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85 lines
3.1 KiB
Go
85 lines
3.1 KiB
Go
package pub_balancer
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import (
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cmap "github.com/orcaman/concurrent-map/v2"
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"github.com/seaweedfs/seaweedfs/weed/pb/mq_pb"
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)
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const (
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MaxPartitionCount = 8 * 9 * 5 * 7 //2520
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LockBrokerBalancer = "broker_balancer"
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)
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// Balancer collects stats from all brokers.
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//
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// When publishers wants to create topics, it picks brokers to assign the topic partitions.
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// When consumers wants to subscribe topics, it tells which brokers are serving the topic partitions.
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//
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// When a partition needs to be split or merged, or a partition needs to be moved to another broker,
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// the balancer will let the broker tell the consumer instance to stop processing the partition.
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// The existing consumer instance will flush the internal state, and then stop processing.
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// Then the balancer will tell the brokers to start sending new messages in the new/moved partition to the consumer instances.
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//
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// Failover to standby consumer instances:
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//
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// A consumer group can have min and max number of consumer instances.
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// For consumer instances joined after the max number, they will be in standby mode.
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//
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// When a consumer instance is down, the broker will notice this and inform the balancer.
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// The balancer will then tell the broker to send the partition to another standby consumer instance.
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type Balancer struct {
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Brokers cmap.ConcurrentMap[string, *BrokerStats] // key: broker address
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// Collected from all brokers when they connect to the broker leader
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TopicToBrokers cmap.ConcurrentMap[string, *PartitionSlotToBrokerList] // key: topic name
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}
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func NewBalancer() *Balancer {
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return &Balancer{
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Brokers: cmap.New[*BrokerStats](),
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TopicToBrokers: cmap.New[*PartitionSlotToBrokerList](),
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}
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}
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func (balancer *Balancer) OnBrokerConnected(broker string) (brokerStats *BrokerStats) {
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var found bool
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brokerStats, found = balancer.Brokers.Get(broker)
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if !found {
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brokerStats = NewBrokerStats()
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if !balancer.Brokers.SetIfAbsent(broker, brokerStats) {
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brokerStats, _ = balancer.Brokers.Get(broker)
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}
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}
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return brokerStats
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}
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func (balancer *Balancer) OnBrokerDisconnected(broker string, stats *BrokerStats) {
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balancer.Brokers.Remove(broker)
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// update TopicToBrokers
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for _, topic := range stats.Topics {
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partitionSlotToBrokerList, found := balancer.TopicToBrokers.Get(topic.String())
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if !found {
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continue
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}
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partitionSlotToBrokerList.RemoveBroker(broker)
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}
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}
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func (balancer *Balancer) OnBrokerStatsUpdated(broker string, brokerStats *BrokerStats, receivedStats *mq_pb.BrokerStats) {
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brokerStats.UpdateStats(receivedStats)
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// update TopicToBrokers
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for _, topicPartitionStats := range receivedStats.Stats {
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topic := topicPartitionStats.Topic
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partition := topicPartitionStats.Partition
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partitionSlotToBrokerList, found := balancer.TopicToBrokers.Get(topic.String())
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if !found {
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partitionSlotToBrokerList = NewPartitionSlotToBrokerList(MaxPartitionCount)
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if !balancer.TopicToBrokers.SetIfAbsent(topic.String(), partitionSlotToBrokerList) {
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partitionSlotToBrokerList, _ = balancer.TopicToBrokers.Get(topic.String())
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}
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}
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partitionSlotToBrokerList.AddBroker(partition, broker)
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}
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}
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