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redis-trib: better slots allocation strategy for resharding

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antirez 2011-09-30 18:41:25 +02:00
parent 841cd7684c
commit 6c0047c430
1 changed files with 14 additions and 2 deletions
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16
src/redis-trib.rb
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@ -287,10 +287,22 @@ class RedisTrib
# instance.
def compute_reshard_table(sources,numslots)
moved = []
sources.each{|s|
# Sort from bigger to smaller instance, for two reasons:
# 1) If we take less slots than instanes it is better to start getting from
# the biggest instances.
# 2) We take one slot more from the first instance in the case of not perfect
# divisibility. Like we have 3 nodes and need to get 10 slots, we take
# 4 from the first, and 3 from the rest. So the biggest is always the first.
sources = sources.sort{|a,b| b.slots.length <=> a.slots.length}
sources.each_with_index{|s,i|
# Every node will provide a number of slots proportional to the
# slots it has assigned.
n = (numslots.to_f/4096*s.slots.length).ceil
n = (numslots.to_f/4096*s.slots.length)
if i == 0
n = n.ceil
else
n = n.floor
end
s.slots.keys.sort[(0...n)].each{|slot|
if moved.length < numslots
moved << {:source => s, :slot => slot}