{"id":475,"date":"2014-03-30T08:07:27","date_gmt":"2014-03-30T08:07:27","guid":{"rendered":"http:\/\/www.selinuxplus.com\/?p=475"},"modified":"2014-03-30T08:08:47","modified_gmt":"2014-03-30T08:08:47","slug":"ceph%e5%ad%a6%e4%b9%a0-5%e4%b8%80%e8%87%b4%e6%80%a7hash%e7%ae%97%e6%b3%95","status":"publish","type":"post","link":"http:\/\/www.selinuxplus.com\/?p=475","title":{"rendered":"[ceph\u5b66\u4e60-5]\u4e00\u81f4\u6027hash\u7b97\u6cd5"},"content":{"rendered":"

\u4e00\u81f4\u6027hash\u7b97\u6cd5\uff0c1997\u5e74\u9ebb\u7701\u7406\u5de5\u5b66\u9662\u63d0\u51fa\u7684\u4e00\u79cd\u5206\u5e03\u5f0fhash\uff08DHT\uff09\u5b9e\u73b0\u7b97\u6cd5\uff0c\u8bbe\u8ba1\u76ee\u6807\u662f\u4e3a\u4e86\u89e3\u51b3\u56e0\u7279\u7f51\u4e2d\u70ed\u70b9\uff08Hot spot\uff09\u95ee\u9898\u3002hash\u7b97\u6cd5\u7684\u5224\u65ad\u4ece\u56db\u4e2a\u65b9\u9762\u6765\u5224\u65ad\uff1a\u5e73\u8861\u6027\u3001\u5355\u8c03\u6027\u3001\u5206\u6563\u6027\u3001\u8d1f\u8f7d\u3002<\/p>\n

\u666e\u901a\u7684hash\uff08\u786chash\uff09\u91c7\u7528\u7b80\u5355\u7684\u53d6\u6a21\u65b9\u5f0f\uff0c\u8fdb\u884c\u6563\u5217\u3002\u4e00\u81f4\u6027hash\u7b97\u6cd5\u5b9e\u73b0\u7684\u57fa\u672c\u539f\u7406\u662f\u5c06\u8282\u70b9\u548ckey\u503c\u90fd\u6309\u7167\u4e00\u6837hash\u7b97\u6cd5\u6620\u5c04\u52300-2^32\u7684\u73af\u4e0a\u3002\u5230\u6709\u4e00\u4e2a\u7f13\u5b58\u7684\u8bf7\u6c42\u5230\u6765\u65f6\uff0c\u8ba1\u7b97key\u503ck\u5bf9\u5e94\u7684hash(K)\uff0c\u5982\u679c\u8be5\u503c\u6b63\u597d\u5bf9\u5e94\u4e4b\u524d\u67d0\u4e2a\u673a\u5668\u8282\u70b9\u7684hash\u503c\uff0c\u5219\u76f4\u63a5\u5199\u5165\u8be5\u673a\u5668\u8282\u70b9\uff0c\u5982\u679c\u6ca1\u6709\u5bf9\u5e94\u7684\u8282\u70b9\uff0c\u987a\u65f6\u9488\u67e5\u5230\u5230\u4e0b\u4e00\u4e2a\u8282\u70b9\uff0c\u8fdb\u884c\u5199\u5165\u3002\u5982\u679c\u8d85\u8fc72^32\u8fd8\u6ca1\u6709\u5bf9\u5e94\u8282\u70b9\uff0c\u5219\u4ece0\u5f00\u59cb\u67e5\u627e\u3002
\n\u4e00\u81f4\u6027\u7b97\u6cd5Consistent-hashing\uff1aURL\uff1a<\/p>\n

http:\/\/www.codeproject.com\/Articles\/56138\/Consistent-hashing<\/pre>\n
Consistent-hashing \u4e00\u81f4\u6027hash\u7b97\u6cd5
\nlibconshash \u6e90\u7801\u4f7f\u7528\u4e86\u7ea2\u9ed1\u6811\u6765\u5b58\u653e\u865a\u62df\u8282\u70b9\u4fe1\u606f\u3002
\n1 \u9996\u5148\u5bf9node\u7684\u6807\u5fd7(“%s-%03d”,  node->iden, \u8282\u70b9\u540d replica_idx\uff0c\u8282\u70b9\u7d22\u5f15number)\u8fdb\u884cmd5\u8ba1\u7b97\uff0c\u7136\u540e\u5bf9\u6574\u6570\u8fdb\u884c4\u5b57\u8282\u7684\u6574\u6570hash\u7b97\u6cd5( MurmurHash, \u4e00\u79cd\u975e\u52a0\u5bc6\u578b\u54c8\u5e0c\u51fd\u6570\uff0c \u7531Austin Appleby\u57282008\u5e74\u53d1\u660e\uff0c\u5e76\u4e14\u6709\u591a\u4e2a\u53d8\u79cd  \u7279\u70b9\uff1a\u5bf9\u4e8e\u89c4\u5f8b\u6027\u8f83\u5f3a\u7684key\uff0cMurmurHash\u7684\u968f\u673a\u5206\u5e03\u7279\u6027\u8868\u73b0\u66f4\u826f\u597d\uff09\uff0c\u5f97\u5230\u4e86\u4e00\u4e2a\u957f\u6574\u6570<\/p>\n
