Using provider pattern for cluster metadata.
Change-Id: I5a572b3df9149be959dde9868a9c594dec26a3e0
diff --git a/core/api/src/main/java/org/onosproject/cluster/ClusterMetadataProvider.java b/core/api/src/main/java/org/onosproject/cluster/ClusterMetadataProvider.java
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+/*
+ * Copyright 2015-2016 Open Networking Laboratory
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.onosproject.cluster;
+
+import java.util.Set;
+
+import org.onosproject.net.provider.Provider;
+import org.onosproject.store.service.Versioned;
+
+/**
+ * Abstraction of a {@link ClusterMetadata cluster metadata} provider.
+ */
+public interface ClusterMetadataProvider extends Provider {
+
+ /**
+ * Tells if this provider is currently available and therefore can provide ClusterMetadata.
+ * @return {@code true} if this provider is available and can provide cluster metadata.
+ */
+ boolean isAvailable();
+
+ /**
+ * Returns the current cluster metadata.
+ * @return cluster metadata
+ */
+ Versioned<ClusterMetadata> getClusterMetadata();
+
+ /**
+ * Updates cluster metadata.
+ * @param metadata new metadata
+ */
+ void setClusterMetadata(ClusterMetadata metadata);
+
+ /**
+ * Adds a controller node to the list of active members for a partition.
+ * <p>
+ * Active members of a partition are those that are actively participating
+ * in the data replication protocol being employed. When a node first added
+ * to a partition, it is in a passive or catch up mode where it attempts to
+ * bring it self up to speed with other active members in the partition.
+ * @param partitionId partition identifier
+ * @param nodeId identifier of controller node
+ */
+ void addActivePartitionMember(PartitionId partitionId, NodeId nodeId);
+
+ /**
+ * Removes a controller node from the list of active members for a partition.
+ * @param partitionId partition identifier
+ * @param nodeId identifier of controller node
+ */
+ void removeActivePartitionMember(PartitionId partitionId, NodeId nodeId);
+
+ /**
+ * Returns the set of controller nodes that are the active members for a partition.
+ * <p>
+ * Active members of a partition are typically those that are actively
+ * participating in the data replication protocol being employed. When
+ * a node first added to a partition, it is in a passive or catch up mode where
+ * it attempts to bring it self up to speed with other active members in the partition.
+ * <p>
+ * <b>Note:</b>If is possible for this list to different from the list of partition members
+ * specified by cluster meta data. The discrepancy can arise due to the fact that
+ * adding/removing members from a partition requires a data hand-off mechanism to complete.
+ * @param partitionId partition identifier
+ * @return identifiers of controller nodes that are active members
+ */
+ Set<NodeId> getActivePartitionMembers(PartitionId partitionId);
+}