[GitHub] [ignite] alex-plekhanov commented on a change in pull request #8668: IGNITE-13560 Add node attribute colocated affinity backup filter

[GitBox <gi...@apache.org>]

alex-plekhanov commented on a change in pull request #8668:
URL: https://github.com/apache/ignite/pull/8668#discussion_r564553049



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File path: modules/core/src/main/java/org/apache/ignite/cache/affinity/rendezvous/ClusterNodeAttributeColocatedBackupFilter.java
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@@ -0,0 +1,114 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You 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.apache.ignite.cache.affinity.rendezvous;
+
+import java.util.List;
+import java.util.Objects;
+import org.apache.ignite.cluster.ClusterNode;
+import org.apache.ignite.lang.IgniteBiPredicate;
+
+/**
+ * This class can be used as a {@link RendezvousAffinityFunction#affinityBackupFilter } to create
+ * cache templates in Spring that force each partition's primary and backup to be co-located on nodes with the same
+ * attribute value.
+ * <p>
+ *
+ * Partition copies co-location can be helpful to group nodes into cells when fixed baseline topology is used. If all
+ * copies of each partition are located inside only one cell, in case of {@code backup + 1} nodes leave the cluster
+ * there will be data lost only if all leaving nodes belong to the same cell. Without partition copies co-location
+ * within a cell, most probably there will be data lost if any {@code backup + 1} nodes leave the cluster.
+ *
+ * Note: Baseline topology change can lead to inter-cell partitions migration, i.e. rebalance can affect all copies
+ * of some partitions even if only one node is changed in the baseline topology.
+ * <p>
+ *
+ * This implementation will discard backups rather than place copies on nodes with different attribute values. This
+ * avoids trying to cram more data onto remaining nodes when some have failed.
+ * <p>
+ * A node attribute to compare is provided on construction.
+ *
+ * Note: All cluster nodes, on startup, automatically register all the environment and system properties as node
+ * attributes.
+ *
+ * Note: Node attributes persisted in baseline topology at the time of baseline topology change. If the co-location
+ * attribute of some node was updated, but the baseline topology wasn't changed, the outdated attribute value can be
+ * used by the backup filter when this node left the cluster. To avoid this, the baseline topology should be updated
+ * after changing the co-location attribute.
+ * <p>
+ * This class is constructed with a node attribute name, and a candidate node will be rejected if previously selected
+ * nodes for a partition have a different value for attribute on the candidate node.
+ * </pre>
+ * <h2 class="header">Spring Example</h2>
+ * Create a partitioned cache template plate with 1 backup, where the backup will be placed in the same cell
+ * as the primary.   Note: This example requires that the environment variable "CELL" be set appropriately on
+ * each node via some means external to Ignite.
+ * <pre name="code" class="xml">
+ * &lt;property name="cacheConfiguration"&gt;
+ *     &lt;list&gt;
+ *         &lt;bean id="cache-template-bean" abstract="true" class="org.apache.ignite.configuration.CacheConfiguration"&gt;
+ *             &lt;property name="name" value="JobcaseDefaultCacheConfig*"/&gt;
+ *             &lt;property name="cacheMode" value="PARTITIONED" /&gt;
+ *             &lt;property name="backups" value="1" /&gt;
+ *             &lt;property name="affinity"&gt;
+ *                 &lt;bean class="org.apache.ignite.cache.affinity.rendezvous.RendezvousAffinityFunction"&gt;
+ *                     &lt;property name="affinityBackupFilter"&gt;
+ *                         &lt;bean class="org.apache.ignite.cache.affinity.rendezvous.ClusterNodeAttributeColocatedBackupFilter"&gt;
+ *                             &lt;!-- Backups must go to the same CELL as primary --&gt;
+ *                             &lt;constructor-arg value="CELL" /&gt;
+ *                         &lt;/bean&gt;
+ *                     &lt;/property&gt;
+ *                 &lt;/bean&gt;
+ *             &lt;/property&gt;
+ *         &lt;/bean&gt;
+ *     &lt;/list&gt;
+ * &lt;/property&gt;
+ * </pre>
+ * <p>
+ */
+public class ClusterNodeAttributeColocatedBackupFilter implements IgniteBiPredicate<ClusterNode, List<ClusterNode>> {
+    /** */
+    private static final long serialVersionUID = 1L;
+
+    /** Attribute name. */
+    private final String attrName;
+
+    /**
+     * @param attrName The attribute name for the attribute to compare.
+     */
+    public ClusterNodeAttributeColocatedBackupFilter(String attrName) {
+        this.attrName = attrName;
+    }
+
+    /**
+     * Defines a predicate which returns {@code true} if a node is acceptable for a backup
+     * or {@code false} otherwise. An acceptable node is one where its attribute value
+     * is exact match with previously selected nodes.  If an attribute does not
+     * exist on exactly one node of a pair, then the attribute does not match.  If the attribute
+     * does not exist both nodes of a pair, then the attribute matches.
+     *
+     * @param candidate          A node that is a candidate for becoming a backup node for a partition.
+     * @param previouslySelected A list of primary/backup nodes already chosen for a partition.
+     *                           The primary is first.
+     */
+    @Override public boolean apply(ClusterNode candidate, List<ClusterNode> previouslySelected) {
+        for (ClusterNode node : previouslySelected)
+            return Objects.equals(candidate.attribute(attrName), node.attribute(attrName));
+
+        return true;
+    }

Review comment:
       Fixed




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