workqueuefrontier.html

用JAVA编写的,在做实验的时候留下来的,本来想删的,但是传上来,大家分享吧

<a name="564" href="#564">564</a> <em>     * </em>
<a name="565" href="#565">565</a> <em>     * @param q</em>
<a name="566" href="#566">566</a> <em>     */</em>
<a name="567" href="#567">567</a>     <strong>private</strong> <strong>void</strong> unretireQueue(<a href="../../../../org/archive/crawler/frontier/WorkQueue.html">WorkQueue</a> q) {
<a name="568" href="#568">568</a>         deactivateQueue(q);
<a name="569" href="#569">569</a>         q.setRetired(false); 
<a name="570" href="#570">570</a>         incrementQueuedUriCount(q.getCount());
<a name="571" href="#571">571</a>     }
<a name="572" href="#572">572</a> 
<a name="573" href="#573">573</a>     <em>/**<em>*</em></em>
<a name="574" href="#574">574</a> <em>     * Return the work queue for the given CrawlURI's classKey. URIs</em>
<a name="575" href="#575">575</a> <em>     * are ordered and politeness-delayed within their 'class'.</em>
<a name="576" href="#576">576</a> <em>     * If the requested queue is not found, a new instance is created.</em>
<a name="577" href="#577">577</a> <em>     * </em>
<a name="578" href="#578">578</a> <em>     * @param curi CrawlURI to base queue on</em>
<a name="579" href="#579">579</a> <em>     * @return the found or created ClassKeyQueue</em>
<a name="580" href="#580">580</a> <em>     */</em>
<a name="581" href="#581">581</a>     <strong>protected</strong> <strong>abstract</strong> <a href="../../../../org/archive/crawler/frontier/WorkQueue.html">WorkQueue</a> getQueueFor(<a href="../../../../org/archive/crawler/datamodel/CrawlURI.html">CrawlURI</a> curi);
<a name="582" href="#582">582</a> 
<a name="583" href="#583">583</a>     <em>/**<em>*</em></em>
<a name="584" href="#584">584</a> <em>     * Return the work queue for the given classKey, or null</em>
<a name="585" href="#585">585</a> <em>     * if no such queue exists.</em>
<a name="586" href="#586">586</a> <em>     * </em>
<a name="587" href="#587">587</a> <em>     * @param classKey key to look for</em>
<a name="588" href="#588">588</a> <em>     * @return the found WorkQueue</em>
<a name="589" href="#589">589</a> <em>     */</em>
<a name="590" href="#590">590</a>     <strong>protected</strong> <strong>abstract</strong> <a href="../../../../org/archive/crawler/frontier/WorkQueue.html">WorkQueue</a> getQueueFor(String classKey);
<a name="591" href="#591">591</a>     
<a name="592" href="#592">592</a>     <em>/**<em>*</em></em>
<a name="593" href="#593">593</a> <em>     * Return the next CrawlURI to be processed (and presumably</em>
<a name="594" href="#594">594</a> <em>     * visited/fetched) by a a worker thread.</em>
<a name="595" href="#595">595</a> <em>     *</em>
<a name="596" href="#596">596</a> <em>     * Relies on the readyClassQueues having been loaded with</em>
<a name="597" href="#597">597</a> <em>     * any work queues that are eligible to provide a URI. </em>
<a name="598" href="#598">598</a> <em>     *</em>
<a name="599" href="#599">599</a> <em>     * @return next CrawlURI to be processed. Or null if none is available.</em>
<a name="600" href="#600">600</a> <em>     *</em>
<a name="601" href="#601">601</a> <em>     * @see org.archive.crawler.framework.Frontier#next()</em>
<a name="602" href="#602">602</a> <em>     */</em>
<a name="603" href="#603">603</a>     <strong>public</strong> <a href="../../../../org/archive/crawler/datamodel/CrawlURI.html">CrawlURI</a> next()
<a name="604" href="#604">604</a>     throws InterruptedException, <a href="../../../../org/archive/crawler/framework/exceptions/EndedException.html">EndedException</a> {
<a name="605" href="#605">605</a>         <strong>while</strong> (<strong>true</strong>) { <em class="comment">// loop left only by explicit return or exception</em>
<a name="606" href="#606">606</a>             <strong>long</strong> now = System.currentTimeMillis();
<a name="607" href="#607">607</a> 
<a name="608" href="#608">608</a>             <em class="comment">// Do common checks for pause, terminate, bandwidth-hold</em>
<a name="609" href="#609">609</a>             preNext(now);
<a name="610" href="#610">610</a>             
<a name="611" href="#611">611</a>             <strong>synchronized</strong>(readyClassQueues) {
