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Alex Auvolat 2021-02-25 11:27:13 +01:00
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doc/Load_Balancing.md
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@ -8,7 +8,7 @@ I have conducted a quick study of different methods to load-balance data over di
- *minimal disruption*: when adding or removing a node, as few partitions as possible should have to move around - *minimal disruption*: when adding or removing a node, as few partitions as possible should have to move around
- *order-agnostic*: the same set of nodes (associated with a datacenter name - *order-agnostic*: the same set of nodes (each associated with a datacenter name
and a capacity) should always return the same distribution of partition and a capacity) should always return the same distribution of partition
replicas, independently of the order in which nodes were added/removed (this replicas, independently of the order in which nodes were added/removed (this
is to keep the implementation simple) is to keep the implementation simple)
@ -19,10 +19,12 @@ I have conducted a quick study of different methods to load-balance data over di
This strategy can be used with any ring-like algorithm to make it aware of the *multi-datacenter* requirement: This strategy can be used with any ring-like algorithm to make it aware of the *multi-datacenter* requirement:
- the ring is a list of positions, each associated with a single node in the cluster In this method, the ring is a list of positions, each associated with a single node in the cluster.
- look up position of item on ring Partitions contain all the keys between two consecutive items of the ring.
- select the node for that position To find the nodes that store replicas of a given partition:
- go clockwise, skipping nodes that:
- select the node for the position of the partition's lower bound
- go clockwise on the ring, skipping nodes that:
- we halve already selected - we halve already selected
- are in a datacenter of a node we have selected, except if we already have nodes from all possible datacenters - are in a datacenter of a node we have selected, except if we already have nodes from all possible datacenters