[MNG-5729] Use monotonic time measurements

Author: gnodet

api/maven-api-core/pom.xml

@@ -59,6 +59,12 @@
       <groupId>org.apache.maven</groupId>
       <artifactId>maven-api-di</artifactId>
     </dependency>
+
+    <dependency>
+      <groupId>org.junit.jupiter</groupId>
+      <artifactId>junit-jupiter-api</artifactId>
+      <scope>test</scope>
+    </dependency>
   </dependencies>
 
 </project>

api/maven-api-core/src/main/java/org/apache/maven/api/MonotonicTime.java

@@ -0,0 +1,265 @@
+/*
+ * 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.maven.api;
+
+import java.time.Duration;
+import java.time.Instant;
+import java.time.ZoneId;
+import java.time.temporal.ChronoField;
+import java.time.temporal.ChronoUnit;
+import java.time.temporal.Temporal;
+import java.time.temporal.TemporalField;
+import java.time.temporal.TemporalQueries;
+import java.time.temporal.TemporalQuery;
+import java.time.temporal.TemporalUnit;
+import java.time.temporal.UnsupportedTemporalTypeException;
+import java.time.temporal.ValueRange;
+import java.util.Objects;
+import java.util.concurrent.TimeUnit;
+
+/**
+ * Represents a point in time using both monotonic and wall clock measurements.
+ * This class combines the monotonic precision of {@link System#nanoTime()} with
+ * wall clock time from {@link Instant#now()}, providing accurate duration measurements
+ * while maintaining human-readable timestamps.
+ * <p>
+ * This class implements {@link Temporal} by delegating to its computed wall time,
+ * allowing it to be used with standard Java time formatting and querying operations.
+ */
+public final class MonotonicTime implements Temporal {
+
+    /**
+     * Reference point representing the time when this class was first loaded.
+     * Can be used as a global start time for duration measurements.
+     */
+    public static final MonotonicTime START = new MonotonicTime(System.nanoTime(), Instant.now());
+
+    private final long nanoTime;
+    private volatile Instant wallTime;
+
+    // Opened for testing
+    MonotonicTime(long nanoTime, Instant wallTime) {
+        this.nanoTime = nanoTime;
+        this.wallTime = wallTime;
+    }
+
+    /**
+     * Creates a new {@code MonotonicTime} instance capturing the current time
+     * using both monotonic and wall clock measurements.
+     *
+     * @return a new {@code MonotonicTime} instance
+     */
+    public static MonotonicTime now() {
+        return new MonotonicTime(System.nanoTime(), null);
+    }
+
+    /**
+     * Calculates the duration between this time and {@link #START}.
+     * This measurement uses monotonic time and is not affected by system clock changes.
+     *
+     * @return the duration since JVM startup
+     */
+    public Duration durationSinceStart() {
+        return durationSince(START);
+    }
+
+    /**
+     * Calculates the duration between this time and the specified start time.
+     * This measurement uses monotonic time and is not affected by system clock changes.
+     *
+     * @param start the starting point for the duration calculation
+     * @return the duration between the start time and this time
+     */
+    public Duration durationSince(MonotonicTime start) {
+        return Duration.ofNanos(this.nanoTime - start.nanoTime);
+    }
+
+    /**
+     * Returns the raw monotonic time value from System.nanoTime().
+     * <p>
+     * This value represents a monotonic time measurement that can only be compared
+     * with other MonotonicTime instances obtained within the same JVM session.
+     * The absolute value has no meaning on its own and is not related to any epoch or wall clock time.
+     * <p>
+     * This value has nanosecond precision but not necessarily nanosecond accuracy -
+     * the actual precision depends on the underlying system.
+     * <p>
+     * For timing intervals, prefer using {@link #durationSince(MonotonicTime)} instead of
+     * manually calculating differences between nanoTime values.
+     *
+     * @return the raw nanosecond value from System.nanoTime()
+     * @see System#nanoTime()
+     */
+    public long getNanoTime() {
+        return nanoTime;
+    }
+
+    /**
+     * Returns the wall clock time for this instant.
+     * The time is computed lazily based on START's wall time and the monotonic duration since START.
+     *
+     * @return the {@link Instant} representing the wall clock time
+     */
+    public Instant getWallTime() {
+        Instant local = wallTime;
+        if (local == null) {
+            // Double-checked locking pattern
+            synchronized (this) {
+                local = wallTime;
+                if (local == null) {
+                    local = START.getWallTime().plus(durationSince(START));
+                    wallTime = local;
+                }
+            }
+        }
+        return local;
+    }
+
+    /**
