| // |
| // ======================================================================== |
| // Copyright (c) 1995-2017 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.AsyncContext; |
| import javax.servlet.AsyncEvent; |
| import javax.servlet.AsyncListener; |
| 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.server.handler.ContextHandler; |
| import org.eclipse.jetty.util.annotation.ManagedAttribute; |
| import org.eclipse.jetty.util.annotation.ManagedObject; |
| import org.eclipse.jetty.util.log.Log; |
| import org.eclipse.jetty.util.log.Logger; |
| |
| /** |
| * Quality of Service Filter. |
| * <p/> |
| * 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/> |
| * 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/> |
| * 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/> |
| * 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/> |
| * 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. |
| */ |
| @ManagedObject("Quality of Service Filter") |
| public class QoSFilter implements Filter |
| { |
| private static final Logger LOG = Log.getLogger(QoSFilter.class); |
| |
| static final int __DEFAULT_MAX_PRIORITY = 10; |
| static final int __DEFAULT_PASSES = 10; |
| static final int __DEFAULT_WAIT_MS = 50; |
| static final long __DEFAULT_TIMEOUT_MS = -1; |
| |
| static final String MANAGED_ATTR_INIT_PARAM = "managedAttr"; |
| static final String MAX_REQUESTS_INIT_PARAM = "maxRequests"; |
| static final String MAX_PRIORITY_INIT_PARAM = "maxPriority"; |
| static final String MAX_WAIT_INIT_PARAM = "waitMs"; |
| static final String SUSPEND_INIT_PARAM = "suspendMs"; |
| |
| private final String _suspended = "QoSFilter@" + Integer.toHexString(hashCode()) + ".SUSPENDED"; |
| private final String _resumed = "QoSFilter@" + Integer.toHexString(hashCode()) + ".RESUMED"; |
| private long _waitMs; |
| private long _suspendMs; |
| private int _maxRequests; |
| private Semaphore _passes; |
| private Queue<AsyncContext>[] _queues; |
| private AsyncListener[] _listeners; |
| |
| public void init(FilterConfig filterConfig) |
| { |
| int max_priority = __DEFAULT_MAX_PRIORITY; |
| if (filterConfig.getInitParameter(MAX_PRIORITY_INIT_PARAM) != null) |
| max_priority = Integer.parseInt(filterConfig.getInitParameter(MAX_PRIORITY_INIT_PARAM)); |
| _queues = new Queue[max_priority + 1]; |
| _listeners = new AsyncListener[_queues.length]; |
| for (int p = 0; p < _queues.length; ++p) |
| { |
| _queues[p] = new ConcurrentLinkedQueue<>(); |
| _listeners[p] = new QoSAsyncListener(p); |
| } |
| |
| 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; |
| |
| ServletContext context = filterConfig.getServletContext(); |
| if (context != null && Boolean.parseBoolean(filterConfig.getInitParameter(MANAGED_ATTR_INIT_PARAM))) |
| context.setAttribute(filterConfig.getFilterName(), this); |
| } |
| |
| public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException |
| { |
| boolean accepted = false; |
| try |
| { |
| Boolean suspended = (Boolean)request.getAttribute(_suspended); |
| if (suspended == null) |
| { |
| accepted = _passes.tryAcquire(getWaitMs(), TimeUnit.MILLISECONDS); |
| if (accepted) |
| { |
| request.setAttribute(_suspended, Boolean.FALSE); |
| if (LOG.isDebugEnabled()) |
| LOG.debug("Accepted {}", request); |
| } |
| else |
| { |
| request.setAttribute(_suspended, Boolean.TRUE); |
| int priority = getPriority(request); |
| AsyncContext asyncContext = request.startAsync(); |
| long suspendMs = getSuspendMs(); |
| if (suspendMs > 0) |
| asyncContext.setTimeout(suspendMs); |
| asyncContext.addListener(_listeners[priority]); |
| _queues[priority].add(asyncContext); |
| if (LOG.isDebugEnabled()) |
