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Make Lifecycle ignore repeated stop requests #28

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Merged
xvrl merged 1 commit into from
Nov 12, 2015
Merged

Make Lifecycle ignore repeated stop requests #28

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65 changes: 45 additions & 20 deletions src/main/java/com/metamx/common/lifecycle/Lifecycle.java
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Original file line number Diff line number Diff line change
Expand Up @@ -51,6 +51,7 @@ public class Lifecycle

private final Map<Stage, CopyOnWriteArrayList<Handler>> handlers;
private final AtomicBoolean started = new AtomicBoolean(false);
private final AtomicBoolean shutdownHookRegistered = new AtomicBoolean(false);
private volatile Stage currStage = null;

public static enum Stage
Expand All @@ -72,6 +73,7 @@ public Lifecycle()
* Stage.NORMAL. If the lifecycle has already been started, it throws an {@link ISE}
*
* @param o The object to add to the lifecycle
*
* @throws ISE {@link Lifecycle#addHandler(Handler, Stage)}
*/
public <T> T addManagedInstance(T o)
Expand All @@ -84,8 +86,9 @@ public <T> T addManagedInstance(T o)
* Adds a "managed" instance (annotated with {@link LifecycleStart} and {@link LifecycleStop}) to the Lifecycle.
* If the lifecycle has already been started, it throws an {@link ISE}
*
* @param o The object to add to the lifecycle
* @param o The object to add to the lifecycle
* @param stage The stage to add the lifecycle at
*
* @throws ISE {@link Lifecycle#addHandler(Handler, Stage)}
*/
public <T> T addManagedInstance(T o, Stage stage)
Expand All @@ -99,6 +102,7 @@ public <T> T addManagedInstance(T o, Stage stage)
* already been started, it throws an {@link ISE}
*
* @param o The object to add to the lifecycle
*
* @throws ISE {@link Lifecycle#addHandler(Handler, Stage)}
*/
public <T> T addStartCloseInstance(T o)
Expand All @@ -111,8 +115,9 @@ public <T> T addStartCloseInstance(T o)
* Adds an instance with a start() and/or close() method to the Lifecycle. If the lifecycle has already been started,
* it throws an {@link ISE}
*
* @param o The object to add to the lifecycle
* @param o The object to add to the lifecycle
* @param stage The stage to add the lifecycle at
*
* @throws ISE {@link Lifecycle#addHandler(Handler, Stage)}
*/
public <T> T addStartCloseInstance(T o, Stage stage)
Expand All @@ -126,6 +131,7 @@ public <T> T addStartCloseInstance(T o, Stage stage)
* an {@link ISE}
*
* @param handler The hander to add to the lifecycle
*
* @throws ISE {@link Lifecycle#addHandler(Handler, Stage)}
*/
public void addHandler(Handler handler)
Expand All @@ -137,7 +143,8 @@ public void addHandler(Handler handler)
* Adds a handler to the Lifecycle. If the lifecycle has already been started, it throws an {@link ISE}
*
* @param handler The hander to add to the lifecycle
* @param stage The stage to add the lifecycle at
* @param stage The stage to add the lifecycle at
*
* @throws ISE indicates that the lifecycle has already been started and thus cannot be added to
*/
public void addHandler(Handler handler, Stage stage)
Expand All @@ -155,6 +162,7 @@ public void addHandler(Handler handler, Stage stage)
* Stage.NORMAL and starts it if the lifecycle has already been started.
*
* @param o The object to add to the lifecycle
*
* @throws Exception {@link Lifecycle#addMaybeStartHandler(Handler, Stage)}
*/
public <T> T addMaybeStartManagedInstance(T o) throws Exception
Expand All @@ -167,8 +175,9 @@ public <T> T addMaybeStartManagedInstance(T o) throws Exception
* Adds a "managed" instance (annotated with {@link LifecycleStart} and {@link LifecycleStop}) to the Lifecycle
* and starts it if the lifecycle has already been started.
*
* @param o The object to add to the lifecycle
* @param o The object to add to the lifecycle
* @param stage The stage to add the lifecycle at
*
* @throws Exception {@link Lifecycle#addMaybeStartHandler(Handler, Stage)}
*/
public <T> T addMaybeStartManagedInstance(T o, Stage stage) throws Exception
Expand All @@ -182,6 +191,7 @@ public <T> T addMaybeStartManagedInstance(T o, Stage stage) throws Exception
* lifecycle has already been started.
*
* @param o The object to add to the lifecycle
*
* @throws Exception {@link Lifecycle#addMaybeStartHandler(Handler, Stage)}
*/
public <T> T addMaybeStartStartCloseInstance(T o) throws Exception
Expand All @@ -194,8 +204,9 @@ public <T> T addMaybeStartStartCloseInstance(T o) throws Exception
* Adds an instance with a start() and/or close() method to the Lifecycle and starts it if the lifecycle has
* already been started.
*
* @param o The object to add to the lifecycle
* @param o The object to add to the lifecycle
* @param stage The stage to add the lifecycle at
*
* @throws Exception {@link Lifecycle#addMaybeStartHandler(Handler, Stage)}
*/
public <T> T addMaybeStartStartCloseInstance(T o, Stage stage) throws Exception
Expand All @@ -208,6 +219,7 @@ public <T> T addMaybeStartStartCloseInstance(T o, Stage stage) throws Exception
* Adds a handler to the Lifecycle at the Stage.NORMAL stage and starts it if the lifecycle has already been started.
*
* @param handler The hander to add to the lifecycle
*
* @throws Exception {@link Lifecycle#addMaybeStartHandler(Handler, Stage)}
*/
public void addMaybeStartHandler(Handler handler) throws Exception
Expand All @@ -219,7 +231,8 @@ public void addMaybeStartHandler(Handler handler) throws Exception
* Adds a handler to the Lifecycle and starts it if the lifecycle has already been started.
*
* @param handler The hander to add to the lifecycle
* @param stage The stage to add the lifecycle at
* @param stage The stage to add the lifecycle at
*
* @throws Exception an exception thrown from handler.start(). If an exception is thrown, the handler is *not* added
*/
public void addMaybeStartHandler(Handler handler, Stage stage) throws Exception
Expand All @@ -237,7 +250,9 @@ public void addMaybeStartHandler(Handler handler, Stage stage) throws Exception
public void start() throws Exception
{
synchronized (handlers) {
started.set(true);
if (!started.compareAndSet(false, true)) {
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@gianm gianm Aug 18, 2015

