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/*
* Copyright 2011,2012 Metamarkets Group Inc.
*
* 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 com.metamx.common.lifecycle;
import com.google.common.base.Throwables;
import com.google.common.collect.Lists;
import com.google.common.collect.Maps;
import com.metamx.common.ISE;
import com.metamx.common.logger.Logger;
import java.lang.reflect.Method;
import java.util.Arrays;
import java.util.List;
import java.util.ListIterator;
import java.util.Map;
import java.util.concurrent.CopyOnWriteArrayList;
import java.util.concurrent.atomic.AtomicBoolean;
/**
* A manager of object Lifecycles.
*
* This object has methods for registering objects that should be started and stopped. The Lifecycle allows for
* two stages: Stage.NORMAL and Stage.LAST.
*
* Things added at Stage.NORMAL will be started first (in the order that they are added to the Lifecycle instance) and
* then things added at Stage.LAST will be started.
*
* The close operation goes in reverse order, starting with the last thing added at Stage.LAST and working backwards.
*
* There are two sets of methods to add things to the Lifecycle. One set that will just add instances and enforce that
* start() has not been called yet. The other set will add instances and, if the lifecycle is already started, start
* them.
*/
public class Lifecycle
{
private static final Logger log = new Logger(Lifecycle.class);
private final Map> handlers;
private final AtomicBoolean started = new AtomicBoolean(false);
private final AtomicBoolean shutdownHookRegistered = new AtomicBoolean(false);
private volatile Stage currStage = null;
public static enum Stage
{
NORMAL,
LAST
}
public Lifecycle()
{
handlers = Maps.newHashMap();
for (Stage stage : Stage.values()) {
handlers.put(stage, new CopyOnWriteArrayList());
}
}
/**
* Adds a "managed" instance (annotated with {@link LifecycleStart} and {@link LifecycleStop}) to the Lifecycle at
* 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 addManagedInstance(T o)
{
addHandler(new AnnotationBasedHandler(o));
return 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 stage The stage to add the lifecycle at
*
* @throws ISE {@link Lifecycle#addHandler(Handler, Stage)}
*/
public T addManagedInstance(T o, Stage stage)
{
addHandler(new AnnotationBasedHandler(o), stage);
return o;
}
/**
* Adds an instance with a start() and/or close() method to the Lifecycle at 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 addStartCloseInstance(T o)
{
addHandler(new StartCloseHandler(o));
return 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 stage The stage to add the lifecycle at
*
* @throws ISE {@link Lifecycle#addHandler(Handler, Stage)}
*/
public T addStartCloseInstance(T o, Stage stage)
{
addHandler(new StartCloseHandler(o), stage);
return o;
}
/**
* Adds a handler to the Lifecycle at the Stage.NORMAL stage. If the lifecycle has already been started, it throws
* an {@link ISE}
*
* @param handler The hander to add to the lifecycle
*
* @throws ISE {@link Lifecycle#addHandler(Handler, Stage)}
*/
public void addHandler(Handler handler)
{
addHandler(handler, Stage.NORMAL);
}
/**
* 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
*
* @throws ISE indicates that the lifecycle has already been started and thus cannot be added to
*/
public void addHandler(Handler handler, Stage stage)
{
synchronized (handlers) {
if (started.get()) {
throw new ISE("Cannot add a handler after the Lifecycle has started, it doesn't work that way.");
}
handlers.get(stage).add(handler);
}
}
/**
* Adds a "managed" instance (annotated with {@link LifecycleStart} and {@link LifecycleStop}) to the Lifecycle at
* 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 addMaybeStartManagedInstance(T o) throws Exception
{
addMaybeStartHandler(new AnnotationBasedHandler(o));
return o;
}
/**
* 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 stage The stage to add the lifecycle at
*
* @throws Exception {@link Lifecycle#addMaybeStartHandler(Handler, Stage)}
*/
public T addMaybeStartManagedInstance(T o, Stage stage) throws Exception
{
