From b55f742e46a755e96c92eded47d9c69327f774e8 Mon Sep 17 00:00:00 2001
From: Matt Stancliff <matt@genges.com>
Date: Fri, 19 Dec 2014 21:52:48 -0500
Subject: [PATCH] Improve redis-trib replica assignment
This tiny bit of code has gone through so many revisions. Hopefully
it's more correct now.
Fixes #2204
---
src/redis-trib.rb | 67 +++++++++++++++++++++++++++++------------------
1 file changed, 42 insertions(+), 25 deletions(-)
diff --git a/src/redis-trib.rb b/src/redis-trib.rb
index 4002f6309..e5e7f2da7 100755
--- a/src/redis-trib.rb
+++ b/src/redis-trib.rb
@@ -540,7 +540,6 @@ class RedisTrib
nodes_count = @nodes.length
masters_count = @nodes.length / (@replicas+1)
masters = []
- slaves = []
# The first step is to split instances by IP. This is useful as
# we'll try to allocate master nodes in different physical machines
@@ -558,16 +557,22 @@ class RedisTrib
# Select master instances
puts "Using #{masters_count} masters:"
- while masters.length < masters_count
- ips.each{|ip,nodes_list|
- next if nodes_list.length == 0
- masters << nodes_list.shift
- puts masters[-1]
- nodes_count -= 1
- break if masters.length == masters_count
- }
+ interleaved = []
+ stop = false
+ while not stop do
+ # Take one node from each IP until we run out of nodes
+ # across every IP.
+ ips.each do |ip,nodes|
+ stop = nodes.empty? and next
+ interleaved.push nodes.shift
+ end
end
+ masters = interleaved.slice!(0, masters_count)
+ nodes_count -= masters.length
+
+ masters.each{|m| puts m}
+
# Alloc slots on masters
slots_per_node = ClusterHashSlots.to_f / masters_count
first = 0
@@ -594,8 +599,8 @@ class RedisTrib
# all nodes will be used.
assignment_verbose = false
- [:requested,:unused].each{|assign|
- masters.each{|m|
+ [:requested,:unused].each do |assign|
+ masters.each do |m|
assigned_replicas = 0
while assigned_replicas < @replicas
break if nodes_count == 0
@@ -609,21 +614,33 @@ class RedisTrib
"role too (#{nodes_count} remaining)."
end
end
- ips.each{|ip,nodes_list|
- next if nodes_list.length == 0
- # Skip instances with the same IP as the master if we
- # have some more IPs available.
- next if ip == m.info[:host] && nodes_count > nodes_list.length
- slave = nodes_list.shift
- slave.set_as_replica(m.info[:name])
- nodes_count -= 1
- assigned_replicas += 1
- puts "Adding replica #{slave} to #{m}"
- break
- }
+
+ # Return the first node not matching our current master
+ node = interleaved.find{|n| n.info[:host] != m.info[:host]}
+
+ # If we found a node, use it as a best-first match.
+ # Otherwise, we didn't find a node on a different IP, so we
+ # go ahead and use a same-IP replica.
+ if node
+ slave = node
+ interleaved.delete node
+ else
+ slave = interleaved.shift
+ end
+ slave.set_as_replica(m.info[:name])
+ nodes_count -= 1
+ assigned_replicas += 1
+ puts "Adding replica #{slave} to #{m}"
+
+ # If we are in the "assign extra nodes" loop,
+ # we want to assign one extra replica to each
+ # master before repeating masters.
+ # This break lets us assign extra replicas to masters
+ # in a round-robin way.
+ break if assign == :unused
end
- }
- }
+ end
+ end
end
def flush_nodes_config