+     * Creates a {@code MonotonicTime} from a millisecond timestamp.
+     * <p>
+     * <strong>WARNING:</strong> This method is inherently unsafe and should only be used
+     * for legacy integration. It attempts to create a monotonic time measurement from
+     * a wall clock timestamp, which means:
+     * <ul>
+     *   <li>The monotonic timing will be imprecise (millisecond vs. nanosecond precision)</li>
+     *   <li>Duration calculations may be incorrect due to system clock adjustments</li>
+     *   <li>The relationship between wall time and monotonic time will be artificial</li>
+     *   <li>Comparisons with other MonotonicTime instances will be meaningless</li>
+     * </ul>
+     *
+     * @param epochMillis milliseconds since Unix epoch (from System.currentTimeMillis())
+     * @return a new {@code MonotonicTime} instance
+     * @deprecated This method exists only for legacy integration. Use {@link #now()}
+     *             for new code.
+     */
+    @Deprecated(since = "4.0.0", forRemoval = true)
+    public static MonotonicTime ofEpochMillis(long epochMillis) {
+        Instant wallTime = Instant.ofEpochMilli(epochMillis);
+        // Converting to nanos but this relationship is artificial
+        long artificalNanoTime = TimeUnit.MILLISECONDS.toNanos(epochMillis);
+        return new MonotonicTime(artificalNanoTime, wallTime);
+    }
+
+    @Override
+    public boolean isSupported(TemporalField field) {
+        if (field == ChronoField.OFFSET_SECONDS) {
+            return true;
+        }
+        return getWallTime().isSupported(field);
+    }
+
+    @Override
+    public boolean isSupported(TemporalUnit unit) {
+        return unit instanceof ChronoUnit chronoUnit && chronoUnit.isTimeBased(); // This includes DAYS and below
+    }
+
+    @Override
+    public long getLong(TemporalField field) {
+        if (field == ChronoField.OFFSET_SECONDS) {
+            return 0; // We use UTC/Zero offset
+        }
+        return getWallTime().getLong(field);
+    }
+
+    @Override
+    public Temporal with(TemporalField field, long newValue) {
+        throw new UnsupportedTemporalTypeException("MonotonicTime does not support field adjustments");
+    }
+
+    @Override
+    @SuppressWarnings("unchecked")
+    public <R> R query(TemporalQuery<R> query) {
+        if (query == TemporalQueries.zoneId()) {
+            return (R) ZoneId.systemDefault();
+        }
+        if (query == TemporalQueries.precision()) {
+            return (R) ChronoUnit.NANOS;
+        }
+        if (query == TemporalQueries.zone()) {
+            return (R) ZoneId.systemDefault(); // Be consistent with zoneId query
+        }
+        if (query == TemporalQueries.chronology()) {
+            return null;
+        }
+        return getWallTime().query(query);
+    }
+
+    @Override
+    public ValueRange range(TemporalField field) {
+        return getWallTime().range(field);
+    }
+
+    @Override
+    public Temporal plus(long amountToAdd, TemporalUnit unit) {
+        throw new UnsupportedTemporalTypeException("MonotonicTime does not support plus operations");
+    }
+
+    @Override
+    public long until(Temporal endExclusive, TemporalUnit unit) {
+        if (!(unit instanceof ChronoUnit) || !isSupported(unit)) {
+            throw new UnsupportedTemporalTypeException("Unsupported unit: " + unit);
+        }
+
+        if (endExclusive instanceof MonotonicTime other) {
+            Duration duration = Duration.ofNanos(other.nanoTime - this.nanoTime);
+            return switch ((ChronoUnit) unit) {
+                case NANOS -> duration.toNanos();
+                case MICROS -> duration.toNanos() / 1000;
+                case MILLIS -> duration.toMillis();
+                case SECONDS -> duration.toSeconds();
+                case MINUTES -> duration.toMinutes();
+                case HOURS -> duration.toHours();
+                default -> throw new UnsupportedTemporalTypeException("Unsupported unit: " + unit);
+            };
+        }
+
+        return unit.between(getWallTime(), Instant.from(endExclusive));
+    }
+
+    @Override
+    public int get(TemporalField field) {
+        return getWallTime().get(field);
+    }
+
+    @Override
+    public boolean equals(Object obj) {
+        if (!(obj instanceof MonotonicTime)) {
+            return false;
+        }
+        MonotonicTime other = (MonotonicTime) obj;
+        return other.nanoTime == this.nanoTime;
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(nanoTime);
+    }
+
+    /**
+     * Returns a string representation of this time, including both the wall clock time
+     * and the duration since the Unix epoch.
+     *
+     * @return a string representation of this time
+     */
+    @Override
+    public String toString() {
+        return String.format("MonotonicTime[wall=%s, duration=%s]", getWallTime(), Duration.ofNanos(nanoTime));
+    }
+}

