fix: use epoch-based monotonic message ID for BanyanDB writes

oap-server/server-library/library-banyandb-client/src/main/java/org/apache/skywalking/library/banyandb/v1/client/AbstractWrite.java

@@ -19,10 +19,27 @@
 package org.apache.skywalking.library.banyandb.v1.client;
 
 import java.util.Optional;
+import java.util.concurrent.atomic.AtomicLong;
 import lombok.Getter;
 import org.apache.skywalking.banyandb.common.v1.BanyandbCommon;
 
 public abstract class AbstractWrite<P extends com.google.protobuf.GeneratedMessage> {
+    /**
+     * Generates monotonic message IDs for write requests.
+     * <p>
+     * The value is based on the Unix epoch (wall clock) so that message IDs are comparable across
+     * OAP hosts and process restarts, instead of {@link System#nanoTime()} which is only meaningful
+     * within a single JVM instance. An {@link AtomicLong} keeps the value strictly increasing even
+     * under concurrent writes or a temporary wall-clock rollback.
+     */
+    private static final AtomicLong MESSAGE_ID_GENERATOR =
+        new AtomicLong(System.currentTimeMillis() * 1_000_000L);
+
+    protected static long nextMessageId() {
+        return MESSAGE_ID_GENERATOR.updateAndGet(
+            previous -> Math.max(previous + 1, System.currentTimeMillis() * 1_000_000L));
+    }
+
     /**
      * Timestamp represents the time of the current data point, in milliseconds.
      * <p>

oap-server/server-library/library-banyandb-client/src/main/java/org/apache/skywalking/library/banyandb/v1/client/MeasureWrite.java

@@ -88,8 +88,10 @@ protected BanyandbMeasure.WriteRequest build(BanyandbCommon.Metadata metadata) {
         }
 
         builder.setDataPointSpec(datapointValueSpecBuilder);
+        long messageId = nextMessageId();
+        datapointValueBuilder.setVersion(messageId);
         builder.setDataPoint(datapointValueBuilder);
-        builder.setMessageId(System.nanoTime());
+        builder.setMessageId(messageId);
         return builder.build();
     }
 
@@ -122,8 +124,10 @@ protected BanyandbMeasure.WriteRequest buildValues() {
             datapointValueBuilder.addFields(fieldEntry.getValue().serialize());
         }
 
+        long messageId = nextMessageId();
+        datapointValueBuilder.setVersion(messageId);
         builder.setDataPoint(datapointValueBuilder);
-        builder.setMessageId(System.nanoTime());
+        builder.setMessageId(messageId);
         return builder.build();
     }
 

oap-server/server-library/library-banyandb-client/src/main/java/org/apache/skywalking/library/banyandb/v1/client/StreamWrite.java

@@ -93,7 +93,7 @@ protected BanyandbStream.WriteRequest build(BanyandbCommon.Metadata metadata) {
         }
 
         builder.setElement(elemValBuilder);
-        builder.setMessageId(System.nanoTime());
+        builder.setMessageId(nextMessageId());
         return builder.build();
     }
 
@@ -125,7 +125,7 @@ protected BanyandbStream.WriteRequest buildValues() {
         }
 
         builder.setElement(elemValBuilder);
-        builder.setMessageId(System.nanoTime());
+        builder.setMessageId(nextMessageId());
         return builder.build();
     }
 

oap-server/server-library/library-banyandb-client/src/test/java/org/apache/skywalking/library/banyandb/v1/client/MeasureWriteMessageIdTest.java

@@ -0,0 +1,101 @@
+/*
+ * 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.skywalking.library.banyandb.v1.client;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Set;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.TimeUnit;
+import org.apache.skywalking.banyandb.common.v1.BanyandbCommon;
+import org.apache.skywalking.banyandb.measure.v1.BanyandbMeasure;
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+public class MeasureWriteMessageIdTest {
+
+    private static final BanyandbCommon.Metadata METADATA =
+        BanyandbCommon.Metadata.newBuilder()
+                               .setGroup("test-group")
+                               .setName("test-measure")
+                               .build();
+
+    @Test
+    public void messageIdMatchesDataPointVersion() {
+        final MeasureWrite write = new MeasureWrite(METADATA, System.currentTimeMillis());
+        final BanyandbMeasure.WriteRequest request = write.build();
+        assertEquals(request.getMessageId(), request.getDataPoint().getVersion());
+        assertTrue(request.getMessageId() > 0);
+    }
+
+    @Test
+    public void messageIdMatchesDataPointVersionInBuildValues() {
+        final MeasureWrite write = new MeasureWrite(METADATA, System.currentTimeMillis());
+        final BanyandbMeasure.WriteRequest request = write.buildOnlyValues();
+        assertEquals(request.getMessageId(), request.getDataPoint().getVersion());
+        assertTrue(request.getMessageId() > 0);
+    }
+
+    @Test
+    public void messageIdsAreStrictlyIncreasing() {
+        final List<Long> ids = new ArrayList<>();
+        for (int i = 0; i < 10_000; i++) {
+            ids.add(AbstractWrite.nextMessageId());
+        }
+        for (int i = 1; i < ids.size(); i++) {
+            assertTrue(ids.get(i) > ids.get(i - 1), "message ids must be strictly increasing");
+        }
+    }
+
+    @Test
+    public void messageIdsAreUniqueUnderConcurrency() throws InterruptedException {
+        final int threads = 8;
+        final int perThread = 2_000;
+        final ExecutorService executor = Executors.newFixedThreadPool(threads);
+        final CountDownLatch start = new CountDownLatch(1);
+        final Set<Long> seen = ConcurrentHashMap.newKeySet();
+        final CountDownLatch done = new CountDownLatch(threads);
+        try {
+            for (int t = 0; t < threads; t++) {
+                executor.submit(() -> {
+                    try {
+                        start.await();
+                        for (int i = 0; i < perThread; i++) {
+                            seen.add(AbstractWrite.nextMessageId());
+                        }
+                    } catch (InterruptedException e) {
+                        Thread.currentThread().interrupt();
+                    } finally {
+                        done.countDown();
+                    }
+                });
+            }
+            start.countDown();
+            assertTrue(done.await(30, TimeUnit.SECONDS), "concurrent writes timed out");
+        } finally {
+            executor.shutdownNow();
+        }
+        assertEquals(threads * perThread, seen.size(), "all message ids must be unique");
+    }
+}