Move KetchSystem.delay to FileUtils.

This will provide exponential backoff with jitter to other JGit
components too.

Signed-off-by: Han-Wen Nienhuys <hanwen@google.com>
Change-Id: Idd44e3bbaef6d71134ce2e3f7d405f35e7397cbd

org.eclipse.jgit/src/org/eclipse/jgit/internal/ketch/KetchReplica.java

@@ -77,6 +77,7 @@ import org.eclipse.jgit.lib.Repository;
 import org.eclipse.jgit.revwalk.RevWalk;
 import org.eclipse.jgit.transport.ReceiveCommand;
 import org.eclipse.jgit.treewalk.TreeWalk;
+import org.eclipse.jgit.util.FileUtils;
 import org.eclipse.jgit.util.SystemReader;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
@@ -532,9 +533,8 @@ public abstract class KetchReplica {
 		queued.add(0, new ReplicaPushRequest(this, cmds));
 
 		if (!waitingForRetry()) {
-			long delay = KetchSystem.delay(
-					lastRetryMillis,
-					minRetryMillis, maxRetryMillis);
+			long delay = FileUtils
+				.delay(lastRetryMillis, minRetryMillis, maxRetryMillis);
 			if (log.isDebugEnabled()) {
 				log.debug("Retrying {} after {} ms", //$NON-NLS-1$
 						describeForLog(), Long.valueOf(delay));

org.eclipse.jgit/src/org/eclipse/jgit/internal/ketch/KetchSystem.java

@@ -350,25 +350,4 @@ public class KetchSystem {
 		}
 	}
 
-	/**
-	 * Compute a delay in a {@code min..max} interval with random jitter.
-	 *
-	 * @param last
-	 *            amount of delay waited before the last attempt. This is used
-	 *            to seed the next delay interval. Should be 0 if there was no
-	 *            prior delay.
-	 * @param min
-	 *            shortest amount of allowable delay between attempts.
-	 * @param max
-	 *            longest amount of allowable delay between attempts.
-	 * @return new amount of delay to wait before the next attempt.
-	 */
-	static long delay(long last, long min, long max) {
-		long r = Math.max(0, last * 3 - min);
-		if (r > 0) {
-			int c = (int) Math.min(r + 1, Integer.MAX_VALUE);
-			r = RNG.nextInt(c);
-		}
-		return Math.max(Math.min(min + r, max), min);
-	}
 }

org.eclipse.jgit/src/org/eclipse/jgit/util/FileUtils.java

@@ -73,6 +73,7 @@ import java.time.Instant;
 import java.util.ArrayList;
 import java.util.List;
 import java.util.Locale;
+import java.util.Random;
 import java.util.regex.Pattern;
 
 import org.eclipse.jgit.internal.JGitText;
@@ -87,6 +88,8 @@ import org.slf4j.LoggerFactory;
 public class FileUtils {
 	private static final Logger LOG = LoggerFactory.getLogger(FileUtils.class);
 
+	private static final Random RNG = new Random();
+
 	/**
 	 * Option to delete given {@code File}
 	 */
@@ -986,4 +989,28 @@ public class FileUtils {
 		}
 		Files.setLastModifiedTime(f, FileTime.from(Instant.now()));
 	}
+
+	/**
+	 * Compute a delay in a {@code min..max} interval with random jitter.
+	 *
+	 * @param last
+	 *            amount of delay waited before the last attempt. This is used
+	 *            to seed the next delay interval. Should be 0 if there was no
+	 *            prior delay.
+	 * @param min
+	 *            shortest amount of allowable delay between attempts.
+	 * @param max
+	 *            longest amount of allowable delay between attempts.
+	 * @return new amount of delay to wait before the next attempt.
+	 *
+	 * @since 5.6
+	 */
+	public static long delay(long last, long min, long max) {
+		long r = Math.max(0, last * 3 - min);
+		if (r > 0) {
+			int c = (int) Math.min(r + 1, Integer.MAX_VALUE);
+			r = RNG.nextInt(c);
+		}
+		return Math.max(Math.min(min + r, max), min);
+	}
 }