Make all TaskRunner tasks cancelable

This probably should have been the case all along. Unfortunately,
ExecutorService Runnables are not cancelable by default, and that's
where we started.

After implementing all of TaskRunner it looks like where we're
cancelable and where we aren't is totally arbitrary. Making everything
cancelable simplifies the implementation and model.

The last remaining non-cancelable tasks:
 * awaitIdle() which we use in our tests only.
 * MockWebServer, where canceling would leak sockets

mockwebserver/src/main/java/okhttp3/mockwebserver/MockWebServer.kt

@@ -389,7 +389,7 @@ class MockWebServer : ExternalResource(), Closeable {
 
     portField = serverSocket!!.localPort
 
-    taskRunner.newQueue().execute("MockWebServer $portField") {
+    taskRunner.newQueue().execute("MockWebServer $portField", cancelable = false) {
       try {
         logger.info("${this@MockWebServer} starting to accept connections")
         acceptConnections()
@@ -464,7 +464,7 @@ class MockWebServer : ExternalResource(), Closeable {
   }
 
   private fun serveConnection(raw: Socket) {
-    taskRunner.newQueue().execute("MockWebServer ${raw.remoteSocketAddress}") {
+    taskRunner.newQueue().execute("MockWebServer ${raw.remoteSocketAddress}", cancelable = false) {
       try {
         SocketHandler(raw).handle()
       } catch (e: IOException) {

okhttp/src/main/java/okhttp3/internal/cache/DiskLruCache.kt

@@ -168,7 +168,7 @@ class DiskLruCache internal constructor(
   private var nextSequenceNumber: Long = 0
 
   private val cleanupQueue = taskRunner.newQueue()
-  private val cleanupTask = object : Task("OkHttp Cache", cancelable = false) {
+  private val cleanupTask = object : Task("OkHttp Cache") {
     override fun runOnce(): Long {
       synchronized(this@DiskLruCache) {
         if (!initialized || closed) {

okhttp/src/main/java/okhttp3/internal/concurrent/Task.kt

@@ -48,7 +48,7 @@ package okhttp3.internal.concurrent
  */
 abstract class Task(
   val name: String,
-  val cancelable: Boolean
+  val cancelable: Boolean = true
 ) {
   // Guarded by the TaskRunner.
   internal var queue: TaskQueue? = null

okhttp/src/main/java/okhttp3/internal/concurrent/TaskQueue.kt

@@ -54,11 +54,14 @@ class TaskQueue internal constructor(
    * is running when that time is reached, that task is allowed to complete before this task is
    * started. Similarly the task will be delayed if the host lacks compute resources.
    *
-   * @throws RejectedExecutionException if the queue is shut down.
+   * @throws RejectedExecutionException if the queue is shut down and the task is not cancelable.
    */
   fun schedule(task: Task, delayNanos: Long = 0L) {
     synchronized(taskRunner) {
-      if (shutdown) throw RejectedExecutionException()
+      if (shutdown) {
+        if (task.cancelable) return
+        throw RejectedExecutionException()
+      }
 
       if (scheduleAndDecide(task, delayNanos)) {
         taskRunner.kickCoordinator(this)
@@ -70,25 +73,13 @@ class TaskQueue internal constructor(
   inline fun schedule(
     name: String,
     delayNanos: Long = 0L,
-    cancelable: Boolean = true,
     crossinline block: () -> Long
   ) {
-    schedule(object : Task(name, cancelable) {
+    schedule(object : Task(name) {
       override fun runOnce() = block()
     }, delayNanos)
   }
 
-  /** Like [schedule], but this silently discard the task if the queue is shut down. */
-  fun trySchedule(task: Task, delayNanos: Long = 0L) {
-    synchronized(taskRunner) {
-      if (shutdown) return
-
-      if (scheduleAndDecide(task, delayNanos)) {
-        taskRunner.kickCoordinator(this)
-      }
-    }
-  }
-
   /** Executes [block] once on a task runner thread. */
   inline fun execute(
     name: String,
@@ -104,21 +95,6 @@ class TaskQueue internal constructor(
     }, delayNanos)
   }
 
-  /** Like [execute], but this silently discard the task if the queue is shut down. */
-  inline fun tryExecute(
-    name: String,
-    delayNanos: Long = 0L,
-    cancelable: Boolean = true,
-    crossinline block: () -> Unit
-  ) {
-    trySchedule(object : Task(name, cancelable) {
-      override fun runOnce(): Long {
-        block()
-        return -1L
-      }
-    }, delayNanos)
-  }
-
   /** Returns true if this queue became idle before the timeout elapsed. */
   fun awaitIdle(delayNanos: Long): Boolean {
     val latch = CountDownLatch(1)

okhttp/src/main/java/okhttp3/internal/connection/RealConnectionPool.kt

@@ -40,7 +40,7 @@ class RealConnectionPool(
   private val keepAliveDurationNs: Long = timeUnit.toNanos(keepAliveDuration)
 
