{"id":173,"date":"2014-08-18T00:29:03","date_gmt":"2014-08-17T16:29:03","guid":{"rendered":"http:\/\/www.codeeel.com\/?p=173"},"modified":"2014-08-18T00:29:03","modified_gmt":"2014-08-17T16:29:03","slug":"%e4%b8%80%e8%87%b4%e6%80%a7%e5%93%88%e5%b8%8c%e7%ae%97%e6%b3%95%e4%bb%a5%e5%8f%8a%e5%85%b6php%e5%ae%9e%e7%8e%b0","status":"publish","type":"post","link":"https:\/\/www.codeeel.com\/?p=173","title":{"rendered":"\u4e00\u81f4\u6027\u54c8\u5e0c\u7b97\u6cd5\u4ee5\u53ca\u5176PHP\u5b9e\u73b0"},"content":{"rendered":"<p>\u5728\u505a\u670d\u52a1\u5668\u8d1f\u8f7d\u5747\u8861\u65f6\u5019\u53ef\u4f9b\u9009\u62e9\u7684\u8d1f\u8f7d\u5747\u8861\u7684\u7b97\u6cd5\u6709\u5f88\u591a\uff0c\u5305\u62ec\uff1a\u00a0 \u8f6e\u5faa\u7b97\u6cd5\uff08Round Robin\uff09\u3001\u54c8\u5e0c\u7b97\u6cd5\uff08HASH\uff09\u3001\u6700\u5c11\u8fde\u63a5\u7b97\u6cd5\uff08Least Connection\uff09\u3001\u54cd\u5e94\u901f\u5ea6\u7b97\u6cd5\uff08Response Time\uff09\u3001\u52a0\u6743\u6cd5\uff08Weighted \uff09\u7b49\u3002\u5176\u4e2d\u54c8\u5e0c\u7b97\u6cd5\u662f\u6700\u4e3a\u5e38\u7528\u7684\u7b97\u6cd5.<\/p>\n<p>\u5178\u578b\u7684\u5e94\u7528\u573a\u666f\u662f\uff1a \u6709N\u53f0\u670d\u52a1\u5668\u63d0\u4f9b\u7f13\u5b58\u670d\u52a1\uff0c\u9700\u8981\u5bf9\u670d\u52a1\u5668\u8fdb\u884c\u8d1f\u8f7d\u5747\u8861\uff0c\u5c06\u8bf7\u6c42\u5e73\u5747\u5206\u53d1\u5230\u6bcf\u53f0\u670d\u52a1\u5668\u4e0a\uff0c\u6bcf\u53f0\u673a\u5668\u8d1f\u8d231\/N\u7684\u670d\u52a1\u3002<\/p>\n<p>\u5e38\u7528\u7684\u7b97\u6cd5\u662f\u5bf9hash\u7ed3\u679c\u53d6\u4f59\u6570 (hash() mod<code>\u00a0N<\/code>)\uff1a\u5bf9\u673a\u5668\u7f16\u53f7\u4ece0\u5230N-1\uff0c\u6309\u7167\u81ea\u5b9a\u4e49\u7684hash()\u7b97\u6cd5\uff0c\u5bf9\u6bcf\u4e2a\u8bf7\u6c42\u7684hash()\u503c\u6309N\u53d6\u6a21\uff0c\u5f97\u5230\u4f59\u6570i\uff0c\u7136\u540e\u5c06\u8bf7\u6c42\u5206\u53d1\u5230\u7f16\u53f7\u4e3ai\u7684\u673a\u5668\u3002\u4f46\u8fd9\u6837\u7684\u7b97\u6cd5\u65b9\u6cd5\u5b58\u5728\u81f4\u547d\u95ee\u9898\uff0c\u5982\u679c\u67d0\u4e00\u53f0\u673a\u5668\u5b95\u673a\uff0c\u90a3\u4e48\u5e94\u8be5\u843d\u5728\u8be5\u673a\u5668\u7684\u8bf7\u6c42\u5c31\u65e0\u6cd5\u5f97\u5230\u6b63\u786e\u7684\u5904\u7406\uff0c\u8fd9\u65f6\u9700\u8981\u5c06\u5f53\u6389\u7684\u670d\u52a1\u5668\u4ece\u7b97\u6cd5\u4ece\u53bb\u9664\uff0c\u6b64\u65f6\u5019\u4f1a\u6709(N-1)\/N\u7684\u670d\u52a1\u5668\u7684\u7f13\u5b58\u6570\u636e\u9700\u8981\u91cd\u65b0\u8fdb\u884c\u8ba1\u7b97\uff1b\u5982\u679c\u65b0\u589e\u4e00\u53f0\u673a\u5668\uff0c\u4f1a\u6709N \/(N+1)\u7684\u670d\u52a1\u5668\u7684\u7f13\u5b58\u6570\u636e\u9700\u8981\u8fdb\u884c\u91cd\u65b0\u8ba1\u7b97\u3002\u5bf9\u4e8e\u7cfb\u7edf\u800c\u8a00\uff0c\u8fd9\u901a\u5e38\u662f\u4e0d\u53ef\u63a5\u53d7\u7684\u98a0\u7c38\uff08\u56e0\u4e3a\u8fd9\u610f\u5473\u7740\u5927\u91cf\u7f13\u5b58\u7684\u5931\u6548\u6216\u8005\u6570\u636e\u9700\u8981\u8f6c\u79fb\uff09\u3002\u90a3\u4e48\uff0c\u5982\u4f55\u8bbe\u8ba1\u4e00\u4e2a\u8d1f\u8f7d\u5747\u8861\u7b56\u7565\uff0c\u4f7f\u5f97\u53d7\u5230\u5f71\u54cd\u7684\u8bf7\u6c42\u5c3d\u53ef\u80fd\u7684\u5c11\u5462\uff1f<br \/>\n\u5728Memcached\u3001Key-Value Store\u3001Bittorrent DHT\u3001LVS\u4e2d\u90fd\u91c7\u7528\u4e86Consistent Hashing\u7b97\u6cd5\uff0c\u53ef\u4ee5\u8bf4Consistent Hashing \u662f\u5206\u5e03\u5f0f\u7cfb\u7edf\u8d1f\u8f7d\u5747\u8861\u7684\u9996\u9009\u7b97\u6cd5\u3002<\/p>\n<h3><strong>1\u3001Consistent Hashing\u7b97\u6cd5\u63cf\u8ff0<\/strong><\/h3>\n<p>\u4e0b\u9762\u4ee5Memcached\u4e2d\u7684Consisten Hashing\u7b97\u6cd5\u4e3a\u4f8b\u8bf4\u660e\u3002<\/p>\n<p>\u7531\u4e8ehash\u7b97\u6cd5\u7ed3\u679c\u4e00\u822c\u4e3aunsigned int\u578b\uff0c\u56e0\u6b64\u5bf9\u4e8ehash\u51fd\u6570\u7684\u7ed3\u679c\u5e94\u8be5\u5747\u5300\u5206\u5e03\u5728[0,2<sup>32<\/sup>-1]\u95f4\uff0c\u5982\u679c\u6211\u4eec\u628a\u4e00\u4e2a\u5706\u73af\u75282<sup>32\u00a0<\/sup>\u4e2a\u70b9\u6765\u8fdb\u884c\u5747\u5300\u5207\u5272\uff0c\u9996\u5148\u6309\u7167hash(key)\u51fd\u6570\u7b97\u51fa\u670d\u52a1\u5668\uff08\u8282\u70b9\uff09\u7684\u54c8\u5e0c\u503c\uff0c \u5e76\u5c06\u5176\u5206\u5e03\u52300\uff5e2<sup>32<\/sup>\u7684\u5706\u4e0a\u3002<\/p>\n<p>\u7528\u540c\u6837\u7684hash(key)\u51fd\u6570\u6c42\u51fa\u9700\u8981\u5b58\u50a8\u6570\u636e\u7684\u952e\u7684\u54c8\u5e0c\u503c\uff0c\u5e76\u6620\u5c04\u5230\u5706\u4e0a\u3002\u7136\u540e\u4ece\u6570\u636e\u6620\u5c04\u5230\u7684\u4f4d\u7f6e\u5f00\u59cb\u987a\u65f6\u9488\u67e5\u627e\uff0c\u5c06\u6570\u636e\u4fdd\u5b58\u5230\u627e\u5230\u7684\u7b2c\u4e00\u4e2a\u670d\u52a1\u5668\uff08\u8282\u70b9\uff09\u4e0a\u3002<\/p>\n<p><a href=\"http:\/\/www.codeeel.com\/wp-content\/uploads\/2014\/08\/1.png\"><img