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Dada selects MySQL Enterprise Unlimited to handle over 7 million online subscribers

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Dada selects MySQL Enterprise Unlimited to handle over 7 million online subscribers

Dada selects MySQL Enterprise Unlimited to handle over 7 million online subscribers

Milan, Italy -- April 3rd, 2007 -- MySQL AB, developer of the world''s most popular open source database, today announced that Dada, a leading international provider of Web and mobile community and entertainment services, has selected MySQL Enterprise Unlimited to power its subscriber database storing the information of over 7 million users.
Dada’s consumer offering is characterized by a rich range of fee-based community and entertainment products and services accessible via the PC and the mobile phone. This offering is available to users in 15 countries throughout the world for a total “addressable market” of over 700 million mobile users on second- and third-generation networks.
"Dada is a leader in the field of Web-based and mobile multimedia entertainment services, and our subscriber database is a vital part of our core business,” said Angelo Falchetti, Managing Director of Dada. “With the exponential growth of Dada user subscriptions, averaging a daily increase of 20,000, we wanted to be able to rely on the outstanding expertise and support of MySQL AB. MySQL Enterprise Unlimited made it easy for us to join forces with MySQL to help ensure the effective real time management of our subscribers’ information.”
“We are very pleased that Dada, a leading vendor of mobile and online entertainment services has selected MySQL Enterprise to power such a critical piece of their business infrastructure,” said Richard Mason, vice president of EMEA for MySQL AB. “Our new unlimited offering is designed to make it simpler and more cost-effective for companies to develop, deploy and manage their applications using MySQL, the world’s most popular open source database.”
MySQL AB unveiled its MySQL Enterprise Unlimited site subscription offering last January. More information is available at: http://www.mysql.com/products/enterprise/unlimited.html
About Dada
Dada offers Web and Mobile services through its dada.net community www.dada.net of 7 million people located in 15 different countries throughout the world including Italy, the USA through its subsidiary Dada USA, Spain through the subsidiary Dada Iberia, Brazil through its subsidiary Dada Brazil, and Portugal, Germany, the United Kingdom, France, Belgium, the Netherlands, Austria, Hungary, Canada, China and Australia. The services provide a way for having fun, meeting people and communicating. Dada.net has three distinct brands: life.Dada.net (blogging & personal space), mobi.Dada.net (digital music & mobile entertainment) and love.Dada.net (community & dating).
Dada is listed on the Italian Stock Exchange (MTAX STAR: DA.MI) and apart from the Dada management and founders, it has among its shareholders the RCS MediaGroup, with approximately 44.2% of the share capital.
About MySQL
MySQL AB develops and supports a family of high-performance, affordable database products. The company’s flagship offering is ‘MySQL Enterprise’, a comprehensive set of production-tested software, proactive monitoring tools, and premium support services.
MySQL is the world''s most popular open source database software, with over 10 million active installations. Many of the world''s largest and fastest-growing organizations use MySQL to save time and money powering their high-volume Websites, business-critical systems and packaged software -- including industry leaders such as Yahoo!, Alcatel, The Associated Press, Suzuki and NASA.
With headquarters in the United States and Sweden -- and operations around the world -- MySQL AB supports both open source values and corporate customers'' needs in a profitable, sustainable business model. For more information about MySQL, please visit www.mysql.com.
###
MySQL is a registered trademark of MySQL AB in the United States and other countries. Other names may be trademarks of their respective companies.
本文出自 “MySQL 中文网” 博客 http://www.imysql.cn/

2019CCPC秦皇岛 K MUV LUV UNLIMITED(博弈)

2019CCPC秦皇岛 K MUV LUV UNLIMITED(博弈)

MUV LUV UNLIMITED

Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 131072/131072 K (Java/Others)
Total Submission(s): 143    Accepted Submission(s): 16


Problem Description
联合国太平洋方面第11军横滨基地的娱乐活动很少。207小队的成员通常会在晚饭后聚在PX玩游戏。然而无论玩什么游戏,白银武总是会输。于是白银武决定利用另一个世界中的博弈论知识来让自己转败为胜。

白银武向战友们介绍了这样一个游戏:

给出一棵 n个点以1为根的有根树。两个人轮流进行操作。操作人需要选出至少1个叶子(即没有儿子的点)删掉。无法操作的人输。

不幸的是,白银武发现自己的博弈论知识并不能判断自己应该选择先手还是后手。所以请你帮他判断,在双方都进行最优决策的情况下,是先手必胜还是后手必胜。
 

 

