ryannedolan commented on a change in pull request #9395:
URL: https://github.com/apache/kafka/pull/9395#discussion_r502672494
##########
File path:
connect/mirror-client/src/main/java/org/apache/kafka/connect/mirror/ReplicationPolicy.java
##########
@@ -57,4 +57,9 @@ default boolean isInternalTopic(String topic) {
return topic.endsWith(".internal") || topic.endsWith("-internal") ||
topic.startsWith("__")
|| topic.startsWith(".");
}
+
+ /** Checks if the policy can track back to the source of the topic. */
+ default boolean canTrackSource(String topic) {
Review comment:
If a public API change like this is required, you will need to propose a
small KIP. I'm unclear why it's required tho, and ideally we would not alter
the existing API if possible.
If a new method is required, I think "track" is too ambiguous and should not
be used here.
##########
File path:
connect/mirror-client/src/main/java/org/apache/kafka/connect/mirror/ReplicationPolicy.java
##########
@@ -57,4 +57,9 @@ default boolean isInternalTopic(String topic) {
return topic.endsWith(".internal") || topic.endsWith("-internal") ||
topic.startsWith("__")
|| topic.startsWith(".");
}
+
+ /** Checks if the policy can track back to the source of the topic. */
Review comment:
I'm not sure what you mean by "track back to the source of the topic".
The word "track" might mean a few things here, and it's not obvious what you
mean. Can you clarify?
##########
File path:
connect/mirror-client/src/main/java/org/apache/kafka/connect/mirror/LegacyReplicationPolicy.java
##########
@@ -0,0 +1,96 @@
+/*
+ * 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.connect.mirror;
+
+import org.apache.kafka.common.Configurable;
+
+import java.util.Map;
+
+import static
org.apache.kafka.connect.mirror.MirrorClientConfig.HEARTBEATS_TOPIC;
+
+/**
+ * The replication policy that imitates the behavior of MirrorMaker 1.
+ *
+ * <p>The policy doesn't rename topics: {@code topic1} remains {@code topic1}
after replication.
+ * There is one exception to this: for {@code heartbeats}, it behaves
identical to {@link DefaultReplicationPolicy}.
+ *
+ * <p>The policy has some notable limitations. The most important one is that
the policy is unable to detect
+ * cycles for any topic apart from {@code heartbeats}. This makes
cross-replication effectively impossible.
+ *
+ * <p>Another limitation is that {@link MirrorClient#remoteTopics()} will be
able to list only
+ * {@code heartbeats} topics.
+ *
+ * <p>{@link MirrorClient#countHopsForTopic(String, String)} will return
{@code -1} for any topic
+ * apart from {@code heartbeats}.
+ *
+ * <p>The policy supports {@link DefaultReplicationPolicy}'s configurations
+ * for the behavior related to {@code heartbeats}.
+ */
+public class LegacyReplicationPolicy implements ReplicationPolicy,
Configurable {
+ // Replication sub-policy for heartbeats topics
+ private final DefaultReplicationPolicy heartbeatTopicReplicationPolicy =
new DefaultReplicationPolicy();
+
+ @Override
+ public void configure(final Map<String, ?> props) {
+ heartbeatTopicReplicationPolicy.configure(props);
+ }
+
+ @Override
+ public String formatRemoteTopic(final String sourceClusterAlias, final
String topic) {
+ if (isOriginalTopicHeartbeats(topic)) {
+ return
heartbeatTopicReplicationPolicy.formatRemoteTopic(sourceClusterAlias, topic);
+ } else {
+ return topic;
+ }
+ }
+
+ @Override
+ public String topicSource(final String topic) {
+ if (isOriginalTopicHeartbeats(topic)) {
+ return heartbeatTopicReplicationPolicy.topicSource(topic);
+ } else {
+ return null;
Review comment:
I've seen alternative solutions floating around that use a configurable
source here. Basically, the configuration passed to configure() is consulted to
find the "source cluster", rather than looking at the topic name. That approach
lets you return an actual source here, which obviates the new canTrackSource()
method etc.
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