nizhikov commented on code in PR #11044:
URL: https://github.com/apache/ignite/pull/11044#discussion_r1400052707


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modules/core/src/main/java/org/apache/ignite/internal/cdc/CdcManager.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.internal.cdc;
+
+import java.nio.ByteBuffer;
+import java.util.Iterator;
+import org.apache.ignite.cdc.CdcConsumer;
+import org.apache.ignite.internal.pagemem.wal.record.CdcManagerRecord;
+import org.apache.ignite.internal.pagemem.wal.record.CdcManagerStopRecord;
+import org.apache.ignite.internal.processors.cache.GridCacheSharedManager;
+import org.apache.ignite.internal.processors.cache.persistence.wal.WALPointer;
+import org.jetbrains.annotations.Nullable;
+
+/**
+ * CDC manager responsible for logic of capturing data within Ignite node. 
There is a contract between {@link CdcManager}
+ * and {@link CdcMain}. Communication between these components are built with 
over WAL records. {@link CdcManager} can
+ * write some records, while {@link CdcMain} must listen to them.
+ * <ul>
+ *     <li>
+ *         This manager can write {@link CdcManagerRecord} that contains info 
about consumer state.
+ *         This record must be handled by {@link CdcMain} the same way it 
handles {@link CdcConsumer#onEvents(Iterator)}
+ *         when it returns {@code true}.
+ *     </li>
+ *     <li>
+ *         This manager writes {@link CdcManagerStopRecord} after it stopped 
handling records by any reason.
+ *         {@link CdcMain} should start consume records instead since last 
consumed {@link CdcManagerRecord}.
+ *     </li>
+ *     <li>
+ *         The current behavior of {@link CdcManager} is persisted within 
{@link CdcConsumerState#saveCdcMode(CdcMode)}.
+ *         After the mode set to {@link CdcMode#CDC_UTILITY_ACTIVE} it will 
not reset.
+ *     </li>
+ * </ul>
+ *
+ * @see CdcConsumer#onEvents(Iterator)
+ * @see CdcConsumerState#saveCdcMode(CdcMode)
+ */
+public interface CdcManager extends GridCacheSharedManager {
+    /**
+     * Collects byte buffer contains WAL records.
+     *
+     * @param dataBuf Buffer that contains data to collect.
+     * @param off Offset of the data within the buffer.
+     * @param limit Limit of the data within the buffer.
+     */
+    public void collect(ByteBuffer dataBuf, int off, int limit);

Review Comment:
   Do we have an ability to check correctness of the usage of the buffer?
   How bugs of the implementations will affect Ignite node?
   Can this method throw any RuntimeException?



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