{"id":765,"date":"2016-04-19T13:41:04","date_gmt":"2016-04-19T05:41:04","guid":{"rendered":"https:\/\/yanjingang.com\/blog\/?p=765"},"modified":"2018-12-17T20:26:55","modified_gmt":"2018-12-17T12:26:55","slug":"%e4%b8%80%e8%87%b4%e6%80%a7hash%e7%ae%97%e6%b3%95%e8%af%a6%e8%a7%a3","status":"publish","type":"post","link":"https:\/\/yanjingang.com\/blog\/?p=765","title":{"rendered":"\u4e00\u81f4\u6027HASH\u7b97\u6cd5\u8be6\u89e3"},"content":{"rendered":"<h3>\u57fa\u672c\u573a\u666f<\/h3>\n<p>\u6bd4\u5982\u4f60\u6709 N \u4e2a cache \u670d\u52a1\u5668\uff08\u540e\u9762\u7b80\u79f0 cache \uff09\uff0c\u90a3\u4e48\u5982\u4f55\u5c06\u4e00\u4e2a\u5bf9\u8c61 object \u6620\u5c04\u5230 N \u4e2a cache \u4e0a\u5462\uff0c\u4f60\u5f88\u53ef\u80fd\u4f1a\u91c7\u7528\u7c7b\u4f3c\u4e0b\u9762\u7684\u901a\u7528\u65b9\u6cd5\u8ba1\u7b97 object \u7684 hash \u503c\uff0c\u7136\u540e\u5747\u5300\u7684\u6620\u5c04\u5230\u5230 N \u4e2a cache \uff1b<\/p>\n<blockquote><p>\u6c42\u4f59\u7b97\u6cd5: hash(object)%N<\/p><\/blockquote>\n<p>\u4e00\u5207\u90fd\u8fd0\u884c\u6b63\u5e38\uff0c\u518d\u8003\u8651\u5982\u4e0b\u7684\u4e24\u79cd\u60c5\u51b5\uff1b<br \/>\n1 \u4e00\u4e2a cache \u670d\u52a1\u5668 m down \u6389\u4e86\uff08\u5728\u5b9e\u9645\u5e94\u7528\u4e2d\u5fc5\u987b\u8981\u8003\u8651\u8fd9\u79cd\u60c5\u51b5\uff09\uff0c\u8fd9\u6837\u6240\u6709\u6620\u5c04\u5230 cache m \u7684\u5bf9\u8c61\u90fd\u4f1a\u5931\u6548\uff0c\u600e\u4e48\u529e\uff0c\u9700\u8981\u628a cache m \u4ece cache \u4e2d\u79fb\u9664\uff0c\u8fd9\u65f6\u5019 cache \u662f N-1 \u53f0\uff0c\u6620\u5c04\u516c\u5f0f\u53d8\u6210\u4e86 hash(object)%(N-1) \uff1b<br \/>\n2 \u7531\u4e8e\u8bbf\u95ee\u52a0\u91cd\uff0c\u9700\u8981\u6dfb\u52a0 cache \uff0c\u8fd9\u65f6\u5019 cache \u662f N+1 \u53f0\uff0c\u6620\u5c04\u516c\u5f0f\u53d8\u6210\u4e86 hash(object)%(N+1) \uff1b<br \/>\n1 \u548c 2 \u610f\u5473\u7740\u4ec0\u4e48\uff1f\u8fd9\u610f\u5473\u7740\u7a81\u7136\u4e4b\u95f4\u51e0\u4e4e\u6240\u6709\u7684 cache \u90fd\u5931\u6548\u4e86\u3002\u5bf9\u4e8e\u670d\u52a1\u5668\u800c\u8a00\uff0c\u8fd9\u662f\u4e00\u573a\u707e\u96be\uff0c\u6d2a\u6c34\u822c\u7684\u8bbf\u95ee\u90fd\u4f1a\u76f4\u63a5\u51b2\u5411\u540e\u53f0\u670d\u52a1\u5668\uff1b<br \/>\n\u518d\u6765\u8003\u8651\u7b2c\u4e09\u4e2a\u95ee\u9898\uff0c\u7531\u4e8e\u786c\u4ef6\u80fd\u529b\u8d8a\u6765\u8d8a\u5f3a\uff0c\u4f60\u53ef\u80fd\u60f3\u8ba9\u540e\u9762\u6dfb\u52a0\u7684\u8282\u70b9\u591a\u505a\u70b9\u6d3b\uff0c\u663e\u7136\u4e0a\u9762\u7684 hash \u7b97\u6cd5\u4e5f\u505a\u4e0d\u5230\u3002<br \/>\n\u6709\u4ec0\u4e48\u65b9\u6cd5\u53ef\u4ee5\u6539\u53d8\u8fd9\u4e2a\u72b6\u51b5\u5462\uff0c\u8fd9\u5c31\u662f consistent hashing&#8230;<\/p>\n<h3>hash \u7b97\u6cd5\u548c\u5355\u8c03\u6027<\/h3>\n<p>Hash \u7b97\u6cd5\u7684\u4e00\u4e2a\u8861\u91cf\u6307\u6807\u662f\u5355\u8c03\u6027\uff08 Monotonicity \uff09\uff0c\u5b9a\u4e49\u5982\u4e0b\uff1a<br \/>\n\u5355\u8c03\u6027\u662f\u6307\u5982\u679c\u5df2\u7ecf\u6709\u4e00\u4e9b\u5185\u5bb9\u901a\u8fc7\u54c8\u5e0c\u5206\u6d3e\u5230\u4e86\u76f8\u5e94\u7684\u7f13\u51b2\u4e2d\uff0c\u53c8\u6709\u65b0\u7684\u7f13\u51b2\u52a0\u5165\u5230\u7cfb\u7edf\u4e2d\u3002\u54c8\u5e0c\u7684\u7ed3\u679c\u5e94\u80fd\u591f\u4fdd\u8bc1\u539f\u6709\u5df2\u5206\u914d\u7684\u5185\u5bb9\u53ef\u4ee5\u88ab\u6620\u5c04\u5230\u65b0\u7684\u7f13\u51b2\u4e2d\u53bb\uff0c\u800c\u4e0d\u4f1a\u88ab\u6620\u5c04\u5230\u65e7\u7684\u7f13\u51b2\u96c6\u5408\u4e2d\u7684\u5176\u4ed6\u7f13\u51b2\u533a\u3002<br \/>\n\u5bb9\u6613\u770b\u5230\uff0c\u4e0a\u9762\u7684\u7b80\u5355\u6c42\u4f59\u7b97\u6cd5 hash(object)%N \u96be\u4ee5\u6ee1\u8db3\u5355\u8c03\u6027\u8981\u6c42\u3002<\/p>\n<h3>Consistent Hashing \u4e00\u81f4\u6027hash\u7684\u539f\u7406<\/h3>\n<p>consistent hashing \u662f\u4e00\u79cd hash \u7b97\u6cd5\uff0c\u7b80\u5355\u7684\u8bf4\uff0c\u5728\u79fb\u9664 \/ \u6dfb\u52a0\u4e00\u4e2a cache \u65f6\uff0c\u5b83\u80fd\u591f\u5c3d\u53ef\u80fd\u5c0f\u7684\u6539\u53d8\u5df2\u5b58\u5728key \u6620\u5c04\u5173\u7cfb\uff0c\u5c3d\u53ef\u80fd\u7684\u6ee1\u8db3\u5355\u8c03\u6027\u7684\u8981\u6c42\u3002<\/p>\n<h6>1. \u73af\u5f62hash \u7a7a\u95f4<\/h6>\n<p>\u8003\u8651\u901a\u5e38\u7684 hash \u7b97\u6cd5\u90fd\u662f\u5c06 value \u6620\u5c04\u5230\u4e00\u4e2a 32 \u4e3a\u7684 key \u503c\uff0c\u4e5f\u5373\u662f 0~2^32-1 \u6b21\u65b9\u7684\u6570\u503c\u7a7a\u95f4\uff1b\u6211\u4eec\u53ef\u4ee5\u5c06\u8fd9\u4e2a\u7a7a\u95f4\u60f3\u8c61\u6210\u4e00\u4e2a\u9996\uff08 0 \uff09\u5c3e\uff08 2^32-1 \uff09\u76f8\u63a5\u7684\u5706\u73af\uff0c\u5982\u4e0b\u9762\u56fe 1 \u6240\u793a\u7684\u90a3\u6837\u3002<\/p>\n<div class=\"image-package imagebubble\"><a href=\"https:\/\/yanjingang.com\/blog\/wp-content\/uploads\/2016\/04\/1.jpg\" rel=\"attachment wp-att-766\"><img loading=\"lazy\" class=\"alignnone size-full wp-image-766\" src=\"https:\/\/yanjingang.com\/blog\/wp-content\/uploads\/2016\/04\/1.jpg\" alt=\"1\" width=\"91\" height=\"104\" \/><\/a><\/p>\n<div class=\"image-caption\">circle space<\/div>\n<\/div>\n<h6>2. \u628a\u9700\u8981\u7f13\u5b58\u7684\u5185\u5bb9(\u5bf9\u8c61)\u6620\u5c04\u5230hash \u7a7a\u95f4<\/h6>\n<p>\u63a5\u4e0b\u6765\u8003\u8651 4 \u4e2a\u5bf9\u8c61 object1~object4 \uff0c\u901a\u8fc7 hash \u51fd\u6570\u8ba1\u7b97\u51fa\u7684 hash \u503c key \u5728\u73af\u4e0a\u7684\u5206\u5e03\u5982\u56fe 2 \u6240\u793a\u3002<br \/>\nhash(object1) = key1;<br \/>\n\u2026 \u2026<br \/>\nhash(object4) = key4;<\/p>\n<div class=\"image-package imagebubble\"><a href=\"https:\/\/yanjingang.com\/blog\/wp-content\/uploads\/2016\/04\/2.jpg\" rel=\"attachment wp-att-767\"><img loading=\"lazy\" class=\"alignnone size-full wp-image-767\" src=\"https:\/\/yanjingang.com\/blog\/wp-content\/uploads\/2016\/04\/2.jpg\" alt=\"2\" width=\"234\" height=\"253\" \/><\/a><\/p>\n<div class=\"image-caption\">object<\/div>\n<\/div>\n<h6>3 .