   private val cleanupQueue: TaskQueue = taskRunner.newQueue()
-  private val cleanupTask = object : Task("OkHttp ConnectionPool", cancelable = true) {
+  private val cleanupTask = object : Task("OkHttp ConnectionPool") {
     override fun runOnce() = cleanup(System.nanoTime())
   }
 

okhttp/src/main/java/okhttp3/internal/http2/Http2Connection.kt

@@ -315,7 +315,7 @@ class Http2Connection internal constructor(builder: Builder) : Closeable {
     streamId: Int,
     errorCode: ErrorCode
   ) {
-    writerQueue.tryExecute("$connectionName[$streamId] writeSynReset") {
+    writerQueue.execute("$connectionName[$streamId] writeSynReset") {
       try {
         writeSynReset(streamId, errorCode)
       } catch (e: IOException) {
@@ -336,7 +336,7 @@ class Http2Connection internal constructor(builder: Builder) : Closeable {
     streamId: Int,
     unacknowledgedBytesRead: Long
   ) {
-    writerQueue.tryExecute("$connectionName[$streamId] windowUpdate") {
+    writerQueue.execute("$connectionName[$streamId] windowUpdate") {
       try {
         writer.windowUpdate(streamId, unacknowledgedBytesRead)
       } catch (e: IOException) {
@@ -625,8 +625,7 @@ class Http2Connection internal constructor(builder: Builder) : Closeable {
           streams[streamId] = newStream
 
           // Use a different task queue for each stream because they should be handled in parallel.
-          val taskName = "$connectionName[$streamId] onStream"
+          taskRunner.newQueue().execute("$connectionName[$streamId] onStream") {
-          taskRunner.newQueue().execute(taskName, cancelable = false) {
             try {
               listener.onStream(newStream)
             } catch (e: IOException) {
@@ -654,7 +653,7 @@ class Http2Connection internal constructor(builder: Builder) : Closeable {
     }
 
     override fun settings(clearPrevious: Boolean, settings: Settings) {
-      writerQueue.tryExecute("$connectionName applyAndAckSettings") {
+      writerQueue.execute("$connectionName applyAndAckSettings") {
         applyAndAckSettings(clearPrevious, settings)
       }
     }
@@ -697,7 +696,7 @@ class Http2Connection internal constructor(builder: Builder) : Closeable {
 
           peerSettings = newPeerSettings
 
-          settingsListenerQueue.tryExecute("$connectionName onSettings", cancelable = false) {
+          settingsListenerQueue.execute("$connectionName onSettings") {
             listener.onSettings(this@Http2Connection, newPeerSettings)
           }
         }
@@ -732,7 +731,7 @@ class Http2Connection internal constructor(builder: Builder) : Closeable {
         }
       } else {
         // Send a reply to a client ping if this is a server and vice versa.
-        writerQueue.tryExecute("$connectionName ping") {
+        writerQueue.execute("$connectionName ping") {
           writePing(true, payload1, payload2)
         }
       }
@@ -819,7 +818,7 @@ class Http2Connection internal constructor(builder: Builder) : Closeable {
       }
       currentPushRequests.add(streamId)
     }
-    pushQueue.tryExecute("$connectionName[$streamId] onRequest") {
+    pushQueue.execute("$connectionName[$streamId] onRequest") {
       val cancel = pushObserver.onRequest(streamId, requestHeaders)
       ignoreIoExceptions {
         if (cancel) {
@@ -837,7 +836,7 @@ class Http2Connection internal constructor(builder: Builder) : Closeable {
     requestHeaders: List<Header>,
     inFinished: Boolean
   ) {
-    pushQueue.tryExecute("$connectionName[$streamId] onHeaders") {
+    pushQueue.execute("$connectionName[$streamId] onHeaders") {
       val cancel = pushObserver.onHeaders(streamId, requestHeaders, inFinished)
       ignoreIoExceptions {
         if (cancel) writer.rstStream(streamId, ErrorCode.CANCEL)
@@ -864,7 +863,7 @@ class Http2Connection internal constructor(builder: Builder) : Closeable {
     val buffer = Buffer()
     source.require(byteCount.toLong()) // Eagerly read the frame before firing client thread.
     source.read(buffer, byteCount.toLong())
-    pushQueue.tryExecute("$connectionName[$streamId] onData") {
+    pushQueue.execute("$connectionName[$streamId] onData") {
       ignoreIoExceptions {
         val cancel = pushObserver.onData(streamId, buffer, byteCount, inFinished)
         if (cancel) writer.rstStream(streamId, ErrorCode.CANCEL)
@@ -878,7 +877,7 @@ class Http2Connection internal constructor(builder: Builder) : Closeable {
   }
 
   internal fun pushResetLater(streamId: Int, errorCode: ErrorCode) {
-    pushQueue.tryExecute("$connectionName[$streamId] onReset", cancelable = false) {
+    pushQueue.execute("$connectionName[$streamId] onReset") {
       pushObserver.onReset(streamId, errorCode)
       synchronized(this@Http2Connection) {
         currentPushRequests.remove(streamId)

okhttp/src/main/java/okhttp3/internal/ws/RealWebSocket.kt

@@ -393,7 +393,7 @@ class RealWebSocket(
 
   private fun runWriter() {
     assert(Thread.holdsLock(this))
-    taskQueue.trySchedule(writerTask!!)
+    taskQueue.schedule(writerTask!!)
   }
 
