| 1 | /* |
| 2 | * Copyright 2006-2007 the original author or authors. |
| 3 | * |
| 4 | * Licensed under the Apache License, Version 2.0 (the "License"); |
| 5 | * you may not use this file except in compliance with the License. |
| 6 | * You may obtain a copy of the License at |
| 7 | * |
| 8 | * http://www.apache.org/licenses/LICENSE-2.0 |
| 9 | * |
| 10 | * Unless required by applicable law or agreed to in writing, software |
| 11 | * distributed under the License is distributed on an "AS IS" BASIS, |
| 12 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| 13 | * See the License for the specific language governing permissions and |
| 14 | * limitations under the License. |
| 15 | */ |
| 16 | |
| 17 | package org.springframework.batch.repeat.support; |
| 18 | |
| 19 | import org.springframework.batch.repeat.RepeatCallback; |
| 20 | import org.springframework.batch.repeat.RepeatContext; |
| 21 | import org.springframework.batch.repeat.RepeatException; |
| 22 | import org.springframework.batch.repeat.RepeatOperations; |
| 23 | import org.springframework.batch.repeat.RepeatStatus; |
| 24 | import org.springframework.core.task.SyncTaskExecutor; |
| 25 | import org.springframework.core.task.TaskExecutor; |
| 26 | import org.springframework.util.Assert; |
| 27 | |
| 28 | /** |
| 29 | * Provides {@link RepeatOperations} support including interceptors that can be |
| 30 | * used to modify or monitor the behaviour at run time.<br/> |
| 31 | * |
| 32 | * This implementation is sufficient to be used to configure transactional |
| 33 | * behaviour for each item by making the {@link RepeatCallback} transactional, |
| 34 | * or for the whole batch by making the execute method transactional (but only |
| 35 | * then if the task executor is synchronous).<br/> |
| 36 | * |
| 37 | * This class is thread safe if its collaborators are thread safe (interceptors, |
| 38 | * terminationPolicy, callback). Normally this will be the case, but clients |
| 39 | * need to be aware that if the task executor is asynchronous, then the other |
| 40 | * collaborators should be also. In particular the {@link RepeatCallback} that |
| 41 | * is wrapped in the execute method must be thread safe - often it is based on |
| 42 | * some form of data source, which itself should be both thread safe and |
| 43 | * transactional (multiple threads could be accessing it at any given time, and |
| 44 | * each thread would have its own transaction).<br/> |
| 45 | * |
| 46 | * @author Dave Syer |
| 47 | * |
| 48 | */ |
| 49 | public class TaskExecutorRepeatTemplate extends RepeatTemplate { |
| 50 | |
| 51 | /** |
| 52 | * Default limit for maximum number of concurrent unfinished results allowed |
| 53 | * by the template. |
| 54 | * {@link #getNextResult(RepeatContext, RepeatCallback, RepeatInternalState)} |
| 55 | * . |
| 56 | */ |
| 57 | public static final int DEFAULT_THROTTLE_LIMIT = 4; |
| 58 | |
| 59 | private int throttleLimit = DEFAULT_THROTTLE_LIMIT; |
| 60 | |
| 61 | private TaskExecutor taskExecutor = new SyncTaskExecutor(); |
| 62 | |
| 63 | /** |
| 64 | * Public setter for the throttle limit. The throttle limit is the largest |
| 65 | * number of concurrent tasks that can be executing at one time - if a new |
| 66 | * task arrives and the throttle limit is breached we wait for one of the |
| 67 | * executing tasks to finish before submitting the new one to the |
| 68 | * {@link TaskExecutor}. Default value is {@link #DEFAULT_THROTTLE_LIMIT}. |
| 69 | * N.B. when used with a thread pooled {@link TaskExecutor} the thread pool |
| 70 | * might prevent the throttle limit actually being reached (so make the core |
| 71 | * pool size larger than the throttle limit if possible). |
| 72 | * |
| 73 | * @param throttleLimit the throttleLimit to set. |
| 74 | */ |
| 75 | public void setThrottleLimit(int throttleLimit) { |
| 76 | this.throttleLimit = throttleLimit; |
| 77 | } |
| 78 | |
| 79 | /** |
