1 /*
2 * ====================================================================
3 * Licensed to the Apache Software Foundation (ASF) under one
4 * or more contributor license agreements. See the NOTICE file
5 * distributed with this work for additional information
6 * regarding copyright ownership. The ASF licenses this file
7 * to you under the Apache License, Version 2.0 (the
8 * "License"); you may not use this file except in compliance
9 * with the License. You may obtain a copy of the License at
10 *
11 * http://www.apache.org/licenses/LICENSE-2.0
12 *
13 * Unless required by applicable law or agreed to in writing,
14 * software distributed under the License is distributed on an
15 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
16 * KIND, either express or implied. See the License for the
17 * specific language governing permissions and limitations
18 * under the License.
19 * ====================================================================
20 *
21 * This software consists of voluntary contributions made by many
22 * individuals on behalf of the Apache Software Foundation. For more
23 * information on the Apache Software Foundation, please see
24 * <http://www.apache.org/>.
25 *
26 */
27 package org.apache.http.impl.client.cache;
28
29 import java.io.Closeable;
30 import java.io.IOException;
31 import java.util.Collections;
32 import java.util.HashSet;
33 import java.util.Set;
34 import java.util.concurrent.RejectedExecutionException;
35
36 import org.apache.commons.logging.Log;
37 import org.apache.commons.logging.LogFactory;
38 import org.apache.http.client.cache.HttpCacheEntry;
39 import org.apache.http.client.methods.HttpExecutionAware;
40 import org.apache.http.client.methods.HttpRequestWrapper;
41 import org.apache.http.client.protocol.HttpClientContext;
42 import org.apache.http.conn.routing.HttpRoute;
43
44 /**
45 * Class used for asynchronous revalidations to be used when the "stale-
46 * while-revalidate" directive is present
47 */
48 class AsynchronousValidator implements Closeable {
49 private final SchedulingStrategy schedulingStrategy;
50 private final Set<String> queued;
51 private final CacheKeyGenerator cacheKeyGenerator;
52 private final FailureCache failureCache;
53
54 private final Log log = LogFactory.getLog(getClass());
55
56 /**
57 * Create AsynchronousValidator which will make revalidation requests
58 * using an {@link ImmediateSchedulingStrategy}. Its thread
59 * pool will be configured according to the given {@link CacheConfig}.
60 * @param config specifies thread pool settings. See
61 * {@link CacheConfig#getAsynchronousWorkersMax()},
62 * {@link CacheConfig#getAsynchronousWorkersCore()},
63 * {@link CacheConfig#getAsynchronousWorkerIdleLifetimeSecs()},
64 * and {@link CacheConfig#getRevalidationQueueSize()}.
65 */
66 public AsynchronousValidator(final CacheConfig config) {
67 this(new ImmediateSchedulingStrategy(config));
68 }
69
70 /**
71 * Create AsynchronousValidator which will make revalidation requests
72 * using the supplied {@link SchedulingStrategy}. Closing the validator
73 * will also close the given schedulingStrategy.
74 * @param schedulingStrategy used to maintain a pool of worker threads and
75 * schedules when requests are executed
76 */
77 AsynchronousValidator(final SchedulingStrategy schedulingStrategy) {
78 this.schedulingStrategy = schedulingStrategy;
79 this.queued = new HashSet<String>();
80 this.cacheKeyGenerator = new CacheKeyGenerator();
81 this.failureCache = new DefaultFailureCache();
82 }
83
84 @Override
85 public void close() throws IOException {
86 schedulingStrategy.close();
87 }
88
89 /**
90 * Schedules an asynchronous revalidation
91 */
92 public synchronized void revalidateCacheEntry(
93 final CachingExec cachingExec,
94 final HttpRoute route,
95 final HttpRequestWrapper request,
96 final HttpClientContext context,
97 final HttpExecutionAware execAware,
98 final HttpCacheEntry entry) {
99 // getVariantURI will fall back on getURI if no variants exist
100 final String uri = cacheKeyGenerator.getVariantURI(context.getTargetHost(), request, entry);
101
102 if (!queued.contains(uri)) {
103 final int consecutiveFailedAttempts = failureCache.getErrorCount(uri);
104 final AsynchronousValidationRequest revalidationRequest =
105 new AsynchronousValidationRequest(
106 this, cachingExec, route, request, context, execAware, entry, uri, consecutiveFailedAttempts);
107
108 try {
109 schedulingStrategy.schedule(revalidationRequest);
110 queued.add(uri);
111 } catch (final RejectedExecutionException ree) {
112 log.debug("Revalidation for [" + uri + "] not scheduled: " + ree);
113 }
114 }
115 }
116
117 /**
118 * Removes an identifier from the internal list of revalidation jobs in
119 * progress. This is meant to be called by
120 * {@link AsynchronousValidationRequest#run()} once the revalidation is
121 * complete, using the identifier passed in during constructions.
122 * @param identifier
123 */
124 synchronized void markComplete(final String identifier) {
125 queued.remove(identifier);
126 }
127
128 /**
129 * The revalidation job was successful thus the number of consecutive
130 * failed attempts will be reset to zero. Should be called by
131 * {@link AsynchronousValidationRequest#run()}.
132 * @param identifier the revalidation job's unique identifier
133 */
134 void jobSuccessful(final String identifier) {
135 failureCache.resetErrorCount(identifier);
136 }
137
138 /**
139 * The revalidation job did fail and thus the number of consecutive failed
140 * attempts will be increased. Should be called by
141 * {@link AsynchronousValidationRequest#run()}.
142 * @param identifier the revalidation job's unique identifier
143 */
144 void jobFailed(final String identifier) {
145 failureCache.increaseErrorCount(identifier);
146 }
147
148 Set<String> getScheduledIdentifiers() {
149 return Collections.unmodifiableSet(queued);
150 }
151 }