{"id":1980,"date":"2019-10-09T08:25:47","date_gmt":"2019-10-09T00:25:47","guid":{"rendered":"https:\/\/coderbee.net\/?p=1980"},"modified":"2019-10-08T22:13:27","modified_gmt":"2019-10-08T14:13:27","slug":"juc-%e5%bb%b6%e8%bf%9f%e9%98%9f%e5%88%97-delayqueue","status":"publish","type":"post","link":"https:\/\/coderbee.net\/index.php\/concurrent\/20191009\/1980","title":{"rendered":"JUC \u5ef6\u8fdf\u961f\u5217 DelayQueue"},"content":{"rendered":"<p>DelayQueue \u4e00\u4e2a\u65e0\u754c\u963b\u585e\u961f\u5217\uff0c\u53ea\u6709\u5728\u5ef6\u8fdf\u671f\u6ee1\u65f6\u624d\u80fd\u4ece\u4e2d\u63d0\u53d6\u5143\u7d20\u3002\u57fa\u4e8e <code>PriorityQueue<\/code> \u5b9e\u73b0\u7684\u5ef6\u8fdf\u961f\u5217\uff0c\u7528 <code>ReentrantLock<\/code> \u63d0\u4f9b\u7ebf\u7a0b\u5b89\u5168\u6027\u3002<\/p>\n<p>\u5176\u5143\u7d20\u5fc5\u987b\u5b9e\u73b0 <code>Delayed<\/code> \u63a5\u53e3\u3002<\/p>\n<p>\u8be5\u7c7b\u53ef\u7528\u6765\u5b9e\u73b0\u5b9a\u65f6\u8c03\u5ea6\u7684\u529f\u80fd\uff0c\u5f53\u524d\u65f6\u95f4\u4e0e\u4efb\u52a1\u7684\u4e0b\u6b21\u6267\u884c\u65f6\u95f4\u7684\u8ddd\u79bb\u4f5c\u4e3a\u5ef6\u8fdf\u65f6\u95f4\u3002<\/p>\n<p>\u5b9e\u73b0\u4e0a\u91c7\u7528 <a href=\"http:\/\/www.cs.wustl.edu\/~schmidt\/POSA\/POSA2\/\">Leader_Follower \u6a21\u5f0f<\/a> \u7684\u53d8\u4f53\u8fdb\u884c\u4f18\u5316\uff1aleader \u8fdb\u884c\u9650\u65f6\u7b49\u5f85\uff0c\u5176\u4ed6\u7ebf\u7a0b\u4f5c\u4e3a follower \u65e0\u9650\u7b49\u5f85\u3002leader \u5728\u7b49\u5f85\u7684\u8fc7\u7a0b\u4e2d\u53ef\u80fd\u63d2\u5165\u4e00\u4e2a\u66f4\u5feb\u5230\u671f\u7684\u5143\u7d20\uff0c\u90a3\u4e48\u65e7 leader \u5c31\u4f1a\u88ab\u4f5c\u5e9f\uff0c\u5982\u679c\u53c8\u6709\u4e00\u4e2a\u7ebf\u7a0b\u6765\u83b7\u53d6\uff0c\u90a3\u4e48\u5b83\u4f1a\u4f5c\u4e3a\u65b0\u7684 leader \u6839\u636e\u65b0\u7684\u961f\u5217\u5934\u5143\u7d20\u8fdb\u884c\u9650\u65f6\u7b49\u5f85\u3002<\/p>\n<p><!--more--><\/p>\n<pre><code class=\"java\">public interface Delayed extends Comparable&lt;Delayed&gt; {\n    \/\/ \u8fd4\u56de\u4e0e\u6b64\u5bf9\u8c61\u76f8\u5173\u7684\u5269\u4f59\u5ef6\u8fdf\u65f6\u95f4\uff0c\u4ee5\u7ed9\u5b9a\u7684\u65f6\u95f4\u5355\u4f4d\u8868\u793a\u3002\n    long getDelay(TimeUnit unit);\n}\n\npublic class DelayQueue&lt;E extends Delayed&gt; extends AbstractQueue&lt;E&gt;\n    implements BlockingQueue&lt;E&gt; {\n\n    private final transient ReentrantLock lock = new ReentrantLock();\n    private final PriorityQueue&lt;E&gt; q = new PriorityQueue&lt;E&gt;();\n\n    \/\/ \u8be5\u53d8\u91cf\u88ab\u8d4b\u503c\u7ed9\u7b49\u5f85\u5143\u7d20\u7684\u961f\u5217\u5934\u7ed3\u70b9\u3002\u8fd9\u662f Leader_Follower \u6a21\u5f0f\u7684\u53d8\u4f53\uff0c\n    \/\/ \u7528\u4e8e\u51cf\u5c11\u9650\u65f6\u7b49\u5f85\u3002\u5f53\u4e00\u4e2a\u7ebf\u7a0b\u6210\u4e3a leader \u65f6\uff0c\u5b83\u53ea\u7b49\u5f85\u4e0b\u4e00\u4e2a\u5ef6\u8fdf\u5230\u8fbe\uff0c\n    \/\/ \u4f46\u5176\u4ed6\u7684\u7ebf\u7a0b\u90fd\u662f\u65e0\u9650\u7b49\u5f85\u7684\u3002\n    \/\/ leader \u7ebf\u7a0b\u5fc5\u987b\u5728\u4ece take() \u6216 poll(...) \u65b9\u6cd5\u8fd4\u56de\u524d\u901a\u77e5\u5176\u4ed6\u7ebf\u7a0b,\n    \/\/ \u9664\u975e\u5176\u4ed6\u7ebf\u7a0b\u5728\u8fd9\u4e2a\u8fc7\u7a0b\u4e2d\u6210\u4e3a\u4e86 leader \u3002\n    \/\/ \u6bcf\u5f53\u961f\u5217\u7684\u5934\u88ab\u4e00\u4e2a\u66f4\u65e9\u5230\u671f\u7684\u5143\u7d20\u53d6\u4ee3\u65f6\uff0cleader \u5b57\u6bb5\u8bbe\u7f6e\u4e3a null \u8868\u793a\u4f5c\u5e9f\uff0c\n    \/\/ \u540c\u65f6\uff0c\u4e00\u4e9b\u7b49\u5f85\u7ebf\u7a0b\u3001\u4e0d\u4e00\u5b9a\u5fc5\u987b\u662f\u5f53\u524d\u7684 leader \u88ab\u901a\u77e5\u3002\n    \/\/ \u56e0\u6b64\u7b49\u5f85\u7ebf\u7a0b\u5fc5\u987b\u51c6\u5907\u597d\u5728\u7b49\u5f85\u8fc7\u7a0b\u4e2d\u83b7\u53d6\u548c\u5931\u53bb leadership\u3002\n    private Thread leader = null;\n\n    \/\/ \u5f53\u4e00\u4e2a\u65b0\u7684\u5143\u7d20\u5728\u961f\u5217\u5934\u90e8\u53d8\u7684\u53ef\u7528\u6216\u65b0\u7684\u7ebf\u7a0b\u53ef\u80fd\u9700\u8981\u6210\u4e3a leader \u65f6\u53d1\u51fa\u901a\u77e5\u3002\n    private final Condition available = lock.newCondition();\n\n    public boolean offer(E e) {\n        final ReentrantLock lock = this.lock;\n        lock.lock();\n        try {\n            q.offer(e);\n            if (q.peek() == e) {\n                \/\/ \u65b0\u5143\u7d20\u6210\u4e3a\u4e86\u961f\u5217\u7684\u5934\uff0c\u4f5c\u5e9f\u5df2\u6709\u7684 leader\uff0c\u901a\u77e5\u7b49\u5f85\u7ebf\u7a0b\u3002\n                \/\/ \u95ee\u98981\uff1a\u4e3a\u5565\u8981\u5e9f\u5f03 leader\uff1f\n                leader = null;\n                available.signal();\n            }\n            return true;\n        } finally {\n            lock.unlock();\n        }\n    }\n\n    public E take() throws InterruptedException {\n        final ReentrantLock lock = this.lock;\n        lock.lockInterruptibly();\n        try {\n            for (;;) {\n                E first = q.peek();\n                if (first == null)\n                    available.await();\n                    \/\/ \u961f\u5217\u4e3a\u7a7a\uff0c\u53ea\u80fd\u65e0\u9650\u7b49\u5f85\n                else {\n                    long delay = first.getDelay(NANOSECONDS);\n\n                    \/\/ \u961f\u5217\u5934\u5230\u671f\u4e86\n                    \/\/ \u6b64\u65f6\u4e0d\u4e00\u5b9a\u662f leader \u83b7\u5f97\u4e86\u961f\u5217\u5934\u5143\u7d20\n                    if (delay &lt;= 0)\n                        return q.poll();\n\n                    \/\/ \u5728\u7b49\u5f85\u7684\u8fc7\u7a0b\u4e2d\u4e0d\u6301\u6709\u5f15\u7528\u3002\n                    \/\/ \u95ee\u98982\uff1a\u4e3a\u5565\u4e13\u95e8\u653e\u5f03\u5f15\u7528\uff1f\n                    first = null;\n\n                    if (leader != null)\n                        \/\/ \u5982\u679c\u5df2\u7ecf\u6709 