h1. Cellar groups

You can define groups in Cellar. A group allows you to define specific nodes and resources that are to be
working together. This permits some nodes (those outside the group) not to need to sync'ed with changes of
a node within a group.

By default, the Cellar nodes go into the default group:

{code}
karaf@root> cluster:group-list
  Node                 Group
* node1.local:5701   default
  node2.local:5702   default
{code}

As for node, the starting * shows the local node/group.

h2. New group

You can create a new group using the group-create command:

{code}
karaf@root> cluster:group-create test
Name                 test
Members              []

{code}

For now, the test group hasn't any nodes:

{code}
kaaf@root> cluster:group-list
  Node                 Group
  node1.local:5701 default
* node2.local:5702 default
  test

{code}

h2. Group configuration

You can see the configuration PID associated with a given group, for instance the default group:

{code}
karaf@root> cluster:config-list default
PIDs for group:default
PID                                     
org.apache.felix.fileinstall.3e4e22ea-8495-4612-9839-a537c8a7a503
org.apache.felix.fileinstall.1afcd688-b051-4b12-a50e-97e40359b24e
org.apache.karaf.features               
org.apache.karaf.log                    
org.apache.karaf.features.obr           
org.ops4j.pax.logging                   
org.apache.karaf.cellar.groups          
org.ops4j.pax.url.mvn                   
org.apache.karaf.jaas                   
org.apache.karaf.shell  
{code}

You can use the cluster:config-proplist and config-propset commands to list, add and edit the configuration.

For instance, in the test group, we don't have any configuration:

{code}
karaf@root> cluster:config-list test
No PIDs found for group:test
{code}

We can create a tstcfg config in the test group, containing name=value property:

{code}
karaf@root> cluster:config-propset test tstcfg name value
{code}

Now, we have this property in the test group:

{code}
karaf@root> cluster:config-list test
PIDs for group:test
PID                                     
tstcfg                                  
karaf@root> cluster:config-proplist test tstcfg
Property list for PID:tstcfg for group:test
Key                                      Value
name                                     value
{code}

h2. Group nodes

You can define a node member of one of more group:

{code}
karaf@root> cluster:group-join test node1.local:5701
  Node                 Group
  node1:5701 default
* node2:5702 default
  node1:5701 test
{code}

The node can be local or remote.

Now, the nodes of a given group will inherit of all configuration defined in the group. This means that
node1 now knows the tstcfg configuration because it's a member of the test group:

{code}
karaf@root> config:edit tstcfg
karaf@root> proplist
  service.pid = tstcfg
  name = value
{code}

h2. Group features

Configuration and features can be assigned to a given group.

{code}
karaf@root> cluster:features-list default
Features for group:default
Name                                                  Version Status 
spring-dm                                               1.2.1 true 
kar                                                     2.2.1 false 
config                                                  2.2.1 true 
http-whiteboard                                         2.2.1 false 
application-without-isolation                             0.3 false 
war                                                     2.2.1 false 
standard                                                2.2.1 false 
management                                              2.2.1 true 
http                                                    2.2.1 false 
transaction                                               0.3 false 
jetty                                         7.4.2.v20110526 false 
wrapper                                                 2.2.1 false 
jndi                                                      0.3 false 
obr                                                     2.2.1 false 
jpa                                                       0.3 false 
webconsole-base                                         2.2.1 false 
hazelcast                                               1.9.3 true 
eventadmin                                              2.2.1 false 
spring-dm-web                                           1.2.1 false 
ssh                                                     2.2.1 true 
spring-web                                      3.0.5.RELEASE false 
hazelcast-monitor                                       1.9.3 false 
jasypt-encryption                                       2.2.1 false 
webconsole                                              2.2.1 false 
spring                                          3.0.5.RELEASE true 
{code}

{code}
karaf@root> cluster:features-list test
Features for group:test
Name                                                  Version Status 
webconsole                                              2.2.1 false 
spring-dm                                               1.2.1 true 
eventadmin                                              2.2.1 false 
http                                                    2.2.1 false 
war                                                     2.2.1 false 
http-whiteboard                                         2.2.1 false 
obr                                                     2.2.1 false 
spring                                          3.0.5.RELEASE true 
hazelcast-monitor                                       1.9.3 false 
webconsole-base                                         2.2.1 false 
management                                              2.2.1 true 
hazelcast                                               1.9.3 true 
jpa                                                       0.3 false 
jndi                                                      0.3 false 
standard                                                2.2.1 false 
jetty                                         7.4.2.v20110526 false 
application-without-isolation                             0.3 false 
config                                                  2.2.1 true 
spring-web                                      3.0.5.RELEASE false 
wrapper                                                 2.2.1 false 
transaction                                               0.3 false 
spring-dm-web                                           1.2.1 false 
ssh                                                     2.2.1 true 
jasypt-encryption                                       2.2.1 false 
kar                                                     2.2.1 false 
{code}

Now we can "install" a feature for a given cluster group:

{code}
karaf@root> cluster:feature-install test eventadmin
karaf@root> cluster:feature-list test|grep -i event
eventadmin                                     2.2.1 true 
{code}

Below, we see that the eventadmin feature has been installed on this member of the test group:

{code}
karaf@root> features:list|grep -i event
[installed  ] [2.2.1 ] eventadmin                    karaf-2.2.1 
{code}