org.apache.hadoop.util.Time Maven / Gradle / Ivy
/**
* 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 java.util.Calendar;
import java.util.TimeZone;
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 TimeZone UTC_ZONE = TimeZone.getTimeZone("UTC");
private static final ThreadLocal DATE_FORMAT =
new ThreadLocal() {
@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);
}
/**
* Get the current UTC time in milliseconds.
* @return the current UTC time in milliseconds.
*/
public static long getUtcTime() {
return Calendar.getInstance(UTC_ZONE).getTimeInMillis();
}
}