{"id":158,"date":"2018-03-12T13:56:23","date_gmt":"2018-03-12T05:56:23","guid":{"rendered":"http:\/\/www.max-shu.com\/blog\/?p=158"},"modified":"2018-03-12T13:56:23","modified_gmt":"2018-03-12T05:56:23","slug":"hadoop%e6%80%a7%e8%83%bd%e6%a8%a1%e5%9e%8b%ef%bc%882%ef%bc%89","status":"publish","type":"post","link":"http:\/\/www.max-shu.com\/blog\/?p=158","title":{"rendered":"Hadoop\u6027\u80fd\u6a21\u578b\uff082\uff09"},"content":{"rendered":"<p><span style=\"font-size: large;\"><b>2. MAP\u9636\u6bb5\u6027\u80fd\u6a21\u578b<\/b><\/span><\/p>\n<p>\u524d\u9762\u8bf4\u8fc7\uff0cmap\u4efb\u52a1\u6267\u884c\u5206\u4e3a\u4e94\u4e2a\u9636\u6bb5\uff1a<br \/>\n1. Read\uff1a\u8bfb\u5165split\uff0c\u5efa\u7acbkey\uff0dvalue\u5bf9\u3002<br \/>\n2. Map\uff1a\u6267\u884c\u7528\u6237\u63d0\u4f9b\u7684map\u51fd\u6570\u3002<br \/>\n3. Collect\uff1a\u6536\u96c6map\u8f93\u51fa\u5230buffer\u6216\u5206\u533a\u3002<br \/>\n4. Spill\uff1a\u6392\u5e8f\uff0c\u9700\u8981\u7684\u8bddcombine\uff0c\u9700\u8981\u7684\u8bdd\u538b\u7f29\uff0c\u6700\u540espill\u5230\u78c1\u76d8\uff0c\u5efa\u7acbspills\u6587\u4ef6\u3002<br \/>\n5. Merge\uff1a\u5408\u5e76spills\u6587\u4ef6\u5230\u4e00\u4e2a\u5355\u4e2a\u6587\u4ef6\uff0c\u5408\u5e76\u4e5f\u8bb8\u6267\u884c\u591a\u8f6e\u3002<\/p>\n<p><span style=\"font-size: medium;\"><b>2.1 Read\u548cMap\u9636\u6bb5\u6a21\u578b<\/b><\/span><\/p>\n<p>\u8fd9\u4e2a\u9636\u6bb5\u8bfb\u5165split\uff0c\u9700\u8981\u7684\u8bdd\u89e3\u538b\u7f29\uff0c\u5efa\u7acbkey\uff0dvalue\u5bf9\uff0c\u628a\u8f93\u5165\u4f20\u7ed9\u7528\u6237\u5b9a\u4e49\u7684map\u51fd\u6570\u3002<br \/>\n<img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-159\" src=\"http:\/\/www.max-shu.com\/blog\/wp-content\/uploads\/2018\/03\/\u4e0b\u8f7d-7.png\" alt=\"\" width=\"904\" height=\"184\" \/><br \/>\n\u8be5\u9636\u6bb5\u7684\u6d88\u8017\uff1a<br \/>\n<img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-160\" src=\"http:\/\/www.max-shu.com\/blog\/wp-content\/uploads\/2018\/03\/\u4e0b\u8f7d-8.png\" alt=\"\" width=\"899\" height=\"147\" \/><br \/>\n\u5047\u5982MR job\u53ea\u6709mapper\uff08\u4f8b\u5982\uff1apNumReduces\uff1d0\uff09\uff0cspill\u548c\u5408\u5e76\u9636\u6bb5\u4e0d\u7528\u6267\u884c\uff0cmap\u8f93\u51fa\u5c06\u76f4\u63a5\u5199\u5230HDFS\u3002<br \/>\n<img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-161\" src=\"http:\/\/www.max-shu.com\/blog\/wp-content\/uploads\/2018\/03\/\u4e0b\u8f7d-9.png\" alt=\"\" width=\"899\" height=\"127\" \/><\/p>\n<p><span style=\"font-size: medium;\"><b>2.2 Collect\u548cSpill\u9636\u6bb5\u6a21\u578b<\/b><\/span><\/p>\n<p>map\u51fd\u6570\u4ea7\u751f\u7684key\uff0dvalue\u5bf9\u5b58\u653e\u5728map\u7684\u5185\u5b58\u4e2d\uff0c\u516c\u5f0f\u5316map\u8f93\u51fa\uff1a<br \/>\n<img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-162\" src=\"http:\/\/www.max-shu.com\/blog\/wp-content\/uploads\/2018\/03\/\u4e0b\u8f7d-10.png\" alt=\"\" width=\"897\" height=\"149\" \/><br \/>\n\u5185\u5b58buffer\u5206\u4e3a\u4e24\u90e8\u5206\uff1a\u4fdd\u5b58key\uff0dvalue\u5bf9\u7684\u5e8f\u5217\u5316\u90e8\u5206\uff0c\u548c\u5b58\u50a8\u6bcf\u5bf9meta\u6570\u636e\u7684\u8ba1\u6570\u90e8\u5206\u3002\u5f53\u8fd9\u4e24\u90e8\u5206\u88ab\u586b\u6ee1\u7684\u65f6\u5019\uff08\u57fa\u4e8epSpillPerc\u95e8\u9650\u503c\uff09\uff0c\u8fd9\u4e9bkey\uff0dvalue\u5bf9\u88ab\u5206\u533a\u3001\u6392\u5e8f\u3001spill\u5230\u78c1\u76d8\uff0c\u5e8f\u5217\u5316buffer\u7684\u6700\u5927key\uff0dvalue\u5bf9\u6570\u662f\uff1a<br \/>\n<img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-163\" src=\"http:\/\/www.max-shu.com\/blog\/wp-content\/uploads\/2018\/03\/\u4e0b\u8f7d-11.png\" alt=\"\" width=\"893\" height=\"60\" \/><br \/>\n\u8ba1\u6570buffer\u7684\u6700\u5927key\uff0dvalue\u5bf9\u6570\u662f\uff1a<br \/>\n<img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-164\" src=\"http:\/\/www.max-shu.com\/blog\/wp-content\/uploads\/2018\/03\/\u4e0b\u8f7d-12.png\" alt=\"\" width=\"894\" height=\"64\" \/><br \/>\nspill\u4e4b\u524d\u7684key\uff0dvalue\u5bf9\u6570\u548cbuffer\u5927\u5c0f\u7684\u5173\u7cfb\u662f\uff1a<br \/>\n<img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-165\" src=\"http:\/\/www.max-shu.com\/blog\/wp-content\/uploads\/2018\/03\/\u4e0b\u8f7d-13.png\" alt=\"\" width=\"901\" height=\"87\" \/><br \/>\n\u6574\u4e2aspill\u7684\u6570\u91cf\u662f\uff1a<br \/>\n<img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-166\" src=\"http:\/\/www.max-shu.com\/blog\/wp-content\/uploads\/2018\/03\/\u4e0b\u8f7d-14.png\" alt=\"\" width=\"896\" height=\"62\" \/><br \/>\n\u8fd9\u4e2akey\uff0dvalue\u5bf9\u6570\u548c\u6bcf\u4e2aspill\u7684\u5927\u5c0f\u53d6\u51b3\u4e8e\u6bcf\u4e2ak\uff0dv\u5bf9\u7684\u5bbd\u5ea6\uff0ccombine\u51fd\u6570\u7684\u4f7f\u7528\u4ee5\u53ca\u4e2d\u95f4\u6570\u636e\u538b\u7f29\u7684\u4f7f\u7528\u3002\u7f3a\u7701sIntermCompressRatio\u8bbe\u7f6e\u4e3a1\uff0c\u610f\u601d\u662f\u4e2d\u95f4\u7ed3\u679c\u4e0d\u538b\u7f29\uff0c\u7f3a\u7701sCombinePairsSel\u8bbe\u7f6e\u4e3a1\uff0c\u610f\u601d\u662f\u6ca1\u6709combine\u51fd\u6570\u4f7f\u7528\u3002<br \/>\n<img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-167\" src=\"http:\/\/www.max-shu.com\/blog\/wp-content\/uploads\/2018\/03\/\u4e0b\u8f7d-15.png\" alt=\"\" width=\"901\" height=\"83\" \/><br \/>\n\u672c\u9636\u6bb5\u7684\u6d88\u8017\uff1a<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-168\" src=\"http:\/\/www.max-shu.com\/blog\/wp-content\/uploads\/2018\/03\/\u4e0b\u8f7d-16.png\" alt=\"\" width=\"894\" height=\"274\" \/><\/p>\n","protected":false},"excerpt":{"rendered":"<p>2. MAP\u9636\u6bb5\u6027\u80fd\u6a21\u578b \u524d\u9762\u8bf4\u8fc7\uff0cmap\u4efb\u52a1\u6267\u884c\u5206\u4e3a\u4e94\u4e2a\u9636\u6bb5\uff1a 1. Read\uff1a\u8bfb\u5165split\uff0c\u5efa\u7acbkey\uff0d &hellip;<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[63],"tags":[80,123,122,120,121],"class_list":["post-158","post","type-post","status-publish","format-standard","hentry","category-63","tag-hadoop","tag-hdfs","tag-mapreduce","tag-120","tag-121"],"views":1565,"_links":{"self":[{"href":"http:\/\/www.max-shu.com\/blog\/index.php?rest_route=\/wp\/v2\/posts\/158","targetHints":{"allow":["GET"]}}],"collection":[{"href":"http:\/\/www.max-shu.com\/blog\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/www.max-shu.com\/blog\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/www.max-shu.com\/blog\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/www.max-shu.com\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=158"}],"version-history":[{"count":1,"href":"http:\/\/www.max-shu.com\/blog\/index.php?rest_route=\/wp\/v2\/posts\/158\/revisions"}],"predecessor-version":[{"id":169,"href":"http:\/\/www.max-shu.com\/blog\/index.php?rest_route=\/wp\/v2\/posts\/158\/revisions\/169"}],"wp:attachment":[{"href":"http:\/\/www.max-shu.com\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=158"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/www.max-shu.com\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=158"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/www.max-shu.com\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=158"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}