Using Multiple Masters

KeyDB now has support with multiple masters when replicating. This mode is enabled with the following configuration line:

multi-master yes

When KeyDB connects with multiple masters it behaves differently than with traditional replication:

  • Multiple invocations of the replicaof command will result in adding additional masters, not replacing the current one
  • KeyDB will not drop its database when sync'ing with the master
  • KeyDB will merge any reads/writes from the master with its own internal database
  • KeyDB will default to last operation wins

This means that a replica with multiple masters will contain a superset of the data of all its masters. If two masters have a value with the same key it is undefined which key will be taken. If a master deletes a key that exists on another master the replica will no longer contain a copy of that key.

This feature is still experimental, if you try it out please let us know how it works for you. Keep an eye on your perf as this feature can occasionally experience traffic storms.

If you are only setting up 2 instances to be masters please use active-replication as it is more stable than multi-master and tested to handle high loads

Setting up Multi-Master

Multiple Master setup is very similar to active replica setup, but allows more than one replica node (all masters). It allows you to read and write to all instances which can increase reads under high load, and have your other master nodes ready to go in a failure scenario of one.

With multi-master setup you make each master a replica of other nodes. This can accept many topologies, you could make different variations of ring topologies or make every master a replica of all other masters. If not all are synced, consider failure scenarios and ensure that one break wont cause others to lose their connections.

An example config file:

Config File

Instance-A config file:

# assuming below parameters were set and IP address of this instance is 10.0.0.2
port 6379
requirepass mypassword123
masterauth mypassword123
# you will need to configure the following
multi-master yes
active-replica yes
replicaof 10.0.0.3 6379
replicaof 10.0.0.4 6379

Instance-B config file:

# assuming below parameters were set and IP address of this instance is 10.0.0.3
port 6379
requirepass mypassword123
masterauth mypassword123
# you will need to configure the following
multi-master yes
active-replica yes
replicaof 10.0.0.2 6379
replicaof 10.0.0.4 6379

Instance-C config file:

# assuming below parameters were set and IP address of this instance is 10.0.0.4
port 6379
requirepass mypassword123
masterauth mypassword123
# you will need to configure the following
multi-master yes
active-replica yes
replicaof 10.0.0.2 6379
replicaof 10.0.0.3 6379

You can also append to config file keydb-server --multi-master yes --active-replica yes --replicaof <ipaddress> <port> --replicaof

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