| // |
| // ======================================================================== |
| // Copyright (c) 1995-2014 Mort Bay Consulting Pty. Ltd. |
| // ------------------------------------------------------------------------ |
| // All rights reserved. This program and the accompanying materials |
| // are made available under the terms of the Eclipse Public License v1.0 |
| // and Apache License v2.0 which accompanies this distribution. |
| // |
| // The Eclipse Public License is available at |
| // http://www.eclipse.org/legal/epl-v10.html |
| // |
| // The Apache License v2.0 is available at |
| // http://www.opensource.org/licenses/apache2.0.php |
| // |
| // You may elect to redistribute this code under either of these licenses. |
| // ======================================================================== |
| // |
| |
| package org.eclipse.jetty.servlets; |
| |
| import java.io.IOException; |
| import java.util.Queue; |
| import java.util.concurrent.ConcurrentLinkedQueue; |
| import java.util.concurrent.Semaphore; |
| import java.util.concurrent.TimeUnit; |
| |
| import javax.servlet.Filter; |
| import javax.servlet.FilterChain; |
| import javax.servlet.FilterConfig; |
| import javax.servlet.ServletContext; |
| import javax.servlet.ServletException; |
| import javax.servlet.ServletRequest; |
| import javax.servlet.ServletResponse; |
| import javax.servlet.http.HttpServletRequest; |
| import javax.servlet.http.HttpServletResponse; |
| import javax.servlet.http.HttpSession; |
| |
| import org.eclipse.jetty.continuation.Continuation; |
| import org.eclipse.jetty.continuation.ContinuationListener; |
| import org.eclipse.jetty.continuation.ContinuationSupport; |
| import org.eclipse.jetty.server.handler.ContextHandler; |
| |
| /** |
| * Quality of Service Filter. |
| * |
| * This filter limits the number of active requests to the number set by the "maxRequests" init parameter (default 10). |
| * If more requests are received, they are suspended and placed on priority queues. Priorities are determined by |
| * the {@link #getPriority(ServletRequest)} method and are a value between 0 and the value given by the "maxPriority" |
| * init parameter (default 10), with higher values having higher priority. |
| * </p><p> |
| * This filter is ideal to prevent wasting threads waiting for slow/limited |
| * resources such as a JDBC connection pool. It avoids the situation where all of a |
| * containers thread pool may be consumed blocking on such a slow resource. |
| * By limiting the number of active threads, a smaller thread pool may be used as |
| * the threads are not wasted waiting. Thus more memory may be available for use by |
| * the active threads. |
| * </p><p> |
| * Furthermore, this filter uses a priority when resuming waiting requests. So that if |
| * a container is under load, and there are many requests waiting for resources, |
| * the {@link #getPriority(ServletRequest)} method is used, so that more important |
| * requests are serviced first. For example, this filter could be deployed with a |
| * maxRequest limit slightly smaller than the containers thread pool and a high priority |
| * allocated to admin users. Thus regardless of load, admin users would always be |
| * able to access the web application. |
| * </p><p> |
| * The maxRequest limit is policed by a {@link Semaphore} and the filter will wait a short while attempting to acquire |
| * the semaphore. This wait is controlled by the "waitMs" init parameter and allows the expense of a suspend to be |
| * avoided if the semaphore is shortly available. If the semaphore cannot be obtained, the request will be suspended |
| * for the default suspend period of the container or the valued set as the "suspendMs" init parameter. |
| * </p><p> |
| * If the "managedAttr" init parameter is set to true, then this servlet is set as a {@link ServletContext} attribute with the |
| * filter name as the attribute name. This allows context external mechanism (eg JMX via {@link ContextHandler#MANAGED_ATTRIBUTES}) to |
