Felix Meschberger | 9e60059 | 2010-10-10 21:14:10 +0000 | [diff] [blame] | 1 | /* |
| 2 | * Licensed to the Apache Software Foundation (ASF) under one |
| 3 | * or more contributor license agreements. See the NOTICE file |
| 4 | * distributed with this work for additional information |
| 5 | * regarding copyright ownership. The ASF licenses this file |
| 6 | * to you under the Apache License, Version 2.0 (the |
| 7 | * "License"); you may not use this file except in compliance |
| 8 | * with the License. You may obtain a copy of the License at |
| 9 | * |
| 10 | * http://www.apache.org/licenses/LICENSE-2.0 |
| 11 | * |
| 12 | * Unless required by applicable law or agreed to in writing, |
| 13 | * software distributed under the License is distributed on an |
| 14 | * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY |
| 15 | * KIND, either express or implied. See the License for the |
| 16 | * specific language governing permissions and limitations |
| 17 | * under the License. |
| 18 | */ |
| 19 | package org.apache.felix.coordination.impl; |
| 20 | |
| 21 | import java.util.ArrayList; |
| 22 | import java.util.Collection; |
Felix Meschberger | 0055b31 | 2010-10-13 07:39:32 +0000 | [diff] [blame^] | 23 | import java.util.Collections; |
Felix Meschberger | 9e60059 | 2010-10-10 21:14:10 +0000 | [diff] [blame] | 24 | import java.util.HashMap; |
| 25 | import java.util.Map; |
Felix Meschberger | 0055b31 | 2010-10-13 07:39:32 +0000 | [diff] [blame^] | 26 | import java.util.TimerTask; |
Felix Meschberger | 9e60059 | 2010-10-10 21:14:10 +0000 | [diff] [blame] | 27 | |
| 28 | import org.apache.felix.service.coordination.Coordination; |
| 29 | import org.apache.felix.service.coordination.Participant; |
| 30 | |
| 31 | @SuppressWarnings("deprecation") |
| 32 | public class CoordinationImpl implements Coordination { |
| 33 | |
| 34 | private enum State { |
| 35 | /** Active */ |
| 36 | ACTIVE, |
| 37 | |
| 38 | /** Coordination termination started */ |
| 39 | TERMINATING, |
| 40 | |
| 41 | /** Coordination completed */ |
| 42 | TERMINATED, |
| 43 | |
| 44 | /** Coordination failed */ |
| 45 | FAILED; |
| 46 | } |
| 47 | |
Felix Meschberger | 0055b31 | 2010-10-13 07:39:32 +0000 | [diff] [blame^] | 48 | private final CoordinationMgr mgr; |
| 49 | |
Felix Meschberger | 9e60059 | 2010-10-10 21:14:10 +0000 | [diff] [blame] | 50 | private final long id; |
| 51 | |
| 52 | private final String name; |
| 53 | |
| 54 | // TODO: timeout must be enforced |
| 55 | private long timeOutInMs; |
| 56 | |
Felix Meschberger | 0055b31 | 2010-10-13 07:39:32 +0000 | [diff] [blame^] | 57 | /** |
| 58 | * Access to this field must be synchronized as long as the expected state |
| 59 | * is {@link State#ACTIVE}. Once the state has changed, further updates to |
| 60 | * this instance will not take place any more and the state will only be |
| 61 | * modified by the thread successfully setting the state to |
| 62 | * {@link State#TERMINATING}. |
| 63 | */ |
| 64 | private volatile State state; |
Felix Meschberger | 9e60059 | 2010-10-10 21:14:10 +0000 | [diff] [blame] | 65 | |
Felix Meschberger | 0055b31 | 2010-10-13 07:39:32 +0000 | [diff] [blame^] | 66 | private int mustFail; |
Felix Meschberger | 9e60059 | 2010-10-10 21:14:10 +0000 | [diff] [blame] | 67 | |
Felix Meschberger | 0055b31 | 2010-10-13 07:39:32 +0000 | [diff] [blame^] | 68 | private Throwable failReason; |
Felix Meschberger | 9e60059 | 2010-10-10 21:14:10 +0000 | [diff] [blame] | 69 | |
| 70 | private ArrayList<Participant> participants; |
| 71 | |
| 72 | private HashMap<Class<?>, Object> variables; |
| 73 | |
Felix Meschberger | 0055b31 | 2010-10-13 07:39:32 +0000 | [diff] [blame^] | 74 | private TimerTask timeoutTask; |
| 75 | |
| 76 | private Thread initiatorThread; |
| 77 | |
| 78 | public CoordinationImpl(final CoordinationMgr mgr, final long id, |
| 79 | final String name, final long defaultTimeOutInMs) { |
