handle clock drift #18

CHANGELOG.md

@@ -6,6 +6,10 @@ All notable changes to this project will be documented in this file.
 
 Nothing unreleased.
 
+## [4.2.1] - 2022-04-21
+
+Handle clock drift. #18
+
 ## [4.2.0] - 2022-04-21
 
 Handle clock drift. #18
@@ -282,7 +286,8 @@ Project created as an alternative Java implementation of [ULID spec](https://git
 -   Added `LICENSE`
 -   Added test cases
 
-[unreleased]: https://github.com/f4b6a3/ulid-creator/compare/ulid-creator-4.2.0...HEAD
+[unreleased]: https://github.com/f4b6a3/ulid-creator/compare/ulid-creator-4.2.1...HEAD
+[4.2.1]: https://github.com/f4b6a3/ulid-creator/compare/ulid-creator-4.2.0...ulid-creator-4.2.1
 [4.2.0]: https://github.com/f4b6a3/ulid-creator/compare/ulid-creator-4.1.2...ulid-creator-4.2.0
 [4.1.2]: https://github.com/f4b6a3/ulid-creator/compare/ulid-creator-4.1.1...ulid-creator-4.1.2
 [4.1.1]: https://github.com/f4b6a3/ulid-creator/compare/ulid-creator-4.1.0...ulid-creator-4.1.1

LICENSE

@@ -1,6 +1,6 @@
 MIT License
 
-Copyright (c) 2020-2021 Fabio Lima
+Copyright (c) 2020-2022 Fabio Lima
 
 Permission is hereby granted, free of charge, to any person obtaining a copy
 of this software and associated documentation files (the "Software"), to deal