Input
1行一个整数T,代表数据组数。

对于每组数据,

1行一个正整数n,代表树上结点个数。

接下来一行n1个数字,依次表示2n点的父亲编号。

2n106

每个测试文件中的n之和不超过106
 

 

Output
若在双方都选择最优决策的情况下,先手必胜,请输出"Takeru";否则输出"Meiya"。
 

 

Sample Input
2 3 1 1 4 1 2 3
 

 

Sample Output
Takeru Meiya
Hint
对于第一组数据,先手选择删去2号点,那么后手只能删去3号点,之后先手删去1号点取得胜利。
 

 

Source
642ccpcQHD
 题解:
如果存在一个叶子节点 x,且它的父亲节点的出度大于 1,那么先手一定必胜。考虑当先手只取 x 这一个节点后:变成先手必败态,那么当前先手自然是必胜的变成先手必胜态,那么存在一个方案使得去掉 x 以及其他某个叶子节点集合 S 后,能够到达一个先手必败态。而由于删除 x 后没有产生其他叶子节点,即 S 中所有点在删除 x 前就已经是叶子节点了,所以先手可以直接删除 {x}∪S 而转移到先手必败态
接下来考虑所有叶子节点的父亲的出度都等于 1 的情况。求出每个叶子节点的链长(即到达第一个出度不为 1 的祖先需要经过多少条边)。如果所有链长均为偶数则先手必败,否则先手必胜。其中必胜的策略为将所有链长为奇数的叶子删去使得他们链长变为偶数。时间复杂度:O(∑n)。
参考代码:

分享图片

分享图片

#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
#define pii pair<int,int>
#define pil pair<int,ll>
#define mkp make_pair
const int INF=0x3f3f3f3f;
const ll inf=1e18;
const int maxn=1e6+10;
int siz[maxn],fa[maxn],cnt[maxn];
int T,n,m;
vector<int> vec;
struct Edge{
    int v,nxt;
} edge[maxn<<1];
int head[maxn],tot;

void Init()
{
    tot=0; fa[1]=-1;
    for(int i=0;i<=n;++i) 
        head[i]=-1,cnt[i]=0;
    vec.clear();
}

void AddEdge(int x,int y)
{
    edge[tot].v=y;
    edge[tot].nxt=head[x];
    head[x]=tot++;
}

void dfs(int u)
{
    for(int i=head[u];~i;i=edge[i].nxt)
    {
        int v=edge[i].v;
        if(v==fa[u]) continue;
        fa[v]=u;
        dfs(v);
    }
}

int main()
{
    scanf("%d",&T) ;
    while(T--)
    {
        scanf("%d",&n);
        Init();
        
        for(int i=2;i<=n;++i)
        {
            int x;
            scanf("%d",&x);
            cnt[x]++;cnt[i]++;
            AddEdge(i,x);AddEdge(x,i); 
        }
        dfs(1); cnt[1]++;
        
        for(int i=1;i<=n;++i) 
            if(cnt[i]==1) vec.push_back(i);
        
        int flag=0;
        for(int i=0,len=vec.size();i<len;++i)
        {
            int v=vec[i];
            if(cnt[fa[v]]>2) {flag=1;break;}
            int res=1;
            
            while(cnt[fa[v]]==2)
            {
                v=fa[v];
                res++;
            }
            if(res&1) flag=1;
        }
        
        if(flag==1) puts("Takeru");
        else puts("Meiya");
    }
       
    return 0;    
}
View Code

4种DNS安全协议对比:DNSSEC,DNSCrypt,DNS over TLS,DNS over HTTPS

4种DNS安全协议对比:DNSSEC,DNSCrypt,DNS over TLS,DNS over HTTPS

DNS域名系统(Domain Name System的缩写),是一个将域名和IP地址相互映射的分布式数据库,能够使人通过便于记忆的域名地址访问互联网(比如:沃通官网www.wosign.com),而无需记住长串毫无关联性的IP地址(比如:123.196.2.455)。DNS可以理解为“互联网的地址簿”,是互联网的一项基础服务。

DNS的重要性也让其成了黑客主要攻击对象,常见的DNS攻击包括:DNS劫持、缓存投毒、DNS欺骗等等,目的就是通过各种攻击手段将正常访问合法网站的用户,引到黑客控制的假冒服务器上,进行钓鱼欺诈、窃取用户凭证或敏感数据等非法行为。

为了防止针对DNS系统的攻击,强化域名系统的安全性,互联网诞生了4种提升DNS安全性的协议,分别是DNSSEC,DNSCrypt,DNS over TLS,DNS over HTTPS。

 