\u628a\u670d\u52a1\u5668(\u8282\u70b9)\u6620\u5c04\u5230hash \u7a7a\u95f4<\/h6>\n<p>Consistent hashing \u7684\u57fa\u672c\u601d\u60f3\u5c31\u662f\u5c06\u5bf9\u8c61\u548c cache \u90fd\u6620\u5c04\u5230\u540c\u4e00\u4e2a hash \u6570\u503c\u7a7a\u95f4\u4e2d\uff0c\u5e76\u4e14\u4f7f\u7528\u76f8\u540c\u7684 hash\u7b97\u6cd5\u3002<br \/>\n\u5047\u8bbe\u5f53\u524d\u6709 A,B \u548c C \u5171 3 \u53f0\u670d\u52a1\u5668(\u8282\u70b9)\uff0c\u90a3\u4e48\u5176\u6620\u5c04\u7ed3\u679c\u5c06\u5982\u56fe 3 \u6240\u793a\uff0c\u4ed6\u4eec\u5728 hash \u7a7a\u95f4\u4e2d\uff0c\u4ee5\u5bf9\u5e94\u7684 hash \u503c\u6392\u5217\u3002<br \/>\n\u4e00\u822c\u7684\u65b9\u6cd5\u53ef\u4ee5\u4f7f\u7528 \u670d\u52a1\u5668(\u8282\u70b9) \u673a\u5668\u7684 IP \u5730\u5740\u6216\u8005\u673a\u5668\u540d\u4f5c\u4e3a hash\u8f93\u5165\u3002<br \/>\nhash(cache A) = key A;<br \/>\n\u2026 \u2026<br \/>\nhash(cache C) = key C;<\/p>\n<div class=\"image-package imagebubble\"><a href=\"https:\/\/yanjingang.com\/blog\/wp-content\/uploads\/2016\/04\/3.jpg\" rel=\"attachment wp-att-768\"><img loading=\"lazy\" class=\"alignnone size-full wp-image-768\" src=\"https:\/\/yanjingang.com\/blog\/wp-content\/uploads\/2016\/04\/3.jpg\" alt=\"3\" width=\"283\" height=\"253\" \/><\/a><\/p>\n<div class=\"image-caption\">cache<\/div>\n<\/div>\n<h6>4 .\u628a\u5bf9\u8c61\u6620\u5c04\u5230cache<\/h6>\n<p>\u73b0\u5728cache\u548c\u5bf9\u8c61\u90fd\u5df2\u7ecf\u901a\u8fc7\u540c\u4e00\u4e2a hash \u7b97\u6cd5\u6620\u5c04\u5230 hash \u6570\u503c\u7a7a\u95f4\u4e2d\u4e86\uff0c\u63a5\u4e0b\u6765\u8981\u8003\u8651\u7684\u5c31\u662f\u5982\u4f55\u5c06\u5bf9\u8c61\u6620\u5c04\u5230 cache \u4e0a\u9762\u4e86\u3002<br \/>\n\u5728\u8fd9\u4e2a\u73af\u5f62\u7a7a\u95f4\u4e2d\uff0c\u5982\u679c\u6cbf\u7740\u987a\u65f6\u9488\u65b9\u5411\u4ece\u5bf9\u8c61\u7684 key \u503c\u51fa\u53d1\uff0c\u76f4\u5230\u9047\u89c1\u4e00\u4e2a cache \uff0c\u90a3\u4e48\u5c31\u5c06\u8be5\u5bf9\u8c61\u5b58\u50a8\u5728\u8fd9\u4e2a cache \u4e0a\uff0c\u56e0\u4e3a\u5bf9\u8c61\u548c cache \u7684 hash \u503c\u662f\u56fa\u5b9a\u7684\uff0c\u56e0\u6b64\u8fd9\u4e2a cache \u5fc5\u7136\u662f\u552f\u4e00\u548c\u786e\u5b9a\u7684\u3002\u8fd9\u6837\u4e0d\u5c31\u627e\u5230\u4e86\u5bf9\u8c61\u548c cache \u7684\u6620\u5c04\u65b9\u6cd5\u4e86\u5417\uff1f\uff01<br \/>\n\u4f9d\u7136\u7ee7\u7eed\u4e0a\u9762\u7684\u4f8b\u5b50\uff0c\u90a3\u4e48\u6839\u636e\u4e0a\u9762\u7684\u65b9\u6cd5\uff0c\u5bf9\u8c61 object1 \u5c06\u88ab\u5b58\u50a8\u5230 cache A \u4e0a\uff1b object2 \u548cobject3 \u5bf9\u5e94\u5230 cache C \uff1b object4 \u5bf9\u5e94\u5230 cache B \uff1b<\/p>\n<h6>5. \u8003\u5bdfcache \u7684\u53d8\u52a8<\/h6>\n<p>\u524d\u9762\u8bb2\u8fc7\uff0c\u901a\u8fc7 hash \u7136\u540e\u6c42\u4f59\u7684\u65b9\u6cd5\u5e26\u6765\u7684\u6700\u5927\u95ee\u9898\u5c31\u5728\u4e8e\u4e0d\u80fd\u6ee1\u8db3\u5355\u8c03\u6027\uff0c\u5f53 cache \u6709\u6240\u53d8\u52a8\u65f6\uff0c cache\u4f1a\u5931\u6548\uff0c\u8fdb\u800c\u5bf9\u540e\u53f0\u670d\u52a1\u5668\u9020\u6210\u5de8\u5927\u7684\u51b2\u51fb\uff0c\u73b0\u5728\u5c31\u6765\u5206\u6790\u5206\u6790 consistent hashing \u7b97\u6cd5\u3002<\/p>\n<ul>\n<li>5.1 <strong>\u79fb\u9664 cache<\/strong><br \/>\n\u8003\u8651\u5047\u8bbe cache B \u6302\u6389\u4e86\uff0c\u6839\u636e\u4e0a\u9762\u8bb2\u5230\u7684\u6620\u5c04\u65b9\u6cd5\uff0c\u8fd9\u65f6\u53d7\u5f71\u54cd\u7684\u5c06\u4ec5\u662f\u90a3\u4e9b\u6cbf cache B \u9006\u65f6\u9488\u904d\u5386\u76f4\u5230\u4e0b\u4e00\u4e2a