| 80 | * Setter for task executor to be used to run the individual item callbacks. |
| 81 | * |
| 82 | * @param taskExecutor a TaskExecutor |
| 83 | * @throws IllegalArgumentException if the argument is null |
| 84 | */ |
| 85 | public void setTaskExecutor(TaskExecutor taskExecutor) { |
| 86 | Assert.notNull(taskExecutor); |
| 87 | this.taskExecutor = taskExecutor; |
| 88 | } |
| 89 | |
| 90 | /** |
| 91 | * Use the {@link #setTaskExecutor(TaskExecutor)} to generate a result. The |
| 92 | * internal state in this case is a queue of unfinished result holders of |
| 93 | * type {@link ResultHolder}. The holder with the return value should not be |
| 94 | * on the queue when this method exits. The queue is scoped in the calling |
| 95 | * method so there is no need to synchronize access. |
| 96 | * |
| 97 | */ |
| 98 | protected RepeatStatus getNextResult(RepeatContext context, RepeatCallback callback, RepeatInternalState state) |
| 99 | throws Throwable { |
| 100 | |
| 101 | ExecutingRunnable runnable = null; |
| 102 | |
| 103 | ResultQueue<ResultHolder> queue = ((ResultQueueInternalState) state).getResultQueue(); |
| 104 | |
| 105 | do { |
| 106 | |
| 107 | /* |
| 108 | * Wrap the callback in a runnable that will add its result to the |
| 109 | * queue when it is ready. |
| 110 | */ |
| 111 | runnable = new ExecutingRunnable(callback, context, queue); |
| 112 | |
| 113 | /** |
| 114 | * Tell the runnable that it can expect a result. This could have |
| 115 | * been in-lined with the constructor, but it might block, so it's |
| 116 | * better to do it here, since we have the option (it's a private |
| 117 | * class). |
| 118 | */ |
| 119 | runnable.expect(); |
| 120 | |
| 121 | /* |
| 122 | * Start the task possibly concurrently / in the future. |
| 123 | */ |
| 124 | taskExecutor.execute(runnable); |
| 125 | |
| 126 | /* |
| 127 | * Allow termination policy to update its state. This must happen |
| 128 | * immediately before or after the call to the task executor. |
| 129 | */ |
| 130 | update(context); |
| 131 | |
| 132 | /* |
| 133 | * Keep going until we get a result that is finished, or early |
| 134 | * termination... |
| 135 | */ |
| 136 | } while (queue.isEmpty() && !isComplete(context)); |
| 137 | |
| 138 | /* |
| 139 | * N.B. If the queue is empty then take() blocks until a result appears, |
| 140 | * and there must be at least one because we just submitted one to the |
| 141 | * task executor. |
| 142 | */ |
| 143 | ResultHolder result = queue.take(); |
| 144 | if (result.getError() != null) { |
| 145 | throw result.getError(); |
| 146 | } |
| 147 | return result.getResult(); |
| 148 | } |
| 149 | |
| 150 | /** |
| 151 | * Wait for all the results to appear on the queue and execute the after |
| 152 | * interceptors for each one. |
| 153 | * |
| 154 | * @see org.springframework.batch.repeat.support.RepeatTemplate#waitForResults(org.springframework.batch.repeat.support.RepeatInternalState) |
| 155 | */ |
| 156 | protected boolean waitForResults(RepeatInternalState state) { |
| 157 | |
| 158 | ResultQueue<ResultHolder> queue = ((ResultQueueInternalState) state).getResultQueue(); |
| 159 | |
| 160 | boolean result = true; |
| 161 | |
| 162 | while (queue.isExpecting()) { |
| 163 | |
| 164 | /* |
| 165 | * Careful that no runnables that are not going to finish ever get |
| 166 | * onto the queue, else this may block forever. |
| 167 | */ |
| 168 | ResultHolder future; |
| 169 | try { |
| 170 | future = queue.take(); |
| 171 | } |
| 172 | catch (InterruptedException e) { |
| 173 | Thread.currentThread().interrupt(); |
| 174 | throw new RepeatException("InterruptedException while waiting for result."); |
| 175 | } |
| 176 | |
| 177 | if (future.getError() != null) { |
| 178 | state.getThrowables().add(future.getError()); |
| 179 | result = false; |
| 180 | } |
| 181 | else { |
| 182 | RepeatStatus status = future.getResult(); |
| 183 | result = result && canContinue(status); |
| 184 | executeAfterInterceptors(future.getContext(), status); |
