WIP ping mangement
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Robinson
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/*
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* Copyright 2020 dorkbox, llc
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package dorkbox.network.ping
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import dorkbox.network.rmi.ResponseWaiter
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import dorkbox.network.rmi.RmiUtils
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import dorkbox.network.rmi.messages.MethodResponse
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import kotlinx.atomicfu.atomic
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import kotlinx.coroutines.CoroutineScope
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import kotlinx.coroutines.CoroutineStart
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import kotlinx.coroutines.channels.Channel
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import kotlinx.coroutines.delay
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import kotlinx.coroutines.launch
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import mu.KLogger
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import java.util.concurrent.locks.ReentrantReadWriteLock
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import kotlin.concurrent.read
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import kotlin.concurrent.write
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/**
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* Manages the "pending response" from pings. This is VERY similar to how RMI works, but tweaked for PING usage
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*
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* response ID's and the memory they hold will leak if the response never arrives!
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*/
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internal class PingResponseManager(private val logger: KLogger, private val actionDispatch: CoroutineScope) {
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companion object {
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val TIMEOUT_EXCEPTION = Exception()
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}
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// Response ID's are for ALL in-flight RMI on the network stack. instead of limited to (originally) 64, we are now limited to 65,535
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// these are just looped around in a ring buffer.
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// These are stored here as int, however these are REALLY shorts and are int-packed when transferring data on the wire
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// 65535 IN FLIGHT RMI method invocations is plenty
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// 0 is reserved for INVALID
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// 1 is reserved for ASYNC
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private val maxValuesInCache = 65535
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private val rmiWaitersInUse = atomic(0)
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private val waiterCache = Channel<ResponseWaiter>(maxValuesInCache)
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private val pendingLock = ReentrantReadWriteLock()
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private val pending = arrayOfNulls<Any?>(maxValuesInCache+1) // +1 because it's possible to have the value 65535 in the cache
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init {
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// create a shuffled list of ID's. This operation is ONLY performed ONE TIME per endpoint!
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val ids = mutableListOf<Int>()
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for (id in Short.MIN_VALUE..-1) {
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ids.add(id)
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}
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// MIN (32768) -> -1 (65535)
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// 2 (2) -> MAX (32767)
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// ZERO is special, and is never added!
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// ONE is special, and is used for ASYNC (the response will never be sent back)
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for (id in 2..Short.MAX_VALUE) {
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ids.add(id)
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}
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ids.shuffle()
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// populate the array of randomly assigned ID's + waiters. This can happen in a new thread
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actionDispatch.launch {
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for (it in ids) {
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waiterCache.offer(ResponseWaiter(it))
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}
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}
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}
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/**
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* resume any pending remote object method invocations (if they are not async, or not manually waiting)
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* NOTE: async RMI will never call this (because async doesn't return a response)
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*/
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suspend fun onRmiMessage(message: MethodResponse) {
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val rmiId = RmiUtils.unpackUnsignedRight(message.packedId)
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val result = message.result
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logger.trace { "RMI return: $rmiId" }
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val previous = pendingLock.write {
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val previous = pending[rmiId]
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pending[rmiId] = result
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previous
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}
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// if NULL, since either we don't exist (because we were async), or it was cancelled
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if (previous is ResponseWaiter) {
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logger.trace { "RMI valid-cancel: $rmiId" }
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// this means we were NOT timed out! (we cannot be timed out here)
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previous.doNotify()
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}
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}
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/**
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* gets the ResponseWaiter (id + waiter) and prepares the pending response map
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*
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* We ONLY care about the ID to get the correct response info. If there is no response, the ID can be ignored.
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*/
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internal suspend fun prep(): ResponseWaiter {
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val responseRmi = waiterCache.receive()
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rmiWaitersInUse.getAndIncrement()
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logger.trace { "RMI count: ${rmiWaitersInUse.value}" }
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// this will replace the waiter if it was cancelled (waiters are not valid if cancelled)
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responseRmi.prep()
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pendingLock.write {
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// this just does a .toUShort().toInt() conversion. This is cleaner than doing it manually
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pending[RmiUtils.unpackUnsignedRight(responseRmi.id)] = responseRmi
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}
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return responseRmi
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}
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/**
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* We only wait for a reply if we are SYNC.