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Should this be an error? I think unlike stop, there's no good reason for start to be called multiple times

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@drcrallen drcrallen Aug 18, 2015

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Maybe? Prior behavior did not throw an error, which is why I did not do so here.

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@gianm gianm Aug 18, 2015

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I feel like it makes sense to either not change the behavior, or to have it throw an error; silently skipping over double starts seems sketchy. At least the old behavior would probably blow up in some way and let us know something was being done wrong.

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@drcrallen drcrallen Oct 26, 2015

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Fixed

throw new ISE("Already started");
}
for (Stage stage : stagesOrdered()) {
currStage = stage;
for (Handler handler : handlers.get(stage)) {
Expand All @@ -250,6 +265,10 @@ public void start() throws Exception
public void stop()
{
synchronized (handlers) {
if (!started.compareAndSet(true, false)) {
log.info("Already stopped and stop was called. Silently skipping");
return;
}
List<Exception> exceptions = Lists.newArrayList();

for (Stage stage : Lists.reverse(stagesOrdered())) {
Expand All @@ -266,30 +285,35 @@ public void stop()
}
}
}
started.set(false);

if (!exceptions.isEmpty()) {
throw Throwables.propagate(exceptions.get(0));
}
}
}

public void join() throws InterruptedException
public void ensureShutdownHook()
{
Runtime.getRuntime().addShutdownHook(
new Thread(
new Runnable()
{
@Override
public void run()
if (shutdownHookRegistered.compareAndSet(false, true)) {
Runtime.getRuntime().addShutdownHook(
new Thread(
new Runnable()
{
log.info("Running shutdown hook");
stop();
@Override
public void run()
{
log.info("Running shutdown hook");
stop();
}
}
}
)
);
)
);
}
}

public void join() throws InterruptedException
{
ensureShutdownHook();
Thread.currentThread().join();
}