什么是DNSSEC

DNSSEC是“Domain Name System Security Extensions”的缩写,代表域名系统安全扩展,允许域名所有者对DNS记录进行数字签名,签名DNS记录的私有签名密钥通常仅由合法域名所有者持有,因此可防止未经授权的第三方修改DNS条目。

DNSSEC诞生于1997年,已经列入互联网标准化文档(参考RFC 4033、RFC 4034、RFC 4035),是最早大规模部署的DNS安全协议,所有的根域名服务器都已经部署了DNSSEC。

虽然DNSSEC已经诞生20年,但APNIC统计其采用率几乎不到19.3%,ICANN敦促业界普及使用DNSSEC协议。不过,DNSSEC协议仅提供真实性和完整性的校验,无法确保DNS流量通信的机密性。

 

什么是DNSCrypt

DNSCrypt是OpenDNS发布的加密DNS工具。与SSL将HTTP流量转换为HTTPS加密流量的原理相同,DNSCrypt也是将常规DNS流量转换为加密DNS流量,这样可以防止窃听和中间人攻击。它不需要对域名或它们的工作方式进行任何更改,只是提供了一种方法,安全加密客户端与DNS服务器之间的通信。在一定程度上,DNSCrypt比DNSSEC的保密性更强,因为DNSSEC只做数字签名的校验,而DNSCrypt既能加密DNS流量也能确保完整性。

不过,DNSCrypt客户端必须明确信任所选提供者的公钥,想使用哪个DNSCrypt服务器,就需要预先安装该服务器的公钥,而不是通过常规浏览器中受信任证书颁发机构列表获取信任;此外,DNSCrypt未申请列入标准化文档,在大规模的应用场景中存在一定的局限性。

 

什么是DNS over TLS

DNS over TLS(简称DoT)是一项安全协议,它可以强制所有和DNS服务器相关的链接都使用TLS,已列入标准文档(参见 RFC 7858 和 RFC 8310)。

DNS over TLS 就是基于 TLS 隧道之上的域名协议,由于 TLS 本身已经实现了保密性与完整性,因此 DoT 自然也就具有这两项特性。DoT通过TLS协议及SSL/TLS证书(如:沃通SSL证书)实现安全加密和身份验证,实现保密性和完整性。

与前述两项协议相比,DNS over TLS更具优势:和DNSSEC相比,DNS over TLS具备了保密性;与 DNSCrypt相比,DNS over TLS已经形成标准化文档。不过,目前支持DNS over TLS 的客户端还不够多,主流浏览器还没有计划增加对DNS over TLS的支持。

 

什么是DNS over HTTPS

很多人将DNS over HTTPS 和DNS over TLS混为一谈,事实上二者是两种不同的协议,DNS over TLS使用TCP作为基本的连接协议,而DNS over HTTPS使用HTTPS和HTTP/2进行连接;DNS over TLS有自己的端口853,DNS over HTTPS则使用HTTPS标准端口443。

不过,两种协议都是通过TLS加密和SSL/TLS证书(如:沃通SSL证书)来实现保密性与完整性。目前,DNS over HTTPS已经形成相应的草案,但还没有形成RFC标准化文档正式发布,但已经受到主流浏览器的青睐,Mozilla 已经决定在Firefox Nightly中测试DNS-over-HTTPS协议。

Web服务器使用HTTPS加密已经得到广泛的普及和认同,而加密DNS服务器流量其实也是同等重要的。但实现DNS流量加密仍然需要DNS服务器、客户端浏览器等生态环境的支持。在DNS加密生态尚未完整建立的初期,沃通CA推荐网站服务器部署超安EV SSL证书,在浏览器上直观显示绿色地址栏及单位名称,网站显示名称具有唯一性,让假冒服务器难以复制仿冒,有效降低用户被假冒网站钓鱼欺诈的风险。此外,也建议域名所有者敦促服务商尽快支持DNS加密,建立安全可信的DNS域名系统使用环境。

 

 

 

CentOS 设置 ulimit -c unlimited 生成core文件

CentOS 设置 ulimit -c unlimited 生成core文件

root下

vim /etc/profile

末尾加上 ulimit -c unlimited

如下:

unset i
unset -f pathmunge
ulimit -c unlimited

work下 执行source /etc/profile 生效

configure-nginx-how-to-handle-500-error-on-upstream-itself-while-nginx-handle

configure-nginx-how-to-handle-500-error-on-upstream-itself-while-nginx-handle

 

 

https://serverfault.com/questions/859667/configure-nginx-how-to-handle-500-error-on-upstream-itself-while-nginx-handle

 

 

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