Jake Slack | 03928ae | 2014-05-13 18:41:56 -0700 | [diff] [blame] | 1 | // |
| 2 | // ======================================================================== |
| 3 | // Copyright (c) 1995-2014 Mort Bay Consulting Pty. Ltd. |
| 4 | // ------------------------------------------------------------------------ |
| 5 | // All rights reserved. This program and the accompanying materials |
| 6 | // are made available under the terms of the Eclipse Public License v1.0 |
| 7 | // and Apache License v2.0 which accompanies this distribution. |
| 8 | // |
| 9 | // The Eclipse Public License is available at |
| 10 | // http://www.eclipse.org/legal/epl-v10.html |
| 11 | // |
| 12 | // The Apache License v2.0 is available at |
| 13 | // http://www.opensource.org/licenses/apache2.0.php |
| 14 | // |
| 15 | // You may elect to redistribute this code under either of these licenses. |
| 16 | // ======================================================================== |
| 17 | // |
| 18 | |
| 19 | package org.eclipse.jetty.servlets; |
| 20 | |
| 21 | import java.io.IOException; |
| 22 | import java.util.Queue; |
| 23 | import java.util.concurrent.ConcurrentLinkedQueue; |
| 24 | import java.util.concurrent.Semaphore; |
| 25 | import java.util.concurrent.TimeUnit; |
| 26 | |
| 27 | import javax.servlet.Filter; |
| 28 | import javax.servlet.FilterChain; |
| 29 | import javax.servlet.FilterConfig; |
| 30 | import javax.servlet.ServletContext; |
| 31 | import javax.servlet.ServletException; |
| 32 | import javax.servlet.ServletRequest; |
| 33 | import javax.servlet.ServletResponse; |
| 34 | import javax.servlet.http.HttpServletRequest; |
| 35 | import javax.servlet.http.HttpServletResponse; |
| 36 | import javax.servlet.http.HttpSession; |
| 37 | |
| 38 | import org.eclipse.jetty.continuation.Continuation; |
| 39 | import org.eclipse.jetty.continuation.ContinuationListener; |
| 40 | import org.eclipse.jetty.continuation.ContinuationSupport; |
| 41 | import org.eclipse.jetty.server.handler.ContextHandler; |
| 42 | |
| 43 | /** |
| 44 | * Quality of Service Filter. |
| 45 | * |
| 46 | * This filter limits the number of active requests to the number set by the "maxRequests" init parameter (default 10). |
| 47 | * If more requests are received, they are suspended and placed on priority queues. Priorities are determined by |
| 48 | * the {@link #getPriority(ServletRequest)} method and are a value between 0 and the value given by the "maxPriority" |
| 49 | * init parameter (default 10), with higher values having higher priority. |
| 50 | * </p><p> |
| 51 | * This filter is ideal to prevent wasting threads waiting for slow/limited |
| 52 | * resources such as a JDBC connection pool. It avoids the situation where all of a |
| 53 | * containers thread pool may be consumed blocking on such a slow resource. |
| 54 | * By limiting the number of active threads, a smaller thread pool may be used as |
| 55 | * the threads are not wasted waiting. Thus more memory may be available for use by |
| 56 | * the active threads. |
| 57 | * </p><p> |
| 58 | * Furthermore, this filter uses a priority when resuming waiting requests. So that if |
| 59 | * a container is under load, and there are many requests waiting for resources, |
| 60 | * the {@link #getPriority(ServletRequest)} method is used, so that more important |
| 61 | * requests are serviced first. For example, this filter could be deployed with a |
| 62 | * maxRequest limit slightly smaller than the containers thread pool and a high priority |
