[{"data":1,"prerenderedAt":242},["ShallowReactive",2],{"archive-2016-9-1":3},{"title":4,"articles":5,"hot_article":27,"month_arch":90,"total":238,"cover":239},"2016年9月 - 独孤影的博客",[6,17],{"id":7,"title":8,"uri":8,"author":9,"tags":10,"created_at":14,"view_count":15,"content":16},47,"关于kill进程链","duguying",[11,12,13],"进程","子进程","kill","2016-09-30 00:02:21",2926,"\u003Cp>之前在做 Goj 项目的时候执行服务器部分使用 go 语言 kill 进程，发现无法 kill 该进程的子进程，后来发现貌似别的语言也无法直接 kill 掉当前进程的子进程链。kill 子进程链的应用场景是这样的，我在做 judger服务器的时候发现我调用 gcc 编译源码会在某些极端的情况下卡死，然后卡死后我需要 kill 掉 gcc 的进程，我使用 go 语言的相关 api kill 掉 gcc (因为我拿得到 gcc 的进程 id)，然而，我发现 gcc 会调用别的命令，记忆中貌似是一个叫做 ar 的命令，实际上是这个子进程卡死了，于是我 kill 掉身为父进程的 gcc 之后，它的子进程依然存在，变成了孤儿进程，继续卡着。但是我没有 api 可以拿到 gcc 卡死的子进程的进程 id，所以我也无法 kill 掉它。我当时的临时解决方案是调用 killall 命令去按照名称杀掉它。\u003C\u002Fp>\u003Cp>之后一次在某个群里提到这件事情，随口问了一句如何获取某个进程的子进程，linux api 中是没有这种 api 的，一位同学提醒了我，你可以从 \u002Fproc 目录中查。今天我用 go 语言实现了它，linux 系统中 \u002Fproc 目录记录了所有的进程信息，但是这些信息中依然没有记录某个信息的子进程，不过它记录了某个进程的父进程，于是我遍历了 \u002Fproc 目录中的所有进程的进程信息，然后根据进程的父代关系构成了一颗进程树，这颗树的顶端必定是 init 进程，于是，我便可以从这颗进程树上从上往下搜索查找出某个进程的子进程了。这样一来，一个简单的进程树便可以让我轻松的查找出某进程的子进程，同样也可以 kill 掉某颗进程树，将当前进程及其子进程 kill 掉已经不再是一件难事了。\u003C\u002Fp>\u003Cp>如果你对此感兴趣，欢迎参阅源码 \u003Ca href=\"https:\u002F\u002Fgithub.com\u002Fgojudge\u002Fproc\" _src=\"https:\u002F\u002Fgithub.com\u002Fgojudge\u002Fproc\">https:\u002F\u002Fgithub.com\u002Fgojudge\u002Fproc\u003C\u002Fa> \u003C\u002Fp>\u003Cp>最后，我要说明的一点是：世界上没有什么事情是一棵树解决不了的，如果有，那么两颗树一定能够解决。\u003C\u002Fp>",{"id":18,"title":19,"uri":19,"author":9,"tags":20,"created_at":24,"view_count":25,"content":26},45,"Hibernate中自动建表unique无效的问题",[21,22,23],"Hibernate","建表","unique","2016-09-10 14:14:32",3560,"\u003Cp>使用Hibernate自动建表，User实体中的username字段希望给个唯一约束，但是自动建表却一直没有unique约束\u003C\u002Fp>\u003Cpre class=\"brush:java;toolbar:false\">@Entity\n@Table(name = "user")\npublic class User {\n\tprivate int id;\n\tprivate String username;\n\n\t@Id\n\t@GeneratedValue(strategy = GenerationType.IDENTITY)\n\tpublic int getId() {\n\t\treturn id;\n\t}\n\n\tpublic void setId(int id) {\n\t\tthis.id = id;\n\t}\n\n\t@Column(unique = true, nullable = false)\n\tpublic String getUsername() {\n\t\treturn username;\n\t}\n\n\tpublic void setUsername(String username) {\n\t\tthis.username = username;\n\t}\n\n}\u003C\u002Fpre>\u003Cp>键表的结果是索引中并没有唯一索引，多番尝试解决如下\u003Cbr\u002F>\u003C\u002Fp>\u003Cpre class=\"brush:java;toolbar:false\">@Entity\n@Table(name = "user")\npublic class User {\n\tprivate int id;\n\tprivate String username;\n\n\t@Id\n\t@GeneratedValue(strategy = GenerationType.IDENTITY)\n\tpublic int getId() {\n\t\treturn id;\n\t}\n\n\tpublic void setId(int id) {\n\t\tthis.id = id;\n\t}\n\n\t@Column(unique = true, length = 20, nullable = false)\n\tpublic String getUsername() {\n\t\treturn username;\n\t}\n\n\tpublic void setUsername(String username) {\n\t\tthis.username = username;\n\t}\n\n}\u003C\u002Fpre>\u003Cp>原因是我未指定 username 字段的长度，然后自动建表的字段长度是255字符，于是没有唯一索引，将长度指定为 20 ，删除表，重新执行建表便有了唯一索引。另需注意的是 nullable = false 。\u003C\u002Fp>",{"title":28,"list":29},"最热文章",[30,36,42,48,54,60,66,72,78,84],{"id":31,"title":32,"uri":33,"author":9,"created_at":34,"view_count":35},28,"docker容器目录与主机目录同步","\u002Farticle\u002Fdocker容器目录与主机目录同步","2014-12-31 12:34:08",15570,{"id":37,"title":38,"uri":39,"author":9,"created_at":40,"view_count":41},21,"beego中使用fis","\u002Farticle\u002Fbeego中使用fis","2014-12-03 10:47:56",9250,{"id":43,"title":44,"uri":45,"author":9,"created_at":46,"view_count":47},20,"用github登录，oauth开发","\u002Farticle\u002F用github登录，oauth开发","2014-11-23 13:33:37",9113,{"id":49,"title":50,"uri":51,"author":9,"created_at":52,"view_count":53},18,"windows服务注册工具nssm","\u002Farticle\u002Fwindows服务注册工具nssm","2014-10-31 21:34:39",9047,{"id":55,"title":56,"uri":57,"author":9,"created_at":58,"view_count":59},49,"用latex排版中文书籍","\u002Farticle\u002F用latex排版中文书籍","2016-10-31 11:12:02",8634,{"id":61,"title":62,"uri":63,"author":9,"created_at":64,"view_count":65},19,"texlive中文书签乱码","\u002Farticle\u002Ftexlive中文书签乱码","2014-11-15 02:54:01",8461,{"id":67,"title":68,"uri":69,"author":9,"created_at":70,"view_count":71},6,"Windows上的软件包管理器chocolatey","\u002Farticle\u002FWindows上的软件包管理器chocolatey","2014-08-10 15:55:22",8009,{"id":73,"title":74,"uri":75,"author":9,"created_at":76,"view_count":77},3,"利用开源和免费资源搭建CI环境","\u002Farticle\u002F利用开源和免费资源搭建CI环境","2014-07-04 16:54:58",7732,{"id":79,"title":80,"uri":81,"author":9,"created_at":82,"view_count":83},16,"php-fpm网站目录权限配置","\u002Farticle\u002Fphp-fpm网站目录权限配置","2014-10-18 01:36:10",7274,{"id":85,"title":86,"uri":87,"author":9,"created_at":88,"view_count":89},27,"sublime text 2插件开发，外部修改文件无法重新加载","\u002Farticle\u002Fsublime text 2插件开发，外部修改文件无法重新加载","2014-12-26 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