cache \uff08 cache C \uff09\u4e4b\u95f4\u7684\u5bf9\u8c61\uff0c\u4e5f\u5373\u662f\u672c\u6765\u6620\u5c04\u5230 cache B \u4e0a\u7684\u90a3\u4e9b\u5bf9\u8c61\u3002<br \/>\n\u56e0\u6b64\u8fd9\u91cc\u4ec5\u9700\u8981\u53d8\u52a8\u5bf9\u8c61 object4 \uff0c\u5c06\u5176\u91cd\u65b0\u6620\u5c04\u5230 cache C \u4e0a\u5373\u53ef\uff1b\u53c2\u89c1\u56fe 4 \u3002<\/p>\n<div class=\"image-package imagebubble\"><a href=\"https:\/\/yanjingang.com\/blog\/wp-content\/uploads\/2016\/04\/4.jpg\" rel=\"attachment wp-att-769\"><img loading=\"lazy\" class=\"alignnone size-full wp-image-769\" src=\"https:\/\/yanjingang.com\/blog\/wp-content\/uploads\/2016\/04\/4.jpg\" alt=\"4\" width=\"283\" height=\"253\" \/><\/a><\/p>\n<div class=\"image-caption\">\u56fe 4 Cache B \u88ab\u79fb\u9664\u540e\u7684 cache \u6620\u5c04<\/div>\n<\/div>\n<\/li>\n<li>5.2 <strong>\u6dfb\u52a0 cache<\/strong><br \/>\n\u518d\u8003\u8651\u6dfb\u52a0\u4e00\u53f0\u65b0\u7684 cache D \u7684\u60c5\u51b5\uff0c\u5047\u8bbe\u5728\u8fd9\u4e2a\u73af\u5f62 hash \u7a7a\u95f4\u4e2d\uff0c cache D \u88ab\u6620\u5c04\u5728\u5bf9\u8c61 object2 \u548cobject3 \u4e4b\u95f4\u3002\u8fd9\u65f6\u53d7\u5f71\u54cd\u7684\u5c06\u4ec5\u662f\u90a3\u4e9b\u6cbf cache D \u9006\u65f6\u9488\u904d\u5386\u76f4\u5230\u4e0b\u4e00\u4e2a cache \uff08 cache B \uff09\u4e4b\u95f4\u7684\u5bf9\u8c61\uff08\u5b83\u4eec\u662f\u4e5f\u672c\u6765\u6620\u5c04\u5230 cache C \u4e0a\u5bf9\u8c61\u7684\u4e00\u90e8\u5206\uff09\uff0c\u5c06\u8fd9\u4e9b\u5bf9\u8c61\u91cd\u65b0\u6620\u5c04\u5230 cache D \u4e0a\u5373\u53ef\u3002<\/li>\n<\/ul>\n<p>\u56e0\u6b64\u8fd9\u91cc\u4ec5\u9700\u8981\u53d8\u52a8\u5bf9\u8c61 object2 \uff0c\u5c06\u5176\u91cd\u65b0\u6620\u5c04\u5230 cache D \u4e0a\uff1b\u53c2\u89c1\u56fe 5 \u3002<\/p>\n<div class=\"image-package imagebubble\"><a href=\"https:\/\/yanjingang.com\/blog\/wp-content\/uploads\/2016\/04\/5.jpg\" rel=\"attachment wp-att-770\"><img loading=\"lazy\" class=\"alignnone size-full wp-image-770\" src=\"https:\/\/yanjingang.com\/blog\/wp-content\/uploads\/2016\/04\/5.jpg\" alt=\"5\" width=\"283\" height=\"253\" \/><\/a><\/p>\n<div class=\"image-caption\">\u56fe 5 \u6dfb\u52a0 cache D \u540e\u7684\u6620\u5c04\u5173\u7cfb<\/div>\n<\/div>\n<h6>6 .\u865a\u62df\u8282\u70b9<\/h6>\n<p>\u8003\u91cf Hash \u7b97\u6cd5\u7684\u53e6\u4e00\u4e2a\u6307\u6807\u662f\u5e73\u8861\u6027 (Balance) \uff0c\u5b9a\u4e49\u5982\u4e0b\uff1a<br \/>\n\u5e73\u8861\u6027<br \/>\n\u5e73\u8861\u6027\u662f\u6307\u54c8\u5e0c\u7684\u7ed3\u679c\u80fd\u591f\u5c3d\u53ef\u80fd\u5206\u5e03\u5230\u6240\u6709\u7684\u7f13\u51b2\u4e2d\u53bb\uff0c\u8fd9\u6837\u53ef\u4ee5\u4f7f\u5f97\u6240\u6709\u7684\u7f13\u51b2\u7a7a\u95f4\u90fd\u5f97\u5230\u5229\u7528\u3002<br \/>\nhash \u7b97\u6cd5\u5e76\u4e0d\u662f\u4fdd\u8bc1\u7edd\u5bf9\u7684\u5e73\u8861\uff0c\u5982\u679c cache \u8f83\u5c11\u7684\u8bdd\uff0c\u5bf9\u8c61\u5e76\u4e0d\u80fd\u88ab\u5747\u5300\u7684\u6620\u5c04\u5230 cache \u4e0a\uff0c\u6bd4\u5982\u5728\u4e0a\u9762\u7684\u4f8b\u5b50\u4e2d\uff0c\u4ec5\u90e8\u7f72 cache A \u548c cache C \u7684\u60c5\u51b5\u4e0b\uff0c\u5728 