| /** |
| * 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.hadoop.util; |
| |
| import java.text.SimpleDateFormat; |
| |
| import org.apache.hadoop.classification.InterfaceAudience; |
| import org.apache.hadoop.classification.InterfaceStability; |
| |
| /** |
| * Utility methods for getting the time and computing intervals. |
| */ |
| @InterfaceAudience.LimitedPrivate({"HDFS", "MapReduce"}) |
| @InterfaceStability.Unstable |
| public final class Time { |
| |
| /** |
| * number of nano seconds in 1 millisecond |
| */ |
| private static final long NANOSECONDS_PER_MILLISECOND = 1000000; |
| |
| private static final ThreadLocal<SimpleDateFormat> DATE_FORMAT = |
| new ThreadLocal<SimpleDateFormat>() { |
| @Override |
| protected SimpleDateFormat initialValue() { |
| return new SimpleDateFormat("yyyy-MM-dd HH:mm:ss,SSSZ"); |
| } |
| }; |
| |
| /** |
| * Current system time. Do not use this to calculate a duration or interval |
| * to sleep, because it will be broken by settimeofday. Instead, use |
| * monotonicNow. |
| * @return current time in msec. |
| */ |
| public static long now() { |
| return System.currentTimeMillis(); |
| } |
| |
| /** |
| * Current time from some arbitrary time base in the past, counting in |
| * milliseconds, and not affected by settimeofday or similar system clock |
| * changes. This is appropriate to use when computing how much longer to |
| * wait for an interval to expire. |
| * This function can return a negative value and it must be handled correctly |
| * by callers. See the documentation of System#nanoTime for caveats. |
| * @return a monotonic clock that counts in milliseconds. |
| */ |
| public static long monotonicNow() { |
| return System.nanoTime() / NANOSECONDS_PER_MILLISECOND; |
| } |
| |
| /** |
| * Same as {@link #monotonicNow()} but returns its result in nanoseconds. |
| * Note that this is subject to the same resolution constraints as |
| * {@link System#nanoTime()}. |
| * @return a monotonic clock that counts in nanoseconds. |
| */ |
| public static long monotonicNowNanos() { |
| return System.nanoTime(); |
| } |
| |
| /** |
| * Convert time in millisecond to human readable format. |
| * @return a human readable string for the input time |
| */ |
| public static String formatTime(long millis) { |
| return DATE_FORMAT.get().format(millis); |
| } |
| } |