loading=\"lazy\" class=\"alignnone size-medium wp-image-174\" title=\"1\" src=\"http:\/\/www.codeeel.com\/wp-content\/uploads\/2014\/08\/1-300x236.png\" alt=\"\" width=\"300\" height=\"236\" srcset=\"https:\/\/www.codeeel.com\/wp-content\/uploads\/2014\/08\/1-300x236.png 300w, https:\/\/www.codeeel.com\/wp-content\/uploads\/2014\/08\/1.png 615w\" sizes=\"(max-width: 300px) 100vw, 300px\" \/><\/a><\/p>\n<p align=\"center\">\u00a0<strong>Consistent Hashing\u539f\u7406\u793a\u610f\u56fe<\/strong><\/p>\n<p>\u00a0\u00a0\u00a0 \u65b0\u589e\u4e00\u4e2a\u8282\u70b9\u7684\u65f6\u5019\uff0c\u53ea\u6709\u5728\u5706\u73af\u4e0a\u65b0\u589e\u8282\u70b9\u9006\u65f6\u9488\u65b9\u5411\u7684\u7b2c\u4e00\u4e2a\u8282\u70b9\u7684\u6570\u636e\u4f1a\u53d7\u5230\u5f71\u54cd\u3002\u5220\u9664\u4e00\u4e2a\u8282\u70b9\u7684\u65f6\u5019\uff0c\u53ea\u6709\u5728\u5706\u73af\u4e0a\u539f\u6765\u5220\u9664\u8282\u70b9\u987a\u65f6\u9488\u65b9\u5411\u7684\u7b2c\u4e00\u4e2a\u8282\u70b9\u7684\u6570\u636e\u4f1a\u53d7\u5230\u5f71\u54cd\uff0c\u56e0\u6b64\u901a\u8fc7Consistent Hashing\u5f88\u597d\u5730\u89e3\u51b3\u4e86\u8d1f\u8f7d\u5747\u8861\u4e2d\u7531\u4e8e\u65b0\u589e\u8282\u70b9\u3001\u5220\u9664\u8282\u70b9\u5f15\u8d77\u7684hash\u503c\u98a0\u7c38\u95ee\u9898\u3002<\/p>\n<p><a href=\"http:\/\/www.codeeel.com\/wp-content\/uploads\/2014\/08\/2.png\"><img loading=\"lazy\" class=\"alignnone size-medium wp-image-175\" title=\"2\" src=\"http:\/\/www.codeeel.com\/wp-content\/uploads\/2014\/08\/2-300x254.png\" alt=\"\" width=\"300\" height=\"254\" srcset=\"https:\/\/www.codeeel.com\/wp-content\/uploads\/2014\/08\/2-300x254.png 300w, https:\/\/www.codeeel.com\/wp-content\/uploads\/2014\/08\/2.png 570w\" sizes=\"(max-width: 300px) 100vw, 300px\" \/><\/a><\/p>\n<p align=\"center\"><strong>Consistent Hashing\u6dfb\u52a0\u670d\u52a1\u5668\u793a\u610f\u56fe<\/strong><\/p>\n<p>\u00a0\u00a0\u00a0\u00a0<strong>\u865a\u62df\u8282\u70b9\uff08virtual nodes\uff09\uff1a<\/strong>\u4e4b\u6240\u4ee5\u8981\u5f15\u8fdb\u865a\u62df\u8282\u70b9\u662f\u56e0\u4e3a\u5728\u670d\u52a1\u5668\uff08\u8282\u70b9\uff09\u6570\u8f83\u5c11\u7684\u60c5\u51b5\u4e0b\uff08\u4f8b\u5982\u53ea\u67093\u53f0\u670d\u52a1\u5668\uff09\uff0c\u901a\u8fc7hash(key)\u7b97\u51fa\u8282\u70b9\u7684\u54c8\u5e0c\u503c\u5728\u5706\u73af\u4e0a\u5e76\u4e0d\u662f\u5747\u5300\u5206\u5e