4 \u4e2a\u5bf9\u8c61\u4e2d\uff0c cache A \u4ec5\u5b58\u50a8\u4e86 object1 \uff0c\u800c cache C \u5219\u5b58\u50a8\u4e86object2 \u3001 object3 \u548c object4 \uff1b\u5206\u5e03\u662f\u5f88\u4e0d\u5747\u8861\u7684\u3002<br \/>\n\u4e3a\u4e86\u89e3\u51b3\u8fd9\u79cd\u60c5\u51b5\uff0c consistent hashing \u5f15\u5165\u4e86\u201c\u865a\u62df\u8282\u70b9\u201d\u7684\u6982\u5ff5\uff0c\u5b83\u53ef\u4ee5\u5982\u4e0b\u5b9a\u4e49\uff1a<br \/>\n\u201c\u865a\u62df\u8282\u70b9\u201d\uff08 virtual node \uff09\u662f\u5b9e\u9645\u8282\u70b9\u5728 hash \u7a7a\u95f4\u7684\u590d\u5236\u54c1\uff08 replica \uff09\uff0c\u4e00\u5b9e\u9645\u4e2a\u8282\u70b9\u5bf9\u5e94\u4e86\u82e5\u5e72\u4e2a\u201c\u865a\u62df\u8282\u70b9\u201d\uff0c\u8fd9\u4e2a\u5bf9\u5e94\u4e2a\u6570\u4e5f\u6210\u4e3a\u201c\u590d\u5236\u4e2a\u6570\u201d\uff0c\u201c\u865a\u62df\u8282\u70b9\u201d\u5728 hash \u7a7a\u95f4\u4e2d\u4ee5 hash \u503c\u6392\u5217\u3002<br \/>\n\u4ecd\u4ee5\u4ec5\u90e8\u7f72 cache A \u548c cache C \u7684\u60c5\u51b5\u4e3a\u4f8b\uff0c\u5728\u56fe 4 \u4e2d\u6211\u4eec\u5df2\u7ecf\u770b\u5230\uff0c cache \u5206\u5e03\u5e76\u4e0d\u5747\u5300\u3002\u73b0\u5728\u6211\u4eec\u5f15\u5165\u865a\u62df\u8282\u70b9\uff0c\u5e76\u8bbe\u7f6e\u201c\u590d\u5236\u4e2a\u6570\u201d\u4e3a 2 \uff0c\u8fd9\u5c31\u610f\u5473\u7740\u4e00\u5171\u4f1a\u5b58\u5728 4 \u4e2a\u201c\u865a\u62df\u8282\u70b9\u201d\uff0c cache A1, cache A2 \u4ee3\u8868\u4e86 cache A\uff1b cache C1, cache C2 \u4ee3\u8868\u4e86 cache C \uff1b\u5047\u8bbe\u4e00\u79cd\u6bd4\u8f83\u7406\u60f3\u7684\u60c5\u51b5\uff0c\u53c2\u89c1\u56fe 6 \u3002<\/p>\n<div class=\"image-package imagebubble\"><a href=\"https:\/\/yanjingang.com\/blog\/wp-content\/uploads\/2016\/04\/6.jpg\" rel=\"attachment wp-att-771\"><img loading=\"lazy\" class=\"alignnone size-full wp-image-771\" src=\"https:\/\/yanjingang.com\/blog\/wp-content\/uploads\/2016\/04\/6.jpg\" alt=\"6\" width=\"283\" height=\"253\" \/><\/a><\/p>\n<div class=\"image-caption\">\u56fe 6 \u5f15\u5165\u201c\u865a\u62df\u8282\u70b9\u201d\u540e\u7684\u6620\u5c04\u5173\u7cfb<\/div>\n<\/div>\n<p>\u6b64\u65f6\uff0c\u5bf9\u8c61\u5230\u201c\u865a\u62df\u8282\u70b9\u201d\u7684\u6620\u5c04\u5173\u7cfb\u4e3a\uff1a<br \/>\nobjec1-&gt;cache A2 \uff1b objec2-&gt;cache A1 \uff1b objec3-&gt;cache C1 \uff1b objec4-&gt;cache C2 \uff1b<br \/>\n\u56e0\u6b64\u5bf9\u8c61 object1 \u548c object2 \u90fd\u88ab\u6620\u5c04\u5230\u4e86 cache A \u4e0a\uff0c\u800c object3 \u548c object4 \u6620\u5c04\u5230\u4e86 cache C \u4e0a\uff1b\u5e73\u8861\u6027\u6709\u4e86\u5f88\u5927\u63d0\u9ad8\u3002<br \/>\n\u5f15\u5165\u201c\u865a\u62df\u8282\u70b9\u201d\u540e\uff0c\u6620\u5c04\u5173\u7cfb\u5c31\u4ece { \u5bf9\u8c61 -&gt; \u8282\u70b9 } \u8f6c\u6362\u5230\u4e86 { \u5bf9\u8c61 -&gt; \u865a\u62df\u8282\u70b9 } \u3002\u67e5\u8be2\u7269\u4f53\u6240\u5728 cache \u65f6\u7684\u6620\u5c04\u5173\u7cfb\u5982\u56fe 7 \u6240\u793a\u3002<\/p>\n<div class=\"image-package imagebubble\"><a href=\"https:\/\/yanjingang.com\/blog\/wp-content\/uploads\/2016\/04\/7.jpg\" rel=\"attachment wp-att-772\"><img