for(i = 0 ;i<4;i++){Md5\u662f\u4e00\u4e2a16\u5b57\u8282\u957f\u5ea6\u7684\u6570\u7ec4\uff0c\u5c0616\u5b57\u8282\u7684\u6570\u7ec4\u6bcf\u56db\u4e2a\u5b57\u8282\u4e00\u7ec4\uff0c\u5206\u522b\u5bf9\u5e94\u4e00\u4e2a\u865a\u62df\u7ed3\u70b9.\n \n\n\n
\r\n    hash += ((long)(digest[i*4 + 3]&0xFF) << 24)\r\n            | ((long)(digest[i*4 + 2]&0xFF) << 16)\r\n            | ((long)(digest[i*4 + 1]&0xFF) <<  8)\r\n            | ((long)(digest[i*4 + 0]&0xFF));\r\n    }<\/pre>\n
\u3002
\n2 \u7136\u540e\u6839\u636e__conhash_add_replicas \u751f\u6210n->replicas\u6570\u91cf\u7684\u865a\u8282\u70b9\u63d2\u5165\u7ea2\u9ed1\u6811 \u3002__conhash_get_rbnode(node, hash); \u5206\u914d\u4e00\u4e2a\u865a\u62df\u8282\u70b9\uff0c\u7136\u540e\u63d2\u5165\u7ea2\u9ed1\u6811\u4e2d\u3002util_rbtree_insert
\n3 __conhash_del_replicas \u5c06\u865a\u8282\u70b9\u4ece\u7ea2\u9ed1\u6811\u4e2d\u5220\u9664
\n\u6bcf\u6b21\u64cd\u4f5c\u90fd\u662f\u5bf9\u6bcf\u4e2a\u865a\u62df\u8282\u70b9vnode\u5355\u72ec\u8c03\u7528malloc\u548cfree\u3002\u5229\u7528\u7ea2\u9ed1\u6811\u6dfb\u52a0\u5220\u9664\u7684\u65f6\u95f4\u8d1f\u8f7d\u5ea6\u4e3aO(logW).\u6570\u7ec4\u7684\u5b9e\u73b0\u56e0\u4e3a\u6bcf\u6b21\u90fd\u8981\u91cd\u65b0\u521d\u59cb\u5316HASH\u73af\uff0c\u56e0\u6b64\u65f6\u95f4\u590d\u6742\u5ea6\u4e3aO(WNlog(WN))(N\u4e3a\u8282\u70b9\u6570)\u3002\u7f3a\u70b9\u4e3a\u76f8\u5bf9\u4e8e\u6570\u7ec4\u5b9e\u73b0\u6765\u8bf4\uff0c\u6bcf\u4e2a\u865a\u62df\u8282\u70b9\u8981\u6d6a\u8d39\u81f3\u5c11\u4e24\u4e2a\u6307\u9488\uff08\u7ea2\u9ed1\u6811\u8282\u70b9\u7684\u5de6\u53f3\u5b57\u6570\u6307\u9488\uff0c\u4ee5\u53ca\u4e00\u4e2a\u989c\u8272\u6807\u8bb0\uff09\u7684\u7a7a\u95f4\u3002<\/p>\n
HAproxy\u7684\u4e00\u81f4\u6027hash\u7b97\u6cd5
\n\u4ee5cache\u4e3a\u4f8b\uff0c\u5b9e\u73b0\u601d\u60f3\uff1a
\n1.     \u6839\u636eserver\uff08cache\uff09\u67d0\u4e2a\u53c2\u6570\u8ba1\u7b97\u51fa\u7684key\uff0c\u5c06server\u6620\u5c04\u52302^31-1\u7684\u73af\u5f62\u7a7a\u95f4\u4e2d\uff1bobject\u5bf9\u8c61\u6839\u636e\u81ea\u8eab\u7684key\u5b58\u50a8\u5230\u76f8\u8fd1\u7684cache server\u4e2d\uff1b\u5f53cache A server down\u4e4b\u540e\uff0c\u53ea\u4f1a\u5f71\u54cd\u73af\u4e2d\u5176key\u9644\u8fd1\u7684object\uff1b<\/p>\n
2.      \u7531\u4e8ecache server\u65e0\u6cd5\u5747\u5300\u7684\u6620\u5c04\u5230\u73af\u5f62\u7a7a\u95f4\u4e2d\uff08\u4e0d\u5747\u8861\u95ee\u9898\uff09\uff0c\u6240\u4ee5\u5f15\u5165\u865a\u62df\u8282\u70b9\u7684\u6982\u5ff5\uff0c\u6bcf\u53f0cache server\u5206\u914dX\u4e2a\u865a\u62df\u8282\u70b9\u6620\u5c04\u5230\u73af\u4e2d\u3002<\/p>\n
