Github user michaelandrepearce commented on a diff in the pull request:
https://github.com/apache/activemq-artemis/pull/1443#discussion_r131530496
--- Diff:
artemis-commons/src/main/java/org/apache/activemq/artemis/utils/critical/CriticalAnalyzerImpl.java
---
@@ -0,0 +1,182 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You 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.apache.activemq.artemis.utils.critical;
+
+import java.util.ConcurrentModificationException;
+import java.util.concurrent.CopyOnWriteArrayList;
+import java.util.concurrent.Semaphore;
+import java.util.concurrent.TimeUnit;
+
+import org.apache.activemq.artemis.utils.collections.ConcurrentHashSet;
+import org.jboss.logging.Logger;
+
+public class CriticalAnalyzerImpl implements CriticalAnalyzer {
+
+ private final Logger logger = Logger.getLogger(CriticalAnalyzer.class);
+
+ private volatile long timeout;
+
+ private volatile long checkTime;
+
+ @Override
+ public void clear() {
+ actions.clear();
+ components.clear();
+ }
+
+ private CopyOnWriteArrayList<CriticalAction> actions = new
CopyOnWriteArrayList<>();
+
+ private Thread thread;
+
+ private final Semaphore running = new Semaphore(1);
+
+ private final ConcurrentHashSet<CriticalComponent> components = new
ConcurrentHashSet<>();
+
+ @Override
+ public void add(CriticalComponent component) {
+ components.add(component);
+ }
+
+ @Override
+ public void remove(CriticalComponent component) {
+ components.remove(component);
+ }
+
+ @Override
+ public CriticalAnalyzer setCheckTime(long timeout) {
+ this.checkTime = timeout;
+ return this;
+ }
+
+ @Override
+ public long getCheckTime() {
+ if (checkTime == 0) {
+ checkTime = getTimeout() / 2;
+ }
+ return checkTime;
+ }
+
+ @Override
+ public CriticalAnalyzer setTimeout(long timeout) {
+ this.timeout = timeout;
+ return this;
+ }
+
+ @Override
+ public long getTimeout() {
+ if (timeout == 0) {
+ timeout = TimeUnit.MINUTES.toMillis(2);
+ }
+ return timeout;
+ }
+
+ @Override
+ public CriticalAnalyzer addAction(CriticalAction action) {
+ this.actions.add(action);
+ return this;
+ }
+
+ @Override
+ public void check() {
+ boolean retry = true;
+ while (retry) {
+ try {
+ for (CriticalComponent component : components) {
+
+ int pathReturned = component.isExpired(timeout);
+ if (pathReturned >= 0) {
+ fireAction(component, pathReturned);
+ // no need to keep running if there's already a
component failed
+ return;
+ }
+ }
+ retry = false; // got to the end of the list, no need to retry
+ } catch (ConcurrentModificationException dontCare) {
+ // lets retry on the loop
+ }
+ }
+ }
+
+ private void fireAction(CriticalComponent component, int path) {
+ for (CriticalAction action: actions) {
+ try {
+ action.run(component, path);
+ } catch (Throwable e) {
+ logger.warn(e.getMessage(), e);
+ }
+ }
+ }
+
+ @Override
+ public void start() {
+
+ if (!running.tryAcquire()) {
+ // already running
+ return;
+ }
+
+ // we are not using any Thread Pool or any Scheduled Executors from
the ArtemisServer
+ // as that would defeat the purpose,
+ // as in any deadlocks the schedulers may be starving for something
not responding fast enough
+ thread = new Thread("Artemis Critical Analyzer") {
+ @Override
+ public void run() {
+ try {
+ while (true) {
+ if (running.tryAcquire(getCheckTime(),
TimeUnit.MILLISECONDS)) {
+ running.release();
+ // this means that the server has been stopped as we
could acquire the semaphore... returning now
+ break;
+ }
+ check();
+ }
+ } catch (InterruptedException interrupted) {
+ // i will just leave on that case
+ }
+ }
+ };
+
+ thread.setDaemon(true);
+
+ thread.start();
+ }
+
+ @Override
+ public void stop() {
--- End diff --
having start and stop, is a little risky for someone to miss remember to
put the stop in a try, finally block in code which if forgot the stop could be
quite fatal.
An option (but may not be the right solution to the above problem) - is
should it accept a lamda function / runnable / callable being the section to
monitor. as such the try final can be in the core analyser and less likely or
people to forget/miss later.
The other option is that theres some static code analysis check to ensure
if started there is a try finally stop within a method
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