<a name="612" href="#612">612</a>                 <strong>int</strong> activationsNeeded = targetSizeForReadyQueues() - readyClassQueues.size();
<a name="613" href="#613">613</a>                 <strong>while</strong>(activationsNeeded > 0 &amp;&amp; !inactiveQueues.isEmpty()) {
<a name="614" href="#614">614</a>                     activateInactiveQueue();
<a name="615" href="#615">615</a>                     activationsNeeded--;
<a name="616" href="#616">616</a>                 }
<a name="617" href="#617">617</a>             }
<a name="618" href="#618">618</a>                    
<a name="619" href="#619">619</a>             <a href="../../../../org/archive/crawler/frontier/WorkQueue.html">WorkQueue</a> readyQ = <strong>null</strong>;
<a name="620" href="#620">620</a>             Object key = readyClassQueues.poll(DEFAULT_WAIT,TimeUnit.MILLISECONDS);
<a name="621" href="#621">621</a>             <strong>if</strong> (key != <strong>null</strong>) {
<a name="622" href="#622">622</a>                 readyQ = (WorkQueue)<strong>this</strong>.allQueues.get(key);
<a name="623" href="#623">623</a>             }
<a name="624" href="#624">624</a>             <strong>if</strong> (readyQ != <strong>null</strong>) {
<a name="625" href="#625">625</a>                 <strong>while</strong>(<strong>true</strong>) { <em class="comment">// loop left by explicit return or break on empty</em>
<a name="626" href="#626">626</a>                     <a href="../../../../org/archive/crawler/datamodel/CrawlURI.html">CrawlURI</a> curi = <strong>null</strong>;
<a name="627" href="#627">627</a>                     <strong>synchronized</strong>(readyQ) {
<a name="628" href="#628">628</a>                         curi = readyQ.peek(<strong>this</strong>);                     
<a name="629" href="#629">629</a>                         <strong>if</strong> (curi != <strong>null</strong>) {
<a name="630" href="#630">630</a>                             <em class="comment">// check if curi belongs in different queue</em>
<a name="631" href="#631">631</a>                             String currentQueueKey = getClassKey(curi);
<a name="632" href="#632">632</a>                             <strong>if</strong> (currentQueueKey.equals(curi.getClassKey())) {
<a name="633" href="#633">633</a>                                 <em class="comment">// curi was in right queue, emit</em>
<a name="634" href="#634">634</a>                                 noteAboutToEmit(curi, readyQ);
<a name="635" href="#635">635</a>                                 inProcessQueues.add(readyQ);
<a name="636" href="#636">636</a>                                 <strong>return</strong> curi;
<a name="637" href="#637">637</a>                             }
<a name="638" href="#638">638</a>                             <em class="comment">// URI's assigned queue has changed since it</em>
<a name="639" href="#639">639</a>                             <em class="comment">// was queued (eg because its IP has become</em>
<a name="640" href="#640">640</a>                             <em class="comment">// known). Requeue to new queue.</em>
<a name="641" href="#641">641</a>                             curi.setClassKey(currentQueueKey);
<a name="642" href="#642">642</a>                             readyQ.dequeue(<strong>this</strong>);
<a name="643" href="#643">643</a>                             decrementQueuedCount(1);
<a name="644" href="#644">644</a>                             curi.setHolderKey(<strong>null</strong>);
<a name="645" href="#645">645</a>                             <em class="comment">// curi will be requeued to true queue after lock</em>
<a name="646" href="#646">646</a>                             <em class="comment">//  on readyQ is released, to prevent deadlock</em>
<a name="647" href="#647">647</a>                         } <strong>else</strong> {
<a name="648" href="#648">648</a>                             <em class="comment">// readyQ is empty and ready: it's exhausted</em>
<a name="649" href="#649">649</a>                             <em class="comment">// release held status, allowing any subsequent </em>
<a name="650" href="#650">650</a>                             <em class="comment">// enqueues to again put queue in ready</em>
<a name="651" href="#651">651</a>                             readyQ.clearHeld();
