| /* |
| * |
| * 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.bookkeeper.client; |
| |
| import com.google.common.util.concurrent.FutureCallback; |
| import com.google.common.util.concurrent.Futures; |
| import com.google.common.util.concurrent.ListenableFuture; |
| |
| import java.util.concurrent.RejectedExecutionException; |
| import java.util.concurrent.ScheduledExecutorService; |
| import java.util.concurrent.ScheduledFuture; |
| import java.util.concurrent.TimeUnit; |
| |
| import org.slf4j.Logger; |
| import org.slf4j.LoggerFactory; |
| |
| /** |
| * A default implementation of {@link SpeculativeRequestExecutionPolicy}. |
| * |
| * <p>The policy issues speculative requests in a backoff way. The time between two speculative requests |
| * are between {@code firstSpeculativeRequestTimeout} and {@code maxSpeculativeRequestTimeout}. |
| */ |
| public class DefaultSpeculativeRequestExecutionPolicy implements SpeculativeRequestExecutionPolicy { |
| private static final Logger LOG = LoggerFactory.getLogger(DefaultSpeculativeRequestExecutionPolicy.class); |
| final int firstSpeculativeRequestTimeout; |
| final int maxSpeculativeRequestTimeout; |
| final float backoffMultiplier; |
| |
| public DefaultSpeculativeRequestExecutionPolicy(int firstSpeculativeRequestTimeout, |
| int maxSpeculativeRequestTimeout, float backoffMultiplier) { |
| this.firstSpeculativeRequestTimeout = firstSpeculativeRequestTimeout; |
| this.maxSpeculativeRequestTimeout = maxSpeculativeRequestTimeout; |
| this.backoffMultiplier = backoffMultiplier; |
| |
| if (backoffMultiplier <= 0) { |
| throw new IllegalArgumentException("Invalid value provided for backoffMultiplier"); |
| } |
| |
| // Prevent potential over flow |
| if (Math.round((double) maxSpeculativeRequestTimeout * (double) backoffMultiplier) > Integer.MAX_VALUE) { |
| throw new IllegalArgumentException("Invalid values for maxSpeculativeRequestTimeout and backoffMultiplier"); |
| } |
| } |
| |
| /** |
| * Initialize the speculative request execution policy. |
| * |
| * @param scheduler The scheduler service to issue the speculative request |
| * @param requestExecutor The executor is used to issue the actual speculative requests |
| * @return ScheduledFuture, in case caller needs to cancel it. |
| */ |
| @Override |
| public ScheduledFuture<?> initiateSpeculativeRequest(final ScheduledExecutorService scheduler, |
| final SpeculativeRequestExecutor requestExecutor) { |
| return scheduleSpeculativeRead(scheduler, requestExecutor, firstSpeculativeRequestTimeout); |
| } |
| |
| private ScheduledFuture<?> scheduleSpeculativeRead(final ScheduledExecutorService scheduler, |
| final SpeculativeRequestExecutor requestExecutor, |
| final int speculativeRequestTimeout) { |
| try { |
| return scheduler.schedule(new Runnable() { |
| @Override |
| public void run() { |
| ListenableFuture<Boolean> issueNextRequest = requestExecutor.issueSpeculativeRequest(); |
| Futures.addCallback(issueNextRequest, new FutureCallback<Boolean>() { |
| // we want this handler to run immediately after we push the big red button! |
| public void onSuccess(Boolean issueNextRequest) { |
| if (issueNextRequest) { |
| scheduleSpeculativeRead(scheduler, requestExecutor, |
| Math.min(maxSpeculativeRequestTimeout, |
| Math.round((float) speculativeRequestTimeout * backoffMultiplier))); |
| } else { |
| if (LOG.isTraceEnabled()) { |
| LOG.trace("Stopped issuing speculative requests for {}, " |
| + "speculativeReadTimeout = {}", requestExecutor, speculativeRequestTimeout); |
| } |
| } |
| } |
| |
| public void onFailure(Throwable thrown) { |
| LOG.warn("Failed to issue speculative request for {}, speculativeReadTimeout = {} : ", |
| requestExecutor, speculativeRequestTimeout, thrown); |
| } |
| }); |
| } |
| }, speculativeRequestTimeout, TimeUnit.MILLISECONDS); |
| } catch (RejectedExecutionException re) { |
| if (!scheduler.isShutdown()) { |
| LOG.warn("Failed to schedule speculative request for {}, speculativeReadTimeout = {} : ", |
| requestExecutor, speculativeRequestTimeout, re); |
| } |
| } |
| return null; |
| } |
| } |