Package org.apache.ignite.cluster

## Interface ClusterGroup

- All Known Subinterfaces:
    `IgniteCluster`

      public interface ClusterGroup

  Defines a cluster group which contains all or a subset of cluster nodes. The `IgniteCluster` interface itself also extends `ClusterGroup` which makes an instance of `IgniteCluster` into a cluster group containing all cluster nodes.

  # Clustering

  Cluster group allows to group cluster nodes into various subgroups to perform distributed operations on them. All `'forXXX(...)'` methods will create a child cluster group from the existing cluster group. If you create a new cluster group from the current one, then the resulting cluster group will include a subset of nodes from the current one. The following code shows how to create and nest cluster groups:

       Ignite ignite = Ignition.ignite();

       IgniteCluster cluster = ignite.cluster();

       // Cluster group over remote nodes.
       ClusterGroup remoteNodes = cluster.forRemotes();

       // Cluster group over random remote node.
       ClusterGroup randomNode = remoteNodes.forRandom();

       // Cluster group over all nodes with cache named "myCache" enabled.
       ClusterGroup cacheNodes = cluster.forCacheNodes("myCache");

       // Cluster group over all nodes that have the user attribute "group" set to the value "worker".
       ClusterGroup workerNodes = cluster.forAttribute("group", "worker");

- - ### Method Summary

    All Methods Instance Methods Abstract Methods
    Modifier and Type | Method | Description
    --- | --- | ---
    `ClusterGroup` | `forAttribute​(String name, @Nullable Object val)` | Creates a new cluster group for nodes containing given name and value specified in user attributes.
    `ClusterGroup` | `forCacheNodes​(String cacheName)` | Creates a cluster group for all nodes that have cache with specified name, either in client or server modes.
    `ClusterGroup` | `forClientNodes​(String cacheName)` | Creates a cluster group for all client nodes that access cache with the specified name.
    `ClusterGroup` | `forClients()` | Creates a cluster group of nodes started in client mode.
    `ClusterGroup` | `forDataNodes​(String cacheName)` | Creates a cluster group for all data nodes that have the cache with the specified name running.
    `ClusterGroup` | `forHost​(String host, String... hosts)` | Gets cluster group consisting from the nodes running on the hosts specified.
    `ClusterGroup` | `forHost​(ClusterNode node)` | Gets cluster group consisting from the nodes in this cluster group residing on the same host as the given node.
    `ClusterGroup` | `forNode​(ClusterNode node, ClusterNode... nodes)` | Creates a cluster group for the given node.
    `ClusterGroup` | `forNodeId​(UUID id, UUID... ids)` | Creates a cluster group for a node with the specified ID.
    `ClusterGroup` | `forNodeIds​(Collection<UUID> ids)` | Creates a cluster group over nodes with specified node IDs.
    `ClusterGroup` | `forNodes​(Collection<? extends ClusterNode> nodes)` | Creates a cluster group over a given set of nodes.
    `ClusterGroup` | `forOldest()` | Creates a cluster group with one oldest node from the current cluster group.
    `ClusterGroup` | `forOthers​(ClusterGroup prj)` | Creates a cluster group for nodes not included into the given cluster group.
    `ClusterGroup` | `forOthers​(ClusterNode node, ClusterNode... nodes)` | Creates a cluster group for nodes other than the given nodes.
    `ClusterGroup` | `forPredicate​(IgnitePredicate<ClusterNode> p)` | Creates a new cluster group which includes all nodes that pass the given predicate filter.
    `ClusterGroup` | `forRandom()` | Creates a cluster group with one random node from the current cluster group.
    `ClusterGroup` | `forRemotes()` | Gets cluster group consisting from the nodes in this cluster group excluding the local node.
    `ClusterGroup` | `forServers()` | Creates a cluster group of nodes started in server mode.
    `ClusterGroup` | `forYoungest()` | Creates a cluster group with one youngest node in the current cluster group.
    `Collection<String>` | `hostNames()` | Gets the read-only collection of hostnames in this cluster group.
    `Ignite` | `ignite()` | Gets instance of grid.
    `ClusterMetrics` | `metrics()` | Gets a metrics snapshot for this cluster group.
    `ClusterNode` | `node()` | Gets first node from the list of nodes in this cluster group.
    `ClusterNode` | `node​(UUID nid)` | Gets a node for given ID from this cluster group.
    `Collection<ClusterNode>` | `nodes()` | Gets the read-only collection of nodes in this cluster group.
    `IgnitePredicate<ClusterNode>` | `predicate()` | Gets predicate that defines a subset of nodes for this cluster group.