README.md

@@ -39,7 +39,7 @@ Add these lines to your `pom.xml`.
 <dependency>
   <groupId>com.github.f4b6a3</groupId>
   <artifactId>ulid-creator</artifactId>
-  <version>4.2.0</version>
+  <version>4.2.1</version>
 </dependency>
 ```
 See more options in [maven.org](https://search.maven.org/artifact/com.github.f4b6a3/ulid-creator).

src/main/java/com/github/f4b6a3/ulid/UlidFactory.java

@@ -47,7 +47,7 @@ public final class UlidFactory {
 	private final LongFunction<Ulid> ulidFunction;
 
 	public UlidFactory() {
-		this(new UlidFunction(), null);
+		this(new UlidFunction(getRandomSupplier(null)));
 	}
 
 	private UlidFactory(LongFunction<Ulid> ulidFunction) {
@@ -67,7 +67,7 @@ public final class UlidFactory {
 	 * @return {@link UlidFactory}
 	 */
 	public static UlidFactory newInstance() {
-		return new UlidFactory(new UlidFunction());
+		return newInstance(getRandomSupplier(null));
 	}
 
 	/**
@@ -77,7 +77,7 @@ public final class UlidFactory {
 	 * @return {@link UlidFactory}
 	 */
 	public static UlidFactory newInstance(Random random) {
-		return new UlidFactory(new UlidFunction(random));
+		return newInstance(getRandomSupplier(random));
 	}
 
 	/**
@@ -92,26 +92,13 @@ public final class UlidFactory {
 		return new UlidFactory(new UlidFunction(randomSupplier));
 	}
 
-	/**
-	 * Returns a new factory.
-	 * 
-	 * The given random supplier must return an array of 10 bytes.
-	 * 
-	 * @param randomSupplier a random supplier that returns 10 bytes
-	 * @param clock          a custom clock instance for tests
-	 * @return {@link UlidFactory}
-	 */
-	protected static UlidFactory newInstance(Supplier<byte[]> randomSupplier, Clock clock) {
-		return new UlidFactory(new UlidFunction(randomSupplier), clock);
-	}
-
 	/**
 	 * Returns a new monotonic factory.
 	 * 
 	 * @return {@link UlidFactory}
 	 */
 	public static UlidFactory newMonotonicInstance() {
-		return new UlidFactory(new MonotonicFunction());
+		return newMonotonicInstance(getRandomSupplier(null));
 	}
 
 	/**
@@ -121,7 +108,7 @@ public final class UlidFactory {
 	 * @return {@link UlidFactory}
 	 */
 	public static UlidFactory newMonotonicInstance(Random random) {
-		return new UlidFactory(new MonotonicFunction(random));
+		return newMonotonicInstance(getRandomSupplier(random));
 	}
 
 	/**
@@ -178,14 +165,6 @@ public final class UlidFactory {
 		// it must return an array of 10 bytes
 		private Supplier<byte[]> randomSupplier;
 
-		public UlidFunction() {
-			this(new SecureRandom());
-		}
-
-		public UlidFunction(Random random) {
-			this(getRandomSupplier(random));
-		}
-
 		public UlidFunction(Supplier<byte[]> randomSupplier) {
 			this.randomSupplier = randomSupplier;
 		}
@@ -201,8 +180,8 @@ public final class UlidFactory {
 	 */
 	protected static final class MonotonicFunction implements LongFunction<Ulid> {
 
-		private long lastTime = 0;
+		private long lastTime;
-		private Ulid lastUlid = null;
+		private Ulid lastUlid;
 
 		// Used to preserve monotonicity when the system clock is
 		// adjusted by NTP after a small clock drift or when the
@@ -212,16 +191,12 @@ public final class UlidFactory {
 		// it must return an array of 10 bytes
 		private Supplier<byte[]> randomSupplier;
 
-		public MonotonicFunction() {
-			this(new SecureRandom());
-		}
-
-		public MonotonicFunction(Random random) {
-			this(getRandomSupplier(random));
-		}
-
 		public MonotonicFunction(Supplier<byte[]> randomSupplier) {
 			this.randomSupplier = randomSupplier;
+
+			// initialize internal state
+			this.lastTime = Clock.systemUTC().millis();
+			this.lastUlid = new Ulid(lastTime, randomSupplier.get());
 		}
 
 		@Override
@@ -233,10 +208,10 @@ public final class UlidFactory {
 			if ((time > this.lastTime - CLOCK_DRIFT_TOLERANCE) && (time <= this.lastTime)) {
 				this.lastUlid = lastUlid.increment();
 			} else {
+				this.lastTime = time;
 				this.lastUlid = new Ulid(time, this.randomSupplier.get());
 			}
 
-			this.lastTime = lastUlid.getTime();
 			return new Ulid(this.lastUlid);
 		}
 	}
@@ -248,9 +223,10 @@ public final class UlidFactory {
 	 * @return a random supplier that returns 10 bytes
 	 */
 	protected static Supplier<byte[]> getRandomSupplier(Random random) {
+		Random entropy = random != null ? random : new SecureRandom();
 		return () -> {
 			byte[] payload = new byte[Ulid.RANDOM_BYTES];
-			random.nextBytes(payload);
+			entropy.nextBytes(payload);
 			return payload;
 		};
 	}

src/test/java/com/github/f4b6a3/ulid/UlidFactoryDefaultfTest.java

@@ -8,11 +8,7 @@ import com.github.f4b6a3.ulid.UlidFactory;
 
 import static org.junit.Assert.*;
 
-import java.time.Clock;
-import java.time.Instant;
-import java.time.ZoneId;
 import java.util.Random;
-import java.util.function.Supplier;
 
 public class UlidFactoryDefaultfTest extends UlidFactoryTest {
 
@@ -33,97 +29,6 @@ public class UlidFactoryDefaultfTest extends UlidFactoryTest {
 		checkCreationTime(list, startTime, endTime);
 	}
 
-	@Test
-	public void testClockDrift() {
-
-		long diff = UlidFactory.MonotonicFunction.CLOCK_DRIFT_TOLERANCE;
-		long time = Instant.parse("2021-12-31T23:59:59.000Z").toEpochMilli();
-		long times[] = { time, time + 0, time + 1, time + 2, time + 3 - diff, time + 4 - diff, time + 5 };
-
-		Clock clock = new Clock() {
-			private int i;
-
-			@Override
-			public long millis() {
-				return times[i++ % times.length];
-			}
-
-			@Override
-			public ZoneId getZone() {
-				return null;
-			}
-
-			@Override
-			public Clock withZone(ZoneId zone) {
-				return null;
-			}
-
-			@Override
-			public Instant instant() {
-				return null;
-			}
-		};
-
-		Supplier<byte[]> randomSupplier = UlidFactory.getRandomSupplier(new Random());
-		UlidFactory factory = UlidFactory.newInstance(randomSupplier, clock);
-
-		long ms1 = factory.create().getTime(); // time
-		long ms2 = factory.create().getTime(); // time + 0
-		long ms3 = factory.create().getTime(); // time + 1
-		long ms4 = factory.create().getTime(); // time + 2
-		long ms5 = factory.create().getTime(); // time + 3 - 10000 (CLOCK DRIFT)
-		long ms6 = factory.create().getTime(); // time + 4 - 10000 (CLOCK DRIFT)
-		long ms7 = factory.create().getTime(); // time + 5
-		assertEquals(times[0], ms1);
-		assertEquals(times[1], ms2);
-		assertEquals(times[2], ms3);
-		assertEquals(times[3], ms4);
-		assertEquals(times[4], ms5);
-		assertEquals(times[5], ms6);
-		assertEquals(times[6], ms7);
-	}
-
-	@Test
-	public void testLeapSecond() {
-
-		long second = Instant.parse("2021-12-31T23:59:59.000Z").getEpochSecond();
-		long leapSecond = second - 1; // simulate a leap second
-		long times[] = { second, leapSecond };
-
-		Clock clock = new Clock() {
-			private int i;
-
-			@Override
-			public long millis() {
-				return times[i++ % times.length] * 1000;
-			}
-
-			@Override
-			public ZoneId getZone() {
-				return null;
-			}
-
-			@Override
-			public Clock withZone(ZoneId zone) {
-				return null;
-			}
-
-			@Override
-			public Instant instant() {
-				return null;
-			}
-		};
-
-		Supplier<byte[]> randomSupplier = UlidFactory.getRandomSupplier(new Random());
-		UlidFactory factory = UlidFactory.newInstance(randomSupplier, clock);
-
-		long ms1 = factory.create().getTime(); // second
-		long ms2 = factory.create().getTime(); // leap second
-
-		assertEquals(times[0] * 1000, ms1);
-		assertEquals(times[1] * 1000, ms2);
-	}
-
 	@Test
 	public void testGetUlidInParallel() throws InterruptedException {
 

src/test/java/com/github/f4b6a3/ulid/UlidFactoryMonotonicTest.java

@@ -36,7 +36,7 @@ public class UlidFactoryMonotonicTest extends UlidFactoryTest {
 	}
 
 	@Test
-	public void testClockDrift() {
+	public void testGetMonotonicUlidAfterClockDrift() {
 
 		long diff = UlidFactory.MonotonicFunction.CLOCK_DRIFT_TOLERANCE;
 		long time = Instant.parse("2021-12-31T23:59:59.000Z").toEpochMilli();
@@ -85,7 +85,7 @@ public class UlidFactoryMonotonicTest extends UlidFactoryTest {
 	}
 
 	@Test
-	public void testLeapSecond() {
+	public void testGetMonotonicUlidAfterLeapSecond() {
 
 		long second = Instant.parse("2021-12-31T23:59:59.000Z").getEpochSecond();
 		long leapSecond = second - 1; // simulate a leap second