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/*
* Copyright 2016 The gRPC Authors
*
* Licensed 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 io.grpc;
import java.util.Arrays;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.ScheduledFuture;
import java.util.concurrent.TimeUnit;
/**
* An absolute point in time, generally for tracking when a task should be completed. A deadline is
* immutable except for the passage of time causing it to expire.
*
* Many systems use timeouts, which are relative to the start of the operation. However, being
* relative causes them to be poorly suited for managing higher-level tasks where there are many
* components and sub-operations that may not know the time of the initial "start of the operation."
* However, a timeout can be converted to a {@code Deadline} at the start of the operation and then
* passed to the various components unambiguously.
*/
public final class Deadline implements Comparable {
private static final SystemTicker SYSTEM_TICKER = new SystemTicker();
// nanoTime has a range of just under 300 years. Only allow up to 100 years in the past or future
// to prevent wraparound as long as process runs for less than ~100 years.
private static final long MAX_OFFSET = TimeUnit.DAYS.toNanos(100 * 365);
private static final long MIN_OFFSET = -MAX_OFFSET;
private static final long NANOS_PER_SECOND = TimeUnit.SECONDS.toNanos(1);
/**
* Returns the ticker that's based on system clock.
*
* This is EXPERIMENTAL API and may subject to change. If you'd like it to be
* stabilized or have any feedback, please
* let us know.
*
* @since 1.24.0
*/
public static Ticker getSystemTicker() {
return SYSTEM_TICKER;
}
/**
* Create a deadline that will expire at the specified offset based on the {@link #getSystemTicker
* system ticker}.
*
* If the given offset is extraordinarily long, say 100 years, the actual deadline created
* might saturate.
*
* @param duration A non-negative duration.
* @param units The time unit for the duration.
* @return A new deadline.
*/
public static Deadline after(long duration, TimeUnit units) {
return after(duration, units, SYSTEM_TICKER);
}
/**
* Create a deadline that will expire at the specified offset based on the given {@link Ticker}.
*
*
If the given offset is extraordinarily long, say 100 years, the actual deadline created
* might saturate.
*
*
CAUTION: Only deadlines created with the same {@link Ticker} instance can
* be compared by methods like {@link #minimum}, {@link #isBefore} and {@link #compareTo}. Custom
* Tickers should only be used in tests where you fake out the clock. Always use the {@link
* #getSystemTicker system ticker} in production, or serious errors may occur.
*
*
This is EXPERIMENTAL API and may subject to change. If you'd like it to be
* stabilized or have any feedback, please
* let us know.
*
* @param duration A non-negative duration.
* @param units The time unit for the duration.
* @param ticker Where this deadline refer the current time
* @return A new deadline.
*
* @since 1.24.0
*/
public static Deadline after(long duration, TimeUnit units, Ticker ticker) {
checkNotNull(units, "units");
return new Deadline(ticker, units.toNanos(duration), true);
}
private final Ticker ticker;
private final long deadlineNanos;
private volatile boolean expired;
private Deadline(Ticker ticker, long offset, boolean baseInstantAlreadyExpired) {
this(ticker, ticker.nanoTime(), offset, baseInstantAlreadyExpired);
}
private Deadline(Ticker ticker, long baseInstant, long offset,
boolean baseInstantAlreadyExpired) {
this.ticker = ticker;
// Clamp to range [MIN_OFFSET, MAX_OFFSET]
offset = Math.min(MAX_OFFSET, Math.max(MIN_OFFSET, offset));
deadlineNanos = baseInstant + offset;
expired = baseInstantAlreadyExpired && offset <= 0;
}
/**
* Has this deadline expired
* @return {@code true} if it has, otherwise {@code false}.
*/
public boolean isExpired() {
if (!expired) {
if (deadlineNanos - ticker.nanoTime() <= 0) {
expired = true;
} else {
return false;
}
}
return true;
}
/**
* Is {@code this} deadline before another. Two deadlines must be created using the same {@link
* Ticker}.
*/
public boolean isBefore(Deadline other) {
checkTicker(other);
return this.deadlineNanos - other.deadlineNanos < 0;
}
/**
* Return the minimum deadline of {@code this} or an other deadline. They must be created using
* the same {@link Ticker}.
*
* @param other deadline to compare with {@code this}.
*/
public Deadline minimum(Deadline other) {
checkTicker(other);
return isBefore(other) ? this : other;
}
/**
* Create a new deadline that is offset from {@code this}.
