Running a Cluster

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:

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:

listener.protobuf.internal = 127.0.0.1:8087

%% In the pb section of riak_core:

{"127.0.0.1", 8087 },

becomes

listener.protobuf.internal = 192.168.1.10:8087

%% In the pb section of riak_core:

{"192.168.1.10", 8087 },

If you’re using the HTTP interface, you will need to alter your configuration in an analogous way:

listener.http.internal = 127.0.0.1:8098

%% In the riak_core section:

{http, [ {"127.0.0.1", 8098 } ]},

becomes

listener.http.internal = 192.168.1.10:8098

{http, [ {"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:

nodename = riak@127.0.0.1

-name riak@127.0.0.1

becomes

nodename = riak@192.168.1.10

-name 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:

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.

riak-admin cluster replace riak@127.0.0.1 riak@192.168.1.10

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:

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:

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:

   bin/riak-admin status | grep ring_members
   

   With output resembling the following:

   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:

   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:

   # For Protocol Buffers:
   listener.protobuf.internal = 127.0.0.1:8187
   
   # For HTTP:
   listener.http.internal = 127.0.0.1:8198
   
   # For either interface:
   handoff.port = 8199
   

   %% In the pb section of riak_core:
   {"127.0.0.1", 8187 }
   
   %% In the http section of riak_core:
   {"127.0.0.1", 8198}
   

2. Change the name of each node to a unique name. Now, start the nodes, changing path names and nodes as appropriate:

./rel/riak1/bin/riak start
./rel/riak2/bin/riak start
./rel/riak3/bin/riak start

# etc

Next, join the nodes into a cluster:

./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.