| 80 | this.mgr = mgr; |
Felix Meschberger | 9e60059 | 2010-10-10 21:14:10 +0000 | [diff] [blame] | 81 | this.id = id; |
| 82 | this.name = name; |
Felix Meschberger | 0055b31 | 2010-10-13 07:39:32 +0000 | [diff] [blame^] | 83 | this.mustFail = 0; |
Felix Meschberger | 9e60059 | 2010-10-10 21:14:10 +0000 | [diff] [blame] | 84 | this.state = State.ACTIVE; |
| 85 | this.participants = new ArrayList<Participant>(); |
| 86 | this.variables = new HashMap<Class<?>, Object>(); |
Felix Meschberger | 0055b31 | 2010-10-13 07:39:32 +0000 | [diff] [blame^] | 87 | this.timeOutInMs = -defaultTimeOutInMs; |
| 88 | this.initiatorThread = Thread.currentThread(); |
| 89 | |
| 90 | scheduleTimeout(defaultTimeOutInMs); |
Felix Meschberger | 9e60059 | 2010-10-10 21:14:10 +0000 | [diff] [blame] | 91 | } |
| 92 | |
| 93 | public String getName() { |
| 94 | return name; |
| 95 | } |
| 96 | |
| 97 | long getId() { |
| 98 | return this.id; |
| 99 | } |
| 100 | |
Felix Meschberger | 0055b31 | 2010-10-13 07:39:32 +0000 | [diff] [blame^] | 101 | void mustFail(final Throwable reason) { |
| 102 | this.mustFail = FAILED; |
| 103 | this.failReason = reason; |
Felix Meschberger | 9e60059 | 2010-10-10 21:14:10 +0000 | [diff] [blame] | 104 | } |
| 105 | |
Felix Meschberger | 0055b31 | 2010-10-13 07:39:32 +0000 | [diff] [blame^] | 106 | /** |
| 107 | * Initiates a coordination timeout. Called from the timer task scheduled by |
| 108 | * the {@link #scheduleTimeout(long)} method. |
| 109 | * <p> |
| 110 | * This method is inteded to only be called from the scheduled timer task. |
| 111 | */ |
Felix Meschberger | 9e60059 | 2010-10-10 21:14:10 +0000 | [diff] [blame] | 112 | void timeout() { |
Felix Meschberger | 0055b31 | 2010-10-13 07:39:32 +0000 | [diff] [blame^] | 113 | // If a timeout happens, the coordination thread is set to always fail |
| 114 | this.mustFail = TIMEOUT; |
| 115 | |
| 116 | // and interrupted and a small delay happens to allow the initiator to |
| 117 | // clean up by reacting on the interrupt. If the initiator can do this |
| 118 | // clean up normally, the end() method will return TIMEOUT. |
| 119 | try { |
| 120 | initiatorThread.interrupt(); |
| 121 | Thread.sleep(500); // half a second for now |
| 122 | } catch (SecurityException se) { |
| 123 | // thrown by interrupt -- no need to wait if interrupt fails |
| 124 | } catch (InterruptedException ie) { |
| 125 | // someone interrupted us while delaying, just continue |
| 126 | } |
| 127 | |
| 128 | // After this delay the coordination is forcefully failed. |
| 129 | CoordinationImpl.this.fail(null); |
Felix Meschberger | 9e60059 | 2010-10-10 21:14:10 +0000 | [diff] [blame] | 130 | } |
| 131 | |
| 132 | long getTimeOut() { |
| 133 | return this.timeOutInMs; |
| 134 | } |
| 135 | |
| 136 | public int end() throws IllegalStateException { |
Felix Meschberger | 0055b31 | 2010-10-13 07:39:32 +0000 | [diff] [blame^] | 137 | if (startTermination()) { |
| 138 | if (mustFail != 0) { |
| 139 | failInternal(); |
| 140 | return mustFail; |
Felix Meschberger | 9e60059 | 2010-10-10 21:14:10 +0000 | [diff] [blame] | 141 | } |
Felix Meschberger | 0055b31 | 2010-10-13 07:39:32 +0000 | [diff] [blame^] | 142 | return endInternal(); |
Felix Meschberger | 9e60059 | 2010-10-10 21:14:10 +0000 | [diff] [blame] | 143 | } |
| 144 | |
| 145 | // already terminated |
| 146 | throw new IllegalStateException(); |
| 147 | } |
| 148 | |
| 149 | public boolean fail(Throwable reason) { |
Felix Meschberger | 0055b31 | 2010-10-13 07:39:32 +0000 | [diff] [blame^] | 150 | if (startTermination()) { |
| 151 | this.failReason = reason; |
| 152 | failInternal(); |
Felix Meschberger | 9e60059 | 2010-10-10 21:14:10 +0000 | [diff] [blame] | 153 | return true; |
| 154 | } |
| 155 | return false; |
| 156 | } |
| 157 | |
| 158 | public boolean terminate() { |
| 159 | if (state == State.ACTIVE) { |
