[ONOS-6267] Detect and complete blocked futures on I/O threads.
Change-Id: I0488dc5096f9e610b97405ad05c02d0ff3854b5f
diff --git a/utils/misc/src/main/java/org/onlab/util/OrderedExecutor.java b/utils/misc/src/main/java/org/onlab/util/OrderedExecutor.java
new file mode 100644
index 0000000..8fe2cc2
--- /dev/null
+++ b/utils/misc/src/main/java/org/onlab/util/OrderedExecutor.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 order on a shared thread pool.
+ * <p>
+ * The ordered 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 ordered executors.
+ */
+public class OrderedExecutor implements Executor {
+ private final Executor parent;
+ private final LinkedList<Runnable> tasks = new LinkedList<>();
+ private boolean running;
+
+ public OrderedExecutor(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);
+ }
+ }
+ }
+}
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