| * manage the configuration of the filter. |
| * </p> |
| * |
| * |
| */ |
| public class QoSFilter implements Filter |
| { |
| final static int __DEFAULT_MAX_PRIORITY=10; |
| final static int __DEFAULT_PASSES=10; |
| final static int __DEFAULT_WAIT_MS=50; |
| final static long __DEFAULT_TIMEOUT_MS = -1; |
| |
| final static String MANAGED_ATTR_INIT_PARAM="managedAttr"; |
| final static String MAX_REQUESTS_INIT_PARAM="maxRequests"; |
| final static String MAX_PRIORITY_INIT_PARAM="maxPriority"; |
| final static String MAX_WAIT_INIT_PARAM="waitMs"; |
| final static String SUSPEND_INIT_PARAM="suspendMs"; |
| |
| ServletContext _context; |
| |
| protected long _waitMs; |
| protected long _suspendMs; |
| protected int _maxRequests; |
| |
| private Semaphore _passes; |
| private Queue<Continuation>[] _queue; |
| private ContinuationListener[] _listener; |
| private String _suspended="QoSFilter@"+this.hashCode(); |
| |
| /* ------------------------------------------------------------ */ |
| /** |
| * @see javax.servlet.Filter#init(javax.servlet.FilterConfig) |
| */ |
| public void init(FilterConfig filterConfig) |
| { |
| _context=filterConfig.getServletContext(); |
| |
| int max_priority=__DEFAULT_MAX_PRIORITY; |
| if (filterConfig.getInitParameter(MAX_PRIORITY_INIT_PARAM)!=null) |
| max_priority=Integer.parseInt(filterConfig.getInitParameter(MAX_PRIORITY_INIT_PARAM)); |
| _queue=new Queue[max_priority+1]; |
| _listener = new ContinuationListener[max_priority + 1]; |
| for (int p=0;p<_queue.length;p++) |
| { |
| _queue[p]=new ConcurrentLinkedQueue<Continuation>(); |
| |
| final int priority=p; |
| _listener[p] = new ContinuationListener() |
| { |
| public void onComplete(Continuation continuation) |
| {} |
| |
| public void onTimeout(Continuation continuation) |
| { |
| _queue[priority].remove(continuation); |
| } |
| }; |
| } |
| |
| int maxRequests=__DEFAULT_PASSES; |
| if (filterConfig.getInitParameter(MAX_REQUESTS_INIT_PARAM)!=null) |
| maxRequests=Integer.parseInt(filterConfig.getInitParameter(MAX_REQUESTS_INIT_PARAM)); |
| _passes=new Semaphore(maxRequests,true); |
| _maxRequests = maxRequests; |
| |
| long wait = __DEFAULT_WAIT_MS; |
| if (filterConfig.getInitParameter(MAX_WAIT_INIT_PARAM)!=null) |
| wait=Integer.parseInt(filterConfig.getInitParameter(MAX_WAIT_INIT_PARAM)); |
| _waitMs=wait; |
| |
| long suspend = __DEFAULT_TIMEOUT_MS; |
| if (filterConfig.getInitParameter(SUSPEND_INIT_PARAM)!=null) |
| suspend=Integer.parseInt(filterConfig.getInitParameter(SUSPEND_INIT_PARAM)); |
| _suspendMs=suspend; |
| |
| if (_context!=null && Boolean.parseBoolean(filterConfig.getInitParameter(MANAGED_ATTR_INIT_PARAM))) |
| _context.setAttribute(filterConfig.getFilterName(),this); |
| } |
| |
| /* ------------------------------------------------------------ */ |
| /** |
| * @see javax.servlet.Filter#doFilter(javax.servlet.ServletRequest, javax.servlet.ServletResponse, javax.servlet.FilterChain) |
| */ |
| public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) |
| throws IOException, ServletException |
| { |
| boolean accepted=false; |
| try |
| { |
| if (request.getAttribute(_suspended)==null) |
| { |
| accepted=_passes.tryAcquire(_waitMs,TimeUnit.MILLISECONDS); |
| if (accepted) |
| { |
| request.setAttribute(_suspended,Boolean.FALSE); |
| } |
| else |
| { |
| request.setAttribute(_suspended,Boolean.TRUE); |
| int priority = getPriority(request); |
| Continuation continuation = ContinuationSupport.getContinuation(request); |
| if (_suspendMs>0) |
| continuation.setTimeout(_suspendMs); |
| continuation.suspend(); |
| continuation.addContinuationListener(_listener[priority]); |
| _queue[priority].add(continuation); |
| return; |
| } |
| } |
| else |
| { |
| Boolean suspended=(Boolean)request.getAttribute(_suspended); |
| |
| if (suspended.booleanValue()) |
| { |
| request.setAttribute(_suspended,Boolean.FALSE); |
| if (request.getAttribute("javax.servlet.resumed")==Boolean.TRUE) |
| { |
| _passes.acquire(); |