- - ### Method Detail

    - #### ignite

          Ignite ignite()

      Gets instance of grid.
      Returns:
        Grid instance.

    - #### forNodes

          ClusterGroup forNodes​(Collection<? extends ClusterNode> nodes)

      Creates a cluster group over a given set of nodes.
      Parameters:
        `nodes` - Collection of nodes to create the cluster group from.
      Returns:
        Cluster group for the provided grid nodes.

    - #### forNode

          ClusterGroup forNode​(ClusterNode node,
                               ClusterNode... nodes)

      Creates a cluster group for the given node.
      Parameters:
        `node` - Node to create cluster group for.
        `nodes` - Optional additional nodes to include into the cluster group.
      Returns:
        Cluster group for the given nodes.

    - #### forOthers

          ClusterGroup forOthers​(ClusterNode node,
                                 ClusterNode... nodes)

      Creates a cluster group for nodes other than the given nodes.
      Parameters:
        `node` - Node to exclude from the new cluster group.
        `nodes` - Optional additional nodes to exclude from the cluster group.
      Returns:
        Cluster group that will contain all nodes from the original cluster group excluding the given nodes.

    - #### forOthers

          ClusterGroup forOthers​(ClusterGroup prj)

      Creates a cluster group for nodes not included into the given cluster group.
      Parameters:
        `prj` - Cluster group to exclude from the new cluster group.
      Returns:
        Cluster group for nodes not included into the given cluster group.

    - #### forNodeIds

          ClusterGroup forNodeIds​(Collection<UUID> ids)

      Creates a cluster group over nodes with specified node IDs.
      Parameters:
        `ids` - Collection of node IDs.
      Returns:
        Cluster group over nodes with the specified node IDs.

    - #### forNodeId

          ClusterGroup forNodeId​(UUID id,
                                 UUID... ids)

      Creates a cluster group for a node with the specified ID.
      Parameters:
        `id` - Node ID to get the cluster group for.
        `ids` - Optional additional node IDs to include into the cluster group.
      Returns:
        Cluster group over the node with the specified node IDs.

    - #### forPredicate

          ClusterGroup forPredicate​(IgnitePredicate<ClusterNode> p)

      Creates a new cluster group which includes all nodes that pass the given predicate filter.
      Parameters:
        `p` - Predicate filter for nodes to include into the cluster group.
      Returns:
        Cluster group for nodes that passed the predicate filter.

    - #### forAttribute

          ClusterGroup forAttribute​(String name,
                                    @Nullable
                                    @Nullable Object val)

      Creates a new cluster group for nodes containing given name and value specified in user attributes.

      User attributes for every node are optional and can be specified in grid node configuration. See `IgniteConfiguration.getUserAttributes()` for more information.

      Parameters:
        `name` - Name of the attribute.
        `val` - Optional attribute value to match.
      Returns:
        Cluster group for nodes containing specified attribute.