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*
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* ASYNC does not send a response
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*
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* @return the result (can be null) or timeout exception
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*/
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suspend fun waitForReply(responseWaiter: ResponseWaiter, timeoutMillis: Long): Any? {
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val rmiId = RmiUtils.unpackUnsignedRight(responseWaiter.id) // this just does a .toUShort().toInt() conversion. This is cleaner than doing it manually
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logger.trace {
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"RMI waiting: $rmiId"
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}
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// NOTE: we ALWAYS send a response from the remote end (except when async).
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//
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// 'async' -> DO NOT WAIT (no response)
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// 'timeout > 0' -> WAIT w/ TIMEOUT
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// 'timeout == 0' -> WAIT FOREVER
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if (timeoutMillis > 0) {
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@Suppress("EXPERIMENTAL_API_USAGE")
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val responseTimeoutJob = actionDispatch.launch(start = CoroutineStart.UNDISPATCHED) {
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// NOTE: UNDISPATCHED means that this coroutine will start when `rmiWaiter.doWait()` is called (the first suspension point)
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// we want this behavior INSTEAD OF automatically starting this on a new thread.
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delay(timeoutMillis) // this will always wait. if this job is cancelled, this will immediately stop waiting
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// check if we have a result or not
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val maybeResult = pendingLock.read { pending[rmiId] }
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if (maybeResult is ResponseWaiter) {
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logger.trace { "RMI timeout ($timeoutMillis) cancel: $rmiId" }
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maybeResult.cancel()
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}
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}
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// wait for the response.
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//
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// If the response is ALREADY here, the doWait() returns instantly (with result)
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// if no response yet, it will suspend and either
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// A) get response
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// B) timeout
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responseWaiter.doWait()
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// always cancel the timeout
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responseTimeoutJob.cancel()
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} else {
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// wait for the response --- THIS WAITS FOREVER (there is no timeout)!
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//
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// If the response is ALREADY here, the doWait() returns instantly (with result)
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// if no response yet, it will suspend and
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// A) get response
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responseWaiter.doWait()
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}
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val resultOrWaiter = pendingLock.write {
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val previous = pending[rmiId]
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pending[rmiId] = null
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previous
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}
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// always return the waiter to the cache
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waiterCache.send(responseWaiter)
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rmiWaitersInUse.getAndDecrement()
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if (resultOrWaiter is ResponseWaiter) {
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logger.trace { "RMI was canceled ($timeoutMillis): $rmiId" }
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return TIMEOUT_EXCEPTION
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}
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return resultOrWaiter
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}
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///////
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///////
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//// Callback waiting/execution. This is part of this class only because we want to use the SAME RMI SYSTEM for other things,
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//// namely, being able to have an easier time setting up message responses
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///////
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///////
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/**
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* on response, runs the waiting callback
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* NOTE: This uses the RMI-ID mechanism to know what the response ID is (the name is left alone)
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*/
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suspend fun onCallbackMessage(message: MethodResponse) {
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val rmiId = RmiUtils.unpackUnsignedRight(message.packedId)
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val result = message.result
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logger.trace { "RMI return: $rmiId" }
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val previous = pendingLock.write {
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val previous = pending[rmiId]
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pending[rmiId] = result
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previous
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}
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// if NULL, since either we don't exist (because we were async), or it was cancelled
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if (previous is ResponseWaiter) {
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logger.trace { "RMI valid-cancel: $rmiId" }
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// this means we were NOT timed out! (we cannot be timed out here)
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previous.doNotify()
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}
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}
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/**
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* gets the ResponseWaiter (id + waiter) and prepares the pending response map
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*
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* We ONLY care about the ID to get the correct response info.
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* NOTE: This uses the RMI-ID mechanism to know what the response ID is (the name is left alone)
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*/
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internal suspend fun prepForCallback(callback: (Any) -> Unit): ResponseWaiter {
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val responseRmi = waiterCache.receive()
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rmiWaitersInUse.getAndIncrement()
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logger.trace { "RMI2 count: ${rmiWaitersInUse.value}" }
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// this will replace the waiter if it was cancelled (waiters are not valid if cancelled)
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responseRmi.prep()
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// assign the callback that will be notified when the return message is received
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responseRmi.result = callback
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pendingLock.write {
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// this just does a .toUShort().toInt() conversion. This is cleaner than doing it manually
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pending[RmiUtils.unpackUnsignedRight(responseRmi.id)] = responseRmi
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}
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return responseRmi
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}
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suspend fun close() {
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// wait for responses, or wait for timeouts!
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while (rmiWaitersInUse.value > 0) {
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delay(100)
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}
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waiterCache.close()
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pendingLock.write {
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pending.forEachIndexed { index, _ ->
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pending[index] = null
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}
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}
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}
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}
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