1 /*
   2  * Copyright (c) 1996, 2011, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.  Oracle designates this
   8  * particular file as subject to the "Classpath" exception as provided
   9  * by Oracle in the LICENSE file that accompanied this code.
  10  *
  11  * This code is distributed in the hope that it will be useful, but WITHOUT
  12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14  * version 2 for more details (a copy is included in the LICENSE file that
  15  * accompanied this code).
  16  *
  17  * You should have received a copy of the GNU General Public License version
  18  * 2 along with this work; if not, write to the Free Software Foundation,
  19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  20  *
  21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  22  * or visit www.oracle.com if you need additional information or have any
  23  * questions.
  24  */
  25 
  26 package sun.net.www.http;
  27 
  28 import java.io.IOException;
  29 import java.io.NotSerializableException;
  30 import java.util.ArrayList;
  31 import java.util.HashMap;
  32 import java.net.URL;
  33 import jdk.internal.misc.InnocuousThread;
  34 
  35 /**
  36  * A class that implements a cache of idle Http connections for keep-alive
  37  *
  38  * @author Stephen R. Pietrowicz (NCSA)
  39  * @author Dave Brown
  40  */
  41 public class KeepAliveCache
  42     extends HashMap<KeepAliveKey, ClientVector>
  43     implements Runnable {
  44     private static final long serialVersionUID = -2937172892064557949L;
  45 
  46     /* maximum # keep-alive connections to maintain at once
  47      * This should be 2 by the HTTP spec, but because we don't support pipe-lining
  48      * a larger value is more appropriate. So we now set a default of 5, and the value
  49      * refers to the number of idle connections per destination (in the cache) only.
  50      * It can be reset by setting system property "http.maxConnections".
  51      */
  52     static final int MAX_CONNECTIONS = 5;
  53     static int result = -1;
  54     static int getMaxConnections() {
  55         if (result == -1) {
  56             result = java.security.AccessController.doPrivileged(
  57                 new sun.security.action.GetIntegerAction("http.maxConnections",
  58                                                          MAX_CONNECTIONS))
  59                 .intValue();
  60             if (result <= 0)
  61                 result = MAX_CONNECTIONS;
  62         }
  63             return result;
  64     }
  65 
  66     static final int LIFETIME = 5000;
  67 
  68     private Thread keepAliveTimer = null;
  69 
  70     /**
  71      * Constructor
  72      */
  73     public KeepAliveCache() {}
  74 
  75     /**
  76      * Register this URL and HttpClient (that supports keep-alive) with the cache
  77      * @param url  The URL contains info about the host and port
  78      * @param http The HttpClient to be cached
  79      */
  80     public synchronized void put(final URL url, Object obj, HttpClient http) {
  81         boolean startThread = (keepAliveTimer == null);
  82         if (!startThread) {
  83             if (!keepAliveTimer.isAlive()) {
  84                 startThread = true;
  85             }
  86         }
  87         if (startThread) {
  88             clear();
  89             /* Unfortunately, we can't always believe the keep-alive timeout we got
  90              * back from the server.  If I'm connected through a Netscape proxy
  91              * to a server that sent me a keep-alive
  92              * time of 15 sec, the proxy unilaterally terminates my connection
  93              * The robustness to get around this is in HttpClient.parseHTTP()
  94              */
  95             final KeepAliveCache cache = this;
  96             java.security.AccessController.doPrivileged(
  97                 new java.security.PrivilegedAction<>() {
  98                 public Void run() {
  99                     keepAliveTimer = new InnocuousThread(cache, "Keep-Alive-Timer", false);
 100                     keepAliveTimer.setDaemon(true);
 101                     keepAliveTimer.setPriority(Thread.MAX_PRIORITY - 2);
 102                     keepAliveTimer.start();
 103                     return null;
 104                 }
 105             });
 106         }
 107 
 108         KeepAliveKey key = new KeepAliveKey(url, obj);
 109         ClientVector v = super.get(key);
 110 
 111         if (v == null) {
 112             int keepAliveTimeout = http.getKeepAliveTimeout();
 113             v = new ClientVector(keepAliveTimeout > 0?
 114                                  keepAliveTimeout*1000 : LIFETIME);
 115             v.put(http);
 116             super.put(key, v);
 117         } else {
 118             v.put(http);
 119         }
 120     }
 121 
 122     /* remove an obsolete HttpClient from its VectorCache */
 123     public synchronized void remove (HttpClient h, Object obj) {
 124         KeepAliveKey key = new KeepAliveKey(h.url, obj);
 125         ClientVector v = super.get(key);
 126         if (v != null) {
 127             v.remove(h);
 128             if (v.empty()) {
 129                 removeVector(key);
 130             }
 131         }
 132     }
 133 
 134     /* called by a clientVector thread when all its connections have timed out
 135      * and that vector of connections should be removed.
 136      */
 137     synchronized void removeVector(KeepAliveKey k) {
 138         super.remove(k);
 139     }
 140 
 141     /**
 142      * Check to see if this URL has a cached HttpClient
 143      */
 144     public synchronized HttpClient get(URL url, Object obj) {
 145 
 146         KeepAliveKey key = new KeepAliveKey(url, obj);
 147         ClientVector v = super.get(key);
 148         if (v == null) { // nothing in cache yet
 149             return null;
 150         }
 151         return v.get();
 152     }
 153 
 154     /* Sleeps for an alloted timeout, then checks for timed out connections.
 155      * Errs on the side of caution (leave connections idle for a relatively
 156      * short time).
