jvmMain.okio.AsyncTimeout.kt Maven / Gradle / Ivy
/*
* Copyright (C) 2014 Square, Inc.
*
* 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 okio
import java.io.IOException
import java.io.InterruptedIOException
import java.util.concurrent.TimeUnit
import java.util.concurrent.locks.Condition
import java.util.concurrent.locks.ReentrantLock
import kotlin.concurrent.withLock
/**
* This timeout uses a background thread to take action exactly when the timeout occurs. Use this to
* implement timeouts where they aren't supported natively, such as to sockets that are blocked on
* writing.
*
* Subclasses should override [timedOut] to take action when a timeout occurs. This method will be
* invoked by the shared watchdog thread so it should not do any long-running operations. Otherwise,
* we risk starving other timeouts from being triggered.
*
* Use [sink] and [source] to apply this timeout to a stream. The returned value will apply the
* timeout to each operation on the wrapped stream.
*
* Callers should call [enter] before doing work that is subject to timeouts, and [exit] afterward.
* The return value of [exit] indicates whether a timeout was triggered. Note that the call to
* [timedOut] is asynchronous, and may be called after [exit].
*/
open class AsyncTimeout : Timeout() {
private var state = STATE_IDLE
/** The next node in the linked list. */
private var next: AsyncTimeout? = null
/** If scheduled, this is the time that the watchdog should time this out. */
private var timeoutAt = 0L
fun enter() {
val timeoutNanos = timeoutNanos()
val hasDeadline = hasDeadline()
if (timeoutNanos == 0L && !hasDeadline) {
return // No timeout and no deadline? Don't bother with the queue.
}
lock.withLock {
check(state == STATE_IDLE) { "Unbalanced enter/exit" }
state = STATE_IN_QUEUE
insertIntoQueue(this, timeoutNanos, hasDeadline)
}
}
/** Returns true if the timeout occurred. */
fun exit(): Boolean {
lock.withLock {
val oldState = this.state
state = STATE_IDLE
if (oldState == STATE_IN_QUEUE) {
removeFromQueue(this)
return false
} else {
return oldState == STATE_TIMED_OUT
}
}
}
override fun cancel() {
super.cancel()
lock.withLock {
if (state == STATE_IN_QUEUE) {
removeFromQueue(this)
state = STATE_CANCELED
}
}
}
/**
* Returns the amount of time left until the time out. This will be negative if the timeout has
* elapsed and the timeout should occur immediately.
*/
private fun remainingNanos(now: Long) = timeoutAt - now
/**
* Invoked by the watchdog thread when the time between calls to [enter] and [exit] has exceeded
* the timeout.
*/
protected open fun timedOut() {}
/**
* Returns a new sink that delegates to [sink], using this to implement timeouts. This works
* best if [timedOut] is overridden to interrupt [sink]'s current operation.
*/
fun sink(sink: Sink): Sink {
return object : Sink {
override fun write(source: Buffer, byteCount: Long) {
checkOffsetAndCount(source.size, 0, byteCount)
var remaining = byteCount
while (remaining > 0L) {
// Count how many bytes to write. This loop guarantees we split on a segment boundary.
var toWrite = 0L
var s = source.head!!
while (toWrite < TIMEOUT_WRITE_SIZE) {
val segmentSize = s.limit - s.pos
toWrite += segmentSize.toLong()
if (toWrite >= remaining) {
toWrite = remaining
break
}
s = s.next!!
}
// Emit one write. Only this section is subject to the timeout.
withTimeout { sink.write(source, toWrite) }
remaining -= toWrite
}
}
override fun flush() {
withTimeout { sink.flush() }
}
override fun close() {
withTimeout { sink.close() }
}
override fun timeout() = this@AsyncTimeout
override fun toString() = "AsyncTimeout.sink($sink)"
}
}
/**
* Returns a new source that delegates to [source], using this to implement timeouts. This works
* best if [timedOut] is overridden to interrupt [source]'s current operation.
*/
fun source(source: Source): Source {
return object : Source {
override fun read(sink: Buffer, byteCount: Long): Long {
return withTimeout { source.read(sink, byteCount) }
}
override fun close() {
withTimeout { source.close() }
}
override fun timeout() = this@AsyncTimeout
override fun toString() = "AsyncTimeout.source($source)"
}
}
/**
* Surrounds [block] with calls to [enter] and [exit], throwing an exception from
* [newTimeoutException] if a timeout occurred.
*/
inline fun withTimeout(block: () -> T): T {
var throwOnTimeout = false
enter()
try {
val result = block()
throwOnTimeout = true
return result
} catch (e: IOException) {
throw if (!exit()) e else `access$newTimeoutException`(e)
} finally {
val timedOut = exit()
if (timedOut && throwOnTimeout) throw `access$newTimeoutException`(null)
}
}
@PublishedApi // Binary compatible trampoline function
internal fun `access$newTimeoutException`(cause: IOException?) = newTimeoutException(cause)
/**
* Returns an [IOException] to represent a timeout. By default this method returns
* [InterruptedIOException]. If [cause] is non-null it is set as the cause of the
* returned exception.