| 63 | * allocated to admin users. Thus regardless of load, admin users would always be |
| 64 | * able to access the web application. |
| 65 | * </p><p> |
| 66 | * The maxRequest limit is policed by a {@link Semaphore} and the filter will wait a short while attempting to acquire |
| 67 | * the semaphore. This wait is controlled by the "waitMs" init parameter and allows the expense of a suspend to be |
| 68 | * avoided if the semaphore is shortly available. If the semaphore cannot be obtained, the request will be suspended |
| 69 | * for the default suspend period of the container or the valued set as the "suspendMs" init parameter. |
| 70 | * </p><p> |
| 71 | * If the "managedAttr" init parameter is set to true, then this servlet is set as a {@link ServletContext} attribute with the |
| 72 | * filter name as the attribute name. This allows context external mechanism (eg JMX via {@link ContextHandler#MANAGED_ATTRIBUTES}) to |
| 73 | * manage the configuration of the filter. |
| 74 | * </p> |
| 75 | * |
| 76 | * |
| 77 | */ |
| 78 | public class QoSFilter implements Filter |
| 79 | { |
| 80 | final static int __DEFAULT_MAX_PRIORITY=10; |
| 81 | final static int __DEFAULT_PASSES=10; |
| 82 | final static int __DEFAULT_WAIT_MS=50; |
| 83 | final static long __DEFAULT_TIMEOUT_MS = -1; |
| 84 | |
| 85 | final static String MANAGED_ATTR_INIT_PARAM="managedAttr"; |
| 86 | final static String MAX_REQUESTS_INIT_PARAM="maxRequests"; |
| 87 | final static String MAX_PRIORITY_INIT_PARAM="maxPriority"; |
| 88 | final static String MAX_WAIT_INIT_PARAM="waitMs"; |
| 89 | final static String SUSPEND_INIT_PARAM="suspendMs"; |
| 90 | |
| 91 | ServletContext _context; |
| 92 | |
| 93 | protected long _waitMs; |
| 94 | protected long _suspendMs; |
| 95 | protected int _maxRequests; |
| 96 | |
| 97 | private Semaphore _passes; |
| 98 | private Queue<Continuation>[] _queue; |
| 99 | private ContinuationListener[] _listener; |
| 100 | private String _suspended="QoSFilter@"+this.hashCode(); |
| 101 | |
| 102 | /* ------------------------------------------------------------ */ |
| 103 | /** |
| 104 | * @see javax.servlet.Filter#init(javax.servlet.FilterConfig) |
| 105 | */ |
| 106 | public void init(FilterConfig filterConfig) |
| 107 | { |
| 108 | _context=filterConfig.getServletContext(); |
| 109 | |
| 110 | int max_priority=__DEFAULT_MAX_PRIORITY; |
| 111 | if (filterConfig.getInitParameter(MAX_PRIORITY_INIT_PARAM)!=null) |
| 112 | max_priority=Integer.parseInt(filterConfig.getInitParameter(MAX_PRIORITY_INIT_PARAM)); |
| 113 | _queue=new Queue[max_priority+1]; |
| 114 | _listener = new ContinuationListener[max_priority + 1]; |
| 115 | for (int p=0;p<_queue.length;p++) |
| 116 | { |
| 117 | _queue[p]=new ConcurrentLinkedQueue<Continuation>(); |
| 118 | |
| 119 | final int priority=p; |
| 120 | _listener[p] = new ContinuationListener() |
| 121 | { |
| 122 | public void onComplete(Continuation continuation) |
| 123 | {} |
| 124 | |
| 125 | public void onTimeout(Continuation continuation) |
| 126 | { |
| 127 | _queue[priority].remove(continuation); |
| 128 | } |
| 129 | }; |
| 130 | } |
| 131 | |
| 132 | int maxRequests=__DEFAULT_PASSES; |
| 133 | if (filterConfig.getInitParameter(MAX_REQUESTS_INIT_PARAM)!=null) |
| 134 | maxRequests=Integer.parseInt(filterConfig.getInitParameter(MAX_REQUESTS_INIT_PARAM)); |
| 135 | _passes=new Semaphore(maxRequests,true); |
| 136 | _maxRequests = maxRequests; |
| 137 | |
| 138 | long wait = __DEFAULT_WAIT_MS; |
