uuid

         分区创建、文件系统、挂载实验、逐步创建和命令创建 逐步创建： 实验环境：准备一个vmr、centos7、添加一块新硬盘。 fdisk -l 查看新硬盘添加进去了没，查看之后没有发现新硬盘，可以用以下命令来不关机扫描磁盘。 [root@centos7 ~]# fdisk -l . . . . . . Disk /dev/sdc: 21.5 GB, 21474836480 bytes, 41943040 sectors Units = sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk label type: gpt Disk identifier: 223140F2-3EB4-4ADC-A9B0-3869E8A04170 显示这行看第一行，我加的是10G的硬盘没显示，执行下面的命令。 [root@centos7 ~]# echo "- - -" > /sys/class/scsi_host/host0/scan [root@centos7 ~]# fdisk -l . . . . . . Disk /dev/sdd: 10.7 GB,

I have an app that makes use of shortuuid ( https://pypi.python.org/pypi/shortuuid/0.1 ) that is working fine locally when I run it with runapp.py: import os from paste.deploy import loadapp from waitress import serve if __name__ == "__main__": port = int(os.environ.get("PORT", 5000)) app = loadapp('config:production.ini', relative_to='.') serve(app, host='0.0.0.0', port=port) It does not work, however, when I try and run it with ../bin/pserve development.ini. I get the error: import error: no module named shortuuid. When I push it to heroku I get the same error. I have installed shortuuid

synchronized 和 java.util.concurrent.lock.Lock 之间的区别 实现层面不一样。synchronized 是 Java 关键字，JVM层面 实现加锁和释放锁；Lock 是一个接口，在代码层面实现加锁和释放锁 是否自动释放锁。synchronized 在线程代码执行完或出现异常时自动释放锁；Lock 不会自动释放锁，需要在 finally {} 代码块显式地中释放锁 是否一直等待。synchronized 会导致线程拿不到锁一直等待；Lock 可以设置尝试获取锁或者获取锁失败一定时间超时 获取锁成功是否可知。synchronized 无法得知是否获取锁成功；Lock 可以通过 tryLock 获得加锁是否成功 功能复杂性。synchronized 加锁可重入、不可中断、非公平；Lock 可重入、可判断、可公平和不公平、细分读写锁提高效率 java.util.concurrent.lock.Lock 与 java.util.concurrent.lock.ReadWriteLock 之间的区别 ReadWriteLock 定义了获取读锁和写锁的接口，读锁之间不互斥，非常适合读多、写少的场景 适用场景 JDK 1.6 开始，对 synchronized 方式枷锁进行了优化，加入了偏向锁、轻量级锁和锁升级机制，性能得到了很大的提升。性能与

java生成32位UUID，具体代码如下： package com.fxsen.uuid; import java.util.UUID; /** * Copyright: Copyright (c) 2019 ITfxsen * @Description: 生成32位UUID * @ClassName: UuidTest.java * @author: ITfxsen * @date: 2019年10月16日 下午12:52:18 * @version: v1.0.0 */ public class UuidTest { public static void main(String []args){ //生成UUID String uuid = UUID.randomUUID().toString(); System.out.println("UUID:" + uuid); //因为UUID本身为32位只是生成时多了“-”，所以将它们去掉就可 uuid = uuid.replace("-", ""); System.out.println("UUID:" + uuid); } } 来源： https://www.cnblogs.com/fxsenblog/p/11687315.html

There is a bug that I found in MySql 5.5.19. When executing: select uuid(), uuid(); You are getting two equals ids. I run in two this bug when inserted two uuids to my table, I always got same values. Does anyone else run in two this bug? How can I perform insert command that requires two uuids for my keys? Edit : Actually I got wrong they are different in one digit so it was really hard to see c3db913 7 -705e-11e1-ae17-1c6f6531b785 c3db913 f -705e-11e1-ae17-1c6f6531b785 From the docs A UUID is designed as a number that is globally unique in space and time. Since the query is compiled before

懒得多写了，懂的看建表脚本就懂了。。。 -- ---------------------------- -- Table structure for ucb_user -- ---------------------------- DROP TABLE IF EXISTS `ucb_user`; CREATE TABLE `ucb_user` ( `id` char(32) NOT NULL COMMENT '主键(UUID)', `user_type` tinyint(3) unsigned NOT NULL DEFAULT '0' COMMENT '用户类型：0、未定义；1、内部用户；2、合作方用户；3、外部用户', `source` tinyint(3) DEFAULT '0' COMMENT '来源', `code` varchar(8) DEFAULT NULL COMMENT '用户编码', `name` varchar(64) NOT NULL COMMENT '名称', `account` varchar(64) NOT NULL COMMENT '登录账号', `mobile` varchar(32) DEFAULT NULL COMMENT '手机号', `email` varchar(64) DEFAULT NULL COMMENT '电子邮箱',

I have an app that runs in Linux. Each one will try to get a UUID from OS and report to a centralized server. I want to make sure all instance are running with globally unique UUID. If the linux is on bare metal, it can just read the UUID (say, from dmidecode command). But if it's on VM, the UUID (from dmidecode) can potentially be equal since the VM can be copied or moved. Any ideas? By the way, for Linux running on physical hardware (not on VM), if user changes memory, NIC etc, will UUID change? Thanks in advance. If the linux is on bare metal, it can just read the UUID (say, from dmidecode