| accepted=true; |
| } |
| else |
| { |
| // Timeout! try 1 more time. |
| accepted = _passes.tryAcquire(_waitMs,TimeUnit.MILLISECONDS); |
| } |
| } |
| else |
| { |
| // pass through resume of previously accepted request |
| _passes.acquire(); |
| accepted = true; |
| } |
| } |
| |
| if (accepted) |
| { |
| chain.doFilter(request,response); |
| } |
| else |
| { |
| ((HttpServletResponse)response).sendError(HttpServletResponse.SC_SERVICE_UNAVAILABLE); |
| } |
| } |
| catch(InterruptedException e) |
| { |
| _context.log("QoS",e); |
| ((HttpServletResponse)response).sendError(HttpServletResponse.SC_SERVICE_UNAVAILABLE); |
| } |
| finally |
| { |
| if (accepted) |
| { |
| for (int p=_queue.length;p-->0;) |
| { |
| Continuation continutaion=_queue[p].poll(); |
| if (continutaion!=null && continutaion.isSuspended()) |
| { |
| continutaion.resume(); |
| break; |
| } |
| } |
| _passes.release(); |
| } |
| } |
| } |
| |
| /** |
| * Get the request Priority. |
| * <p> The default implementation assigns the following priorities:<ul> |
| * <li> 2 - for a authenticated request |
| * <li> 1 - for a request with valid /non new session |
| * <li> 0 - for all other requests. |
| * </ul> |
| * This method may be specialised to provide application specific priorities. |
| * |
| * @param request |
| * @return the request priority |
| */ |
| protected int getPriority(ServletRequest request) |
| { |
| HttpServletRequest baseRequest = (HttpServletRequest)request; |
| if (baseRequest.getUserPrincipal() != null ) |
| return 2; |
| else |
| { |
| HttpSession session = baseRequest.getSession(false); |
| if (session!=null && !session.isNew()) |
| return 1; |
| else |
| return 0; |
| } |
| } |
| |
| |
| /* ------------------------------------------------------------ */ |
| /** |
| * @see javax.servlet.Filter#destroy() |
| */ |
| public void destroy(){} |
| |
| /* ------------------------------------------------------------ */ |
| /** |
| * Get the (short) amount of time (in milliseconds) that the filter would wait |
| * for the semaphore to become available before suspending a request. |
| * |
| * @return wait time (in milliseconds) |
| */ |
| public long getWaitMs() |
| { |
| return _waitMs; |
| } |
| |
| /* ------------------------------------------------------------ */ |
| /** |
| * Set the (short) amount of time (in milliseconds) that the filter would wait |
| * for the semaphore to become available before suspending a request. |
| * |
| * @param value wait time (in milliseconds) |
| */ |
| public void setWaitMs(long value) |
| { |
| _waitMs = value; |
| } |
| |
| /* ------------------------------------------------------------ */ |
| /** |
| * Get the amount of time (in milliseconds) that the filter would suspend |
| * a request for while waiting for the semaphore to become available. |
| * |
| * @return suspend time (in milliseconds) |
| */ |
| public long getSuspendMs() |
| { |
| return _suspendMs; |
| } |
| |
| /* ------------------------------------------------------------ */ |
| /** |
| * Set the amount of time (in milliseconds) that the filter would suspend |
| * a request for while waiting for the semaphore to become available. |
| * |
| * @param value suspend time (in milliseconds) |
| */ |
| public void setSuspendMs(long value) |
| { |
| _suspendMs = value; |
| } |
| |
| /* ------------------------------------------------------------ */ |
| /** |
| * Get the maximum number of requests allowed to be processed |
| * at the same time. |
| * |
| * @return maximum number of requests |
| */ |
| public int getMaxRequests() |
| { |
| return _maxRequests; |
| } |
| |
| /* ------------------------------------------------------------ */ |
| /** |
| * Set the maximum number of requests allowed to be processed |
| * at the same time. |
| * |
| * @param value the number of requests |
| */ |
| public void setMaxRequests(int value) |
| { |
| _passes = new Semaphore((value-_maxRequests+_passes.availablePermits()), true); |
| _maxRequests = value; |
| } |
| |
| } |