<a name="652" href="#652">652</a>                             <strong>break</strong>;
<a name="653" href="#653">653</a>                         }
<a name="654" href="#654">654</a>                     }
<a name="655" href="#655">655</a>                     <strong>if</strong>(curi!=<strong>null</strong>) {
<a name="656" href="#656">656</a>                         <em class="comment">// complete the requeuing begun earlier</em>
<a name="657" href="#657">657</a>                         sendToQueue(curi);
<a name="658" href="#658">658</a>                     }
<a name="659" href="#659">659</a>                 }
<a name="660" href="#660">660</a>             } <strong>else</strong> {
<a name="661" href="#661">661</a>                 <em class="comment">// ReadyQ key wasn't in all queues: unexpected</em>
<a name="662" href="#662">662</a>                 <strong>if</strong> (key != <strong>null</strong>) {
<a name="663" href="#663">663</a>                     logger.severe(<span class="string">"Key "</span>+ key +
<a name="664" href="#664">664</a>                         <span class="string">" in readyClassQueues but not allQueues"</span>);
<a name="665" href="#665">665</a>                 }
<a name="666" href="#666">666</a>             }
<a name="667" href="#667">667</a> 
<a name="668" href="#668">668</a>             <strong>if</strong>(shouldTerminate) {
<a name="669" href="#669">669</a>                 <em class="comment">// skip subsequent steps if already on last legs</em>
<a name="670" href="#670">670</a>                 <strong>throw</strong> <strong>new</strong> <a href="../../../../org/archive/crawler/framework/exceptions/EndedException.html">EndedException</a>(<span class="string">"shouldTerminate is true"</span>);
<a name="671" href="#671">671</a>             }
<a name="672" href="#672">672</a>                 
<a name="673" href="#673">673</a>             <strong>if</strong>(inProcessQueues.size()==0) {
<a name="674" href="#674">674</a>                 <em class="comment">// Nothing was ready or in progress or imminent to wake; ensure </em>
<a name="675" href="#675">675</a>                 <em class="comment">// any piled-up pending-scheduled URIs are considered</em>
<a name="676" href="#676">676</a>                 <strong>this</strong>.alreadyIncluded.requestFlush();
<a name="677" href="#677">677</a>             }    
<a name="678" href="#678">678</a>         }
<a name="679" href="#679">679</a>     }
<a name="680" href="#680">680</a> 
<a name="681" href="#681">681</a>     <strong>private</strong> <strong>int</strong> targetSizeForReadyQueues() {
<a name="682" href="#682">682</a>         <strong>return</strong> targetSizeForReadyQueues;
<a name="683" href="#683">683</a>     }
<a name="684" href="#684">684</a> 
<a name="685" href="#685">685</a>     <em>/**<em>*</em></em>
<a name="686" href="#686">686</a> <em>     * Return the 'cost' of a CrawlURI (how much of its associated</em>
<a name="687" href="#687">687</a> <em>     * queue's budget it depletes upon attempted processing)</em>
<a name="688" href="#688">688</a> <em>     * </em>
<a name="689" href="#689">689</a> <em>     * @param curi</em>
<a name="690" href="#690">690</a> <em>     * @return the associated cost</em>
<a name="691" href="#691">691</a> <em>     */</em>
<a name="692" href="#692">692</a>     <strong>private</strong> <strong>int</strong> getCost(<a href="../../../../org/archive/crawler/datamodel/CrawlURI.html">CrawlURI</a> curi) {
<a name="693" href="#693">693</a>         <strong>int</strong> cost = curi.getHolderCost();
<a name="694" href="#694">694</a>         <strong>if</strong> (cost == CrawlURI.UNCALCULATED) {
<a name="695" href="#695">695</a>             cost = costAssignmentPolicy.costOf(curi);
<a name="696" href="#696">696</a>             curi.setHolderCost(cost);
<a name="697" href="#697">697</a>         }
<a name="698" href="#698">698</a>         <strong>return</strong> cost;
<a name="699" href="#699">699</a>     }
<a name="700" href="#700">700</a>     
<a name="701" href="#701">701</a>     <em>/**<em>*</em></em>
<a name="702" href="#702">702</a> <em>     * Activate an inactive queue, if any are available. </em>
<a name="703" href="#703">703</a> <em>     */</em>
<a name="704" href="#704">704</a>     <strong>private</strong> <strong>void</strong> activateInactiveQueue() {
<a name="705" href=