 157      */
 158     @Override
 159     public void run() {
 160         do {
 161             try {
 162                 Thread.sleep(LIFETIME);
 163             } catch (InterruptedException e) {}
 164             synchronized (this) {
 165                 /* Remove all unused HttpClients.  Starting from the
 166                  * bottom of the stack (the least-recently used first).
 167                  * REMIND: It'd be nice to not remove *all* connections
 168                  * that aren't presently in use.  One could have been added
 169                  * a second ago that's still perfectly valid, and we're
 170                  * needlessly axing it.  But it's not clear how to do this
 171                  * cleanly, and doing it right may be more trouble than it's
 172                  * worth.
 173                  */
 174 
 175                 long currentTime = System.currentTimeMillis();
 176 
 177                 ArrayList<KeepAliveKey> keysToRemove
 178                     = new ArrayList<>();
 179 
 180                 for (KeepAliveKey key : keySet()) {
 181                     ClientVector v = get(key);
 182                     synchronized (v) {
 183                         int i;
 184 
 185                         for (i = 0; i < v.size(); i++) {
 186                             KeepAliveEntry e = v.elementAt(i);
 187                             if ((currentTime - e.idleStartTime) > v.nap) {
 188                                 HttpClient h = e.hc;
 189                                 h.closeServer();
 190                             } else {
 191                                 break;
 192                             }
 193                         }
 194                         v.subList(0, i).clear();
 195 
 196                         if (v.size() == 0) {
 197                             keysToRemove.add(key);
 198                         }
 199                     }
 200                 }
 201 
 202                 for (KeepAliveKey key : keysToRemove) {
 203                     removeVector(key);
 204                 }
 205             }
 206         } while (size() > 0);
 207 
 208         return;
 209     }
 210 
 211     /*
 212      * Do not serialize this class!
 213      */
 214     private void writeObject(java.io.ObjectOutputStream stream)
 215     throws IOException {
 216         throw new NotSerializableException();
 217     }
 218 
 219     private void readObject(java.io.ObjectInputStream stream)
 220     throws IOException, ClassNotFoundException {
 221         throw new NotSerializableException();
 222     }
 223 }
 224 
 225 /* FILO order for recycling HttpClients, should run in a thread
 226  * to time them out.  If > maxConns are in use, block.
 227  */
 228 
 229 
 230 class ClientVector extends java.util.Stack<KeepAliveEntry> {
 231     private static final long serialVersionUID = -8680532108106489459L;
 232 
 233     // sleep time in milliseconds, before cache clear
 234     int nap;
 235 
 236 
 237 
 238     ClientVector (int nap) {
 239         this.nap = nap;
 240     }
 241 
 242     synchronized HttpClient get() {
 243         if (empty()) {
 244             return null;
 245         } else {
 246             // Loop until we find a connection that has not timed out
 247             HttpClient hc = null;
 248             long currentTime = System.currentTimeMillis();
 249             do {
 250                 KeepAliveEntry e = pop();
 251                 if ((currentTime - e.idleStartTime) > nap) {
 252                     e.hc.closeServer();
 253                 } else {
 254                     hc = e.hc;
 255                 }
 256             } while ((hc== null) && (!empty()));
 257             return hc;
 258         }
 259     }
 260 
 261     /* return a still valid, unused HttpClient */
 262     synchronized void put(HttpClient h) {
 263         if (size() >= KeepAliveCache.getMaxConnections()) {
 264             h.closeServer(); // otherwise the connection remains in limbo
 265         } else {
 266             push(new KeepAliveEntry(h, System.currentTimeMillis()));
 267         }
 268     }
 269 
 270     /*
 271      * Do not serialize this class!
 272      */
 273     private void writeObject(java.io.ObjectOutputStream stream)
 274     throws IOException {
 275         throw new NotSerializableException();
 276     }
 277 
 278     private void readObject(java.io.ObjectInputStream stream)
 279     throws IOException, ClassNotFoundException {
 280         throw new NotSerializableException();
 281     }
 282 }
 283 
 284 
 285 class KeepAliveKey {
 286     private String      protocol = null;
 287     private String      host = null;
 288     private int         port = 0;
 289     private Object      obj = null; // additional key, such as socketfactory
 290 
 291     /**
 292      * Constructor
 293      *
 294      * @param url the URL containing the protocol, host and port information
 295      */
 296     public KeepAliveKey(URL url, Object obj) {
 297         this.protocol = url.getProtocol();
 298         this.host = url.getHost();
 299         this.port = url.getPort();
 300         this.obj = obj;
 301     }
 302 
 303     /**
 304      * Determine whether or not two objects of this type are equal
 305      */
 306     @Override
 307     public boolean equals(Object obj) {
 308         if ((obj instanceof KeepAliveKey) == false)
 309             return false;
 310         KeepAliveKey kae = (KeepAliveKey)obj;
 311         return host.equals(kae.host)
 312             && (port == kae.port)
 313             && protocol.equals(kae.protocol)
 314             && this.obj == kae.obj;
 315     }
 316 
 317     /**
 318      * The hashCode() for this object is the string hashCode() of
 319      * concatenation of the protocol, host name and port.
 320      */
 321     @Override
 322     public int hashCode() {
 323         String str = protocol+host+port;
 324         return this.obj == null? str.hashCode() :
 325             str.hashCode() + this.obj.hashCode();
 326     }
 327 }
 328 
 329 class KeepAliveEntry {
 330     HttpClient hc;
 331     long idleStartTime;
 332 
 333     KeepAliveEntry(HttpClient hc, long idleStartTime) {
 334         this.hc = hc;
 335         this.idleStartTime = idleStartTime;
 336     }
 337 }