| 139 | if (filterConfig.getInitParameter(MAX_WAIT_INIT_PARAM)!=null) |
| 140 | wait=Integer.parseInt(filterConfig.getInitParameter(MAX_WAIT_INIT_PARAM)); |
| 141 | _waitMs=wait; |
| 142 | |
| 143 | long suspend = __DEFAULT_TIMEOUT_MS; |
| 144 | if (filterConfig.getInitParameter(SUSPEND_INIT_PARAM)!=null) |
| 145 | suspend=Integer.parseInt(filterConfig.getInitParameter(SUSPEND_INIT_PARAM)); |
| 146 | _suspendMs=suspend; |
| 147 | |
| 148 | if (_context!=null && Boolean.parseBoolean(filterConfig.getInitParameter(MANAGED_ATTR_INIT_PARAM))) |
| 149 | _context.setAttribute(filterConfig.getFilterName(),this); |
| 150 | } |
| 151 | |
| 152 | /* ------------------------------------------------------------ */ |
| 153 | /** |
| 154 | * @see javax.servlet.Filter#doFilter(javax.servlet.ServletRequest, javax.servlet.ServletResponse, javax.servlet.FilterChain) |
| 155 | */ |
| 156 | public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) |
| 157 | throws IOException, ServletException |
| 158 | { |
| 159 | boolean accepted=false; |
| 160 | try |
| 161 | { |
| 162 | if (request.getAttribute(_suspended)==null) |
| 163 | { |
| 164 | accepted=_passes.tryAcquire(_waitMs,TimeUnit.MILLISECONDS); |
| 165 | if (accepted) |
| 166 | { |
| 167 | request.setAttribute(_suspended,Boolean.FALSE); |
| 168 | } |
| 169 | else |
| 170 | { |
| 171 | request.setAttribute(_suspended,Boolean.TRUE); |
| 172 | int priority = getPriority(request); |
| 173 | Continuation continuation = ContinuationSupport.getContinuation(request); |
| 174 | if (_suspendMs>0) |
| 175 | continuation.setTimeout(_suspendMs); |
| 176 | continuation.suspend(); |
| 177 | continuation.addContinuationListener(_listener[priority]); |
| 178 | _queue[priority].add(continuation); |
| 179 | return; |
| 180 | } |
| 181 | } |
| 182 | else |
| 183 | { |
| 184 | Boolean suspended=(Boolean)request.getAttribute(_suspended); |
| 185 | |
| 186 | if (suspended.booleanValue()) |
| 187 | { |
| 188 | request.setAttribute(_suspended,Boolean.FALSE); |
| 189 | if (request.getAttribute("javax.servlet.resumed")==Boolean.TRUE) |
| 190 | { |
| 191 | _passes.acquire(); |
| 192 | accepted=true; |
| 193 | } |
| 194 | else |
| 195 | { |
| 196 | // Timeout! try 1 more time. |
| 197 | accepted = _passes.tryAcquire(_waitMs,TimeUnit.MILLISECONDS); |
| 198 | } |
| 199 | } |
| 200 | else |
| 201 | { |
| 202 | // pass through resume of previously accepted request |
| 203 | _passes.acquire(); |
| 204 | accepted = true; |
| 205 | } |
| 206 | } |
| 207 | |
| 208 | if (accepted) |
| 209 | { |
| 210 | chain.doFilter(request,response); |
| 211 | } |
| 212 | else |
| 213 | { |
| 214 | ((HttpServletResponse)response).sendError(HttpServletResponse.SC_SERVICE_UNAVAILABLE); |
| 215 | } |
| 216 | } |
| 217 | catch(InterruptedException e) |
| 218 | { |
| 219 | _context.log("QoS",e); |
| 220 | ((HttpServletResponse)response).sendError(HttpServletResponse.SC_SERVICE_UNAVAILABLE); |
| 221 | } |
| 222 | finally |
| 223 | { |
| 224 | if (accepted) |
| 225 | { |
| 226 | for (int p=_queue.length;p-->0;) |
| 227 | { |
| 228 | Continuation continutaion=_queue[p].poll(); |
| 229 | if (continutaion!=null && continutaion.isSuspended()) |
| 230 | { |
| 231 | continutaion.resume(); |
| 232 | break; |
| 233 | } |
| 234 | } |
| 235 | _passes.release(); |
| 236 | } |
| 237 | } |
| 238 | } |
| 239 | |
| 240 | /** |
| 241 | * Get the request Priority. |
| 242 | * <p> The default implementation assigns the following priorities:<ul> |
| 243 | * <li> 2 - for a authenticated request |