Felix Meschberger | 0055b31 | 2010-10-13 07:39:32 +0000 | [diff] [blame^] | 160 | try { |
| 161 | end(); |
| 162 | return true; |
| 163 | } catch (IllegalStateException ise) { |
| 164 | // another thread might have started the termination just |
| 165 | // after the current thread checked the state but before the |
| 166 | // end() method called on this thread was able to change the |
| 167 | // state. Just ignore this exception and continue. |
| 168 | } |
Felix Meschberger | 9e60059 | 2010-10-10 21:14:10 +0000 | [diff] [blame] | 169 | } |
| 170 | return false; |
| 171 | } |
| 172 | |
Felix Meschberger | 0055b31 | 2010-10-13 07:39:32 +0000 | [diff] [blame^] | 173 | /** |
| 174 | * Returns whether the coordination has ended in failure. |
| 175 | * <p> |
| 176 | * The return value of <code>false</code> may be a transient situation if |
| 177 | * the coordination is in the process of terminating due to a failure. |
| 178 | */ |
Felix Meschberger | 9e60059 | 2010-10-10 21:14:10 +0000 | [diff] [blame] | 179 | public boolean isFailed() { |
| 180 | return state == State.FAILED; |
| 181 | } |
| 182 | |
| 183 | public void addTimeout(long timeOutInMs) { |
Felix Meschberger | 0055b31 | 2010-10-13 07:39:32 +0000 | [diff] [blame^] | 184 | if (this.timeOutInMs > 0) { |
| 185 | // already set, ignore |
| 186 | } |
| 187 | |
Felix Meschberger | 9e60059 | 2010-10-10 21:14:10 +0000 | [diff] [blame] | 188 | this.timeOutInMs = timeOutInMs; |
Felix Meschberger | 0055b31 | 2010-10-13 07:39:32 +0000 | [diff] [blame^] | 189 | scheduleTimeout(timeOutInMs); |
Felix Meschberger | 9e60059 | 2010-10-10 21:14:10 +0000 | [diff] [blame] | 190 | } |
| 191 | |
Felix Meschberger | 0055b31 | 2010-10-13 07:39:32 +0000 | [diff] [blame^] | 192 | /** |
| 193 | * Adds the participant to the end of the list of participants of this |
| 194 | * coordination. |
| 195 | * <p> |
| 196 | * This method blocks if the given participant is currently participating in |
| 197 | * another coordination. |
| 198 | * <p> |
| 199 | * Participants can only be added to a coordination if it is active. |
| 200 | * |
| 201 | * @throws org.apache.felix.service.coordination.CoordinationException if |
| 202 | * the participant cannot currently participate in this |
| 203 | * coordination |
| 204 | */ |
Felix Meschberger | 9e60059 | 2010-10-10 21:14:10 +0000 | [diff] [blame] | 205 | public boolean participate(Participant p) { |
Felix Meschberger | 0055b31 | 2010-10-13 07:39:32 +0000 | [diff] [blame^] | 206 | |
| 207 | // ensure participant only pariticipates on a single coordination |
| 208 | // this blocks until the participant can participate or until |
| 209 | // a timeout occurrs (or a deadlock is detected) |
| 210 | mgr.lockParticipant(p, this); |
| 211 | |
| 212 | // synchronize access to the state to prevent it from being changed |
| 213 | // while adding the participant |
| 214 | synchronized (this) { |
| 215 | if (state == State.ACTIVE) { |
| 216 | if (!participants.contains(p)) { |
| 217 | participants.add(p); |
| 218 | } |
| 219 | return true; |
Felix Meschberger | 9e60059 | 2010-10-10 21:14:10 +0000 | [diff] [blame] | 220 | } |
Felix Meschberger | 0055b31 | 2010-10-13 07:39:32 +0000 | [diff] [blame^] | 221 | return false; |
Felix Meschberger | 9e60059 | 2010-10-10 21:14:10 +0000 | [diff] [blame] | 222 | } |
Felix Meschberger | 9e60059 | 2010-10-10 21:14:10 +0000 | [diff] [blame] | 223 | } |
| 224 | |
| 225 | public Collection<Participant> getParticipants() { |
Felix Meschberger | 0055b31 | 2010-10-13 07:39:32 +0000 | [diff] [blame^] | 226 | // synchronize access to the state to prevent it from being changed |
| 227 | // while we create a copy of the participant list |
| 228 | synchronized (this) { |
| 229 | if (state == State.ACTIVE) { |
| 230 | return new ArrayList<Participant>(participants); |
| 231 | } |
| 232 | } |
| 233 | |
| 234 | return Collections.<Participant> emptyList(); |
