Running a Cluster
Contents
1. Configure the First Node
2. Add a Second Node to Your Cluster
3. Running Multiple Nodes on One Host
4. Multiple Clusters on One Host
Configuring a Riak cluster involves instructing each node to listen on a non-local interface, i.e.
not 127.0.0.1, and then joining all of the nodes together to participate in the cluster.
Most configuration changes will be applied to the configuration file located in
your rel/riak/etc directory (if you compiled from source) or /etc (if you used a binary install of Riak).
The commands below presume that you are running from a source install, but if you have installed Riak with a
binary install, you can substitute the usage of bin/riak with sudo /usr/sbin/riak and bin/riak-
admin with sudo /usr/sbin/riak-admin. The riak and riak-admin scripts are located in
the /bin directory of your installation.
Note on changing the name value
If possible, you should avoid starting Riak prior to editing the name of a node. This setting corresponds to
the nodename parameter in the riak.conf file if you are using the newer configuration system, and to the -
name parameter in vm.args (as described below) if you are using the older configuration system. If you have
already started Riak with the default settings, you cannot change the -name setting and then successfully
restart the node.
If you cannot restart after changing the -name value you have two options:
Discard the existing ring metadata by removing the contents of the ring directory. This will
require rejoining all nodes into a cluster again.
*Rename the node using the riak-admin cluster replace command. This will not work if you have
previously only started Riak with a single node.
Configure the First Node
First, stop your Riak node if it is currently running:
SHELL
riak stop
Select an IP address and port
Let’s say that the IP address for your cluster is 192.168.1.10 and that you’ll be using the default port (8087). If
you’re using the Protocol Buffers interface to Riak (which we recommend over the HTTP interface due to
performance gains), you should change your configuration file:
RIAK.CONF
APP.CONFIG
listener.protobuf.internal = 127.0.0.1:8087
becomes
RIAK.CONF
APP.CONFIG
listener.protobuf.internal = 192.168.1.10:8087
Note on upgrading to 2.0
If you are upgrading to Riak version 2.0 or later from an pre-2.0 release, you can use either your
old app.config/ vm.args configuration files or the newer riak.conf if you wish. If you have installed Riak
2.0 directly, you should use only riak.conf.
Below, examples will be provided for both the old and new configuration systems. Bear in mind that you need
to use either the older or the newer but never both simultaneously.
More on configuring Riak can be found in the Configuration documentation.
If you’re using the HTTP interface, you will need to alter your configuration in an analogous way:
RIAK.CONF
APP.CONFIG
listener.http.internal = 127.0.0.1:8098
becomes
RIAK.CONF
APP.CONFIG
listener.http.internal = 192.168.1.10:8098
Name your node
Every node in Riak has a name associated with it. The default name is riak@127.0.0.1. Let’s say that
you want to change the name to riak@192.168.1.10:
RIAK.CONF
VM.ARGS
nodename = riak@ 127.0.0.1
becomes
RIAK.CONF
VM.ARGS
nodename = riak@ 192.168.1.10
Node Names
Use fully qualified domain names (FQDNs) rather than IP addresses for the cluster member node names. For
example, riak@cluster.example.com and riak@192.168.1.10 are both acceptable node naming
schemes, but using the FQDN style is preferred.
Once a node has been started, in order to change the name you must either remove ring files from
the /data/ring directory or riak-admin cluster force-replace the node.
Start the node
Now that your node is properly configured, you can start it:
SHELL
riak start
If the Riak node has been previously started, you must use the riak-admin cluster
replace command to change the node name and update the node’s ring file.
SHELL
riak-admin cluster replace riak@127.0.0.1 riak@192.168.1.10
Note on single nodes
If a node is started singly using default settings, as you might do when you are building your first test
environment, you will need to remove the ring files from the data directory after you edit your configuration
files. riak-admin cluster replace will not work since the node has not been joined to a cluster.
As with all cluster changes, you need to view the planned changes by running riak-admin cluster
plan and then running riak-admin cluster commit to finalize those changes.