| 244 | * <li> 1 - for a request with valid /non new session |
| 245 | * <li> 0 - for all other requests. |
| 246 | * </ul> |
| 247 | * This method may be specialised to provide application specific priorities. |
| 248 | * |
| 249 | * @param request |
| 250 | * @return the request priority |
| 251 | */ |
| 252 | protected int getPriority(ServletRequest request) |
| 253 | { |
| 254 | HttpServletRequest baseRequest = (HttpServletRequest)request; |
| 255 | if (baseRequest.getUserPrincipal() != null ) |
| 256 | return 2; |
| 257 | else |
| 258 | { |
| 259 | HttpSession session = baseRequest.getSession(false); |
| 260 | if (session!=null && !session.isNew()) |
| 261 | return 1; |
| 262 | else |
| 263 | return 0; |
| 264 | } |
| 265 | } |
| 266 | |
| 267 | |
| 268 | /* ------------------------------------------------------------ */ |
| 269 | /** |
| 270 | * @see javax.servlet.Filter#destroy() |
| 271 | */ |
| 272 | public void destroy(){} |
| 273 | |
| 274 | /* ------------------------------------------------------------ */ |
| 275 | /** |
| 276 | * Get the (short) amount of time (in milliseconds) that the filter would wait |
| 277 | * for the semaphore to become available before suspending a request. |
| 278 | * |
| 279 | * @return wait time (in milliseconds) |
| 280 | */ |
| 281 | public long getWaitMs() |
| 282 | { |
| 283 | return _waitMs; |
| 284 | } |
| 285 | |
| 286 | /* ------------------------------------------------------------ */ |
| 287 | /** |
| 288 | * Set the (short) amount of time (in milliseconds) that the filter would wait |
| 289 | * for the semaphore to become available before suspending a request. |
| 290 | * |
| 291 | * @param value wait time (in milliseconds) |
| 292 | */ |
| 293 | public void setWaitMs(long value) |
| 294 | { |
| 295 | _waitMs = value; |
| 296 | } |
| 297 | |
| 298 | /* ------------------------------------------------------------ */ |
| 299 | /** |
| 300 | * Get the amount of time (in milliseconds) that the filter would suspend |
| 301 | * a request for while waiting for the semaphore to become available. |
| 302 | * |
| 303 | * @return suspend time (in milliseconds) |
| 304 | */ |
| 305 | public long getSuspendMs() |
| 306 | { |
| 307 | return _suspendMs; |
| 308 | } |
| 309 | |
| 310 | /* ------------------------------------------------------------ */ |
| 311 | /** |
| 312 | * Set the amount of time (in milliseconds) that the filter would suspend |
| 313 | * a request for while waiting for the semaphore to become available. |
| 314 | * |
| 315 | * @param value suspend time (in milliseconds) |
| 316 | */ |
| 317 | public void setSuspendMs(long value) |
| 318 | { |
| 319 | _suspendMs = value; |
| 320 | } |
| 321 | |
| 322 | /* ------------------------------------------------------------ */ |
| 323 | /** |
| 324 | * Get the maximum number of requests allowed to be processed |
| 325 | * at the same time. |
| 326 | * |
| 327 | * @return maximum number of requests |
| 328 | */ |
| 329 | public int getMaxRequests() |
| 330 | { |
| 331 | return _maxRequests; |
| 332 | } |
| 333 | |
| 334 | /* ------------------------------------------------------------ */ |
| 335 | /** |
| 336 | * Set the maximum number of requests allowed to be processed |
| 337 | * at the same time. |
| 338 | * |
| 339 | * @param value the number of requests |
| 340 | */ |
| 341 | public void setMaxRequests(int value) |
| 342 | { |
| 343 | _passes = new Semaphore((value-_maxRequests+_passes.availablePermits()), true); |
| 344 | _maxRequests = value; |
| 345 | } |
| 346 | |
| 347 | } |