[GitHub] [ignite-3] sanpwc commented on a diff in pull request #896: IGNITE-17214 A Hybrid Logical Clock implementation.

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

sanpwc commented on code in PR #896:
URL: https://github.com/apache/ignite-3/pull/896#discussion_r907545447


##########
modules/core/src/main/java/org/apache/ignite/hlc/HybridClock.java:
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@@ -0,0 +1,75 @@
+/*
+ * 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.hlc;
+
+import java.time.Clock;
+import org.apache.ignite.internal.tostring.S;
+
+/**
+ * A Hybrid Logical Clock.
+ */
+public class HybridClock {
+    /** Latest timestamp. */
+    private HybridTimestamp latestTime;
+
+    /**
+     * The constructor which initializes the latest time to current time by system clock.
+     */
+    public HybridClock() {
+        this.latestTime = new HybridTimestamp(Clock.systemUTC().instant().toEpochMilli(), 0);
+    }
+
+    /**
+     * Creates a timestamp for new event.
+     *
+     * @return The hybrid timestamp.
+     */
+    public synchronized HybridTimestamp now() {
+        long currentTimeMillis = Clock.systemUTC().instant().toEpochMilli();
+
+        if (latestTime.getPhysical() >= currentTimeMillis) {
+            latestTime = latestTime.addTicks(1);
+        } else {
+            latestTime = new HybridTimestamp(currentTimeMillis, 0);
+        }
+
+        return latestTime;
+    }
+
+    /**
+     * Creates a timestamp for a received event.
+     *
+     * @param requestTime Timestamp from request.
+     * @return The hybrid timestamp.
+     */
+    public synchronized HybridTimestamp tick(HybridTimestamp requestTime) {
+        HybridTimestamp now = new HybridTimestamp(Clock.systemUTC().instant().toEpochMilli(), -1);

Review Comment:
   Do we really need to create HybridTimestamp instance in order to only compare it's physical?
   I believe should postpone new gerHybridTIme instantiation and do it only if now.physical is bigger than request.physical and latestTime.physical. 



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