   /**
@@ -535,7 +535,7 @@ class RealWebSocket(
     val sink: BufferedSink
   ) : Closeable
 
-  private inner class WriterTask : Task("$name writer", cancelable = true) {
+  private inner class WriterTask : Task("$name writer") {
     override fun runOnce(): Long {
       try {
         if (writeOneFrame()) return 0L

okhttp/src/test/java/okhttp3/internal/concurrent/TaskRunnerTest.kt

@@ -72,7 +72,7 @@ class TaskRunnerTest {
 
   /** Repeat with a delay of 200 but schedule with a delay of 50. The schedule wins. */
   @Test fun executeScheduledEarlierReplacesRepeatedLater() {
-    val task = object : Task("task", cancelable = true) {
+    val task = object : Task("task") {
       val schedules = mutableListOf(50L)
       val delays = mutableListOf(200L, -1L)
       override fun runOnce(): Long {
@@ -99,7 +99,7 @@ class TaskRunnerTest {
 
   /** Schedule with a delay of 200 but repeat with a delay of 50. The repeat wins. */
   @Test fun executeRepeatedEarlierReplacesScheduledLater() {
-    val task = object : Task("task", cancelable = true) {
+    val task = object : Task("task") {
       val schedules = mutableListOf(200L)
       val delays = mutableListOf(50L, -1L)
       override fun runOnce(): Long {
@@ -141,9 +141,12 @@ class TaskRunnerTest {
   }
 
   @Test fun cancelReturnsFalseDoesNotCancel() {
-    redQueue.execute("task", 100L, cancelable = false) {
+    redQueue.schedule(object : Task("task", cancelable = false) {
+      override fun runOnce(): Long {
         log += "run@${taskFaker.nanoTime}"
+        return -1L
       }
+    }, 100L)
 
     taskFaker.advanceUntil(0L)
     assertThat(log).isEmpty()
@@ -191,12 +194,14 @@ class TaskRunnerTest {
   }
 
   @Test fun cancelWhileExecutingDoesNotStopUncancelableTask() {
+    redQueue.schedule(object : Task("task", cancelable = false) {
       val delays = mutableListOf(50L, -1L)
-    redQueue.schedule("task", 100L, cancelable = false) {
+      override fun runOnce(): Long {
         log += "run@${taskFaker.nanoTime}"
         redQueue.cancelAll()
-      return@schedule delays.removeAt(0)
+        return delays.removeAt(0)
       }
+    }, 100L)
 
     taskFaker.advanceUntil(0L)
     assertThat(log).isEmpty()
@@ -227,9 +232,12 @@ class TaskRunnerTest {
   }
 
   @Test fun interruptingCoordinatorAttemptsToCancelsAndFails() {
-    redQueue.execute("task", 100L, cancelable = false) {
+    redQueue.schedule(object : Task("task", cancelable = false) {
+      override fun runOnce(): Long {
         log += "run@${taskFaker.nanoTime}"
+        return -1L
       }
+    }, 100L)
 
     taskFaker.advanceUntil(0L)
     assertThat(log).isEmpty()
@@ -317,7 +325,7 @@ class TaskRunnerTest {
    * cumbersome to implement properly because the active task might be a cancel.
    */
   @Test fun scheduledTasksDoesNotIncludeRunningTask() {
-    val task = object : Task("task one", cancelable = true) {
+    val task = object : Task("task one") {
       val schedules = mutableListOf(200L)
       override fun runOnce(): Long {
         if (schedules.isNotEmpty()) {
@@ -408,10 +416,12 @@ class TaskRunnerTest {
   }
 
   @Test fun shutdownFailsToCancelsScheduledTasks() {
-    redQueue.schedule("task", 100L, cancelable = false) {
+    redQueue.schedule(object : Task("task", false) {
+      override fun runOnce(): Long {
         log += "run@${taskFaker.nanoTime}"
-      return@schedule 50L
+        return 50L
       }
+    }, 100L)
 
     taskFaker.advanceUntil(0L)
     assertThat(log).isEmpty()
@@ -430,7 +440,7 @@ class TaskRunnerTest {
   @Test fun scheduleDiscardsTaskWhenShutdown() {
     redQueue.shutdown()
 
-    redQueue.tryExecute("task", 100L) {
+    redQueue.execute("task", 100L) {
       // Do nothing.
     }
 
@@ -441,9 +451,11 @@ class TaskRunnerTest {
     redQueue.shutdown()
 
     try {
-      redQueue.execute("task", 100L) {
+      redQueue.schedule(object : Task("task", cancelable = false) {
-        // Do nothing.
+        override fun runOnce(): Long {
+          return -1L
         }
+      }, 100L)
       fail()
     } catch (_: RejectedExecutionException) {
     }