/*
* Copyright 2012 Amazon.com, Inc. or its affiliates. All Rights Reserved.
*
* Licensed under the Apache License, Version 2.0 (the "License"). You may not
* use this file except in compliance with the License. A copy of the License is
* located at
*
* http://aws.amazon.com/apache2.0
*
* or in the "license" file accompanying this file. This file 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.amazonaws.services.simpleworkflow.flow.interceptors;
import java.util.concurrent.CancellationException;
import com.amazonaws.services.simpleworkflow.flow.core.Cancelable;
import com.amazonaws.services.simpleworkflow.flow.core.Settable;
import com.amazonaws.services.simpleworkflow.flow.core.Task;
import com.amazonaws.services.simpleworkflow.flow.core.TryCatchFinally;
/**
* Cancels and reexecutes a command when {@link #cancelCurrentAndReexecute()} is
* called. In case of command failures or successful completions it is not
* reexecuted.
*
* @author fateev
*/
public class AsyncCancelAndRetryExecutor implements AsyncExecutor {
private Cancelable currentCommandTryCatchFinally;
private Settable<Void> commandDone;
/**
* Used to inhibit retry in case of failures or successful completions
*/
private boolean cancelledDueToRetryRequest;
protected AsyncRunnable command;
@Override
public void execute(final AsyncRunnable cmd) {
if (currentCommandTryCatchFinally != null) {
throw new IllegalStateException("Already executing a command");
}
command = cmd;
currentCommandTryCatchFinally = new TryCatchFinally() {
@Override
protected void doTry() throws Throwable {
cmd.run();
}
@Override
protected void doCatch(Throwable e) throws Throwable {
if (e instanceof CancellationException && commandDone != null) {
cancelledDueToRetryRequest = true;
}
else {
throw e;
}
}
@Override
protected void doFinally() throws Throwable {
if (!cancelledDueToRetryRequest) {
command = null;
}
if (commandDone != null) {
commandDone.set(null);
}
commandDone = null;
currentCommandTryCatchFinally = null;
}
};
}
public void cancelCurrentAndReexecute() {
if (currentCommandTryCatchFinally != null) {
// Skip duplicated calls to cancelCurrentAndReexecute
if (commandDone == null) {
commandDone = new Settable<Void>();
currentCommandTryCatchFinally.cancel(null);
new Task(commandDone) {
@Override
protected void doExecute() throws Throwable {
if (cancelledDueToRetryRequest) {
execute(command);
}
}
};
}
}
}
}