[ONOS-6267] Support configurable Executors for primitives
- Support user-provided Executors in primitive builders
- Implement default per-partition per-primitive serial executor using a shared thread pool
- Implement Executor wrappers for all primitive types
Change-Id: I53acfb173a9b49a992a9a388983791d9735ed54a
diff --git a/utils/misc/src/main/java/org/onlab/util/BestEffortSerialExecutor.java b/utils/misc/src/main/java/org/onlab/util/BestEffortSerialExecutor.java
new file mode 100644
index 0000000..936a33f
--- /dev/null
+++ b/utils/misc/src/main/java/org/onlab/util/BestEffortSerialExecutor.java
@@ -0,0 +1,76 @@
+/*
+ * Copyright 2017-present Open Networking Laboratory
+ *
+ * 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 org.onlab.util;
+
+import java.util.LinkedList;
+import java.util.concurrent.Executor;
+
+/**
+ * Executor that executes tasks in serial on a shared thread pool, falling back to parallel execution when threads
+ * are blocked.
+ * <p>
+ * This executor attempts to execute tasks in serial as if they occur on a single thread. However, in the event tasks
+ * are blocking a thread (a thread is in the {@link Thread.State#WAITING} or {@link Thread.State#TIMED_WAITING} state)
+ * the executor will execute tasks on parallel on the underlying {@link Executor}. This is useful for ensuring blocked
+ * threads cannot block events, but mimics a single-threaded model otherwise.
+ */
+public class BestEffortSerialExecutor implements Executor {
+ private final Executor parent;
+ private final LinkedList<Runnable> tasks = new LinkedList<>();
+ private volatile Thread thread;
+
+ public BestEffortSerialExecutor(Executor parent) {
+ this.parent = parent;
+ }
+
+ private void run() {
+ synchronized (tasks) {
+ thread = Thread.currentThread();
+ }
+ for (;;) {
+ if (!runTask()) {
+ synchronized (tasks) {
+ thread = null;
+ }
+ return;
+ }
+ }
+ }
+
+ private boolean runTask() {
+ final Runnable task;
+ synchronized (tasks) {
+ task = tasks.poll();
+ if (task == null) {
+ return false;
+ }
+ }
+ task.run();
+ return true;
+ }
+
+ @Override
+ public void execute(Runnable command) {
+ synchronized (tasks) {
+ tasks.add(command);
+ if (thread == null) {
+ parent.execute(this::run);
+ } else if (thread.getState() == Thread.State.WAITING || thread.getState() == Thread.State.TIMED_WAITING) {
+ parent.execute(this::runTask);
+ }
+ }
+ }
+}
diff --git a/utils/misc/src/main/java/org/onlab/util/SerialExecutor.java b/utils/misc/src/main/java/org/onlab/util/SerialExecutor.java
new file mode 100644
index 0000000..9e54ac2
--- /dev/null
+++ b/utils/misc/src/main/java/org/onlab/util/SerialExecutor.java
@@ -0,0 +1,60 @@
+/*
+ * Copyright 2017-present Open Networking Laboratory
+ *
+ * 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 org.onlab.util;
+
+import java.util.LinkedList;
+import java.util.concurrent.Executor;
+
+/**
+ * Executor that executes tasks in serial on a shared thread pool.
+ * <p>
+ * The serial executor behaves semantically like a single-threaded executor, but multiplexes tasks on a shared thread
+ * pool, ensuring blocked threads in the shared thread pool don't block individual serial executors.
+ */
+public class SerialExecutor implements Executor {
+ private final Executor parent;
+ private final LinkedList<Runnable> tasks = new LinkedList<>();
+ private boolean running;
+
+ public SerialExecutor(Executor parent) {
+ this.parent = parent;
+ }
+
+ private void run() {
+ for (;;) {
+ final Runnable task;
+ synchronized (tasks) {
+ task = tasks.poll();
+ if (task == null) {
+ running = false;
+ return;
+ }
+ }
+ task.run();
+ }
+ }
+
+ @Override
+ public void execute(Runnable command) {
+ synchronized (tasks) {
+ tasks.add(command);
+ if (!running) {
+ running = true;
+ parent.execute(this::run);
+ }
+ }
+ }
+}
\ No newline at end of file
diff --git a/utils/misc/src/main/java/org/onlab/util/Tools.java b/utils/misc/src/main/java/org/onlab/util/Tools.java
index cc769c4..883a7c8 100644
--- a/utils/misc/src/main/java/org/onlab/util/Tools.java
+++ b/utils/misc/src/main/java/org/onlab/util/Tools.java
@@ -39,6 +39,7 @@
import java.util.Set;
import java.util.concurrent.CompletableFuture;
import java.util.concurrent.ExecutionException;
+import java.util.concurrent.Executor;
import java.util.concurrent.Future;
import java.util.concurrent.ThreadFactory;
import java.util.concurrent.TimeUnit;
@@ -642,6 +643,32 @@
}
/**
+ * Returns a future that's completed using the given {@link Executor} once the given {@code future} is completed.
+ * <p>
+ * {@link CompletableFuture}'s async methods cannot be relied upon to complete futures on an executor thread. If a
+ * future is completed synchronously, {@code CompletableFuture} async methods will often complete the future on the
+ * current thread, ignoring the provided {@code Executor}. This method ensures a more reliable and consistent thread
+ * model by ensuring that futures are always completed using the provided {@code Executor}.
+ *
+ * @param future the future to convert into an asynchronous future
+ * @param executor the executor with which to complete the returned future
+ * @param <T> future value type
+ * @return a new completable future to be completed using the provided {@code executor} once the provided
+ * {@code future} is complete
+ */
+ public static <T> CompletableFuture<T> asyncFuture(CompletableFuture<T> future, Executor executor) {
+ CompletableFuture<T> newFuture = new CompletableFuture<T>();
+ future.whenComplete((result, error) -> executor.execute(() -> {
+ if (future.isCompletedExceptionally()) {
+ newFuture.completeExceptionally(error);
+ } else {
+ newFuture.complete(result);
+ }
+ }));
+ return newFuture;
+ }
+
+ /**
* Returns a new CompletableFuture completed with a list of computed values
* when all of the given CompletableFuture complete.
*