| LOG.debug("Suspended {}", request); |
| return; |
| } |
| } |
| else |
| { |
| if (suspended) |
| { |
| request.setAttribute(_suspended, Boolean.FALSE); |
| Boolean resumed = (Boolean)request.getAttribute(_resumed); |
| if (resumed == Boolean.TRUE) |
| { |
| _passes.acquire(); |
| accepted = true; |
| if (LOG.isDebugEnabled()) |
| LOG.debug("Resumed {}", request); |
| } |
| else |
| { |
| // Timeout! try 1 more time. |
| accepted = _passes.tryAcquire(getWaitMs(), TimeUnit.MILLISECONDS); |
| if (LOG.isDebugEnabled()) |
| LOG.debug("Timeout {}", request); |
| } |
| } |
| else |
| { |
| // Pass through resume of previously accepted request. |
| _passes.acquire(); |
| accepted = true; |
| if (LOG.isDebugEnabled()) |
| LOG.debug("Passthrough {}", request); |
| } |
| } |
| |
| if (accepted) |
| { |
| chain.doFilter(request, response); |
| } |
| else |
| { |
| if (LOG.isDebugEnabled()) |
| LOG.debug("Rejected {}", request); |
| ((HttpServletResponse)response).sendError(HttpServletResponse.SC_SERVICE_UNAVAILABLE); |
| } |
| } |
| catch (InterruptedException e) |
| { |
| ((HttpServletResponse)response).sendError(HttpServletResponse.SC_SERVICE_UNAVAILABLE); |
| } |
| finally |
| { |
| if (accepted) |
| { |
| for (int p = _queues.length - 1; p >= 0; --p) |
| { |
| AsyncContext asyncContext = _queues[p].poll(); |
| if (asyncContext != null) |
| { |
| ServletRequest candidate = asyncContext.getRequest(); |
| Boolean suspended = (Boolean)candidate.getAttribute(_suspended); |
| if (suspended == Boolean.TRUE) |
| { |
| candidate.setAttribute(_resumed, Boolean.TRUE); |
| asyncContext.dispatch(); |
| break; |
| } |
| } |
| } |
| _passes.release(); |
| } |
| } |
| } |
| |
| /** |
| * Computes the request priority. |
| * <p/> |
| * The default implementation assigns the following priorities: |
| * <ul> |
| * <li> 2 - for an authenticated request |
| * <li> 1 - for a request with valid / non new session |
| * <li> 0 - for all other requests. |
| * </ul> |
| * This method may be overridden to provide application specific priorities. |
| * |
| * @param request the incoming request |
| * @return the computed 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; |
| } |
| } |
| |
| 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) |
| */ |
| @ManagedAttribute("(short) amount of time filter will wait before suspending request (in ms)") |
| 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) |
| */ |
| @ManagedAttribute("amount of time filter will suspend a request for while waiting for the semaphore to become available (in ms)") |
| 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 |
| */ |
| @ManagedAttribute("maximum number of requests to allow processing of at the same time") |
| 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 - getMaxRequests() + _passes.availablePermits()), true); |
| _maxRequests = value; |
| } |
| |
| private class QoSAsyncListener implements AsyncListener |
| { |
| private final int priority; |
| |
| public QoSAsyncListener(int priority) |
| { |
| this.priority = priority; |
| } |
| |
| @Override |
| public void onStartAsync(AsyncEvent event) throws IOException |
| { |
| } |
| |
| @Override |
| public void onComplete(AsyncEvent event) throws IOException |
| { |
| } |
| |
| @Override |
| public void onTimeout(AsyncEvent event) throws IOException |
| { |
| // Remove before it's redispatched, so it won't be |
| // redispatched again at the end of the filtering. |
| AsyncContext asyncContext = event.getAsyncContext(); |
| _queues[priority].remove(asyncContext); |
| asyncContext.dispatch(); |
| } |
| |
| @Override |
| public void onError(AsyncEvent event) throws IOException |
| { |
| } |
| } |
| } |