[GitHub] [ignite-3] rpuch commented on a diff in pull request #1403: IGNITE-18085 Implement logical topology events subscription and notification

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

rpuch commented on code in PR #1403:
URL: https://github.com/apache/ignite-3/pull/1403#discussion_r1039581425


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modules/api/src/main/java/org/apache/ignite/network/LogicalTopologyService.java:
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@@ -0,0 +1,73 @@
+/*
+ * 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.network;
+
+import java.util.concurrent.CompletableFuture;
+
+/**
+ * Used for getting information about the cluster's Logical Topology.
+ *
+ * <p>There are 2 kinds of 'topologies': physical (see {@link TopologyService} and logical.
+ * <ul>
+ *     <li>Physical topology consists of nodes mutually discovered by a membership protocol (like SWIM)</li>
+ *     <li>
+ *         Logical topology is a subset of a physical topology and only contains nodes that have successfully
+ *         <a href="https://cwiki.apache.org/confluence/display/IGNITE/IEP-77%3A+Node+Join+Protocol+and+Initialization+for+Ignite+3">
+ *         joined the cluster</a>
+ *     </li>
+ * </ul>
+ *
+ * @see <a href="https://cwiki.apache.org/confluence/display/IGNITE/IEP-77%3A+Node+Join+Protocol+and+Initialization+for+Ignite+3">
+ *     IEP-77: Node Join Protocol and Initialization for Ignite 3</a>
+ * @see TopologyService
+ */
+public interface LogicalTopologyService {
+    /**
+     * Adds a listener for logical topology events.
+     *
+     * <p>Event listeners are not guaranteed to see events they receive being consistent with the state acquired from
+     * {@link #logicalTopologyOnLeader()} (or local logical topology state obtained in other means). This means that,
+     * if you get an event with topology version N, event listener might see version M less or greater than N if it

Review Comment:
   This information might be crucial for a user of listeners, so it probably should be here. On the other hand, users of `logicalTopologyOnLeader()` are not required to even know about listeners. If they use listeners, they will read this here and will be informed. So I would prefer to leave it as is.



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