*
* If the given offset is extraordinarily long, say 100 years, the actual deadline created
* might saturate.
*/
// TODO(ejona): This method can cause deadlines to grow too far apart. For example:
// Deadline.after(100 * 365, DAYS).offset(100 * 365, DAYS) would be less than
// Deadline.after(-100 * 365, DAYS)
public Deadline offset(long offset, TimeUnit units) {
// May already be expired
if (offset == 0) {
return this;
}
return new Deadline(ticker, deadlineNanos, units.toNanos(offset), isExpired());
}
/**
* How much time is remaining in the specified time unit. Internal units are maintained as
* nanoseconds and conversions are subject to the constraints documented for
* {@link TimeUnit#convert}. If there is no time remaining, the returned duration is how
* long ago the deadline expired.
*/
public long timeRemaining(TimeUnit unit) {
final long nowNanos = ticker.nanoTime();
if (!expired && deadlineNanos - nowNanos <= 0) {
expired = true;
}
return unit.convert(deadlineNanos - nowNanos, TimeUnit.NANOSECONDS);
}
/**
* Schedule a task to be run when the deadline expires.
*
*
Note if this deadline was created with a custom {@link Ticker}, the {@code scheduler}'s
* underlying clock should be synchronized with that Ticker. Otherwise the task won't be run at
* the expected point of time.
*
* @param task to run on expiration
* @param scheduler used to execute the task
* @return {@link ScheduledFuture} which can be used to cancel execution of the task
*/
public ScheduledFuture runOnExpiration(Runnable task, ScheduledExecutorService scheduler) {
checkNotNull(task, "task");
checkNotNull(scheduler, "scheduler");
return scheduler.schedule(task, deadlineNanos - ticker.nanoTime(), TimeUnit.NANOSECONDS);
}
@Override
public String toString() {
long remainingNanos = timeRemaining(TimeUnit.NANOSECONDS);
long seconds = Math.abs(remainingNanos) / NANOS_PER_SECOND;
long nanos = Math.abs(remainingNanos) % NANOS_PER_SECOND;
StringBuilder buf = new StringBuilder();
if (remainingNanos < 0) {
buf.append('-');
}
buf.append(seconds);
if (nanos > 0) {
buf.append(String.format(".%09d", nanos));
}
buf.append("s from now");
if (ticker != SYSTEM_TICKER) {
buf.append(" (ticker=" + ticker + ")");
}
return buf.toString();
}
/**
* {@inheritDoc}
*
*
Both deadlines must be created with the same {@link Ticker}.
*/
@Override
public int compareTo(Deadline that) {
checkTicker(that);
long diff = this.deadlineNanos - that.deadlineNanos;
if (diff < 0) {
return -1;
} else if (diff > 0) {
return 1;
}
return 0;
}
@Override
public int hashCode() {
return Arrays.asList(this.ticker, this.deadlineNanos).hashCode();
}
@Override
public boolean equals(final Object o) {
if (o == this) {
return true;
}
if (!(o instanceof Deadline)) {
return false;
}
final Deadline other = (Deadline) o;
if (this.ticker == null ? other.ticker != null : this.ticker != other.ticker) {
return false;
}
if (this.deadlineNanos != other.deadlineNanos) {
return false;
}
return true;
}
/**
* Time source representing nanoseconds since fixed but arbitrary point in time.
*
*
DO NOT use custom {@link Ticker} implementations in production, because deadlines created
* with custom tickers are incompatible with those created with the system ticker. Always use
* the {@link #getSystemTicker system ticker} whenever you need to provide one in production code.
*
*
This is EXPERIMENTAL API and may subject to change. If you'd like it to be
* stabilized or have any feedback, please
* let us know.
*
* In general implementations should be thread-safe, unless it's implemented and used in a
* localized environment (like unit tests) where you are sure the usages are synchronized.
*
* @since 1.24.0
*/
public abstract static class Ticker {
/** Returns the number of nanoseconds since this source's epoch. */
public abstract long nanoTime();
}
private static class SystemTicker extends Ticker {
@Override
public long nanoTime() {
return System.nanoTime();
}
}
private static T checkNotNull(T reference, Object errorMessage) {
if (reference == null) {
throw new NullPointerException(String.valueOf(errorMessage));
}
return reference;
}
private void checkTicker(Deadline other) {
if (ticker != other.ticker) {
throw new AssertionError(
"Tickers (" + ticker + " and " + other.ticker + ") don't match."
+ " Custom Ticker should only be used in tests!");
}
}
}