Expand All @@ -302,6 +326,7 @@ private static List<Stage> stagesOrdered()
public static interface Handler
{
public void start() throws Exception;

public void stop();
}

Expand Down
139 changes: 139 additions & 0 deletions src/test/java/com/metamx/common/lifecycle/LifecycleTest.java
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -16,17 +16,156 @@

package com.metamx.common.lifecycle;

import com.google.common.base.Throwables;
import com.google.common.collect.Lists;
import com.google.common.util.concurrent.Futures;
import com.google.common.util.concurrent.ListenableFuture;
import com.google.common.util.concurrent.ListeningExecutorService;
import com.google.common.util.concurrent.MoreExecutors;
import com.metamx.common.ISE;
import org.junit.Assert;
import org.junit.Test;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.List;
import java.util.concurrent.CyclicBarrier;
import java.util.concurrent.Executors;
import java.util.concurrent.atomic.AtomicBoolean;
import java.util.concurrent.atomic.AtomicLong;

/**
*/
public class LifecycleTest
{
@Test
public void testConcurrentStartStopOnce() throws Exception
{
final int numThreads = 10;
ListeningExecutorService executorService = MoreExecutors.listeningDecorator(Executors.newFixedThreadPool(numThreads));

final Lifecycle lifecycle = new Lifecycle();
final AtomicLong startedCount = new AtomicLong(0L);
final AtomicLong failedCount = new AtomicLong(0L);
final Lifecycle.Handler exceptionalHandler = new Lifecycle.Handler()
{
final AtomicBoolean started = new AtomicBoolean(false);

@Override
public void start() throws Exception
{
if (!started.compareAndSet(false, true)) {
failedCount.incrementAndGet();
throw new ISE("Already started");
}
startedCount.incrementAndGet();
}

@Override
public void stop()
{
if (!started.compareAndSet(true, false)) {
failedCount.incrementAndGet();
throw new ISE("Not yet started started");
}
}
};
lifecycle.addHandler(exceptionalHandler);
Collection<ListenableFuture<?>> futures = new ArrayList<>(numThreads);
final CyclicBarrier barrier = new CyclicBarrier(numThreads);
final AtomicBoolean started = new AtomicBoolean(false);
for (int i = 0; i < numThreads; ++i) {
futures.add(
executorService.submit(
new Runnable()
{
@Override
public void run()
{
try {
for (int i = 0; i < 1024; ++i) {
if (started.compareAndSet(false, true)) {
lifecycle.start();
}
barrier.await();
lifecycle.stop();
barrier.await();
started.set(false);
barrier.await();
}
}
catch (InterruptedException e) {
Thread.currentThread().interrupt();
throw Throwables.propagate(e);
}
catch (Exception e) {
throw Throwables.propagate(e);
}
}
}
)
);
}
try {
Futures.allAsList(futures).get();
}
finally {
lifecycle.stop();
}
Assert.assertEquals(0, failedCount.get());
Assert.assertTrue(startedCount.get() > 0);
executorService.shutdownNow();
}

@Test
public void testStartStopOnce() throws Exception
{
final Lifecycle lifecycle = new Lifecycle();
final AtomicLong startedCount = new AtomicLong(0L);
final AtomicLong failedCount = new AtomicLong(0L);
Lifecycle.Handler exceptionalHandler = new Lifecycle.Handler()
{
final AtomicBoolean started = new AtomicBoolean(false);

@Override
public void start() throws Exception
{
if (!started.compareAndSet(false, true)) {
failedCount.incrementAndGet();
throw new ISE("Already started");
}
startedCount.incrementAndGet();
}

@Override
public void stop()
{
if (!started.compareAndSet(true, false)) {
failedCount.incrementAndGet();
throw new ISE("Not yet started started");
}
}
};
lifecycle.addHandler(exceptionalHandler);
lifecycle.start();
lifecycle.stop();
lifecycle.stop();
lifecycle.stop();
lifecycle.start();
lifecycle.stop();
Assert.assertEquals(2, startedCount.get());
Assert.assertEquals(0, failedCount.get());
Exception ex = null;
try {
exceptionalHandler.stop();
}
catch (Exception e) {
ex = e;
}
Assert.assertNotNull("Should have exception", ex);
}

@Test
public void testSanity() throws Exception
{
Expand Down