add subscriber coordinator

weed/mq/topic/partition.go

@@ -30,3 +30,20 @@ func FromPbPartition(partition *mq_pb.Partition) Partition {
 		RingSize:   partition.RingSize,
 	}
 }
+
+func SplitPartitions(targetCount int32) []*Partition {
+	partitions := make([]*Partition, 0, targetCount)
+	partitionSize := PartitionCount / targetCount
+	for i := int32(0); i < targetCount; i++ {
+		partitionStop := (i + 1) * partitionSize
+		if i == targetCount-1 {
+			partitionStop = PartitionCount
+		}
+		partitions = append(partitions, &Partition{
+			RangeStart: i * partitionSize,
+			RangeStop:  partitionStop,
+			RingSize:   PartitionCount,
+		})
+	}
+	return partitions
+}