loading=\"lazy\" class=\"alignnone size-full wp-image-772\" src=\"https:\/\/yanjingang.com\/blog\/wp-content\/uploads\/2016\/04\/7.jpg\" alt=\"7\" width=\"529\" height=\"232\" srcset=\"https:\/\/yanjingang.com\/blog\/wp-content\/uploads\/2016\/04\/7.jpg 529w, https:\/\/yanjingang.com\/blog\/wp-content\/uploads\/2016\/04\/7-300x132.jpg 300w\" sizes=\"(max-width: 529px) 100vw, 529px\" \/><\/a><\/p>\n<div class=\"image-caption\">\u56fe 7 \u67e5\u8be2\u5bf9\u8c61\u6240\u5728 cache<\/div>\n<\/div>\n<p>\u201c\u865a\u62df\u8282\u70b9\u201d\u7684 hash \u8ba1\u7b97\u53ef\u4ee5\u91c7\u7528\u5bf9\u5e94\u8282\u70b9\u7684 IP \u5730\u5740\u52a0\u6570\u5b57\u540e\u7f00\u7684\u65b9\u5f0f\u3002\u4f8b\u5982\u5047\u8bbe cache A \u7684 IP \u5730\u5740\u4e3a202.168.14.241 \u3002<br \/>\n\u5f15\u5165\u201c\u865a\u62df\u8282\u70b9\u201d\u524d\uff0c\u8ba1\u7b97 cache A \u7684 hash \u503c\uff1a<br \/>\nHash(\u201c202.168.14.241\u201d);<br \/>\n\u5f15\u5165\u201c\u865a\u62df\u8282\u70b9\u201d\u540e\uff0c\u8ba1\u7b97\u201c\u865a\u62df\u8282\u201d\u70b9 cache A1 \u548c cache A2 \u7684 hash \u503c\uff1a<br \/>\nHash(\u201c202.168.14.241#1\u201d); \/\/ cache A1<br \/>\nHash(\u201c202.168.14.241#2\u201d); \/\/ cache A2<\/p>\n<h3>\u4ee5\u4e0b\u65f6\u4ee3\u7801\u5b9e\u73b0DEMO<\/h3>\n<pre class=\"hljs python\"><code class=\"python\"><span class=\"hljs-comment\">#!\/usr\/bin\/env python<\/span>\n<span class=\"hljs-comment\"># -*- coding: utf-8 -*-<\/span>\n<span class=\"hljs-keyword\">from<\/span> zlib <span class=\"hljs-keyword\">import<\/span> crc32\n<span class=\"hljs-keyword\">import<\/span> memcache\n\n\n<span class=\"hljs-class\"><span class=\"hljs-keyword\">class<\/span> <span class=\"hljs-title\">HashConsistency<\/span><span class=\"hljs-params\">(object)<\/span>:<\/span>\n    <span class=\"hljs-function\"><span class=\"hljs-keyword\">def<\/span> <span class=\"hljs-title\">__init__<\/span><span class=\"hljs-params\">(self, nodes=None, replicas=<span class=\"hljs-number\">5<\/span>)<\/span>:<\/span>\n        <span class=\"hljs-comment\"># \u865a\u62df\u8282\u70b9\u4e0e\u771f\u5b9e\u8282\u70b9\u5bf9\u5e94\u5173\u7cfb<\/span>\n        self.nodes_map = []\n        <span class=\"hljs-comment\"># \u771f\u5b9e\u8282\u70b9\u4e0e\u865a\u62df\u8282\u70b9\u7684\u5b57\u5178\u6620\u5c04<\/span>\n        self.nodes_replicas = {}\n        <span class=\"hljs-comment\"># \u771f\u5b9e\u8282\u70b9<\/span>\n        self.nodes = nodes\n        <span class=\"hljs-comment\"># \u6bcf\u4e2a\u771f\u5b9e\u8282\u70b9\u521b\u5efa\u7684\u865a\u62df\u8282\u70b9\u7684\u4e2a\u6570<\/span>\n        self.replicas = replicas\n\n        <span class=\"hljs-keyword\">if<\/span> self.nodes:\n            <span class=\"hljs-keyword\">for<\/span> node <span class=\"hljs-keyword\">in<\/span> self.nodes:\n                self._add_nodes_map(node)\n            self._sort_nodes()\n\n    <span class=\"hljs-function\"><span class=\"hljs-keyword\">def<\/span> <span class=\"hljs-title\">get_node<\/span><span class=\"hljs-params\">(self, key)<\/span>:<\/span>\n        <span