HAProxy \u5229\u7528EBtree\u6765\u7ba1\u7406node\uff0c\u800c\u4e0d\u662frbtree\u3002\u4f18\u70b9\u662f\uff1a\u662f\u5220\u9664\u64cd\u4f5c\u7684\u590d\u6742\u5ea6\u662fO(1)<\/p>\n
chash_init_server_tree \u865a\u62df\u8282\u70b9\u7684\u5206\u914d\u51fd\u6570\u3002
\n\u865a\u62df\u8282\u70b9\u7684\u4e2a\u6570\u4e3a<\/p>\n
srv->lb_nodes_tot = srv->uweight * BE_WEIGHT_SCALE;\uff08uweight unsigned,32;BE_WEIGHT_SCALE,16) \/\/512<\/pre>\n
\u53731\u53f0server\u4f1a\u6709512\u4e2a\u865a\u62df\u8282\u70b9\uff1b<\/p>\n
hash key\u7684\u8ba1\u7b97
\n\u6bcf\u4e2a\u865a\u62df\u8282\u70b9\u7684hash key\u6309\u5982\u4e0b\u516c\u5f0f\u8ba1\u7b97\uff1a<\/p>\n
for (node = 0; node < srv->lb_nodes_tot; node++) {\r\n         srv->lb_nodes[node].node.key=chash_hash(srv->puid*SRV_EWGHT_RANGE + node);\r\n\r\n        }\r\n<\/pre>\n
\u5176\u4e2d\uff0cpuid\u4e3aserver\u914d\u7f6e\u7684id\u53f7\uff0cSRV_EWGHT_RANGE=4K;<\/p>\n
chash_hash()\u662f\u4e00\u4e2a32\u4f4d\u7684Thomas Wang\u7684HASH\u7b97\u6cd5\uff08homas Wang\u5728Jenkins\u7684\u57fa\u7840\u4e0a\uff0c\u9488\u5bf9\u56fa\u5b9a\u6574\u6570\u8f93\u5165\u505a\u4e86\u76f8\u5e94\u7684Hash\u7b97\u6cd5\uff09<\/p>\n
static inline unsigned int chash_hash(unsigned int a)\r\n{\r\n\r\n\ta = (a+0x7ed55d16) + (a<<12);\r\n\ta = (a^0xc761c23c) ^ (a>>19);\r\n\ta = (a+0x165667b1) + (a<<5);\r\n\ta = (a+0xd3a2646c) ^ (a<<9);\r\n\ta = (a+0xfd7046c5) + (a<<3);\r\n\ta = (a^0xb55a4f09) ^ (a>>16);\r\n\r\n\t\/* ensure values are better spread all around the tree by multiplying\r\n\t * by a large prime close to 3\/4 of the tree.\r\n\t *\/\r\n\treturn a * 3221225473U;\r\n}<\/pre>\n
 \u6dfb\u52a0\/\u5220\u9664\u8282\u70b9\u3002
\n\u91c7\u7528EBtree\u7ba1\u7406\u8282\u70b9\uff0c\u6dfb\u52a0\u5220\u9664\u8282\u70b9\u5728chash_queue_dequeue_srv()\u4e2d\u5b9e\u73b0\uff1b
\nchash_queue_dequeue_srv()\u76f8\u5e94\u64cd\u4f5c\u51fd\u6570\u4e3a\uff1a<\/p>\n
eb32_delete(&s->lb_nodes[s->lb_nodes_now].node);\r\neb32_insert(s->lb_tree, &s->lb_nodes[s->lb_nodes_now].node);<\/pre>\n
\u5bf9\u5e94\u7684\u6587\u4ef6\u4e3aEb32tree.c\u6587\u4ef6\u7684\u51fd\u6570 <\/p>\n
static forceinline struct eb32_node *\r\n__eb32_insert(struct eb_root *root, struct eb32_node *new)\u3002<\/pre>\n
\u65e7\u7248\u672cHAProxy\u66fe\u7ecf\u4f7f\u7528\u8fc7\u7ea2\u9ed1\u6811\uff0c\u7528\u4e8e\u4efb\u52a1\u8c03\u5ea6\u3001\u8d1f\u8f7d\u5747\u8861\u7b49\u65b9\u9762\u3002\u4f46\u662fWilly Tarreau\u8ba4\u4e3a\uff0c\u5728\u4e8b\u4ef6\u54cd\u5e94\u975e\u5e38\u9891\u7e41\u7684\u60c5\u51b5\u4e0b\uff0c\u4efb\u52a1\u63d2\u5165\u3001\u5220\u9664\u7684\u9891\u7387\u975e\u5e38\u9ad8\uff0c\u8fd9\u65f6\u5019\u4f7f\u7528\u7ea2\u9ed1\u6811\u5b58\u5728\u6027\u80fd\u74f6\u9888\uff0c\u5c24\u5176\u4e0d\u80fd\u63a5\u53d7\u7ea2\u9ed1\u6811\u5220\u9664\u8282\u70b9\u7684\u65f6\u95f4\u590d\u6742\u5ea6\u4e3aO(log n)\u3002\u56e0\u6b64\uff0c\u4ed6\u53d1\u660e\u4e86\u4e00\u79cd\u65b0\u7684\u6570\u636e\u7ed3\u6784\uff0c\u53eb\u505a\u5f39\u6027\u4e8c\u53c9\u6811\uff08elastic binary tree\uff09\uff0c\u7b80\u79f0ebtree\u3002<\/p>\n