Felix Meschberger | 9e60059 | 2010-10-10 21:14:10 +0000 | [diff] [blame] | 235 | } |
| 236 | |
| 237 | public Map<Class<?>, ?> getVariables() { |
| 238 | return variables; |
| 239 | } |
| 240 | |
Felix Meschberger | 0055b31 | 2010-10-13 07:39:32 +0000 | [diff] [blame^] | 241 | /** |
| 242 | * If this coordination is still active, this method initiates the |
| 243 | * termination of the coordination by setting the state to |
| 244 | * {@value State#TERMINATING}, unregistering from the |
| 245 | * {@link CoordinationMgr} and ensuring there is no timeout task active any |
| 246 | * longer to timeout this coordination. |
| 247 | * |
| 248 | * @return <code>true</code> If the coordination was active and termination |
| 249 | * can continue. If <code>false</code> is returned, the coordination |
| 250 | * must be considered terminated (or terminating) in the current |
| 251 | * thread and no further termination processing must take place. |
| 252 | */ |
| 253 | private synchronized boolean startTermination() { |
| 254 | if (state == State.ACTIVE) { |
| 255 | state = State.TERMINATING; |
| 256 | mgr.unregister(this); |
| 257 | scheduleTimeout(-1); |
| 258 | return true; |
| 259 | } |
| 260 | |
| 261 | // this coordination is not active any longer, nothing to do |
| 262 | return false; |
| 263 | } |
| 264 | |
| 265 | /** |
| 266 | * Internal implemenation of successful termination of the coordination. |
| 267 | * <p> |
| 268 | * This method must only be called after the {@link #state} field has been |
| 269 | * set to {@link State#TERMINATING} and only be the method successfully |
| 270 | * setting this state. |
| 271 | * |
| 272 | * @return OK or PARTIALLY_ENDED depending on whether all participants |
| 273 | * succeeded or some of them failed ending the coordination. |
| 274 | */ |
| 275 | private int endInternal() { |
| 276 | int reason = OK; |
| 277 | for (Participant part : participants) { |
| 278 | try { |
| 279 | part.ended(this); |
| 280 | } catch (Exception e) { |
| 281 | // TODO: log |
| 282 | reason = PARTIALLY_ENDED; |
| 283 | } |
| 284 | |
| 285 | // release the participant for other coordinations |
| 286 | mgr.releaseParticipant(part); |
| 287 | } |
| 288 | state = State.TERMINATED; |
| 289 | return reason; |
| 290 | } |
| 291 | |
| 292 | /** |
| 293 | * Internal implemenation of coordination failure. |
| 294 | * <p> |
| 295 | * This method must only be called after the {@link #state} field has been |
| 296 | * set to {@link State#TERMINATING} and only be the method successfully |
| 297 | * setting this state. |
| 298 | */ |
| 299 | private void failInternal() { |
| 300 | // consider failure reason (if not null) |
| 301 | for (Participant part : participants) { |
| 302 | try { |
| 303 | part.failed(this); |
| 304 | } catch (Exception e) { |
| 305 | // TODO: log |
| 306 | } |
| 307 | |
| 308 | // release the participant for other coordinations |
| 309 | mgr.releaseParticipant(part); |
| 310 | } |
| 311 | state = State.FAILED; |
| 312 | } |
| 313 | |
| 314 | /** |
| 315 | * Helper method for timeout scheduling. If a timer is currently scheduled |
| 316 | * it is canceled. If the new timeout value is a positive value a new timer |
| 317 | * is scheduled to fire of so many milliseconds from now. |
| 318 | * |
| 319 | * @param timeout The new timeout value |
| 320 | */ |
| 321 | private void scheduleTimeout(final long timeout) { |
| 322 | if (timeoutTask != null) { |
| 323 | mgr.schedule(timeoutTask, -1); |
| 324 | timeoutTask = null; |
| 325 | } |
| 326 | |
| 327 | if (timeout > 0) { |
| 328 | timeoutTask = new TimerTask() { |
| 329 | @Override |
| 330 | public void run() { |
| 331 | CoordinationImpl.this.timeout(); |
| 332 | } |
| 333 | }; |
| 334 | |
| 335 | mgr.schedule(timeoutTask, timeout); |
| 336 | } |
| 337 | } |
Felix Meschberger | 9e60059 | 2010-10-10 21:14:10 +0000 | [diff] [blame] | 338 | } |