {
excludedBrokerMap[excludedLeadBroker] = true
}
pickedBrokers := make([]string, 0, count)
for i, broker := range brokers {
if _, found := excludedBrokerMap[broker]; found {
continue
}
if len(pickedBrokers) < count {
pickedBrokers = append(pickedBrokers, broker)
} else {
j := rand.Intn(i + 1)
if j < count {
pickedBrokers[j] = broker
}
}
}
// shuffle the picked brokers
count = len(pickedBrokers)
for i := 0; i < count; i++ {
j := rand.Intn(count)
pickedBrokers[i], pickedBrokers[j] = pickedBrokers[j], pickedBrokers[i]
}
return pickedBrokers
}
func EnsureAssignmentsToActiveBrokers(activeBrokers cmap.ConcurrentMap[string, *BrokerStats], followerCount int, assignments []*mq_pb.BrokerPartitionAssignment) (hasChanges bool) {
candidates := make([]string, 0, activeBrokers.Count())
for brokerStatsItem := range activeBrokers.IterBuffered() {
candidates = append(candidates, brokerStatsItem.Key)
}
for _, assignment := range assignments {
// count how many brokers are needed
count := 0
if assignment.LeaderBroker == "" {
count++
} else if _, found := activeBrokers.Get(assignment.LeaderBroker); !found {
assignment.LeaderBroker = ""
count++
}
for i:=0; i<followerCount; i++ {
if i >= len(assignment.FollowerBrokers) {
count++
continue
}
if assignment.FollowerBrokers[i] == "" {
count++
} else if _, found := activeBrokers.Get(assignment.FollowerBrokers[i]); !found {
assignment.FollowerBrokers[i] = ""
count++
}
}
if count > 0 {
pickedBrokers := pickBrokersExcluded(candidates, count, assignment.LeaderBroker, assignment.FollowerBrokers)
i := 0
if assignment.LeaderBroker == "" {
assignment.LeaderBroker = pickedBrokers[i]
i++
}
j := 0
for ; j<len(assignment.FollowerBrokers); j++ {
if assignment.FollowerBrokers[j] == "" {
assignment.FollowerBrokers[j] = pickedBrokers[i]
i++
}
}
if i < len(pickedBrokers) {
assignment.FollowerBrokers = append(assignment.FollowerBrokers, pickedBrokers[i:]...)
}
}
hasChanges = hasChanges || count > 0
}
return
}