    - #### forServers

          ClusterGroup forServers()

      Creates a cluster group of nodes started in server mode.
      Returns:
        Cluster group of nodes started in server mode.
      See Also:
        `Ignition.setClientMode(boolean)`, `IgniteConfiguration.setClientMode(boolean)`

    - #### forClients

          ClusterGroup forClients()

      Creates a cluster group of nodes started in client mode.
      Returns:
        Cluster group of nodes started in client mode.
      See Also:
        `Ignition.setClientMode(boolean)`, `IgniteConfiguration.setClientMode(boolean)`

    - #### forCacheNodes

          ClusterGroup forCacheNodes​(String cacheName)

      Creates a cluster group for all nodes that have cache with specified name, either in client or server modes.
      Parameters:
        `cacheName` - Cache name.
      Returns:
        Cluster group over nodes that have specified cache running.

    - #### forDataNodes

          ClusterGroup forDataNodes​(String cacheName)

      Creates a cluster group for all data nodes that have the cache with the specified name running.
      Parameters:
        `cacheName` - Cache name.
      Returns:
        Cluster group over nodes that have the cache with the specified name running.

    - #### forClientNodes

          ClusterGroup forClientNodes​(String cacheName)

      Creates a cluster group for all client nodes that access cache with the specified name.
      Parameters:
        `cacheName` - Cache name.
      Returns:
        Cluster group over nodes that have the specified cache running.

    - #### forRemotes

          ClusterGroup forRemotes()

      Gets cluster group consisting from the nodes in this cluster group excluding the local node.
      Returns:
        Cluster group consisting from the nodes in this cluster group excluding the local node.

    - #### forHost

          ClusterGroup forHost​(ClusterNode node)

      Gets cluster group consisting from the nodes in this cluster group residing on the same host as the given node.
      Parameters:
        `node` - Node to select the host for.
      Returns:
        Cluster group for nodes residing on the same host as the specified node.

    - #### forHost

          ClusterGroup forHost​(String host,
                               String... hosts)

      Gets cluster group consisting from the nodes running on the hosts specified.
      Parameters:
        `host` - Host name to get nodes to put in cluster
        `hosts` - Host names to get nodes to put in cluster.
      Returns:
        Cluster group for nodes residing on the hosts specified.

    - #### forRandom

          ClusterGroup forRandom()

      Creates a cluster group with one random node from the current cluster group.
      Returns:
        Cluster group containing one random node from the current cluster group.

    - #### forOldest

          ClusterGroup forOldest()

      Creates a cluster group with one oldest node from the current cluster group. The resulting cluster group is dynamic and will always pick the next oldest node if the previous one leaves topology even after the cluster group has been created.

      Use `node()` method to get the oldest node.

      Returns:
        Cluster group containing one oldest node from the current cluster group.

    - #### forYoungest

          ClusterGroup forYoungest()

      Creates a cluster group with one youngest node in the current cluster group. The resulting cluster group is dynamic and will always pick the newest node in the topology, even if more nodes entered after the cluster group has been created.
      Returns:
        Cluster group containing one youngest node from the current cluster group.

    - #### nodes

          Collection<ClusterNode> nodes()

      Gets the read-only collection of nodes in this cluster group.
      Returns:
        All nodes in this cluster group.

    - #### node

          ClusterNode node​(UUID nid)

      Gets a node for given ID from this cluster group.
      Parameters:
        `nid` - Node ID.
      Returns:
        Node with given ID from this cluster group or `null`, if such node does not exist.

    - #### node

          ClusterNode node()

      Gets first node from the list of nodes in this cluster group. This method is specifically useful for cluster groups with one node only.
      Returns:
        First node from the list of nodes in this cluster group or `null` if the cluster group is empty.

    - #### hostNames

          Collection<String> hostNames()

      Gets the read-only collection of hostnames in this cluster group.
      Returns:
        All hostnames in this cluster group.

    - #### predicate

          IgnitePredicate<ClusterNode> predicate()

      Gets predicate that defines a subset of nodes for this cluster group.
      Returns:
        Predicate that defines a subset of nodes for this cluster group.

    - #### metrics

          ClusterMetrics metrics()
                          throws IgniteException

      Gets a metrics snapshot for this cluster group.
      Returns:
        Metrics snapshot.
      Throws:
        `IgniteException` - If this cluster group is empty.