leader \u4e86\uff0c\u4f5c\u4e3a follower \u8fdb\u884c\u65e0\u9650\u7b49\u5f85\n                        available.await();\n\n                    else {\n                        \/\/ \u961f\u5217\u91cc\u6709\u672a\u5230\u671f\u7684\u5143\u7d20\u3001\u4e14\u6ca1\u6709 leader\uff0c\u81ea\u5df1\u6210\u4e3a leader\u3002\n                        Thread thisThread = Thread.currentThread();\n                        leader = thisThread;\n                        \/\/ \u4f5c\u4e3a leader \u8fdb\u884c\u9650\u65f6\u7b49\u5f85\n                        try {\n                            available.awaitNanos(delay);\n                        } finally {\n                            \/\/ \u4f5c\u5e9f leader\u3002\n                            if (leader == thisThread)\n                                \/\/ \u95ee\u98983\uff1a\u4e3a\u5565\u5728\u8fd9\u91cc\u4f5c\u5e9f leader\uff1f\n                                leader = null;\n                        }\n                    }\n                }\n            }\n        } finally {\n            \/\/ leader \u4e0d\u4e3a\u7a7a\u8bf4\u660e leader \u7ebf\u7a0b\u8fd8\u5728\u9650\u65f6\u7b49\u5f85\uff0c\u4e0d\u9700\u8981\u5524\u9192\n            if (leader == null &amp;&amp; q.peek() != null)\n                available.signal();\n\n            lock.unlock();\n        }\n    }\n}\n<\/code><\/pre>\n<h2>\u95ee\u9898\u56de\u7b54<\/h2>\n<ul>\n<li>\n<p>\u95ee\u98981\uff1a\u6b64\u65f6\u53ef\u80fd\u662f\u65b0\u5143\u7d20\u6bd4\u539f\u6765\u7684 leader \u7684\u7b49\u5f85\u65f6\u95f4\u66f4\u77ed\uff0c\u539f\u6765\u7684 leader \u5931\u53bb\u4e86 leadership\u3002\u6b64\u5904\u4f5c\u5e9f\u662f\u4e3a\u4e86\u8ba9\u65e7 leader \u7b49\u5f85\u7684\u5143\u7d20\u4e4b\u524d\u7684\u5143\u7d20\u80fd\u591f\u5c3d\u5feb\u88ab\u5904\u7406\u3002\u6bd4\u5982\u65e7 leader \u8fdb\u884c\u9650\u65f6\u7b49\u5f85 1000ms\uff0c\u6b64\u65f6\u8fde\u7eed\u8fdb\u6765 30ms\/50ms \u7684\u4e24\u4e2a\u5143\u7d20\uff1b\u5982\u679c\u6b64\u65f6\u4e0d\u4f5c\u5e9f\uff0c\u540e\u7eed\u5c31\u6709\u7ebf\u7a0b\u6765\u83b7\u53d6\u5143\u7d20\uff0c\u4f1a\u56e0\u4e3a\u6709\u65e7 leader \u8fdb\u5165\u65e0\u9650\u7b49\u5f85\uff1b\u4f5c\u5e9f\u540e\uff0c\u540e\u7eed\u7684\u7ebf\u7a0b\u53ef\u80fd\u53ea\u9700\u8981\u9650\u65f6\u7b49\u5f85 30ms\uff0c\u63d0\u9ad8\u4e86\u5ef6\u8fdf\u961f\u5217\u7684\u51c6\u786e\u6027\u3002<\/p>\n<\/li>\n<li>\n<p>\u95ee\u98982\uff1a\u56e0\u4e3a\u5728\u7b49\u5f85\u8fc7\u7a0b\u4e2d\uff0c\u8fd9\u4e2a\u5143\u7d20\u53ef\u80fd\u88ab\u5176\u4ed6\u7ebf\u7a0b\u5904\u7406\u3001\u9700\u8981\u8fdb\u884c\u5783\u573e\u56de\u6536\uff0c\u9632\u6b62\u88ab\u8fd9\u4e2a\u7ebf\u7a0b\u7684\u6808\u5f15\u7528\u4e86\u800c\u6ca1\u6cd5\u5783\u573e\u56de\u6536\u3002<\/p>\n<\/li>\n<li>\n<p>\u95ee\u98983\uff1a\u9996\u5148\uff0cleader \u53ef\u80fd\u5728\u7b49\u5f85\u7684\u8fc7\u7a0b\u4e2d\u53d8\u4e86\uff0c\u56e0\u6b64\u9700\u8981\u5148\u5224\u65ad <code>leader == thisThread<\/code>\u3002\u5982\u679c\u5728 return \u8bed\u53e5\u524d\u8fdb\u884c\u4f5c\u5e9f\uff0c\u5bf9\u4e8e\u83b7\u53d6\u7ade\u4e89\u4e0d\u6fc0\u70c8\u7684\u573a\u666f\u662f\u4e0d\u9700\u8981\u4f5c\u5e9f\uff0c\u8fd9\u6837\u4f1a\u591a\u51fa\u4e00\u4e9b\u6ca1\u5fc5\u8981\u7684\u5224\u65ad <code>leader == thisThread<\/code>\u3002\u53e6\u5916\u662f\u9650\u65f6\u7b49\u5f85\u5230\u65f6\u540e\u5e94\u8be5\u90fd\u80fd\u83b7\u5f97\u5143\u7d20\uff0c\u7ebf\u7a0b\u5230\u65f6\u5524\u9192\u540e\u4f5c\u5e9f leader \u4e5f\u662f\u5408\u7406\u7684\u3002<\/p>\n<\/li>\n<\/ul>\n<h2>\u5c0f\u7ed3<\/h2>\n<p>\u5f15\u5165 leader_follower \u6a21\u5f0f\u662f\u4e3a\u4e86\u4f18\u5316\u5728\u9ad8\u5e76\u53d1\u4e0b\u7684\u7b49\u5f85\uff0c\u5c3d\u91cf\u7528\u65e0\u9650\u7b49\u5f85\u66ff\u4ee3\u9650\u65f6\u7b49\u5f85\uff0c\u4e5f\u9632\u6b62\u4e86\u591a\u4e2a\u7ebf\u7a0b\u540c\u65f6\u7ade\u4e89\u5934\u7ed3\u70b9\u3002<\/p>\n<p>\u5b9e\u73b0\u4e0a\u505a\u5230\u4e86 GC \u53cb\u597d\u3002<\/p>\n<hr \/>\n<p>\u6b22\u8fce\u5173\u6ce8\u6211\u7684\u5fae\u4fe1\u516c\u4f17\u53f7: <strong>coderbee\u7b14\u8bb0<\/strong>\uff0c\u53ef\u4ee5\u66f4\u53ca\u65f6\u56de\u590d\u4f60\u7684\u8ba8\u8bba\u3002<br \/>\n<img loading=\"lazy\" decoding=\"async\" width=\"258\" height=\"258\" src=\"https:\/\/coderbee.net\/wp-content\/uploads\/2019\/01\/coderbee-note.jpg\" class=\"alignnone size-full wp-image-1707\" \/><\/p>\n","protected":false},"excerpt":{"rendered":"<p>DelayQueue \u4e00\u4e2a\u65e0\u754c\u963b\u585e\u961f\u5217\uff0c\u53ea\u6709\u5728\u5ef6\u8fdf\u671f\u6ee1\u65f6\u624d\u80fd\u4ece\u4e2d\u63d0\u53d6\u5143\u7d20\u3002\u57fa\u4e8e  &hellip; <a href=\"https:\/\/coderbee.net\/index.php\/concurrent\/20191009\/1980\">\u7ee7\u7eed\u9605\u8bfb <span class=\"meta-nav\">&rarr;<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[121],"tags":[330,329],"_links":{"self":[{"href":"https:\/\/coderbee.net\/index.php\/wp-json\/wp\/v2\/posts\/1980"}],"collection":[{"href":"https:\/\/coderbee.net\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/coderbee.net\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/coderbee.net\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/coderbee.net\/index.php\/wp-json\/wp\/v2\/comments?post=1980"}],"version-history":[{"count":2,"href":"https:\/\/coderbee.net\/index.php\/wp-json\/wp\/v2\/posts\/1980\/revisions"}],"predecessor-version":[{"id":1982,"href":"https:\/\/coderbee.net\/index.php\/wp-json\/wp\/v2\/posts\/1980\/revisions\/1982"}],"wp:attachment":[{"href":"https:\/\/coderbee.net\/index.php\/wp-json\/wp\/v2\/media?parent=1980"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/coderbee.net\/index.php\/wp-json\/wp\/v2\/categories?post=1980"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/coderbee.net\/index.php\/wp-json\/wp\/v2\/tags?post=1980"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}