api/maven-api-core/src/main/java/org/apache/maven/api/ProtoSession.java

@@ -19,7 +19,6 @@
 package org.apache.maven.api;
 
 import java.nio.file.Path;
-import java.time.Instant;
 import java.util.HashMap;
 import java.util.Map;
 
@@ -64,7 +63,7 @@ public interface ProtoSession {
      * @return the start time as an Instant object, never {@code null}
      */
     @Nonnull
-    Instant getStartTime();
+    MonotonicTime getStartTime();
 
     /**
      * Gets the directory of the topmost project being built, usually the current directory or the
@@ -106,13 +105,13 @@ default Builder toBuilder() {
      * Returns new builder from scratch.
      */
     static Builder newBuilder() {
-        return new Builder().withStartTime(Instant.now());
+        return new Builder().withStartTime(MonotonicTime.now());
     }
 
     class Builder {
         private Map<String, String> userProperties;
         private Map<String, String> systemProperties;
-        private Instant startTime;
+        private MonotonicTime startTime;
         private Path topDirectory;
         private Path rootDirectory;
 
@@ -121,7 +120,7 @@ private Builder() {}
         private Builder(
                 Map<String, String> userProperties,
                 Map<String, String> systemProperties,
-                Instant startTime,
+                MonotonicTime startTime,
                 Path topDirectory,
                 Path rootDirectory) {
             this.userProperties = userProperties;
@@ -141,7 +140,7 @@ public Builder withSystemProperties(@Nonnull Map<String, String> systemPropertie
             return this;
         }
 
-        public Builder withStartTime(@Nonnull Instant startTime) {
+        public Builder withStartTime(@Nonnull MonotonicTime startTime) {
             this.startTime = requireNonNull(startTime, "startTime");
             return this;
         }
@@ -163,14 +162,14 @@ public ProtoSession build() {
         private static class Impl implements ProtoSession {
             private final Map<String, String> userProperties;
             private final Map<String, String> systemProperties;
-            private final Instant startTime;
+            private final MonotonicTime startTime;
             private final Path topDirectory;
             private final Path rootDirectory;
 
             private Impl(
                     Map<String, String> userProperties,
                     Map<String, String> systemProperties,
-                    Instant startTime,
+                    MonotonicTime startTime,
                     Path topDirectory,
                     Path rootDirectory) {
                 this.userProperties = requireNonNull(userProperties);
@@ -191,7 +190,7 @@ public Map<String, String> getSystemProperties() {
             }
 
             @Override
-            public Instant getStartTime() {
+            public MonotonicTime getStartTime() {
                 return startTime;
             }