Start YB-Masters


  • The number of nodes in a cluster running YB-Masters must equal the replication factor.
  • The number of comma-separated addresses present in master_addresses should also equal the replication factor.
  • For running a single cluster across multiple data centers or 2 clusters in 2 data centers, refer to the Multi-DC deployments section.
  • Read more about the yb-master service architecture.

This section covers deployment for a single region or data center in a multi-zone/multi-rack configuration. Note that single zone configuration is a special case of multi-zone where all placement-related flags are set to the same value across every node.

Example scenario

  • Create a six-node cluster with replication factor of 3.
    • YB-Master server should run on only three nodes, the YB-TServer server should run on all six nodes.
    • Assume the three YB-Master private IP addresses are, and
    • Cloud will be aws, region will be us-west, and the three AZs will be us-west-2a, us-west-2b, and us-west-2c. Two nodes will be placed in each AZ in such a way that one replica for each tablet (aka shard) gets placed in any one node for each AZ.
  • Multiple data drives mounted on /home/centos/disk1, /home/centos/disk2.

Run YB-Master servers with command line flags

Run the yb-master server on each of the three nodes as shown below. Note how multiple directories can be provided to the --fs_data_dirs flag. Replace the --rpc_bind_addresses value with the private IP address of the host as well as the set the placement_cloud,placement_region and placement_zone values appropriately. For single zone deployment, use the same value for the placement_zone flag.

$ ./bin/yb-master \
  --master_addresses,, \
  --rpc_bind_addresses \
  --fs_data_dirs "/home/centos/disk1,/home/centos/disk2" \
  --placement_cloud aws \
  --placement_region us-west \
  --placement_zone us-west-2a \
  >& /home/centos/disk1/yb-master.out &

For the full list of configuration flags, see the YB-Master reference.

Run YB-Master servers with configuration file

Alternatively, you can also create a master.conf file with the following flags and then run yb-master with the --flagfile option as shown below. For each YB-Master server, replace the --rpc-bind-addresses configuration flag with the private IP address of the YB-Master server.

$ ./bin/yb-master --flagfile master.conf >& /home/centos/disk1/yb-master.out &

Verify health

Make sure all the three YB-Masters are now working as expected by inspecting the INFO log. The default logs directory is always inside the first directory specified in the --fs_data_dirs flag.

$ cat /home/centos/disk1/yb-data/master/logs/yb-master.INFO

You can see that the three YB-Masters were able to discover each other and were also able to elect a Raft leader among themselves (the remaining two act as Raft followers).

For the masters that become followers, you will see the following line in the log.

I0912 16:11:07.419591  8030] T 00000000000000000000000000000000 P bc42e1c52ffe4419896a816af48226bc [sys.catalog]: This master's current role is: FOLLOWER

For the master that becomes the leader, you will see the following line in the log.

I0912 16:11:06.899287 27220] T 00000000000000000000000000000000 P 21171528d28446c8ac0b1a3f489e8e4b [term 2 LEADER]: Becoming Leader. State: Replica: 21171528d28446c8ac0b1a3f489e8e4b, State: 1, Role: LEADER


Remember to add the command with which you launched yb-master to a cron to restart it if it goes down.

Next step

Now you are ready to start the YB-TServers.