cluster_shard_follow.go

package topology

import "fmt"

// ClusterShard has the tuple of server id and shard id in a cluster.
type ClusterShard struct {
	ShardId  int
	ServerId int
}

func (shard ClusterShard) String() string {
	return fmt.Sprintf("%d.%d", shard.ServerId, shard.ShardId)
}

// PeerShards list peer shards that are on other cluster nodes
func PeerShards(selfServerId int, selfShardId int, clusterSize int, replicationFactor int) (peers []ClusterShard) {

	if selfShardId >= clusterSize {
		return
	}

	for i := 0; i < replicationFactor && i < clusterSize; i++ {
		serverId := selfShardId + i
		if serverId >= clusterSize {
			serverId -= clusterSize
		}
		if serverId == selfServerId {
			continue
		}
		peers = append(peers, ClusterShard{
			ShardId:  selfShardId,
			ServerId: serverId,
		})
	}

	return
}

// PartitionShards list shards that belongs to the same partition
func PartitionShards(selfServerId int, selfShardId int, clusterSize int, replicationFactor int) (shards []ClusterShard) {

	if selfShardId >= clusterSize {
		return
	}

	for i := 0; i < replicationFactor && i < clusterSize; i++ {
		serverId := selfShardId + i
		if serverId >= clusterSize {
			serverId -= clusterSize
		}
		shards = append(shards, ClusterShard{
			ShardId:  selfShardId,
			ServerId: serverId,
		})
	}

	return
}

// LocalShards list shards that local node should have
func LocalShards(selfServerId int, clusterSize int, replicationFactor int) (shards []ClusterShard) {

	if selfServerId >= clusterSize {
		return
	}

	for i := 0; i < replicationFactor && i < clusterSize; i++ {
		shardId := selfServerId - i
		if shardId < 0 {
			shardId += clusterSize
		}
		shards = append(shards, ClusterShard{
			ShardId:  shardId,
			ServerId: selfServerId,
		})
	}
	return
}

// IsShardInLocal returns true if the tuple if shard should be on current server
func IsShardInLocal(shardId int, selfServerId int, clusterSize int, replicationFactor int) bool {
	shards := LocalShards(selfServerId, clusterSize, replicationFactor)
	for _, shard := range shards {
		if shardId == shard.ShardId {
			return true
		}
	}
	return false
}

// ShardListContains check whether shards contains one target shard
func ShardListContains(shards []ClusterShard, targetShard ClusterShard) bool {

	for _, shard := range shards {
		if shard.ShardId == targetShard.ShardId && shard.ServerId == targetShard.ServerId {
			return true
		}
	}

	return false
}