addMaybeStartHandler(new AnnotationBasedHandler(o), stage);
return o;
}
/**
* Adds an instance with a start() and/or close() method to the Lifecycle at 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 addMaybeStartStartCloseInstance(T o) throws Exception
{
addMaybeStartHandler(new StartCloseHandler(o));
return o;
}
/**
* 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 stage The stage to add the lifecycle at
*
* @throws Exception {@link Lifecycle#addMaybeStartHandler(Handler, Stage)}
*/
public T addMaybeStartStartCloseInstance(T o, Stage stage) throws Exception
{
addMaybeStartHandler(new StartCloseHandler(o), stage);
return o;
}
/**
* 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
{
addMaybeStartHandler(handler, Stage.NORMAL);
}
/**
* 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
*
* @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
{
synchronized (handlers) {
if (started.get()) {
if (currStage == null || stage.compareTo(currStage) < 1) {
handler.start();
}
}
handlers.get(stage).add(handler);
}
}
public void start() throws Exception
{
synchronized (handlers) {
if (!started.compareAndSet(false, true)) {
throw new ISE("Already started");
}
for (Stage stage : stagesOrdered()) {
currStage = stage;
for (Handler handler : handlers.get(stage)) {
handler.start();
}
}
}
}
public void stop()
{
synchronized (handlers) {
if (!started.compareAndSet(true, false)) {
log.info("Already stopped and stop was called. Silently skipping");
return;
}
List exceptions = Lists.newArrayList();
for (Stage stage : Lists.reverse(stagesOrdered())) {
final CopyOnWriteArrayList stageHandlers = handlers.get(stage);
final ListIterator iter = stageHandlers.listIterator(stageHandlers.size());
while (iter.hasPrevious()) {
final Handler handler = iter.previous();
try {
handler.stop();
}
catch (Exception e) {
log.warn(e, "exception thrown when stopping %s", handler);
exceptions.add(e);
}
}
}
if (!exceptions.isEmpty()) {
throw Throwables.propagate(exceptions.get(0));
}
}
}
public void ensureShutdownHook()
{
if (shutdownHookRegistered.compareAndSet(false, true)) {
Runtime.getRuntime().addShutdownHook(
new Thread(
new Runnable()
{
@Override
public void run()
{
log.info("Running shutdown hook");
stop();
}
}
)
);
}
}
public void join() throws InterruptedException
{
ensureShutdownHook();
Thread.currentThread().join();
}
private static List stagesOrdered()
{
return Arrays.asList(Stage.NORMAL, Stage.LAST);
}
public static interface Handler
{
public void start() throws Exception;
public void stop();
}
private static class AnnotationBasedHandler implements Handler
{
private static final Logger log = new Logger(AnnotationBasedHandler.class);
private final Object o;
public AnnotationBasedHandler(Object o)
{
this.o = o;
}
@Override
public void start() throws Exception
{
for (Method method : o.getClass().getMethods()) {
if (method.getAnnotation(LifecycleStart.class) != null) {
log.info("Invoking start method[%s] on object[%s].", method, o);
method.invoke(o);
}
}
}
@Override
public void stop()
{
for (Method method : o.getClass().getMethods()) {
if (method.getAnnotation(LifecycleStop.class) != null) {
log.info("Invoking stop method[%s] on object[%s].", method, o);
try {
method.invoke(o);
}
catch (Exception e) {
log.error(e, "Exception when stopping method[%s] on object[%s]", method, o);
}
}
}
}
}
public boolean isStarted()
{
return started.get();
}
private static class StartCloseHandler implements Handler
{
private static final Logger log = new Logger(StartCloseHandler.class);
private final Object o;
private final Method startMethod;
private final Method stopMethod;
public StartCloseHandler(Object o)
{
this.o = o;
try {
startMethod = o.getClass().getMethod("start");
stopMethod = o.getClass().getMethod("close");
}
catch (NoSuchMethodException e) {
throw new RuntimeException(e);
}
}
@Override
public void start() throws Exception
{
log.info("Starting object[%s]", o);
startMethod.invoke(o);
}
@Override
public void stop()
{
log.info("Stopping object[%s]", o);
try {
stopMethod.invoke(o);
}
catch (Exception e) {
log.error(e, "Unable to invoke stopMethod() on %s", o.getClass());
}
}
}
}
