[GitHub] [kafka] ableegoldman commented on a change in pull request #8541: KAFKA-6145: KIP-441: Add TaskAssignor class config

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ableegoldman commented on a change in pull request #8541:
URL: https://github.com/apache/kafka/pull/8541#discussion_r414227525



##########
File path: streams/src/main/java/org/apache/kafka/streams/processor/internals/StreamsPartitionAssignor.java
##########
@@ -713,23 +713,18 @@ private boolean assignTasksToClients(final Set<String> allSourceTopics,
             allTasks, clientStates, numStandbyReplicas());
 
         final TaskAssignor taskAssignor;
-        if (highAvailabilityEnabled) {
-            if (lagComputationSuccessful) {
-                taskAssignor = new HighAvailabilityTaskAssignor(
-                    clientStates,
-                    allTasks,
-                    statefulTasks,
-                    assignmentConfigs);
-            } else {
-                log.info("Failed to fetch end offsets for changelogs, will return previous assignment to clients and "
-                             + "trigger another rebalance to retry.");
-                setAssignmentErrorCode(AssignorError.REBALANCE_NEEDED.code());
-                taskAssignor = new StickyTaskAssignor(clientStates, allTasks, statefulTasks, assignmentConfigs, true);
-            }
+        if (!lagComputationSuccessful) {

Review comment:
       Fine with me (although it does slightly detract from the opt-out possibility). WDYT about adding a retry backoff though? I'm a bit concerned we might just end up stuck in a loop of useless rebalancing, and waiting the full `probing.rebalance.interval` doesn't feel right either

##########
File path: streams/src/main/java/org/apache/kafka/streams/processor/internals/assignment/AssignorConfiguration.java
##########
@@ -41,8 +42,8 @@
 import static org.apache.kafka.streams.processor.internals.assignment.StreamsAssignmentProtocolVersions.LATEST_SUPPORTED_VERSION;
 
 public final class AssignorConfiguration {
-    public static final String HIGH_AVAILABILITY_ENABLED_CONFIG = "internal.high.availability.enabled";
-    private final boolean highAvailabilityEnabled;
+    public static final String INTERNAL_TASK_ASSIGNOR_CLASS = "internal.task.assignor.class";

Review comment:
       Should we put this with the other Streams internal configs? And/or follow the pattern of prefix+suffixing with `__` ?

##########
File path: streams/src/main/java/org/apache/kafka/streams/processor/internals/assignment/HighAvailabilityTaskAssignor.java
##########
@@ -95,6 +94,11 @@ public boolean assign() {
 
         assignStatelessActiveTasks();
 
+        log.info("Decided on assignment: " +

Review comment:
       I'm all for useful logging 👍 

##########
File path: streams/src/main/java/org/apache/kafka/streams/processor/internals/assignment/PriorTaskAssignor.java
##########
@@ -0,0 +1,40 @@
+/*
+ * 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.streams.processor.internals.assignment;
+
+import org.apache.kafka.streams.processor.TaskId;
+import org.apache.kafka.streams.processor.internals.assignment.AssignorConfiguration.AssignmentConfigs;
+
+import java.util.Map;
+import java.util.Set;
+import java.util.UUID;
+
+public class PriorTaskAssignor implements TaskAssignor {
+    private final StickyTaskAssignor delegate;
+
+    public PriorTaskAssignor() {
+        delegate = new StickyTaskAssignor(true);

Review comment:
       Thanks for the improvement, this feels a lot nicer




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