class=\"hljs-string\">\"\"\" \u6839\u636eKEY\u503c\u7684hash\u503c\uff0c\u8fd4\u56de\u5bf9\u5e94\u7684\u8282\u70b9\n        \u7b97\u6cd5\u662f\uff1a \u8fd4\u56de\u6700\u65e9\u6bd4key_hash\u5927\u7684\u8282\u70b9\n        \"\"\"<\/span>\n        key_hash = abs(crc32(key))\n        <span class=\"hljs-comment\">#print '(%s' % key_hash<\/span>\n        <span class=\"hljs-keyword\">for<\/span> node <span class=\"hljs-keyword\">in<\/span> self.nodes_map:\n            <span class=\"hljs-keyword\">if<\/span> key_hash &gt; node[<span class=\"hljs-number\">0<\/span>]:\n                <span class=\"hljs-keyword\">continue<\/span>\n            <span class=\"hljs-keyword\">return<\/span> node\n        <span class=\"hljs-keyword\">return<\/span> <span class=\"hljs-keyword\">None<\/span>\n\n    <span class=\"hljs-function\"><span class=\"hljs-keyword\">def<\/span> <span class=\"hljs-title\">add_node<\/span><span class=\"hljs-params\">(self, node)<\/span>:<\/span>\n        <span class=\"hljs-comment\"># \u6dfb\u52a0\u8282\u70b9<\/span>\n        self._add_nodes_map(node)\n        self._sort_nodes()\n\n    <span class=\"hljs-function\"><span class=\"hljs-keyword\">def<\/span> <span class=\"hljs-title\">remove_node<\/span><span class=\"hljs-params\">(self, node)<\/span>:<\/span>\n        <span class=\"hljs-comment\"># \u5220\u9664\u8282\u70b9<\/span>\n        <span class=\"hljs-keyword\">if<\/span> node <span class=\"hljs-keyword\">not<\/span> <span class=\"hljs-keyword\">in<\/span> self.nodes_replicas.keys():\n            <span class=\"hljs-keyword\">pass<\/span>\n        discard_rep_nodes = self.nodes_replicas[node]\n        self.nodes_map = filter(<span class=\"hljs-keyword\">lambda<\/span> x: x[<span class=\"hljs-number\">0<\/span>] <span class=\"hljs-keyword\">not<\/span> <span class=\"hljs-keyword\">in<\/span> discard_rep_nodes, self.nodes_map)\n\n    <span class=\"hljs-function\"><span class=\"hljs-keyword\">def<\/span> <span class=\"hljs-title\">_add_nodes_map<\/span><span class=\"hljs-params\">(self, node)<\/span>:<\/span>\n        <span class=\"hljs-comment\"># \u589e\u52a0\u865a\u62df\u8282\u70b9\u5230nodes_map\u5217\u8868<\/span>\n        nodes_reps = []\n        <span class=\"hljs-keyword\">for<\/span> i <span class=\"hljs-keyword\">in<\/span> xrange(self.replicas):\n            rep_node = <span class=\"hljs-string\">'%s_%d'<\/span> % (node, i)\n            node_hash = abs(crc32(rep_node))\n            self.nodes_map.append((node_hash, node))\n            nodes_reps.append(node_hash)\n        <span class=\"hljs-comment\"># \u771f\u5b9e\u8282\u70b9\u4e0e\u865a\u62df\u8282\u70b9\u7684\u5b57\u5178\u6620\u5c04<\/span>\n        self.nodes_replicas[node] = nodes_reps\n\n    <span class=\"hljs-function\"><span class=\"hljs-keyword\">def<\/span> <span class=\"hljs-title\">_sort_nodes<\/span><span class=\"hljs-params\">(self)<\/span>:<\/span>\n        <span class=\"hljs-comment\"># \u6309\u987a\u5e8f\u6392\u5217\u865a\u62df\u8282\u70b9<\/span>\n        self.nodes_map = sorted(self.nodes_map, key=<span class=\"hljs-keyword\">lambda<\/span> x:x[<span