[GitHub] [kafka] dajac commented on a diff in pull request #13637: KAFKA-14462; [10/N] Add TargetAssignmentBuilder

["dajac (via GitHub)" <gi...@apache.org>]

dajac commented on code in PR #13637:
URL: https://github.com/apache/kafka/pull/13637#discussion_r1179071413


##########
group-coordinator/src/main/java/org/apache/kafka/coordinator/group/consumer/TargetAssignmentBuilder.java:
##########
@@ -0,0 +1,327 @@
+/*
+ * 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.kafka.coordinator.group.consumer;
+
+import org.apache.kafka.common.Uuid;
+import org.apache.kafka.coordinator.group.Record;
+import org.apache.kafka.coordinator.group.assignor.AssignmentMemberSpec;
+import org.apache.kafka.coordinator.group.assignor.AssignmentSpec;
+import org.apache.kafka.coordinator.group.assignor.AssignmentTopicMetadata;
+import org.apache.kafka.coordinator.group.assignor.GroupAssignment;
+import org.apache.kafka.coordinator.group.assignor.MemberAssignment;
+import org.apache.kafka.coordinator.group.assignor.PartitionAssignor;
+import org.apache.kafka.coordinator.group.assignor.PartitionAssignorException;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Map;
+import java.util.Objects;
+import java.util.Optional;
+import java.util.Set;
+
+import static org.apache.kafka.coordinator.group.RecordHelpers.newTargetAssignmentEpochRecord;
+import static org.apache.kafka.coordinator.group.RecordHelpers.newTargetAssignmentRecord;
+
+/**
+ * Build a new Target Assignment based on the provided parameters. As a result,
+ * it yields the records that must be persisted to the log and the new member
+ * assignments as a map.
+ *
+ * Records are only created for members which have a new target assignment. If
+ * their assignment did not change, no new record is needed.
+ *
+ * When a member is deleted, it is assumed that its target assignment record
+ * is deleted as part of the member deletion process. In other words, this class
+ * does not yield a tombstone for remove members.
+ */
+public class TargetAssignmentBuilder {
+    /**
+     * The assignment result returned by {{@link TargetAssignmentBuilder#build()}}.
+     */
+    public static class TargetAssignmentResult {
+        /**
+         * The records that must be applied to the __consumer_offsets
+         * topics to persist the new target assignment.
+         */
+        private final List<Record> records;
+
+        /**
+         * The new target assignment for all members.
+         */
+        private final Map<String, Assignment> assignments;
+
+        TargetAssignmentResult(
+            List<org.apache.kafka.coordinator.group.Record> records,
+            Map<String, Assignment> assignments
+        ) {
+            Objects.requireNonNull(records);
+            Objects.requireNonNull(assignments);
+            this.records = records;
+            this.assignments = assignments;
+        }
+
+        /**
+         * @return The records.
+         */
+        public List<Record> records() {
+            return records;
+        }
+
+        /**
+         * @return The assignment.
+         */
+        public Map<String, Assignment> assignments() {
+            return assignments;
+        }
+    }
+
+    /**
+     * The group id.
+     */
+    private final String groupId;
+
+    /**
+     * The group epoch.
+     */
+    private final int groupEpoch;
+
+    /**
+     * The partition assignor to compute the assignment.
+     */
+    private final PartitionAssignor assignor;
+
+    /**
+     * The members in the group.
+     */
+    private Map<String, ConsumerGroupMember> members = Collections.emptyMap();
+
+    /**
+     * The subscription metadata.
+     */
+    private Map<String, TopicMetadata> subscriptionMetadata = Collections.emptyMap();
+
+    /**
+     * The current target assignment.
+     */
+    private Map<String, Assignment> assignments = Collections.emptyMap();
+
+    /**
+     * The members which have been updated or deleted. Deleted members
+     * are signaled by a null value.
+     */
+    private Map<String, ConsumerGroupMember> updatedMembers = new HashMap<>();
+
+    /**
+     * Constructs the object.
+     *
+     * @param groupId       The group id.
+     * @param groupEpoch    The group epoch to compute a target assignment for.
+     * @param assignor      The assignor to use to compute the target assignment.
+     */
+    public TargetAssignmentBuilder(
+        String groupId,
+        int groupEpoch,
+        PartitionAssignor assignor
+    ) {
+        this.groupId = Objects.requireNonNull(groupId);
+        this.groupEpoch = groupEpoch;
+        this.assignor = Objects.requireNonNull(assignor);
+    }
+
+    /**
+     * Adds all the current members.
+     *
+     * @param members   The current members in the consumer groups.
+     * @return This object.
+     */
+    public TargetAssignmentBuilder withMembers(
+        Map<String, ConsumerGroupMember> members
+    ) {
+        this.members = members;
+        return this;
+    }
+
+    /**
+     * Adds the subscription metadata to use.
+     *
+     * @param subscriptionMetadata  The subscription metadata.
+     * @return This object.
+     */
+    public TargetAssignmentBuilder withSubscriptionMetadata(
+        Map<String, TopicMetadata> subscriptionMetadata
+    ) {
+        this.subscriptionMetadata = subscriptionMetadata;
+        return this;
+    }
+
+    /**
+     * Adds the current target assignments.
+     *
+     * @param assignments   The current assignments.

Review Comment:
   I agree. How about using `the last target assignment`.



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