The node is now properly set up to join other nodes for cluster participation. You can proceed to adding a
second node to the cluster.
Add a Second Node to Your Cluster
Repeat the above steps for a second host on the same network, providing the second node with a host/port and
node name. Once the second node has started, use riak-admin cluster join to join the second node
to the first node, thereby creating an initial Riak cluster. Let’s say that we’ve named our second
node riak@192.168.1.11. From the new node’s /bin directory:
SHELL
riak-admin cluster join riak@192.168.1.10
Output from the above should resemble:
Success: staged join request for `riak@192.168.1.11` to `riak@192.168.1.10`
Next, plan and commit the changes:
SHELL
riak-admin cluster plan
riak-admin cluster commit
After the last command, you should see:
Cluster changes committed
If your output was similar, then the second Riak node is now part of the cluster and has begun syncing with
the first node. Riak provides several ways to determine the cluster’s ring status. Here are two ways to examine
your Riak cluster’s ring:
1. Using the riak-admin command:
SHELL
bin/riak-admin status | grep ring_members
With output resembling the following:
SHELL
ring_members : [ 'riak@192.168.1.10','riak@192.168.1.11']
2. Running the riak attach command. This will open up an Erlang shell, into which you can type
the following command:
ERLANG
1 > {ok, R} = riak_core_ring_manager:get_my_ring().
%% Response:
{ok,{chstate,'riak@ 192.168.1.10',.........
(riak@ 192.168.52.129)2> riak_core_ring:all_members(R).
['riak@ 192.168.1.10','riak@192.168.1.11']
To join additional nodes to your cluster, repeat the above steps. You can also find more detailed instructions
about adding and removing nodes from a cluster.
Ring Creation Size
All nodes in the cluster must have the same initial ring size setting in order to join, and participate in cluster
activity. This setting can be adjusted in your configuration file using the ring_creation_size parameter if
you’re using the older configuration system or ring_size in the new system.
Check the value of all nodes if you receive a message like this: Failed: riak@10.0.1.156 has a
different ring_creation_size
Running Multiple Nodes on One Host
If you built Riak from source code, or if you are using the Mac OS X pre-built package, then you can easily
run multiple Riak nodes on the same machine. The most common scenario for doing this is to experiment with
running a Riak cluster.
Note: If you have installed the .deb or .rpm package, then you will need to download and build Riak from
source to follow the directions below.
To run multiple nodes, make copies of the riak directory.
If you ran make all rel, then this can be found in ./rel/riak under the Riak source root
directory.
If you are running Mac OS X, then this is the directory where you unzipped the .tar.gz file.
Presuming that you copied ./rel/riak into ./rel/riak1, ./rel/riak2, ./rel/riak3, and so
on, you need to make two changes:
1. Set your handoff port and your Protocol Buffers or HTTP port (depending on which interface you are
using) to different values on each node. For example:
o RIAK.CONF
o APP.CONFIG
2. # For Protocol Buffers:
3. listener.protobuf.internal = 127.0.0.1:8187
4.
5. # For HTTP:
6. listener.http.internal = 127.0.0.1:8198
7.
8. # For either interface:
9. handoff.port = 8199
10. Change the name of each node to a unique name. Now, start the nodes, changing path names and
nodes as appropriate:
SHELL
./rel/riak1/bin/riak start
./rel/riak2/bin/riak start
./rel/riak3/bin/riak start
# etc
Next, join the nodes into a cluster:
SHELL
./rel/riak2/bin/riak-admin cluster join riak1@127.0.0.1
./rel/riak3/bin/riak-admin cluster join riak1@127.0.0.1
./rel/riak2/bin/riak-admin cluster plan
./rel/riak2/bin/riak-admin cluster commit
Multiple Clusters on One Host
Using the above technique, it is possible to run multiple clusters on one computer. If a node hasn’t joined an
existing cluster, it will behave just as a cluster would. Running multiple clusters on one computer is simply a
matter of having two or more distinct nodes or groups of clustered nodes.