class=\"hljs-number\">0<\/span>])\n\n\nmemcache_servers = [\n    <span class=\"hljs-string\">'127.0.0.1:7001'<\/span>,\n    <span class=\"hljs-string\">'127.0.0.1:7002'<\/span>,\n    <span class=\"hljs-string\">'127.0.0.1:7003'<\/span>,\n    <span class=\"hljs-string\">'127.0.0.1:7004'<\/span>,\n]\n\nh = HashConsistency(memcache_servers)\n\n<span class=\"hljs-keyword\">for<\/span> k <span class=\"hljs-keyword\">in<\/span> h.nodes_map:\n    <span class=\"hljs-keyword\">print<\/span> k\n\nmc_servers_dict = {}\n<span class=\"hljs-keyword\">for<\/span> ms <span class=\"hljs-keyword\">in<\/span>  memcache_servers:\n    mc = memcache.Client([ms], debug=<span class=\"hljs-number\">0<\/span>)\n    mc_servers_dict[ms] = mc\n\n<span class=\"hljs-comment\"># \u5faa\u73af10\u6b64\u7ed9memcache \u6dfb\u52a0key\uff0c\u8fd9\u91cc\u4f7f\u7528\u4e86\u4e00\u81f4\u6027hash\uff0c\u90a3\u4e48key\u5c06\u4f1a\u6839\u636ehash\u503c\u843d\u70b9\u5230\u5bf9\u5e94\u7684\u865a\u62df\u8282\u70b9\u4e0a<\/span>\n<span class=\"hljs-keyword\">for<\/span> i <span class=\"hljs-keyword\">in<\/span> xrange(<span class=\"hljs-number\">10<\/span>):\n    key = <span class=\"hljs-string\">'key_%s'<\/span> % i\n    <span class=\"hljs-keyword\">print<\/span> key\n    server = h.get_node(key)[<span class=\"hljs-number\">1<\/span>]\n    mc = mc_servers_dict[server]\n    mc.set(key, i)\n    <span class=\"hljs-keyword\">print<\/span> <span class=\"hljs-string\">'SERVER :%s'<\/span> % server\n    <span class=\"hljs-keyword\">print<\/span> mc<\/code><\/pre>\n<div>\u6587\uff0fcooffeelis\uff08\u7b80\u4e66\u4f5c\u8005\uff09<br \/>\n\u539f\u6587\u94fe\u63a5\uff1ahttp:\/\/www.jianshu.com\/p\/e8fb89bb3a61<\/div>\n","protected":false},"excerpt":{"rendered":"<p>\u6bd4\u5982\u4f60\u6709 N \u4e2a cache \u670d\u52a1\u5668\uff08\u540e\u9762\u7b80\u79f0 cache \uff09\uff0c\u90a3\u4e48\u5982\u4f55\u5c06\u4e00\u4e2a\u5bf9\u8c61 object \u6620\u5c04\u5230 N \u4e2a cache \u4e0a\u5462?<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":[],"categories":[104,124],"tags":[372,106,371,128],"_links":{"self":[{"href":"https:\/\/yanjingang.com\/blog\/index.php?rest_route=\/wp\/v2\/posts\/765"}],"collection":[{"href":"https:\/\/yanjingang.com\/blog\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/yanjingang.com\/blog\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/yanjingang.com\/blog\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/yanjingang.com\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=765"}],"version-history":[{"count":0,"href":"https:\/\/yanjingang.com\/blog\/index.php?rest_route=\/wp\/v2\/posts\/765\/revisions"}],"wp:attachment":[{"href":"https:\/\/yanjingang.com\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=765"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/yanjingang.com\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=765"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/yanjingang.com\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=765"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}