03\u7684\uff08\u7a00\u758f\u7684\uff09\uff0c\u4ecd\u7136\u4f1a\u51fa\u73b0\u5404\u8282\u70b9\u8d1f\u8f7d\u4e0d\u5747\u8861\u7684\u95ee\u9898\u3002\u865a\u62df\u8282\u70b9\u53ef\u4ee5\u8ba4\u4e3a\u662f\u5b9e\u9645\u8282\u70b9\u7684\u590d\u5236\u54c1\uff08replicas\uff09\uff0c\u672c\u8d28\u4e0a\u4e0e\u5b9e\u9645\u8282\u70b9\u5b9e\u9645\u4e0a\u662f\u4e00\u6837\u7684\uff08key\u5e76\u4e0d\u76f8\u540c\uff09\u3002\u5f15\u5165\u865a\u62df\u8282\u70b9\u540e\uff0c\u901a\u8fc7\u5c06\u6bcf\u4e2a\u5b9e\u9645\u7684\u670d\u52a1\u5668\uff08\u8282\u70b9\uff09\u6570\u6309\u7167\u4e00\u5b9a\u7684\u6bd4\u4f8b(\u4f8b\u5982200\u500d)\u6269\u5927\u540e\u5e76\u8ba1\u7b97\u5176hash(key)\u503c\u4ee5\u5747\u5300\u5206\u5e03\u5230\u5706\u73af\u4e0a\u3002\u5728\u8fdb\u884c\u8d1f\u8f7d\u5747\u8861\u65f6\u5019\uff0c\u843d\u5230\u865a\u62df\u8282\u70b9\u7684\u54c8\u5e0c\u503c\u5b9e\u9645\u5c31\u843d\u5230\u4e86\u5b9e\u9645\u7684\u8282\u70b9\u4e0a\u3002\u7531\u4e8e\u6240\u6709\u7684\u5b9e\u9645\u8282\u70b9\u662f\u6309\u7167\u76f8\u540c\u7684\u6bd4\u4f8b\u590d\u5236\u6210\u865a\u62df\u8282\u70b9\u7684\uff0c\u56e0\u6b64\u89e3\u51b3\u4e86\u8282\u70b9\u6570\u8f83\u5c11\u7684\u60c5\u51b5\u4e0b\u54c8\u5e0c\u503c\u5728\u5706\u73af\u4e0a\u5747\u5300\u5206\u5e03\u7684\u95ee\u9898\u3002<\/p>\n<p><a href=\"http:\/\/www.codeeel.com\/wp-content\/uploads\/2014\/08\/3.png\"><img loading=\"lazy\" class=\"alignnone size-medium wp-image-176\" title=\"3\" src=\"http:\/\/www.codeeel.com\/wp-content\/uploads\/2014\/08\/3-300x300.png\" alt=\"\" width=\"300\" height=\"300\" srcset=\"https:\/\/www.codeeel.com\/wp-content\/uploads\/2014\/08\/3-300x300.png 300w, https:\/\/www.codeeel.com\/wp-content\/uploads\/2014\/08\/3-150x150.png 150w, https:\/\/www.codeeel.com\/wp-content\/uploads\/2014\/08\/3.png 400w\" sizes=\"(max-width: 300px) 100vw, 300px\" \/><\/a><\/p>\n<p align=\"center\"><strong>\u865a\u62df\u8282\u70b9\u5bf9Consistent Hashing\u7ed3\u679c\u7684\u5f71\u54cd<\/strong><\/p>\n<p align=\"left\">\u00a0\u00a0\u00a0 \u4ece\u4e0a\u56fe\u53ef\u4ee5\u770b\u51fa\uff0c\u5728\u8282\u70b9\u6570\u4e3a10\u4e2a\u7684\u60c5\u51b5\u4e0b\uff0c\u6bcf\u4e2a\u5b9e\u9645\u8282\u70b9\u7684\u865a\u62df\u8282\u70b9\u6570\u4e3a\u5b9e\u9645\u8282\u70b9\u7684100-200\u500d\u7684\u65f6\u5019\uff0c\u7ed3\u679c\u8fd8\u662f\u5f88\u5747\u8861\u7684\u3002<\/p>\n<p>&nbsp;<\/p>\n<p>&nbsp;<\/p>\n<p>\u7b2c3\u6bb5\u4e2d\u6709\u8fd9\u4e9b\u6587\u5b57\uff1a\u201c\u4f46\u8fd9\u6837\u7684\u7b97\u6cd5\u65b9\u6cd5\u5b58\u5728\u81f4\u547d\u95ee\u9898\uff0c\u5982\u679c\u67d0\u4e00\u53f0\u673a\u5668\u5b95\u673a\uff0c\u90a3\u4e48\u5e94\u8be5\u843d\u5728\u8be5\u673a\u5668\u7684\u8bf7\u6c42\u5c31\u65e0\u6cd5\u5f97\u5230\u6b63\u786e\u7684\u5904\u7406\uff0c\u8fd9\u65f6\u9700\u8981\u5c06\u5f53\u6389\u7684\u670d\u52a1\u5668\u4ece\u7b97\u6cd5\u4ece\u53bb\u9664\uff0c\u6b64\u65f6\u5019\u4f1a\u6709<strong>(N-1)\/N<\/strong>\u7684\u670d\u52a1\u5668\u7684\u7f13\u5b58\u6570\u636e\u9700\u8981<strong>\u91cd\u65b0\u8fdb\u884c\u8ba1\u7b97<\/strong>\uff1b\u201d<\/p>\n<p>\u4e3a\u4f55\u662f\u00a0(N-1)\/N\u00a0\u5462\uff1f\u89e3\u91ca\u5982\u4e0b\uff1a<\/p>\n<p>\u6bd4\u5982\u6709 3 \u53f0\u673a\u5668\uff0chash\u503c\u00a01-6 \u5728\u8fd93\u53f0\u4e0a\u7684\u5206\u5e03\u5c31\u662f\uff1a<\/p>\n<p>host 1:\u00a0<strong>1<\/strong>\u00a04<\/p>\n<p>host 2:\u00a0<strong>2<\/strong>\u00a05<\/p>\n<p>host 3: 3 6<\/p>\n<p>\u5982\u679c\u6302\u6389\u4e00\u53f0\uff0c\u53ea\u5269\u4e24\u53f0\uff0c\u6a21\u6570\u53d6 2 \uff0c\u90a3\u4e48\u5206\u5e03\u60c5\u51b5\u5c31\u53d8\u6210\uff1a<\/p>\n<p>host 1:\u00a0<strong>1<\/strong>\u00a03 5<\/p>\n<p>host 2:\u00a0<strong>2<\/strong>\u00a04 6<\/p>\n<p>\u53ef\u4ee5\u770b\u5230\uff0c\u8fd8\u5728\u6570\u636e\u4f4d\u7f6e\u4e0d\u53d8\u7684\u53ea\u67092\u4e2a\uff1a\u00a01\uff0c2\uff0c\u4f4d\u7f6e\u53d1\u751f\u6539\u53d8\u7684\u67094\u4e2a\uff0c\u5360\u51716\u4e2a\u6570\u636e\u7684\u6bd4\u7387\u662f 4\/6 = 2\/3<\/p>\n<p>\u8fd9\u6837\u7684\u8bdd\uff0c\u53d7\u5f71\u54cd\u7684\u6570\u636e\u592a\u591a\u4e86\uff0c\u52bf\u5fc5\u592a\u591a\u7684\u6570\u636e\u9700\u8981\u91cd\u65b0\u4ece DB\u00a0\u52a0\u8f7d\u5230 cache \u4e2d\uff0c\u4e25\u91cd\u5f71\u54cd\u6027\u80fd<\/p>\n<p>&nbsp;<\/p>\n<p>\u3010consistent hashing \u7684\u529e\u6cd5\u3011<\/p>\n<p>\u4e0a\u9762\u63d0\u5230\u7684 hash \u53d6\u6a21\uff0c\u6a21\u6570\u53d6\u7684\u6bd4\u8f83\u5c0f\uff0c\u4e00\u822c\u662f\u8d1f\u8f7d\u7684\u6570\u91cf\uff0c\u800c consistent hashing \u7684\u672c\u8d28\u662f\u5c06\u6a21\u6570\u53d6\u7684\u6bd4\u8f83\u5927\uff0c\u4e3a\u00a02\u768432\u6b21\u65b9\u51cf1\uff0c\u5373\u4e00\u4e2a\u6700\u5927\u7684 32 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