*/
protected open fun newTimeoutException(cause: IOException?): IOException {
val e = InterruptedIOException("timeout")
if (cause != null) {
e.initCause(cause)
}
return e
}
private class Watchdog : Thread("Okio Watchdog") {
init {
isDaemon = true
}
override fun run() {
while (true) {
try {
var timedOut: AsyncTimeout?
lock.withLock {
timedOut = awaitTimeout()
// The queue is completely empty. Let this thread exit and let another watchdog thread
// get created on the next call to scheduleTimeout().
if (timedOut === head) {
head = null
return
}
}
// Close the timed out node, if one was found.
timedOut?.timedOut()
} catch (ignored: InterruptedException) {
}
}
}
}
private companion object {
val lock: ReentrantLock = ReentrantLock()
val condition: Condition = lock.newCondition()
/**
* Don't write more than 64 KiB of data at a time, give or take a segment. Otherwise slow
* connections may suffer timeouts even when they're making (slow) progress. Without this,
* writing a single 1 MiB buffer may never succeed on a sufficiently slow connection.
*/
private const val TIMEOUT_WRITE_SIZE = 64 * 1024
/** Duration for the watchdog thread to be idle before it shuts itself down. */
private val IDLE_TIMEOUT_MILLIS = TimeUnit.SECONDS.toMillis(60)
private val IDLE_TIMEOUT_NANOS = TimeUnit.MILLISECONDS.toNanos(IDLE_TIMEOUT_MILLIS)
/*
* .-------------.
* | |
* .------------ exit() ------| CANCELED |
* | | |
* | '-------------'
* | ^
* | | cancel()
* v |
* .-------------. .-------------.
* | |---- enter() ----->| |
* | IDLE | | IN QUEUE |
* | |<---- exit() ------| |
* '-------------' '-------------'
* ^ |
* | | time out
* | v
* | .-------------.
* | | |
* '------------ exit() ------| TIMED OUT |
* | |
* '-------------'
*
* Notes:
* * enter() crashes if called from a state other than IDLE.
* * If there's no timeout (ie. wait forever), then enter() is a no-op. There's no state to
* track entered but not in the queue.
* * exit() is a no-op from IDLE. This is probably too lenient, but it made it simpler for
* early implementations to support cases where enter() as a no-op.
* * cancel() is a no-op from every state but IN QUEUE.
*/
private const val STATE_IDLE = 0
private const val STATE_IN_QUEUE = 1
private const val STATE_TIMED_OUT = 2
private const val STATE_CANCELED = 3
/**
* The watchdog thread processes a linked list of pending timeouts, sorted in the order to be
* triggered. This class synchronizes on AsyncTimeout.class. This lock guards the queue.
*
* Head's 'next' points to the first element of the linked list. The first element is the next
* node to time out, or null if the queue is empty. The head is null until the watchdog thread
* is started and also after being idle for [AsyncTimeout.IDLE_TIMEOUT_MILLIS].
*/
private var head: AsyncTimeout? = null
private fun insertIntoQueue(node: AsyncTimeout, timeoutNanos: Long, hasDeadline: Boolean) {
// Start the watchdog thread and create the head node when the first timeout is scheduled.
if (head == null) {
head = AsyncTimeout()
Watchdog().start()
}
val now = System.nanoTime()
if (timeoutNanos != 0L && hasDeadline) {
// Compute the earliest event; either timeout or deadline. Because nanoTime can wrap
// around, minOf() is undefined for absolute values, but meaningful for relative ones.
node.timeoutAt = now + minOf(timeoutNanos, node.deadlineNanoTime() - now)
} else if (timeoutNanos != 0L) {
node.timeoutAt = now + timeoutNanos
} else if (hasDeadline) {
node.timeoutAt = node.deadlineNanoTime()
} else {
throw AssertionError()
}
// Insert the node in sorted order.
val remainingNanos = node.remainingNanos(now)
var prev = head!!
while (true) {
if (prev.next == null || remainingNanos < prev.next!!.remainingNanos(now)) {
node.next = prev.next
prev.next = node
if (prev === head) {
// Wake up the watchdog when inserting at the front.
condition.signal()
}
break
}
prev = prev.next!!
}
}
/** Returns true if the timeout occurred. */
private fun removeFromQueue(node: AsyncTimeout) {
var prev = head
while (prev != null) {
if (prev.next === node) {
prev.next = node.next
node.next = null
return
}
prev = prev.next
}
error("node was not found in the queue")
}
/**
* Removes and returns the node at the head of the list, waiting for it to time out if
* necessary. This returns [head] if there was no node at the head of the list when starting,
* and there continues to be no node after waiting [IDLE_TIMEOUT_NANOS]. It returns null if a
* new node was inserted while waiting. Otherwise, this returns the node being waited on that
* has been removed.
*/
@Throws(InterruptedException::class)
fun awaitTimeout(): AsyncTimeout? {
// Get the next eligible node.
val node = head!!.next
// The queue is empty. Wait until either something is enqueued or the idle timeout elapses.
if (node == null) {
val startNanos = System.nanoTime()
condition.await(IDLE_TIMEOUT_MILLIS, TimeUnit.MILLISECONDS)
return if (head!!.next == null && System.nanoTime() - startNanos >= IDLE_TIMEOUT_NANOS) {
head // The idle timeout elapsed.
} else {
null // The situation has changed.
}
}
val waitNanos = node.remainingNanos(System.nanoTime())
// The head of the queue hasn't timed out yet. Await that.
if (waitNanos > 0) {
condition.await(waitNanos, TimeUnit.NANOSECONDS)
return null
}
// The head of the queue has timed out. Remove it.
head!!.next = node.next
node.next = null
node.state = STATE_TIMED_OUT
return node
}
}
}
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