ebtree\u662f\u4e0d\u5e73\u8861\u7684\u4e8c\u53c9\u641c\u7d22\u6811\uff08BST\uff09\uff0c\u800c\u7ea2\u9ed1\u6811\u3001AVL\u6811\u7b49\u90fd\u662f\u5e73\u8861\u7684BST\u3002\u4f20\u7edf\u7684BST\u6700\u6015\u7684\u5c31\u662f\u9000\u5316\u6210\u7ebf\u6027\u641c\u7d22\uff0c\u56e0\u6b64\uff0c\u7ea2\u9ed1\u6811\u7b49BST\u63d2\u5165\u3001\u5220\u9664\u65f6\u90fd\u9700\u8981\u5bf9\u6811\u8fdb\u884c\u5e73\u8861\u5316\uff0c\u800c\u5e73\u8861\u5316\u662f\u4e00\u4e2a\u4ece\u53f6\u5b50\u8282\u70b9\u5f00\u59cb\uff0c\u5411\u6839\u8282\u70b9\u65b9\u5411\u9012\u5f52\u5411\u4e0a\u7684\u8fc7\u7a0b\uff0c\u65f6\u95f4\u590d\u6742\u5ea6\u662fO(log n)\u3002<\/p>\n
\u6709\u9274\u4e8e\u6b64\uff0cebtree\u4e3a\u4e86\u5b9e\u73b0\u5220\u9664\u8282\u70b9\u65f6O(1)\u7684\u65f6\u95f4\u590d\u6742\u5ea6\uff0c\u5fc5\u7136\u653e\u5f03\u4fdd\u6301\u6811\u7684\u5e73\u8861\uff0c\u4e3a\u4e86\u62d2\u7edd\u7531\u6b64\u800c\u6765\u7684\u526f\u4f5c\u7528\u2014\u2014\u9000\u5316\u6210\u7ebf\u6027\u641c\u7d22\uff08\u6216\u8005\u66f4\u51c6\u786e\u5730\u8bf4\uff0c\u9000\u5316\u6210\u4e0d\u53d7\u9650\u5236\u7684\u7ebf\u6027\u641c\u7d22\uff09\uff0c\u4e0d\u53ef\u907f\u514d\u5730\u5f15\u5165\u4e86\u4e00\u4e9b\u65b0\u7684\u6210\u5458\u548c\u65b0\u7684\u601d\u8def\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"
\u4e00\u81f4\u6027hash\u7b97\u6cd5\uff0c1997\u5e74\u9ebb\u7701\u7406\u5de5\u5b66\u9662\u63d0\u51fa\u7684\u4e00…<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[84,83],"tags":[96,95],"_links":{"self":[{"href":"http:\/\/www.selinuxplus.com\/index.php?rest_route=\/wp\/v2\/posts\/475"}],"collection":[{"href":"http:\/\/www.selinuxplus.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/www.selinuxplus.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/www.selinuxplus.com\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/www.selinuxplus.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=475"}],"version-history":[{"count":3,"href":"http:\/\/www.selinuxplus.com\/index.php?rest_route=\/wp\/v2\/posts\/475\/revisions"}],"predecessor-version":[{"id":478,"href":"http:\/\/www.selinuxplus.com\/index.php?rest_route=\/wp\/v2\/posts\/475\/revisions\/478"}],"wp:attachment":[{"href":"http:\/\/www.selinuxplus.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=475"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/www.selinuxplus.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=475"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/www.selinuxplus.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=475"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}