Deleting master node from existing Redis Cluster - redis

Question

I want to delete a master node from existing Redis Cluster. I tried following the instructions from http://redis.io/topics/cluster-tutorial but unable to follow. Help??

Answer 1

As per previous answer, to delete a master node it must be empty. That means we've to flushall the data or migrate hash slot to another existing master.
But as redis reconfiguration and redis cluster resharding says, additional steps may need to be added after step 5 in the previous answer.
A solution that works for me is as following according to redis official docs. The order is important here.
We'll call the node that has the current ownership of the hash slot the source node, and the node where we want to migrate the destination node.
For each slot:
Send CLUSTER SETSLOT <slot> IMPORTING <source-node-id> to destination node to set the slot to importing state.
Send CLUSTER SETSLOT <slot> MIGRATING <destination-node-id> to source node to set the slot to migrating state.
Get keys from the source node with CLUSTER GETKEYSINSLOT command and move them into the destination node using the following MIGRATE command.
MIGRATE target_host target_port key target_database_id timeout
In Redis Cluster there is no need to specify a database other than 0, but MIGRATE is a general command that can be used for other tasks not involving Redis Cluster.
When the migration process is finally finished, use CLUSTER SETSLOT <slot> NODE <destination-node-id> in both source node and destination node in order to set the slot to their normal state again. The same command is usually sent to all other nodes to avoid waiting for the natural propagation of the new configuration across the cluster.
A simple example bash script to do this is also given here:
source-ip: 172.17.0.5. source-id: 1f70a5107e0042a7d33a9efaf88dbdfecd78076a
destination-ip: 172.17.0.4. destination-id: 7e428bae84697a3882ecad19bd0d13ac7ee97d02
another master ip: 172.17.0.7
for i in `seq 0 5460`; do
redis-cli -c -h 172.17.0.4 cluster setslot ${i} importing 1f70a5107e0042a7d33a9efaf88dbdfecd78076a
redis-cli -c -h 172.17.0.5 cluster setslot ${i} migrating 7e428bae84697a3882ecad19bd0d13ac7ee97d02
while true; do
key=`redis-cli -c -h 172.17.0.5 cluster getkeysinslot ${i} 1`
if [ "" = "$key" ]; then
echo "there are no key in this slot ${i}"
break
fi
redis-cli -h 172.17.0.5 migrate 172.17.0.4 6379 ${key} 0 5000
done
redis-cli -c -h 172.17.0.5 cluster setslot ${i} node 7e428bae84697a3882ecad19bd0d13ac7ee97d02
redis-cli -c -h 172.17.0.4 cluster setslot ${i} node 7e428bae84697a3882ecad19bd0d13ac7ee97d02
redis-cli -c -h 172.17.0.7 cluster setslot ${i} node 7e428bae84697a3882ecad19bd0d13ac7ee97d02
done

Answer 2

Node should be empty before deleting it. As such, we need to move the data and also slots before deleting a node.
Follow below steps to migrate:
Connect to destination node:
cluster setslot (slot no) importing (source node id)
Connect to source node:
cluster setslot (slot no) migrating (destination node id)
migrate (destination ip) (destination port) key (destination db) (timeout)
Connect to destination node:
cluster setslot (slot no) node (dest node)
We can do the above in a loop for all the slots and keys and then delete the source node.