| 185 | } |
| 186 | |
| 187 | } |
| 188 | |
| 189 | Assert.state(queue.isEmpty(), "Future results queue should be empty at end of batch."); |
| 190 | |
| 191 | return result; |
| 192 | } |
| 193 | |
| 194 | protected RepeatInternalState createInternalState(RepeatContext context) { |
| 195 | // Queue of pending results: |
| 196 | return new ResultQueueInternalState(throttleLimit); |
| 197 | } |
| 198 | |
| 199 | /** |
| 200 | * A runnable that puts its result on a queue when it is done. |
| 201 | * |
| 202 | * @author Dave Syer |
| 203 | * |
| 204 | */ |
| 205 | private class ExecutingRunnable implements Runnable, ResultHolder { |
| 206 | |
| 207 | private final RepeatCallback callback; |
| 208 | |
| 209 | private final RepeatContext context; |
| 210 | |
| 211 | private final ResultQueue<ResultHolder> queue; |
| 212 | |
| 213 | private volatile RepeatStatus result; |
| 214 | |
| 215 | private volatile Throwable error; |
| 216 | |
| 217 | public ExecutingRunnable(RepeatCallback callback, RepeatContext context, ResultQueue<ResultHolder> queue) { |
| 218 | |
| 219 | super(); |
| 220 | |
| 221 | this.callback = callback; |
| 222 | this.context = context; |
| 223 | this.queue = queue; |
| 224 | |
| 225 | } |
| 226 | |
| 227 | /** |
| 228 | * Tell the queue to expect a result. |
| 229 | */ |
| 230 | public void expect() { |
| 231 | try { |
| 232 | queue.expect(); |
| 233 | } |
| 234 | catch (InterruptedException e) { |
| 235 | Thread.currentThread().interrupt(); |
| 236 | throw new RepeatException("InterruptedException waiting for to acquire lock on input."); |
| 237 | } |
| 238 | } |
| 239 | |
| 240 | /** |
| 241 | * Execute the batch callback, and store the result, or any exception |
| 242 | * that is thrown for retrieval later by caller. |
| 243 | * |
| 244 | * @see java.lang.Runnable#run() |
| 245 | */ |
| 246 | public void run() { |
| 247 | boolean clearContext = false; |
| 248 | try { |
| 249 | if (RepeatSynchronizationManager.getContext() == null) { |
| 250 | clearContext = true; |
| 251 | RepeatSynchronizationManager.register(context); |
| 252 | } |
| 253 | |
| 254 | if (logger.isDebugEnabled()) { |
| 255 | logger.debug("Repeat operation about to start at count=" + context.getStartedCount()); |
| 256 | } |
| 257 | |
| 258 | result = callback.doInIteration(context); |
| 259 | |
| 260 | } |
| 261 | catch (Exception e) { |
| 262 | error = e; |
| 263 | } |
| 264 | finally { |
| 265 | |
| 266 | if (clearContext) { |
| 267 | RepeatSynchronizationManager.clear(); |
| 268 | } |
| 269 | |
| 270 | queue.put(this); |
| 271 | |
| 272 | } |
| 273 | } |
| 274 | |
| 275 | /** |
| 276 | * Get the result - never blocks because the queue manages waiting for |
| 277 | * the task to finish. |
| 278 | */ |
| 279 | public RepeatStatus getResult() { |
| 280 | return result; |
| 281 | } |
| 282 | |
| 283 | /** |
| 284 | * Get the error - never blocks because the queue manages waiting for |
| 285 | * the task to finish. |
| 286 | */ |
| 287 | public Throwable getError() { |
| 288 | return error; |
| 289 | } |
| 290 | |
| 291 | /** |
| 292 | * Getter for the context. |
| 293 | */ |
| 294 | public RepeatContext getContext() { |
| 295 | return this.context; |
| 296 | } |
| 297 | |
| 298 | } |
| 299 | |
| 300 | /** |
| 301 | * @author Dave Syer |
| 302 | * |
| 303 | */ |
| 304 | private static class ResultQueueInternalState extends RepeatInternalStateSupport { |
| 305 | |
| 306 | private final ResultQueue<ResultHolder> results; |
| 307 | |
| 308 | /** |
| 309 | * @param throttleLimit the throttle limit for the result queue |
| 310 | */ |
| 311 | public ResultQueueInternalState(int throttleLimit) { |
| 312 | super(); |
| 313 | this.results = new ResultHolderResultQueue(throttleLimit); |
| 314 | } |
| 315 | |
| 316 | /** |
| 317 | * @return the result queue |
| 318 | */ |
| 319 | public ResultQueue<ResultHolder> getResultQueue() { |
| 320 | return results; |
| 321 | } |
| 322 | |
| 323 | } |
| 324 | |
| 325 | } |